Occupational Exposure to Beryllium:

Preliminary OSHA

Health Effects Evaluation

August 3, 2010

HEALTH EFFECTS

Beryllium is a relatively rare naturally occurring metal with an atomic
number of 4.  Beryllium, its compounds and alloys are commercially
valuable metals and gemstones with many industrial uses.
Beryllium-associated diseases can lead to a number of highly
debilitating and life-altering conditions including pneumonitis, loss of
lung capacity (reduction in pulmonary function leading to pulmonary
dysfunction), loss of physical capacity associated with reduced lung
capacity, systemic effects related to pulmonary dysfunction, and
decreased life expectancy (National Institute for Occupational Safety
and Health (NIOSH), 1972).  OSHA considers CBD to be a progressive
illness with a continuous spectrum of symptoms ranging from no
symptomology at its earliest stage following sensitization to mild
symptoms such as a slight almost imperceptible shortness of breath, to
loss of pulmonary function, debilitating lung disease, and, in some
cases, death.

This section presents information on beryllium and its compounds, the
fate of beryllium in the body, research that relates to its toxic
mechanisms of action, and the scientific literature on the diseases
associated with beryllium exposure, including acute beryllium disease
(ABD), beryllium sensitization (BeS), chronic beryllium disease (CBD),
and lung cancer.  This section also discusses the nature of these
illnesses, the scientific evidence that they are causally associated
with occupational exposure to beryllium, and the probable mechanism of
action.  In addition, this section reviews the mechanism underlying
these conditions as well as a more thorough review of the supporting
studies.

Beryllium and Beryllium Compounds

Particle physical/chemical properties

Beryllium (Be; CAS No. 7440-41-7) is a steel-grey, brittle metal with an
atomic number of 4 and an atomic weight of 9.01 (Group IIA of the
periodic table).  Beryllium is a relatively rate naturally occurring
element found in earth’s surface rocks at levels of approximately 1-15
mg/kg (World Health Organization (WHO), 1993).  Because of its high
reactivity, beryllium is not found as a free metal in nature; however,
there are approximately 45 mineralized forms of beryllium.  The
important beryllium minerals in the world are beryl (3BeO·Al2O3·6SiO2)
and bertrandite (Be4Si2O7(OH)2).  Beryl has been known since ancient
times as the gemstones: emerald (green), aquamarine (light blue), and
beryl (yellow) (Agency for Toxic Substances and Disease Registry
(ATSDR), 2002).  Beryllium, its compounds and alloys, are commercially
valuable metals and gemstones.  The industrial uses of beryllium are
discussed in the Preliminary Economic Assessment that is not subject to
this peer review

Beryllium has two oxidative states: Be0 and Be2+ (ATSDR 2002). It is
most likely the Be2+ state that is most biologically reactive and able
to form a bond with peptides leading to it becoming antigenic (Lawrence
and McCabe, 2002).  This will be discussed in more detail in the
Beryllium Sensitization section below.  Beryllium has a high
charge-to-radius ratio and in addition to forming various types of ionic
bonds, beryllium has a strong tendency for covalent bond formation
(e.g., it can form organometallic compounds such as Be(CH3)2 and many
other complexes) (ATSDR), 2002; Greene et al., 1998).  However, it
appears little to no toxicity studies exist for the organometallic
compounds.

While most beryllium compounds are non-combustible and do not burn they
may decompose upon heating to produce corrosive and/or toxic fumes. Some
beryllium compounds are oxidizers and may ignite combustibles (wood,
paper, oil, clothing, etc). Contact with metals may evolve flammable
hydrogen gas. Additional physical/chemical properties for beryllium
(ICSC 0226), beryllium oxide (ICSC 1325), beryllium sulfate (ICSC 1351),
beryllium nitrate (ICSC 1352), beryllium carbonate (ICSC 1335),
beryllium chloride (ICSC 1354), and beryllium fluoride (ICSC 1355)
obtained from their International Chemical Safety Cards is found in
Table 1 below.

Table 1: Physical/Chemical Properties of Beryllium and Compounds

	Physical Information

Compound Name	Physical Appearance	Chemical Formula	Molecular Mass	Acute
Physical Hazards	Boiling Point	Melting Point	Density	Solubility in Water
at 20°C

Insoluble/Poorly or Sparingly Compounds

Beryllium Metal	Grey to White Powder	Be	9.01	Combustible;

Finely dispersed particles - Explosive	Above 2500°C	1287°C	1.9 g/cm3
none

Beryllium Oxide	White Crystals or Powder	BeO	25.0	Not combustible or
explosive	3900°C	2530°C	3.0 g/cm3	very sparingly soluble

Beryllium Carbonate	White Powder	Be2CO3(OH)

/Be2CO5H2	181.07	Not combustible or explosive	Not reported	Not reported
Not reported	none

(decomposes in hot water)

Soluble Compounds

Beryllium Sulfate	Colorless Crystals	BeSO4	105.1	Not combustible or
explosive	Not reported	550°C	2.44 g/cm3	slightly soluble

Beryllium Nitrate	White to Yellow Solid	BeN2O6/

Be(NO3)2	133.0	Enhances combustion of other substances	100°C	60°C	1.56
g/cm3	very soluble

(1.66 x 106mg/L)

Beryllium Hydroxide	White amorphous powder or crystalline solid	Be(OH)2
43.0	Not reported	Not reported	Decom-poses when heated	1.92 g/cm3
slightly soluble

0.8 x 10-4 mol/L

(3.44 mg/L)

Beryllium Chloride	Colorless to Yellow Crystals	BeCl2	79.9	Not
combustible or explosive	520°C	399.2°C	1.9 g/cm3	Soluble

Beryllium Fluoride	Colorless Lumps	BeF2	47.0	Not combustible or
explosive	1160°C	555°C	1.99 g/cm3	very soluble

Beryllium Phosphate	White solid	Be3(PO4)2	271.0	Not reported	Not
reported	100°C	2.44

g/cm3	Soluble

Beryllium shows a high affinity for oxygen in air and water, resulting
in a thin surface film of beryllium oxide on the bare metal.  If the
surface film is disturbed, it may become airborne or dermal exposure may
occur.  The solubility, particle surface area, and particle size of some
beryllium compounds are examined in more detail below.  These properties
have been evaluated in many toxicological studies. In particular, the
properties related to the calcination (firing temperatures) and
differences in crystal size and solubility are important aspects in
their toxicological profile.

Factors affecting potency and effect of beryllium exposure

The effect and potency of beryllium and its compounds, as for any
toxicant, may be dependent upon the physical state in which it is
presented to a host.  For occupational airborne materials and surface
area contaminants it is especially critical to understand those physical
parameters in order to determine the extent of exposure to the
respiratory tract and skin since these are generally the initial target
organs for this route of exposure.

For example, large particles may have less of an effect in the lung than
smaller particles due to reduced potential to stay airborne to be
inhaled or be deposited along the respiratory tract.  In addition, once
inhalation occurs particle size is critical in determining where the
particle will deposit along the respiratory tract.  Solubility also has
an important part in determining the toxicity and bioavailability of
airborne materials as well.  Respiratory tract deposition and skin
penetration are directly influenced by the solubility and reactivity of
airborne material.

These factors may be responsible, at least in part, to the process
leading exposed workers from BeS to CBD.  Other factors influencing
beryllium-induced toxicity include surface area and persistence in the
lung.  For skin, the physical characteristics of the particle are
important as well since those can influence skin absorption and
bioavailability.  This section addresses certain physical
characteristics (i.e., solubility, particle size, particle surface area)
that are important in influencing the toxicity of beryllium materials in
occupational settings.

Solubility

Solubility may be an important determinant of the toxicity of airborne
materials, influencing the deposition and persistence of inhaled
particles in the respiratory tract, their bioavailability, and the
likelihood of presentation to the immune system.  The ability of
airborne materials to penetrate the skin is similarly influenced by
solubility.  Some chemical agents such as certain polymers, rubber
accelerators, epoxy resins, certain solvents, perfumes and other organic
compounds can penetrate the skin to induce a toxic or immune response
such as sensitization (Boeniger, 2003).  Metals, either in the soluble
or insoluble form, can cause a similar response (Mandervelt et al.,
1997).

This section reviews the relevant information regarding solubility, its
importance in a biological matrix and the relevance to sensitization and
beryllium lung disease.  The weight of evidence presented below suggests
that both soluble and non-soluble forms of beryllium can induce a
sensitization response and result in progression of lung disease.

・4H2O) are all water soluble.  However, soluble beryllium salts can be
converted to less soluble forms in the lung (ATSDR, 1993).  Aqueous
solutions of the soluble beryllium salts are acidic as a result of the
formation of Be(OH2)4 2+, the tetrahydrate, which will react to form
insoluble hydroxides or hydrated complexes within the general
physiological range of pH values (between 5 and 8) (US EPA, 1998).  This
may be an important factor in development of CBD since lower solubility
forms of beryllium have been shown to persist in the lung for longer
periods of time and persistence in the lung may be needed in order for
this disease to occur (NAS, 2008).

Beryllium oxide (BeO), hydroxide (Be(OH)2), carbonate (Be2CO3(OH)2), and
sulfate (anhydrous) (BeSO4) are either insoluble, slightly soluble, or
considered to be sparingly soluble (almost insoluble or extremely slow
rate of dissolution).  The solubility of beryllium oxide, which is
prepared from beryllium hydroxide by calcining (heating to a high
temperature without fusing in order to drive off volatile chemicals) at
temperatures between 500 and 1,750 °C, has an inverse relationship with
calcination temperature.  Although the solubility of the low-fired
crystals can be as much as 10 times that of the high-fired crystals,
low-fired beryllium oxide is still only sparingly soluble (Delic, 1992;
HSE, 1994).  In a study that measured the dissolution kinetics (rate to
dissolve) of beryllium compounds calcined at different temperatures,
Hoover et al. compared beryllium metals to beryllium oxide and found
them to have similar solubilities.  This was attributed to a fine layer
of beryllium oxide that coats the metal particles (Hoover et al., 1989).

Investigators have also attempted to determine how biological fluids can
dissolve beryllium materials.  In one study, insoluble beryllium, taken
up by activated phagocytes, was shown to be ionized by myeloperoxidases
(Leonard and Lauwerys, 1987; Lansdown, 1995).  The positive charge
resulting from ionization enabled the beryllium to bind to receptors on
the surface of cells such as lymphocytes or antigen presenting cells
which could make it more biologically active (NAS, 2008).   In a study
utilizing phagolysosomal-simulating fluid with a pH of 4.5, both
beryllium metal and beryllium oxide dissolved at a greater rate than
that previously reported in water or SUF (simulant fluid) (Stefaniak et
al.,  2006), and the rate of dissolution of the multi-constituent
(mixed) particles was greater than that of the single-constituent
beryllium oxide powder. The authors speculated that copper in the
particles rapidly dissolves, exposing the small inclusions of beryllium
oxide, which have higher specific surface areas (SSA) and therefore
dissolve at a higher rate.

 on the particle size, with smaller particles (< 10 μm) able to
penetrate beyond the larynx (Stephaniak, 2008).  Most inhalation studies
and occupational exposures involve quite small (< 1-2 μm) beryllium
oxide particles that can penetrate deeply into the lungs (Stephaniak,
2008). In inhalation studies with beryllium ores, particle sizes are
generally much larger, with deposition occurring in several areas
throughout the respiratory tract for particles < 10 μm.

The temperature at which beryllium oxide is calcined influences its
particle size, surface area, solubility, and ultimately its toxicity
(Delic, 1992).  Low-fired (500° C) beryllium oxide is predominantly
made up of poorly crystallized small particles, while higher firing
temperatures (1000 - 1750° C) result in larger particle sizes (Delic,
1992; HSE, 1994).

In order to determine the extent to which particle size plays a role in
the toxicity of beryllium in occupational settings several key studies
are reviewed and detailed below.  The findings on particle size have
been related, where possible, to work process and biologically relevant
toxicity endpoints of either BeS or CBD.

μm or less) with 30 percent of that fraction being particles of less
than 0.6 μm.  A study by Thorat et al. (2003) found similar results
with ore mixing, crushing, powder production and machining ranging from
5.0 to 9.5 μm.  Kent et al. (2001) measured airborne beryllium using
size-selective samplers in five furnace areas at a beryllium processing
facility.  This study found a significant association between BeS and
CBD and beryllium concentration of particles less than 3.5 μm and less
than 10 μm in size (collected with a MOUDI (Micro-Orifice Uniform
Deposit Impactor)) but no association with the total mass concentration
of airborne beryllium.  The study authors suggested that the
concentration of alveolar-deposited particles (e.g., <3.5 μm) may be a
better predictor of BeS and CBD than the total mass concentration of
airborne beryllium.

Particle surface area

Surface area has been postulated as an important metric for beryllium
exposure.  Several studies have demonstrated a relationship between the
inflammatory and tumorigenic potential of ultrafine particles and their
increased surface area (Driscoll, 1996; Miller, 1997; Oberdorster et
al., 1994).  While the exact mechanism explaining how particle surface
area influences its biological activity is not known, a greater particle
surface area has been shown to increase inflammation, cytokine
production, anti-oxidant defenses and apoptosis (Elder et at., 2005;
Carter et al., 2006; Refsne et al., 2006).

Finch et al. (1988) found that beryllium oxide calcined at 500°C had
3.3 times greater specific surface area (SSA) than beryllium oxide
calcined at 1000°C, although there was no difference in size or
structure of the particles as a function of calcining temperature.  The
beryllium-metal aerosol (airborne beryllium particles), although similar
to the beryllium oxide aerosols in aerodynamic size, had an SSA about 30
percent that of the beryllium oxide calcined at 1000°C.  As discussed
above, a later study by Delic (1992) found calcining temperatures also
had an effect on SSA but did not have an effect on particle size.

Several studies have investigated the lung toxicity of beryllium oxide
calcined at different temperatures and generally had found that those
calcined at lower temperatures have greater toxicity and effect than
materials calcined at higher temperatures.  This may be because
beryllium oxide fired at the lower temperature has a loosely formed
crystalline structure with greater specific surface area than the fused
crystal structure of beryllium oxide fired at the higher temperature.
For example, beryllium oxide calcined at 500° C has been found to have
stronger pathogenic effects than material calcined at 1,000° C, as
shown in several of the beagle dog, rat, mouse and guinea pig studies
discussed in the section on CBD pathogenesis that follows (Finch et al.,
1984; Polak et al., 1968; Haley et al., 1989; Haley et al., 1992; Hall
et al., 1950).  Finch et al. have also observed higher toxicity of
beryllium oxide calcined at 500° C, an observation they attribute to
the greater surface area of beryllium particles calcined at the lower
temperature (Finch et al., 1988).  These authors found that the in
vitro cytotoxicity to Chinese hamster ovary (CHO) cells and cultured
lung epithelial cells of 500° C beryllium oxide was greater than that
of 1,000° C beryllium oxide, which in turn was greater than that of
beryllium metal. However, when toxicity was expressed in terms of
particle surface area, the cytotoxicity of all three forms was similar.
Similar results were observed in a study comparing the cytotoxicity of
beryllium metal particles of various sizes to cultured rat alveolar
macrophages, although specific surface area did not entirely predict
cytotoxicity (Finch et al., 1991).

Stefaniak et al. (2003b) investigated the particle structure and surface
area of particles (powder and process-sampled) of beryllium metal,
beryllium oxide, and copper-beryllium alloy.  Each of these samples was
separated by aerodynamic size and their chemical compositions and
structures were determined with x-ray diffraction and transmission
electron microscopy, respectively. In summary, beryllium-metal powder
varied remarkably from beryllium oxide powder and alloy particles. The
metal powder consisted of compact particles while the alloys and oxides
consisted of small primary particles in clusters.  SSA for the metal
powders varied based on production and manufacturing process with
variations of samples as high as a factor of 37.  Stephaniak et al.
(2003b) found lesser variation in SSA for the alloys or oxides.  This is
consistent with data from other studies summarized above showing that
process may affect particle size and surface area.  Particle size and/or
surface area may explain differences in the rate of BeS and CBD observed
in some epidemiological studies.  However, these properties have not
been consistently characterized in most studies.

Kinetics and Metabolism of Beryllium

Beryllium enters the body by inhalation, ingestion, or absorption
through the skin.  For occupational exposure, the airways and the skin
are the primary routes of uptake.

Exposure via the respiratory system

The respiratory tract, especially the lung, is the primary target of
inhalation exposure in animals and humans.  Inhaled beryllium particles
are deposited along the respiratory tract in a size dependent manner.
In general, particles less than 0.3 μm and greater than 5 μm in
aerodynamic diameter deposit along the tracheobronchial region.
Particles ranging greater than 0.3 μm but less than 5 μm tend to
deposit in the pulmonary or alveolar region.  Particles larger than
10μm tend to deposit in the nasal region (Figures 1 and 2).  For
particles below 1 μm, regional deposition changes dramatically.
Ultrafine particles (generally considered to be 100 nm or lower) have a
high rate of depositing in the nasal passage, where these particles can
encounter immune cells more readily.  While deposition still occurs
along the entire respiratory tract less is deposited in the alveolar
region.  However, those particles that do deposit in the alveolar region
can move into the interstitium of the lung where they may encounter
immunologic cells or may move into the vascular region where they are
free to leave the lung and can contribute to systemic beryllium
concentrations. (ICRP model, 1994 and ACGIH, 2009).

Figure 1: ACGIH model for respiratory tract deposition (2009)

The data represents the fractional deposition of particle size for each
region of the respiratory tract.  These particle sizes are based on the
International Organization

for Standardization/European Standardization Committee (ISO/CEN).

 Figure 2: ICRP model

Beryllium is removed from the respiratory tract by various clearance
mechanisms. Soluble beryllium is removed from the respiratory tract via
absorption.  Sparingly or insoluble beryllium may remain in the lungs
for many years after exposure, as has been observed in workers (e.g.,
Schepers, 1962).  Clearance mechanisms for sparingly soluble or
insoluble beryllium particles include: in the nasal passage, sneezing,
mucociliary transport to the throat, or dissolving; in the
tracheobronchial region, mucociliary transport, coughing, phagocytosis,
or dissolving; in the pulmonary or alveolar region it is phagocytosis,
movement through the interstitium (translocation) or dissolving
(Schlesinger, 1999).

Clearance mechanisms may occur slowly in humans, which is consistent
with some animal studies.  For example, subjects in the Beryllium Case
Registry (BCR) that identifies and track cases of acute and chronic
beryllium diseases had elevated concentrations of beryllium in lung
tissue (e.g. 0.32 pg/g in a metastinal node) more than 20 years after
termination of short-term (generally less than 2 years) occupational
exposure to beryllium (Sprince et al., 1976).

Clearance rates may depend on the solubility, dose, and size of the
beryllium particles inhaled as well as the sex and species of the animal
tested.  More soluble beryllium compounds generally tend to be cleared
from the respiratory system and absorbed into the bloodstream more
rapidly than less soluble compounds (Van Cleave and Kaylor, 1955; Hart
et al., 1980; Finch et al., 1990).  Animal inhalation or intratracheal
instillation studies administering soluble beryllium salts demonstrated
significant absorption at approximately 20 percent of the initial lung
burden, while, sparingly soluble compounds such as beryllium oxide
demonstrated that absorption was slower and less significant (Delic,
1992; HSE, 1994).  Additional animal studies have demonstrated that
clearance of soluble and sparingly soluble beryllium compounds was
biphasic; a more rapid initial mucociliary transport phase of particles
from the tracheobronchial tree to the gastrointestinal tract, followed
by a slower phase via translocation to tracheobronchial lymph nodes,
alveolar macrophages uptake, and beryllium particles dissolution (Camner
et al., 1977; Sanders et al., 1978; Delic, 1992; HSE, 1994).
Confirmatory studies in rats have shown the half-time for the rapid
phase was between 1 - 60 days, and the slow phase was ranged from 0.6 -
2.3 years.  It was also shown that this process was influenced by the
solubility of the beryllium compounds; weeks/months for soluble
compounds, months/years, for sparingly soluble compounds. (Reeves and
Vorwald, 1967; Reeves et al., 1967; Zorn et al., 1977; Rhoads and
Sanders, 1985).  Studies in guinea-pigs and rats indicate that 40 - 50
percent of the inhaled soluble beryllium salts are retained in the
respiratory tract.  Similar data could not be found for the sparingly or
less soluble beryllium compounds or metal administered by this exposure
route. (ATSDR, 2002)

Evidence from animal studies suggests that greater amounts of beryllium
deposited in the lung may result in slower clearance times.  A
comparative study of rats and mice using a single-dose of inhaled
aerosolized beryllium metal demonstrated that an acute inhalation
exposure to beryllium metal can slow particle clearance and induce lung
damage in rats (Haley et al., 1990) and mice (Finch et al., 1998a).  In
another study Finch et al. (1994) exposed male F344/N rats to beryllium
metal at concentrations resulting in beryllium lung burdens of 1.8, 10,
and 100 µg.  These exposure levels resulted in an estimated clearance
half-life ranging from 250 and 380 days for the three concentrations.
For mice (Finch et al., 1998a), lung clearance half-lives were 91–150
days (for 1.7- and 2.6-μg lung burden groups) or 360–400 days (for
12- and 34-μg lung burden groups).  While the lower exposure groups
were quite different for rats and mice, the highest groups were similar
in clearance half-lives for both species.

Beryllium absorbed from the respiratory system into the bloodstream is
mainly distributed to the tracheobronchial lymph nodes and the skeleton,
which is the ultimate site of beryllium storage (Stokinger et al., 1953;
Clary et al., 1975; Sanders et al., 1975; Finch et al., 1990).  Trace
amounts are distributed throughout the body (Zorn et al., 1977).
Studies in rats have demonstrated accumulation of beryllium chloride in
the skeletal system following intraperitoneal injection (Crowley et al.,
1949; Scott et al., 1950) and accumulation of beryllium phosphate and
beryllium sulfate in both nonparenchymal and parenchymal cells of the
liver after intravenous administration in rats (Skilleter and Price,
1978).  Studies have also demonstrated intracellular accumulation of
beryllium oxide in bone marrow throughout the skeletal system after
intravenous administration to rabbits (Fodor, 1977).

Systemic distribution of the more soluble compounds appears to be
greater than that of the insoluble compounds (Stokinger et al., 1953).
Distribution has also been shown to be dose dependent in research using
intravenous administration of beryllium in rats; small doses were
preferentially taken up in the skeleton, while higher doses were
initially distributed preferentially to the liver.  Beryllium was later
mobilized from the liver and transferred to the skeleton (IARC 1993).  A
half-life of 450 days has been estimated for beryllium in the human
skeleton (ICRP, 1960).  This indicates the skeleton may serve as a
repository of beryllium that may be later reabsorbed by the circulatory
system making beryllium available to the immunological system.

Dermal exposure

The ATSDR estimated that less than 0.1 percent of beryllium compounds
are absorbed through the skin (ATSDR, 2002).  However, even minute
contact and absorption across the skin may directly elicit an
immunological sensitization response (Deubner, 2001).  Recent studies by
Tinkle et al. (2003) showed that penetration of beryllium oxide
particles was possible ex vivo for human intact skin at particle sizes
of ≤ 1μm, as confirmed by scanning electron microscopy.  Using
confocal microscopy, Tinkle et al. demonstrated that surrogate
fluorescent particles up to 1 μm in size could penetrate the mouse
epidermis and dermis layers in model designed to mimic the flexing and
stretching of human skin in motion.  Other poorly soluble particles,
such as titanium dioxide, have been shown to penetrate normal human skin
(Tan et al., 1996) suggesting the flexing and stretching motion as a
plausible mechanism for dermal penetration of beryllium as well.

Since 1945 it has been known that beryllium can enter the body through
wounded skin (Van Ordstrand, 1945).  Introduction of soluble or
insoluble beryllium compounds into or under the skin as a result of
abrasions or cuts at work have been shown to result in chronic
ulcerations with granuloma formation (Van Orstrand et al., 1945; Lederer
and Savage 1954).  Beryllium absorption through bruises and cuts has
been demonstrated as well (Rossman et al., 1991).  In a study by
Invannikov et al. (1982), beryllium chloride was applied directly to
skin of live animals with three types of wounds: abrasions (superficial
skin trauma), cuts (skin and superficial muscle trauma), and penetration
wounds (deep muscle trauma).  The percentage of the applied dose
absorbed into the systemic circulation during a 24-hour exposure was
significant, ranging from 7.8 percent to 11.4 percent for abrasions,
from 18.3 percent to 22.9 percent for cuts, and from 34 percent to 38.8
percent for penetration wounds.

A study by Deubner et al. (2001) conclude that exposure across damaged
skin can contribute as much systemic loading of beryllium as inhalation
(Deubner, 2001).  Deubner et al. (2001) estimated dermal loading (amount
of particles penetrating into the skin) in workers as compared to
inhalation exposure.  Deubner's calculations assume dermal loading rate
of beryllium on skin to 0.43 μg/cm2, based on the studies of loading on
skin after workers cleaned up (Sanderson et al., 1999), multiplied by a
factor of 10 to approximate the workplace concentrations and the very
low absorption rate of 0.001 percent (taken from EPA estimates).  It
should be noted these calculations did not take into account absorption
of soluble beryllium salts that might occur across nasal mucus
membranes, which may result from contact between contaminated skin and
the nose.

Oral and gastrointestinal exposure

Gastrointestinal absorption of beryllium can occur by both the
inhalation and oral routes of exposure.  In the case of inhalation, a
portion of the inhaled material is transported to the gastrointestinal
tract by the mucociliary escalator or by the swallowing of the insoluble
material deposited in the upper respiratory tract (Kjellstrom and
Kennedy, 1984).  Animal studies have shown oral administration of
beryllium compounds to result in very limited absorption and storage (as
reviewed by US EPA, 1991).  In animal ingestion studies using
radio-labeled beryllium chloride in rats, mice, dogs, and monkeys, the
vast majority of the ingested dose passed through the gastrointestinal
tract unabsorbed and was excreted in the feces.  In most studies, <1
percent of the administered radioactivity was absorbed into the
bloodstream and subsequently excreted in the urine (Crowley et al.,
1949; Furchner et al., 1973; LeFevre and Joel, 1986).  Research using
soluble beryllium sulfate has shown that as the compound passes into the
intestine, which has a higher pH than the stomach (approximate ph of 6
to 8 for the intestine, pH of 1 or 2 for the stomach), the beryllium is
precipitated as the insoluble phosphate and thus is no longer available
for absorption (Reeves, 1965).

Urinary excretion of beryllium has been shown to correlate with the
amount of occupational exposure (Klemperer et al., 1951).  Beryllium
that is absorbed into the bloodstream is excreted primarily in the urine
(Crowley et al., 1949; Scott et al., 1950; Furchner et al., 1973;
Stiefel et al., 1980), whereas excretion of unabsorbed beryllium is
primarily via the fecal route (Hart et al., 1980; Finch et al., 1990).
A far higher percentage of the beryllium administered parenterally in
various animal species was eliminated in the urine than in the feces
(Crowley et al., 1949; Scott et al., 1950; Furchner et al., 1973),
confirming that beryllium found in the feces following oral exposure is
primarily unabsorbed material.  A study using percutaneous incorporation
of soluble beryllium nitrate in rats similarly demonstrated that more
than 90 percent of the beryllium in the bloodstream was eliminated via
urine (Zorn et al., 1977).  More than 99 percent of ingested beryllium
chloride was excreted in the feces (Mullen et al., 1972).  Elimination
half-times of 890 - 1,770 days (2.4 - 4.8 years) were calculated for
mice, rats, monkeys, and dogs injected intravenously with beryllium
chloride (Furchner et al., 1973).  Mean daily excretion of beryllium
metal was 4.6 × 10–6 percent of the dose administered by
intratracheal instillation in baboons and 3.1 × 10–6 percent in rats
(Andre et al., 1987).

Metabolism

Beryllium and its compounds are not metabolized or biotransformed, but
soluble beryllium salts may be converted to less soluble forms in the
lung (Reeves and Vorwald, 1967).  As stated earlier, solubility is an
important factor for persistence of beryllium in the lung.  Insoluble
beryllium, engulfed by activated phagocytes, can be ionized by
myeloperoxidases (Leonard and Lauwerys, 1987; Lansdown, 1995) and this
positive charge could potentially make it more biologically reactive
because it may allow the beryllium to bind to a peptide or protein and
be presented to the T cell receptor or antigen presenting cell
(Fontenot, 2000).

BERYLLIUM-INDUCED RESPIRATORY DISEASES

This section provides an overview of the respiratory diseases associated
with beryllium exposure and review of the scientific literature on the
immunology and pathogenesis of BeS and CBD, with particular attention to
the role of skin sensitization, particle size, beryllium compound
solubility, and genetic variability in individuals' susceptibility to
BeS and CBD.

Acute Beryllium Disease

100μg/m3 and may be fatal in 10 percent of cases.  The disease is a
fulminating inflammatory reaction of the entire respiratory tract,
involving the nasal passages, pharynx, bronchial airways and alveoli,
and results in lung swelling, fever, and shortness of breath. Other
tissues including skin and conjunctivae may be affected as well.  The
clinical features of ABD include a nonproductive cough, chest pain,
cyanosis and a sharp drop in the vital functioning and capacity of the
lungs. Clinicians may also look for edematous distension; round cell
infiltration of the septa; proteinaceous materials, and desquamated
alveolar cells in the lung.  Monocytes, lymphocytes and plasma cells
within the alveoli are also characteristic of the acute disease process.
(Freiman and Hardy, 1970)

Two types of acute beryllium disease have been characterized in the
literature: a rapid and severe course of acute fulminating pneumonitis
generally developing within 48 hours of a massive exposure, and a second
form that takes several days to develop from exposure to lower
concentrations of beryllium (still above the levels set by regulatory
and guidance agencies) (Hall, 1950; Newman and Kreiss, 1992).  Severity
of the acute disease has been reported to have a dose-response
relationship to the concentration of beryllium (Stokinger, 1950).
Recovery from either type of ABD is generally complete after a period of
several weeks or months (DeNardi et al., 1953). However, deaths have
been reported in more severe cases (Freiman and Hardy, 1970).  There
also have been documented cases of progression to CBD (ACCP, 1965; Hall,
1950) suggesting an immune component to this disease, which would be
expected (Cummings et al., 2009).  According to the BCR, in the United
States, approximately 17 percent of ABD patients developed CBD (BCR,
2010).  The majority of ABD cases occurred between 1932 and 1970
(Eisenbud, 1983; Middleton, 1998).  ABD is extremely rare in the
workplace today due to more stringent exposure controls implemented
following occupational and environmental standards set in 1972 (AIHA,
1972; ACGIH, 1972; ANSI, 1972) and 1974 (EPA, 1974).

Chronic Beryllium Disease

Chronic beryllium disease (CBD), formerly known as “berylliosis” or
“chronic berylliosis,” is a granulomatous disorder primarily
affecting the lungs.  CBD was recognized as early as 1951 as a chronic
disease resulting from immune sensitization to beryllium (Sterner and
Eisenbud, 1951; Curtis, 1959; Nishimura, 1966).  CBD shares many
clinical and histopathological features with pulmonary sarcoidosis, a
granulomatous lung disease of unknown cause.  This includes such
debilitating effects as obstructive functioning of the lung,
diminishment of physical capacity associated with reduced lung function,
possible depression associated with decreased physical capacity and the
possibility of decreased life expectancy.  Without appropriate
information, CBD may be difficult to distinguish from sarcoidosis.  It
is estimated that up to 6 percent of all patients diagnosed with
sarcoidosis may actually have CBD (Fireman et al., 2003; Rossman and
Kreider, 2003).  Among patients diagnosed with sarcoidosis in which
beryllium exposure can be confirmed, as many as 40 percent may actually
have CBD (Muller-Quernheim et al., 2006).

Clinical signs and symptoms of CBD may include, but are not limited to a
simple cough and shortness of breath, fever, weight loss or anorexia,
skin lesions, clubbing of fingers, cyanosis, night sweats, cor pulmonale
(enlargement of the heart’s right ventricle caused by a disorder of
the lungs or of the pulmonary blood vessels), tachycardia, and edema.
Changes or loss of pulmonary function also occur with CBD such as
decrease in vital capacity, reduced diffusing capacity, restrictive
breathing patterns.  The signs and symptoms of CBD constitute a
continuum of symptoms that are progressive in nature with no clear
demarcation between any stages in the disease (Rossman, 1996; NAS,
2008).

In contrast to ABD, CBD can result from inhalation exposure to beryllium
at levels below the current PEL, can take months to years after initial
beryllium exposure before signs and symptoms of CBD occur (Newman 1996,
2005 and 2007; Henneberger, 2001), and may continue to progress
following removal from beryllium exposure (Newman, 2005; Sawyer et al.,
2005).  Patients with CBD can progress to a chronic obstructive lung
disorder resulting in loss of quality of life and the potential for
decreased life expectancy (Rossman, et al., 1998).

In contrast to some occupationally related lung diseases, the early
detection of chronic beryllium disease may be useful since treatment of
this condition can lead not only to regression of the signs and
symptoms, but also may prevent further progression of the disease in
certain individuals (Marchand-Adam, 2008; NAS, 2008).  The management of
CBD is based on the hypothesis that suppression of the hypersensitivity
reaction (i.e., granulomatous process) will prevent the development of
fibrosis.  However, once fibrosis has developed, therapy cannot reverse
the damage.

To date, there have been no controlled studies to determine the optimal
treatment for CBD (Rossman, 1996).  Management of CBD is generally
modeled after sarcoidosis treatment.  Oral corticosteroid treatment can
be initiated in patient with evidence of disease (either by bronchoscopy
or other diagnostic measures before progression of disease or after
clinical signs of pulmonary deterioration occur).  This includes
treatment with oral corticosteroids or other anti-inflammatory agents
(NAS, 2008).  It should be noted however, that treatment with
corticosteroids has side-effects of their own that need to be measured
against the possibility of progression of disease (Gibson et al., 1996;
Zaki et al., 1987).

Development Beryllium Sensitization (BeS)

Sensitization to beryllium is the essential first step for a worker to
develop CBD.  Sensitization to beryllium can result from inhalation
exposure to beryllium (Newman et al., 2005), and may also result from
skin exposure to beryllium (Newman et al., 1996).  Although there may be
no clinical symptoms associated with BeS, a sensitized worker's immune
function is altered such that exposure to beryllium can now trigger
serious lung disease (Kreiss et al., 1996; Kreiss et al., 1997; Kelleher
et al., 2001, and Rossman, 2001).  Since the pathogenesis of CBD
involves a beryllium-specific, cell-mediated immune response, CBD cannot
occur in the absence of sensitization (NAS 2008).  Inhalation or dermal
exposure to beryllium is one of several factors that determine whether
an individual becomes sensitized to beryllium.  It has been shown that
genetic susceptibility is another factor influencing risk of BeS and
CBD.  Skin exposure to small beryllium particles or beryllium-containing
solutions may also lead to BeS (Tinkle et al., 2003).

Sensitization occurs via the formation of a beryllium-protein complex
(an antigen) that causes an immunological response after repeated
exposure. While only very limited evidence has described humoral changes
in certain patients with CBD (Cianciara et al., 1980), clear evidence
exists for an immune cell mediated response, specifically the T-cell
(NAS, 2008).  Following inhalation or skin absorption for sensitization
to occur beryllium must complex with a protein in the body, denaturing
the protein and thereby uncovering a peptide of the protein that had not
been exposed in its previous configuration and this is known as a
“cryptic peptide.”  Because the immune system has not developed to
recognize these cryptic peptides as "self," a T-cell lymphocyte
complexes with the beryllium antigen, becoming a CD4+ T-cell with a
beryllium-specific binding site that can then identify and respond to
the beryllium antigen.  The CD4+ T-cell proliferates, creating a large
number of beryllium-specific T-cells.  At this point an individual is
immunologically sensitized to beryllium.  In the peripheral blood T
cells need a receptor site known as CD28 because the cells have not
developed a memory response (no T-effector memory cells) (Mack et al.,
2008; Fontenot et al., 2005).  However, after repeated exposures in the
lung, a mature population of T cells develop that do not require
co-stimulation by CD28 and have developed a population of T effector
memory cells (Tem cells) (Fontenot et al., 2005).  This may be one of
the mechanisms that leads to the more severe reactions observed
specifically in the lung (Fontenot et al., 2005).

To extend this observation, CBD is described as an immunologic response
characterized by the formation of an Ag-specific [beryllium acting as a
hapten, binds to peptides forming a major histocompability complex (MHC)
class II molecule (Saltini et al., 1989, 1990)]; CD4+ T cell mediated
immune response to beryllium.  CD4+ T lymphocytes created in the
sensitization process recognize the beryllium antigen, and respond by
proliferating and secreting cytokines and inflammatory mediators,
including IL-2, IFN-γ, and TNF-α (Tinkle et al., 1997a and b; Fontenot
et al., 2002) and MIP-1α and GRO-1 (Hong-Geller 2006).  This also
results in the accumulation of mononuclear cells (mostly CD4+ T cells)
in the bronchoalveolar lavage fluid (BAL fluid) (Saltini et al., 1989,
1990).  The T cells in the bronchoalveolar lavage have been shown to
express markers that are consistent with an effector-memory cell
phenotype (Fontenot et al., 2003).  The T effector-memory cells were
found to recognize beryllium in a CD28-costimulated-independent fashion,
which is unlike the beryllium reactive cells in the periphery that
require CD28 co-stimulation (Fontenot et al., 2003).  This finding is
important because it may show the progression of disease from BeS to CBD
as characterized by an increase in the frequency of beryllium specific
competent CD4+ T cells in the lung.  In other words, the memory T cells
in the lung are more differentiated than those in the periphery in
patients with CBD.  This response has the potential to be used as a
screening technique to indicate progression of disease from BeS to CBD
(see Figure 3).

Figure 3: Immune response to beryllium

Source: Fontenot and Maier 2005. Reprinted with permission;

copyright 2005, Trends in Immunology.

Development of CBD

Following sensitization, inhaled beryllium that deposits and persists in
the lung (or that was present in the lung prior to immune sensitization)
can trigger a cell-mediated immune response (hypersensitivity reaction).
 This process is the maturation stage of disease and leads to the
activation and recruitment of Tem cells (T effector memory cells).  As
the beryllium disease progresses in the lung more Tem cells are
developed and proliferate in the lung causing an increase in the cascade
of events which lead to recruiting more inflammatory cells causing
damage to healthy tissue (Saltini et al., 1989, 1990).  This results in
the formation of a mass of immune and inflammatory cells around a
beryllium particle lodged in the interstitium of the lung, known as a
noncaseating granulomatous lesions.  A granulomatous lesion is damaged
tissue caused by an agglomeration of immune cells.  In the case of
beryllium associated granulomas or granulomatous lesions, the beryllium
is presented by mononuclear cells that may fuse together to form
multinucleated giant cells.  This also results in the accumulation of
mononuclear cells (mostly CD4+ T cells) in the BAL fluid (Saltini et
al., 1989, 1990).

Over time, the granulomas spread and can lead to lung fibrosis and
abnormal pulmonary function, with symptoms including a persistent dry
cough and shortness of breath (Saber and Dweik, 2000).  At this point,
some people may also experience fatigue, night sweats, chest and joint
pain, clubbing of fingers (due to impaired oxygen exchange), loss of
appetite or unexplained weight loss and cor pulmonale as the disease
progresses. (Conradi et al., 1971; ACCP, 1965; Kriebel et al., 1988a and
b). While CBD primarily affects the lungs, it can also involve other
organs such as the liver, skin, spleen, and kidneys.

Research studies suggest an apoptosis driven mechanism may be a
mechanism that enhances inflammatory cell recruitment, cytokine
production and inflammation, thus creating a scenario for progressive
granulomatous inflammation.  As the immune response in the lung
progresses, apoptosis may also play an important role in the progression
of CBD.  Macrophages and neutrophils can phagocytize beryllium particles
in an attempt to remove the beryllium from the lung.  Multiple studies
(Sawyer et al., 2004; Dettle et al., 2002) using BAL cells (mostly
macrophages and neutrophils) from patients with CBD found that in vitro
stimulation with beryllium sulfate induced the production of TNF-α (one
of many cytokines produced in response to beryllium), and that
production of TNF-α might induce apoptosis in CBD and Sarcoidosis
patients (Bost et al., 1994; Dai et al., 1999).  The stimulation of
CBD-derived macrophages by beryllium sulphate resulted in cells becoming
apoptotic, as measured by propidium iodide.  These results were
confirmed in a mouse macrophage cell-line (p388D1) (Sawyer et al.,
2000).

imulated by beryllium to produce TNF-α and TNF-α in turns stimulates
the cells to become apoptotic the cells release beryllium back into the
lung.  Thus additional immune cells are recruited to the site where
beryllium has been reintroduced and the loop continues.

Genetic susceptibility

Evidence from a variety of sources indicates genetic susceptibility may
play an important role in the development of CBD in certain individuals,
especially at levels low enough not to invoke a response in other
individuals (Sterner and Eisenbud, 1951).  Early occupational studies
proposed that CBD was an immune reaction with a genetic component, based
on the high susceptibility of some individuals to become sensitized and
progress to CBD and the lack of CBD in others who were exposed to levels
several orders of magnitude higher (Sterner and Eisenbud, 1951).
Additional in vitro human research has identified genes coding for
specific protein molecules on the surface of their immune cells that
place carriers at greater risk of becoming sensitized to beryllium and
developing CBD (McCanlies et al., 2004).

One genetic marker that has been linked to CBD susceptibility is the MHC
class II region, which includes the HLA-DR, DQ, and DP genes. Fontenot
et al. (2000) demonstrated that beryllium presentation by certain
alleles of the class II human leukokyte antigen-DP (HLA-DP) to CD4+ T
cells is the mechanism underlying the development of CBD.  Richeldi et
al. (1993) reported a strong association between the MHC class II allele
HLA-DP 1, which has a glutamate at position 69, and the development of
CBD in beryllium-exposed workers from a Tucson, AZ facility.  This
marker was found in 32 of the 33 workers who developed CBD, but in only
14 of 44 similarly exposed workers without CBD.  Additional studies by
Amicosante et al. (2005) using blood lymphocytes derived from
beryllium-exposed workers found a high frequency of this gene in those
sensitized to beryllium.  In a study of 82 CBD patients (beryllium
exposed workers), Stubbs et al. (1996) also found a relationship between
the HLA-DP 1 allele and BeS. The glutamine-69 allele was present in 86
percent of sensitized subjects, but in only 48 percent of
beryllium-exposed, non-sensitized subjects. Stubbs et al. also found a
biased distribution of the MHC class II HLA-DR gene between sensitized
and non-sensitized subjects. Neither of these markers was completely
specific for CBD, as each study found BeS or CBD among individuals
without the genetic risk factor.

In a study using cells from CBD patients Saltini et al. were able to
elucidate the role of the MHC class II region in the development of CBD.
 The investigators found that MHC class II antigens and functional IL-2
receptors are needed in order for the T cells to proliferate in response
to beryllium stimulation (Saltini et al., 1989).  That is, the T cells
only respond to the antigen (in this case, beryllium or beryllium plus
some protein) in association with MHC class II molecules on the surface
of the antigen-presenting cell.  This requirement, known as class II
restriction, is typical of the response of CD4+ T cells to soluble
antigens, and not nonspecific mitogens, demonstrating a very specific
response to beryllium.

There remains uncertainty as to which, if any, of the MHC class II genes
interact directly with the beryllium ion.  Antibody inhibition data
suggest that the HLA-DR gene product may be involved in the presentation
of beryllium to T lymphocytes (Amicosanti et al., 2002).  In addition,
structure-function studies of MHC class II molecules indicate that the
amino acid change that Richeldi et al. (1993) linked to CBD, a glutamate
at position 69 of the HLA-DP 1, may play a critical role in antigen
binding (Richeldi et al., 1993).  The more common allele of the HLA-DP 1
variant is negatively charged at this site and could directly interact
with the beryllium ion.  The high percentage (~30 percent) of
beryllium-exposed workers without CBD who had this allele indicates that
other factors also contribute to the development of CBD.  (EPA, 1998)

Computational chemistry has been used to identify gene variants to the
HLA-DPB1 shown to code for Glu69 (Weston et al., 2005).  By assigning
odds ratios for specific alleles on the basis of previous studies
discussed above the researchers found a strong correlation (88 percent)
between the reported risk of CBD and the predicted surface electrostatic
potential and charge of the isotypes of the genes.  They were able to
conclude that the alleles associated with the most negatively charged
proteins carry the greatest risk of developing BeS and CBD.  This
confirms the importance of beryllium charge as a key factor in
haptogenic potential.

BeS and CBD in the Workforce

Sensitization to beryllium is currently detected in the workforce with
the beryllium lymphocyte proliferation test (BeLPT), a laboratory blood
test developed in the 1980s, also commonly referred to as the LTT or
BeLT.  In this test, lymphocytes obtained from either BAL fluid or from
peripheral blood are cultured in vitro and exposed to beryllium sulfate
to stimulate lymphocyte proliferation.  The observation of
beryllium-specific proliferation indicates beryllium sensitization.
This test is described in more detail below.

CBD also can be detected at a subclinical stage by a number of
techniques including bronchoalveolar lavage and biopsy (Cordeiro et al.,
2007; Maier, 2001).  Bronchoalveolar lavage is a method of “washing”
the lungs with fluid inserted via a tube, removing the fluid and
analyzing the content for the inclusion of immune cells indicative of
beryllium exposure, as described earlier in this section.  Fiberoptic
bronchoscopy can be used to detect granulomatous lung inflammation prior
to the onset of CBD symptoms as well, and has been used in combination
with the BeLPT to diagnose pre-symptomatic CBD in a number of recent
screening studies of beryllium-exposed workers, which are discussed in
the following section detailing diagnostic procedures.  Of workers who
were found to be sensitized and underwent clinical evaluation, 36-100
percent of them were diagnosed with CBD (Kreiss et al., 1993; Newman et
al., 1996, 2005, 2007).  It has been estimated from ongoing surveillance
studies of sensitized individuals with an average follow-up time of 4.5
years that 37 percent of beryllium-exposed employees were estimated to
progress to CBD (Newman et al., 2005).  A study of nuclear weapons
facility employees enrolled in an ongoing medical surveillance program
found that only 20 percent of sensitized workers employed less than 5
years eventually were diagnosed with CBD, while 40 percent of sensitized
workers employed10 years or more developed CBD. (Stange et al., 2001)

	CBD has a clinical spectrum ranging from evidence of BeS and granulomas
in the lung with little symptomology to loss of lung function and end
stage disease which may result in the need for lung transplantation and
decreased life expectancy.  Unfortunately, there are very few published
clinical studies describing the full range and progression of CBD from
the beginning to the end stages and very few of the risk factors for
progression of disease have been delineated (NAS, 2008).  Clinical
management of CBD is modeled after sarcoidosis where oral corticosteroid
treatment is initiated in patients who have evidence of progressive lung
disease, although progressive lung disease has not been well defined
(NAS, 2008).  In advanced cases of CBD corticosteroids is the standard
treatment (NAS, 2008).  No studies have been published measuring the
effect of removal of workers from beryllium exposure on BeS and CBD
(NAS, 2008)

Human Epidemiological Studies

This section describes the human epidemiological data supporting the
mechanistic overview of beryllium-induced disease in workers.  It is
divided into reviews of epidemiological studies performed prior to
development and implementation of the BeLPT in the late 1980s and after
wide use of the BeLPT for screening purposes.  Use of the BeLPT has
allowed investigators to screen for BeS and CBD prior to the onset of
clinical symptoms providing a more sensitive and thorough analysis of
the worker population.  The discussion of the studies is further divided
by manufacturing processes that may have similar exposure profiles.

μg/m3.  Several studies show that the prevalence of BeS and CBD is
related to the level of airborne exposure, including a cross-sectional
survey of employees at a beryllium ceramics plant in Tucson, AZ
(Henneberger et al., 2001), and case-control studies of workers at the
Rocky Flats nuclear weapons facility (Viet et al., 2000) and workers
from a beryllium machining plant in Cullman, AL (Kelleher et al., 2001).
 The prevalence of BeS also may be related to dermal to exposure.  A
study of a comprehensive preventive program at the ceramics plant, which
included expanded respiratory protection, provided dermal protection,
and improved control of beryllium dust migration, substantially reduced
the rate of BeS among new hires (Cummings et al., 2007).

The epidemiological evidence presented in this section demonstrates that
BeS and CBD are continuing to occur from present-day exposures below
OSHA’s PEL.  The available literature discussed below shows that
disease prevalence can be reduced by reducing inhalation exposure.
However, epidemiological studies also indicate that it may be necessary
to minimize skin exposure to further reduce the incidence of BeS.

Studies conducted prior to the BeLPT

First reports of CBD came from studies performed by Hardy and Tabershaw
(1946).  Cases were observed in industrial plants that were refining and
manufacturing beryllium metal and beryllium alloys and in plants
manufacturing fluorescent light bulbs (NAS, 2008).  From the late 1940s
through the 1960s clusters of CBD cases were identified around beryllium
refineries in Ohio and Pennsylvania, and outbreaks in family members of
beryllium factory workers were assumed to be from exposure to
contaminated clothes (Hardy, 1980).  It had been established that the
risk of disease among beryllium workers was variable and generally rose
with the levels of airborne concentrations (Machle et al., 1948).  And
while there was a relationship between air concentrations of beryllium
and risk of developing disease both in and surrounding these plants, the
disease rates outside the plants were higher than expected and not very
different from the rate of CBD within the plants (Eisenbud et al., 1949;
Lieben and Metzner, 1959).  There remained considerable uncertainty
regarding diagnosis due to lack of well-defined cohorts, modern
diagnostic methods, or inadequate follow-up.  In fact, many patients
with CBD may have been misdiagnosed with sarcoidosis (NAS, 2008).

The difficulties in distinguishing lung disease caused by beryllium from
other lung diseases led to the establishment of the BCR in 1952 to
identify and track cases of ABD and CBD.  A uniform diagnostic criterion
was introduced in 1959 as a way to delineate CBD from sarcoidosis.  The
BCR listed the following criteria for diagnosing CBD:

(1)	Establishment of significant beryllium exposure based on sound
epidemiologic history;

(2)	Objective evidence of lower respiratory tract disease and clinical
course consistent with beryllium disease;

(3)	Chest X-ray films with radiologic evidence of interstitial
fibronodular disease;

(4)	Evidence of restrictive or obstructive defect with diminished carbon
monoxide diffusing capacity (DLCO) by physiologic studies of lung
function;

(5)	Pathologic changes consistent with beryllium disease on examination
of lung tissue; and

(6)	Presence of beryllium in lung tissue or thoracic lymph nodes.

The criteria for entry in the BCR included either documented past
exposure to beryllium or the presence of beryllium in lung tissue as
well as clinical evidence of beryllium disease (Hardy et al., 1967).
Cases were entered into the registry if they met at least three of the
criteria above (Hasan and Kazemi, 1974).  Patients were registered and
added to this registry from 1952 through 1983 (Eisenbud and Lisson,
1983).

Studies conducted following the development of the BeLPT

The criteria for diagnosis of CBD have evolved over time as more
advanced diagnostic technology, such as the BeLPT test, has become
available. More recent diagnostic criteria have both higher specificity
than earlier methods and higher sensitivity, identifying subclinical
effects. Recent studies typically use the following criteria (Newman et
al., 1989; Pappas and Newman 1993; Maier, et al., 1999):

(1)	History of beryllium exposure;

(2)	Histopathological evidence of noncaseating granulomas or mononuclear
cell infiltrates in the absence of infection; and

(3)	Positive blood or BAL BeLPT (Newman et al., 1989). The availability
of transbronchial lung biopsy facilitates the evaluation of the second
criterion, by making histopathological confirmation possible in almost
all cases.

A significant component for the identification of CBD is the
demonstration of a confirmed abnormal BeLPT result in a blood or BAL
sample (Newman, 1996).  Since the development of the BeLPT in the 1980s,
it has been used to screen beryllium-exposed workers for sensitization
in a number of studies to be discussed below.  The BeLPT is a
non-invasive in-vitro blood test which measures the beryllium
antigen-specific T-cell mediated immune response and is the most
commonly available diagnostic tool for identifying BeS.  The test
measures the degree to which beryllium stimulates lymphocytes to
prolifereate under a specific set of conditions and is interpreted based
upon the number of stimulation indices that exceed the normal value.
The ‘cut-off’ is based on the mean value of the peak stimulation
index among controls plus 2 or 3 standard deviations.  This methodology
was modeled into a statistical method known as the “least absolute
values” or “statistical-biological positive” method and relies on
natural log modeling of the median stimulation index values (DOE, 2001;
Frome, 2003).  In most applications, two or more stimulation indices
that exceed the cut-off constitute an abnormal test.

Early versions of the BeLPT test had high variability, but the use of
tritiated thymidine to identify proliferating cells has led to a more
reliable test (Mroz et al., 1991; Rossman et al., 2001). In recent
years, the peripheral blood test has been found to be as sensitive as
the BAL assay, although larger abnormal responses have been observed
with the BAL assay (Kreiss et al., 1993; Pappas and Newman, 1993).
False negative results have also been observed with the BAL BeLPT in
cigarette smokers who have marked excess of alveolar macrophages in
lavage fluid (Kreiss et al., 1993).  The BeLPT has also been a useful
tool in animal studies to identify those species with a
beryllium-specific immune response.

Screenings for BeS have been conducted using the BeLPT in several
occupational surveys and surveillance programs, including nuclear
weapons facilities operated by the Department of Energy (Viet et al.,
2000; Strange et al., 2001; DOE/HSS Report, 2006), a beryllium ceramics
plant in Arizona (Kreiss et al., 1996; Henneberger et al., 2001;
Cummings et al., 2007), a beryllium production plant in Ohio (Kreiss et
al., 1997; Kent et al., 2001), a beryllium machining facility in Alabama
(Kelleher et al., 2001; Madl et al., 2007), a beryllium alloy plant
(Schuler et al., 2005, Thomas et al., 2009 ), and another beryllium
processing plant (Rosenman et al., 2005) in Pennsylvania.  In most of
these studies, individuals with an abnormal BeLPT result were retested
and were identified as sensitized (i.e. BeS positive) if the abnormal
result was repeated.

Most epidemiological studies have reported rates of BeS and disease
based on a single screening of a working population ('cross-sectional'
or 'population prevalence' rates).  Studies of workers in a beryllium
machining plant and a nuclear weapons facility have included follow-up
of the population originally screened, resulting in the detection of
additional cases of beryllium BeS over several years (Newman et al.,
2001, Stange et al., 2001).

Beryllium Mining and Extraction

Mining and extraction of beryllium usually involves the two major
beryllium minerals beryl (an aluminosilicate containing up to 4 percent
beryllium) and bertrandite (a beryllium silicate hydrate containing
generally less than 1 percent beryllium) (WHO, 2001).  The United States
is the world leader in beryllium extraction and also leads the world in
production and use of beryllium and its alloys (WHO, 2001).  Most
exposures from mining and extraction come in the form of beryllium ore,
beryllium salts, or beryllium hydroxide (NAS 2008).

Deubner et al. published a study of 75 workers employed at a beryllium
mining and extraction facility in Delta, UT (Deubner et al., 2001b).  Of
the 75 workers screened with the BeLPT, three were identified as
sensitized as confirmed by having an abnormal BeLPT.  One of those found
to be sensitized was diagnosed with CBD.  Exposures at the facility
included primarily beryllium ore and salts; workers were not exposed to
beryllium oxide.  General area (GA), breathing zone (BZ), and personal
lapel (LP) exposure samples were collected from 1970 to 1999.  Jobs
involving beryllium hydrolysis and wet-grinding activities had the
highest air concentrations, with an annual median GA concentration
ranging from 0.1 to 0.4 μg/m3.  Median BZ concentrations were higher
than either LP or GA    The average duration of exposure for beryllium
sensitized workers was 21.3 years (27.7 years for the worker with CBD),
compared to an average duration for all workers of 14.9 years.  However,
these exposures were less than either the Elmore, OH, or Tucson, AZ,
facilities described below, which also had higher reported rates of BeS
and CBD.

There was no BeS or CBD among those who worked only at the mine where
exposure to beryllium resulted solely from working with bertrandite ore.
 The authors concluded that the results of this study indicated that
beryllium ore and salts may pose less of a hazard than beryllium metal
and beryllium hydroxide. These results are consistent with the
previously discussed animal studies examining solubility and particle
size.

Beryllium Metal Processing and Alloy Production

Kreiss et al. (1997) conducted a study of workers at a beryllium
production facility in Elmore, OH.  The plant, which opened in 1953 and
initially specialized in production of beryllium-copper alloy, later
expanded its operations to include beryllium metal, beryllium oxide, and
beryllium-aluminum alloy production; beryllium and beryllium alloy
machining; and beryllium ceramics production, which was moved to a
different factory in the early 1980s. Production operations included a
wide variety of jobs and processes, such as work in arc furnaces and
furnace rebuilding, alloy melting and casting, beryllium powder
processing, and work in the pebble plant.  Non-production work included
jobs in the analytical laboratory, engineering research and development,
maintenance, laundry, production-area management, and office-area
administration. While the publication refers to the use of respiratory
protection in some areas, such as the pebble plant, the extent of its
use across all jobs or time periods was not reported.  Use of dermal PPE
was not reported.

μg/m3.  Particularly high beryllium concentrations were reported in
beryllium powder production and laundry areas, alloy arc furnace
(approximately 40 percent of DWA estimates over 2.0 μg/m3) and furnace
rebuild (28.6 percent of short-term BZ samples over the OSHA STEL of 5
μg/m3). LP samples (n = 179), which were available from 1990 to 1992,
had a median value of 1 μg/m3.

Of 655 workers employed at the time of the study, 627 underwent BeLPT
screening. Blood samples were divided and split between two labs for
analysis, with repeat testing for results that were abnormal or
indeterminate. Thirty-one workers had an abnormal blood test upon
initial testing and at least one of two subsequent tests was classified
as sensitized. These workers, together with 19 workers who had an
initial abnormal result and one subsequent indeterminate result, were
offered clinical evaluation for CBD including the BAL-BeLPT and
transbronchial lung biopsy.  Nine with an initial abnormal test followed
by two subsequent normal tests were not clinically evaluated, although
four were found to be sensitized upon retesting in 1995. Of 47 workers
who proceeded with evaluation for CBD (3 declined to participate), 24
were diagnosed with CBD based on evidence of granulomas on lung biopsy
(20) or on other findings consistent with CBD (4) (Kreiss et al. p.
607). After including five workers who had been diagnosed prior to the
study, a total of 29 (4.6 percent) current workers were found to have
CBD.  In addition, the plant medical department identified 24 former
workers diagnosed with CBD before the study.

Kreiss et al. reported that the highest prevalence of BeS and CBD
occurred among workers employed in beryllium metal production, even
though the highest airborne total mass concentrations of beryllium were
generally among employees operating the beryllium alloy furnaces in a
different area of the plant (Kreiss et al., 1997).  Preliminary
follow-up investigations of particle size-specific sampling at five
furnace sites within the plant determined that the highest respirable
(e.g., particles <10 μm in diameter) and alveolar-deposited (e.g.
particles <1 μm in diameter) beryllium mass and particle number
concentrations, as collected by a general area impactor device, were
measured at the beryllium metal production furnaces rather than the
beryllium alloy furnaces (Kent et al., 2001; McCawley et al., 2001).  A
statistically significant linear trend was reported between the above
alveolar deposited particle mass concentration and prevalence of CBD and
BeS in the furnace production areas.  The authors concluded that
alveolar deposited particles may be a more relevant exposure metric for
predicting the incidence of CBD or BeS than the total mass concentration
of airborne beryllium.

Rosenman et al. (2005) studied a group of several hundred workers who
had been employed at a beryllium production and processing facility that
operated in eastern Pennsylvania between 1957 and 1978.  Of 715 former
workers located, 577 were screened for BeS with the BLPT and 544
underwent chest radiography to identify cases of beryllium BeS and CBD.
Workers were reported to have exposure to beryllium dust and fume in a
variety of chemical forms including beryl ore, beryllium metal,
beryllium fluoride, beryllium hydroxide, and beryllium oxide.

epresentative task-based IH samples ranged from 0.9 μg/m3 to 84 μg/m3
in the 1960s, falling to a range of 0.5 - 16.7 μg/m3 in the 1970s.  An
overwhelming number of workers’ mean DWA estimates (91 percent) were
above the OSHA PEL of 2.0 μg/m3, although a few workers had mean DWA
exposures between 0.2 and 2.0 μg/m3 (6 percent) or below 0.02 μg/m3 (3
percent) (Rosenman et al., Table 11).

Blood samples for the BeLPT were collected between 1996 and 2001 and
were evaluated at a single laboratory.  Individuals with an abnormal
test result were offered repeat testing, and were classified as
sensitized if the second test was also abnormal.  Sixty workers with
two positive BeLPTs and 50 additional workers with chest radiography
suggestive of disease were offered clinical evaluation, including
bronchoscopy with bronchial biopsy and BAL-BeLPT.  Seven workers met
both criteria.  Only 56 (51 percent) of these workers proceeded with
clinical evaluation, including 57 percent of those referred on the basis
of confirmed abnormal BeLPT and 47 percent of those with abnormal
radiographs.

Of those workers who underwent bronchoscopy, 32 (5.5 percent) with
evidence of granulomas were classified as “definite” CBD cases.
Twelve (2.1 percent) additional workers with positive BAL-BLPT or
confirmed positive BeLPT and radiographical evidence of upper lobe
fibrosis were classified as “probable” CBD cases.  Forty workers
(6.9 percent) without upper lobe fibrosis who had confirmed abnormal
BeLPT but who were not biopsied or who underwent biopsy with no evidence
of granuloma, were classified as sensitized without disease.  It is not
clear how many of the 40 workers underwent biopsy.  Another 12 (2.1
percent) workers with upper lobe fibrosis and negative or unconfirmed
positive BeLPT were classified as “possible” CBD cases.  Nine
additional workers who were diagnosed with CBD before the screening were
included in some parts of the authors’ analysis.

μg/m3.  Of those, 35 (8 percent) had definite or probable CBD and
another 33 (8 percent) were classified as sensitized without disease.
The true prevalence of BeS and CBD in the group may be higher than
reported, due to the low rate of clinical evaluation among sensitized
workers.

Although most of the workers in this study had high exposures, BeS and
CBD also were observed within the small subgroup of participants
believed to have relatively low beryllium exposures.  Five cases of CBD
and four additional cases of BeS occurred among 38 workers with mean DWA
exposures below OSHA’s PEL of 2.0 µg/m3, including one case of CBD
and two sensitized-only workers with mean DWAs below 0.02 µg/m3
(Rosenman et al., Table 11).  Fifteen cases of BeS and CBD were found
among office and clerical workers, who were believed to have low
exposures (levels not reported).

Workers in this study who became sensitized during their employment had
a minimum of 20 years to develop CBD prior to screening.  In this sense
the cohort is especially well suited to compare the exposure patterns of
workers with CBD and those sensitized without disease, in contrast to
several other studies of workers with only recent beryllium exposures.
Rosenman et al. characterized and compared the exposures of workers with
definite and probable CBD,  BeS only, and no disease or BeS using
chi-squared tests for discrete outcomes and analysis of variance (ANOVA)
for continuous variables (cumulative, mean, and peak exposure levels).
Exposure-response relationships were further examined with logistic
regression analysis, adjusting for potential confounders including
smoking, age, and beryllium exposure from outside of the plant.  The
authors found that cumulative, peak, and duration of exposure were
significantly higher for workers with CBD than for sensitized workers
without disease (p < 0.05), suggesting that the risk of progressing from
BeS to CBD is related to the level or extent of exposure a worker
experiences.  The risk of developing CBD following BeS appeared strongly
related to exposure to insoluble forms of beryllium, which are cleared
slowly from the lung and increase beryllium lung burden more rapidly
than quickly mobilized soluble forms.  Individuals with CBD had higher
exposures to insoluble beryllium than those classified as sensitized
without disease, while exposure to soluble beryllium was higher among
sensitized individuals than those with CBD.

Cumulative, mean, peak, and duration of exposure were found to be
comparable for workers with CBD and workers without BeS or CBD
(“normal” workers).  Cumulative, peak, and duration of exposure were
significantly lower for sensitized workers without disease than for
normal workers.  Rosenman et al. suggested that genetic predisposition
to BeS and CBD may have obscured an exposure-response relationship in
this study, and plan to control for genetic risk factors in future
studies.  Exposure misclassification from the 1950s and 1960s may have
been another limitation in this study, introducing bias that could have
influenced the lack of exposure response.  It is also unknown if the 25
percent who died from CBD-related conditions may have had higher
exposures.

Beryllium Machining Operations

Newman et al. (2001) and Kelleher et al. (2001) studied a group of 235
workers at a beryllium metal machining plant.  Since the plant opened in
1969, its primary operations have been machining and polishing beryllium
metal and high-beryllium content composite materials, with occasional
machining of beryllium oxide/metal matrix ('E-metal'), and beryllium
alloys. Other functions include machining of metals other than
beryllium; receipt and inspection of materials; acid etching; final
inspection, quality control, and shipping of finished materials; tool
making; and engineering, maintenance, administrative and supervisory
functions (Newman et al., 2001; Madl et al., 2007). Machining
operations, including milling, grinding, lapping, deburring, lathing,
and electrical discharge machining (EDM), were performed in an
open-floor plan production area. Most non-machining jobs were located in
a separate, adjacent area; however, non-production employees had access
to the machining area.

Engineering and administrative measures, rather than PPE, were primarily
used to control beryllium exposures at the plant (Madl, 2007).  Based on
interviews with long-standing employees of the plant, Kelleher et al.
reported that work practices were relatively stable until 1994, when a
worker was diagnosed with CBD and a new exposure control program was
initiated.  Between 1995 and 1999 new engineering and work practice
controls were implemented, including removal of pressurized air hoses
and discouragement of dry sweeping (1995), enclosure of deburring
processes (1996), mandatory uniforms (1997), and installation or
updating of local exhaust ventilation (LEV) in EDM, lapping, deburring,
and grinding processes (1998) (Madl et al., 2007).  Throughout the
plant’s history respiratory protection was used mainly for
“unusually large, anticipated exposures” to beryllium (Kelleher et
al., 2001), and was not routinely used otherwise (Newman et al., 2001).

All workers at the plant participated in a beryllium disease
surveillance program initiated in 1994, and were screened for BeS with
the BeLPT beginning in 1995.  A BeLPT result was considered abnormal if
two or more of six stimulation indices exceeded the normal range (see
section on BeLPT testing above), and was considered borderline if one of
the indices exceeded the normal range. A repeat BeLPT was conducted for
workers with abnormal or borderline initial results.  Workers were
identified as beryllium sensitized and referred for a clinical
evaluation, including bronchoalveolar lavage (BAL) and transbronchial
lung biopsy, if the repeat test was abnormal.  CBD was diagnosed upon
evidence of BeS with granulomas or mononuclear cell infiltrates in the
lung tissue (Newman et al., 2001).  Following the initial plant-wide
screening, plant employees were offered BeLPT testing at 2-year
intervals.  Workers hired after the initial screening were offered a
BeLPT within 3 months of their hire date, and at 2-year intervals
thereafter (Madl et al., 2007)

f beryllium particles less than 6 μm, particles, less than 1 μm in
diameter, and total mass.  The great majority of workers’ exposures
were below the OSHA PEL of 2 μg/m3.  However, a few higher levels were
observed in machining jobs including deburring, lathe, lapping, and
grinding.  Based on a statistical comparison between their samples and
historical data provided by the plant, the authors concluded that worker
beryllium exposures across all time periods could be approximated using
the 1996-1999 data.  They estimated workers’ cumulative and
‘lifetime weighted’ (LTW) beryllium exposure based on the exposure
samples they collected for each job in 1996-1999 and company records of
each worker’s job history.

The case group for the case-control analysis was composed of 20 workers
who were found to be sensitized during the surveillance conducted by
Newman et al.  Thirteen of these workers were diagnosed with CBD based
on lung biopsy evidence of granulomas and/or mononuclear cell
infiltrates (11) or positive BAL results with evidence of lymphocytosis
(2).  Seven were evaluated for CBD and found to be sensitized only;
three declined evaluation.  Nine of the remaining 215 workers were
excluded due to incomplete job history information, leaving 206 workers
in the control group.

level and other variables. Median cumulative exposures for total mass,
particles < 6 μm, and particles < 1 μm were approximately three times
higher among the cases than controls, although the relationships
observed were not statistically significant (p values ~ 0.2).  No clear
difference between cases and controls was observed for the median LTW
exposures. Odds ratios with BeS and CBD as outcomes were elevated in
high (upper third) and intermediate exposure groups relative to low
(lowest third) exposure groups for both cumulative and LTW exposure,
though the results were not statistically significant (p > 0.1). In the
logistic regression analysis, only machinist work history was a
significant predictor of case status in the final model.  Quantitative
exposure measures were not significant predictors of BeS or disease
risk.

EL of 2 μg/m3, and no cases of BeS or CBD were observed among workers
with LTW exposure < 0.02 μg/m3. Twelve (60 percent) of the 20
sensitized workers had LTW exposures > 0.20 μg/m3.

In 2007, Madl et al. published an additional study of 27 workers at the
machining plant who were found to be sensitized or diagnosed with CBD
between the start of medical surveillance in 1995 and 2005.  As
previously described, workers were offered a BeLPT in the initial 1995
screening (or within 3 months of their hire date if hired after 1995)
and at 2-year intervals after their first screening.  Workers with two
positive BeLPTs were identified as sensitized and offered clinical
evaluation for CBD, including bronchoscopy with BAL and transbronchial
lung biopsy.  The criteria for CBD in this study were somewhat stricter
than those used in the Newman et al. study, requiring evidence of
granulomas on lung biopsy or detection of X-ray or pulmonary function
changes associated with CBD, in combination with two positive BeLPTs or
one positive BAL-BeLPT.

Based on the history of the plant’s control efforts and their analysis
of historical IH data, Madl et al. identified three “exposure control
eras”: a relatively uncontrolled period from 1980-1995; a transitional
period from 1996 to 1999; and a relatively well-controlled “modern”
period from 2000-2005.  They found that the engineering and work
practice controls instituted in the mid-1990s reduced workers' exposures
substantially, with nearly a 15-fold difference in reported exposure
levels between the pre-control and the modern period (Madl et al.,
2007).  Madl et al. estimated workers’ exposures using LP samples
collected between 1980 and 2005, including those collected by Kelleher
et al., and work histories provided by the plant.  As described more
fully in the study, they used a variety of approaches to describe
individual workers’ exposures, including approaches designed to
characterize the highest exposures workers were likely to have
experienced.  Their exposure-response analysis was based primarily on an
exposure metric they derived by identifying the year and job of each
worker’s pre-diagnosis work history with the highest reported
exposures.  They used the upper 95th percentile of the LP samples
collected in that job and year (in some cases supplemented with data
from other years) to characterize the worker's upper-level exposures.

μg/m3 as an 8-hour TWA at some point in their history of employment in
the plant.  They also concluded that most BeS and CBD cases were likely
to have been exposed to levels greater than 0.4 μg/m3 at some point in
their work at the plant.  Madl et al. did not reconstruct exposures for
workers at the plant who did not have BeS or CBD, and therefore, could
not determine whether non-cases had upper-bound exposures lower than
these levels. They found that upper-bound exposure estimates were
generally higher for workers with CBD than for those who were
sensitized, but not diagnosed with CBD at the conclusion of the study
(Madl et al., 2007 p. 464).  Because CBD is an immunological disease and
BeS has been shown to occur within a year of exposure for some workers,
Madl et al. argued that their estimates of workers' short-term
upper-bound exposures may better capture the exposure levels that led to
BeS and disease than estimates of long-term cumulative or average
exposures such as the LTW exposure measure constructed by Kelleher et
al. (Madl et al., 2007).

Beryllium Oxide Ceramics

Kreiss et al. (1993) conducted a screening of current and former workers
at a plant that manufactured beryllium ceramics from beryllium oxide
between 1958 and 1975, and then transitioned to metalizing circuitry
onto beryllium ceramics produced elsewhere.  Of the plant's 1,316
current and 350 retired workers, 505 participated who were not
previously diagnosed with CBD or sarcoidosis, including 377 current and
128 former workers.  Although beryllium exposure was not estimated
quantitatively in this survey, the authors conducted a questionnaire to
assess study participants' exposures qualitatively. Results showed that
55 percent of participants reported working in jobs with exposure to
beryllium dust. Close to 25 percent of participants did not know if they
had exposure to beryllium, and just over 20 percent believed they had
not been exposed.

BeLPT tests were administered to all 505 participants in the 1989-1990
screening period and evaluated at a single lab.  Seven workers had
confirmed abnormal BeLPT results and were identified as sensitized.  All
of them also were diagnosed with CBD based on findings of granulomas
upon clinical evaluation.  Radiograph screening led to clinical
evaluation and diagnosis of two additional CBD cases, who were among
three participants with initially abnormal BeLPT results that could not
be confirmed on repeat testing.  In addition, nine workers had been
previously diagnosed with CBD, and another five were diagnosed shortly
after the screening period, in 1991-1992.

Eight (3.7 percent) of the nine CBD cases identified in the screening
population were hired before the plant stopped producing beryllium
ceramics in 1975, and were among the 216 participants who had reported
having been near or exposed to beryllium dust.  Particularly high CBD
rates of 11.1 - 15.8 percent were found among screening participants who
had worked in process development/engineering, dry pressing, and
ventilation maintenance jobs believed to have high or uncontrolled dust
exposure.  One case (0.6 percent) of CBD was diagnosed among the 171
study participants who had been hired after the plant stopped producing
beryllium ceramics.  Although this worker was hired eight years after
the end of ceramics production, he had worked in an area later found to
be contaminated with beryllium dust.  The authors concluded that the
study results suggested an exposure-response relationship between
beryllium exposure and CBD, and recommended beryllium exposure control
to reduce workers’ risk of CBD.

μg/m3, while LP and short-term BZ samples had medians of 0.3 µg/m3
respectively.  However, 3.6 percent of short-term BZ samples and 0.7
percent of GA samples exceeded 5.0 µg/mg, while LP samples ranged from
0.1 to 1.8 µg/m3.  Machining jobs had the highest beryllium exposure
levels among job tasks, with short-term BZ samples significantly higher
for machining jobs than for non-machining jobs (median 0.6 µg/m3 vs.
0.3 μg/mg, p = 0.0001).  The authors used DWA formulas provided by the
plant to estimate workers’ full-shift exposure levels, and to
calculate cumulative and average beryllium exposures for each worker in
the study.  The median cumulative exposure was 591.7 mg-days/m3 and the
median average exposure was 0.35 µg/m3.

One hundred thirty-six of the 139 workers employed at the plant at the
time of the Kreiss (1996) study underwent BeLPT screening and chest
radiographs in 1992.  Blood samples were split between two laboratories.
 If one or both test results were abnormal, an additional sample was
collected and split between the labs.  Seven workers with an abnormal
result on two draws were initially identified as sensitized.  Those with
confirmed abnormal BeLPTs or abnormal chest X-rays were offered clinical
evaluation for CBD, including transbronchial lung biopsy and BAL BeLPT.
CBD was diagnosed based on observation of granulomas on lung biopsy, in
five of the six sensitized workers who accepted evaluation.  An eighth
case of BeS and sixth case of CBD were diagnosed in one worker hired in
October 1991 whose initial BeLPT was normal, but who was confirmed as
sensitized and found to have lung granulomas less than two years later,
after sustaining a beryllium-contaminated skin wound.  The plant medical
department reported 11 additional cases of CBD among former workers
(Kreiss et al., 1996).  The overall prevalence of BeS in the plant was
5.9 percent, with a 4.4 percent prevalence of CBD.

Kreiss et al. reported that six (75 percent) of the eight sensitized
workers  were exposed as machinists during or before the period October
1985 – March 1988, when measurements were first available for
machining jobs.  The authors reported that 14.3 percent of machinists
were sensitized, compared to 1.2 percent of workers who had never been
machinists (p < 0.01).  Workers’ estimated cumulative and average
beryllium exposures did not differ significantly for machinists and
non-machinists, or for cases and non-cases.  As in the previous ceramics
plant study published by Kreiss et al. in 1993, one case of CBD was
diagnosed in a worker who had never been employed in a production job.
This worker was employed in administration, a job with a median DWA of
0.1 μg/m3 (range 0.1 - 0.3).

In 1998, Henneberger et al. conducted a follow-up cross-sectional survey
of 151 employees employed at the beryllium ceramics plant studied by
Kreiss et al. (1996) (Henneberger et al., 2001).  Employees were
eligible who either had not participated in the Kreiss et al. survey
(“short-term workers” - 74 of those studied by Henneberger), or who
had participated and were not found to have BeS or disease (“long-term
workers” -77 of those studied by Henneberger).

The authors estimated workers' cumulative, average, and peak beryllium
exposures based on the plant's formulas for estimating job-specific DWA
exposures, participants' work histories, and area and short-term
task-specific BZ samples collected from the start of full production at
the plant in 1981 to 1998.  The long-term workers, who were hired before
the 1992 study was conducted, had generally higher estimated exposures
(median of average exposures - 0.39 µg/m3; mean - 14.9 µg/m3) than the
short-term workers, who were hired after 1992 (median 0.28 µg/m3, mean
6.1 µg/m3).

Fifteen cases of BeS were found, including eight among short-term and
seven among long-term workers.  Eight of the 15 workers were found to
have CBD. Of the workers diagnosed with CBD, seven (88 percent) were
long-term workers. One long-term worker and one sensitized long-term
worker declined clinical examination.

Henneberger et al. reported a higher prevalence of BeS among long-term
workers with “high” (greater than median) peak exposures compared to
long-term workers with “low” exposures; however, this relationship
was not statistically significant.  No association was observed for
average or cumulative exposures.  The authors reported higher prevalence
of BeS (but not statistically significant) among short-term workers with
“high” (greater than median) average, cumulative, and peak exposures
compared to short-term workers with “low” exposures of each type.

	Following the 1998 survey, the company continued efforts to reduce
exposures and risk of sensitization and CBD by implementing additional
engineering, administrative, and PPE measures (Cummings et al. 2007).
Respirator use was required in production areas beginning in 1999, and
latex gloves were required beginning in 2000.  The lapping area was
enclosed in 2000, and enclosures were installed for all mechanical
presses in 2001.  Between 2000 and 2003, water-resistant or water-proof
garments, shoe covers, and taped gloves were incorporated to keep
beryllium-containing fluids from wet machining processes off the skin.
The new engineering measures did not appear to substantially reduce
airborne beryllium levels in the plant.  LP samples collected between
2000 and 2003 had a median of 0.18 µg/m3, similar to the 1994-1999
samples.  However, respiratory protection requirements to control
workers’ airborne beryllium exposures were instituted prior to the
2000 sample collections.

To test the efficacy of the new measures instituted after 1998, in
January 2000 the company began screening new workers for sensitization
at the time of hire and at 3, 6, 12, 24, and 48 months of employment.
These more stringent measures appear to have substantially reduced the
risk of sensitization among new employees.  Of 126 workers hired
between 2000 and 2004, 93 completed BeLPT testing at hire and at least
one additional test at 3 months of employment.  One case of
sensitization was identified at 24 months of employment (1 percent).
This worker had experienced a rash after an incident of dermal exposure
to lapping fluid through a gap between his glove and uniform sleeve,
indicating that he may have become sensitized via the skin.  He was
tested again at 48 months of employment, with an abnormal result.

A second worker in the 2000-2004 group had two abnormal BeLPT tests at
the time of hire, and a third had one abnormal test at hire and a second
abnormal test at 3 months. Both had normal BeLPTs at 6 months, and were
not tested thereafter.  A fourth worker had one abnormal BeLPT result at
the time of hire, a normal result at 3 months, an abnormal result at 6
months, and a normal result at 12 months.  Four additional workers had
one abnormal result during surveillance, which could not be confirmed
upon repeat testing.

Cummings et al. calculated two sensitization rates based on these
screening results: (1) a rate using only the sensitized worker
identified at 24 months, and (2) a rate including all four workers who
had repeated abnormal results.  They reported a sensitization incidence
rate (IR) of 0.7 per 1,000 person-months to 2.7 per 1,000 person-months
for the workers hired between 2000 and 2004, using the sum of
sensitization-free months of employment among all 93 workers as the
denominator.

The authors also esimated an IR of 5.6 per 1,000 person-months for
workers hired between 1993 and the 1998 survey.  This estimated IR was
based on one BeLPT screening, rather than BeLPTs conducted throughout
the workers’ employment, the denominator in this case was the total
months of employment until the 1998 screening.  Because sensitized
workers may have been sensitized prior to the screening, the denominator
may overestimate sensitization-free time in the legacy group, and the
actual sensitization IR for legacy workers may be somewhat higher than
5.6 per 1,000 person-months.  Based on comparison of the IRs, the
authors concluded that the addition of respirator use, dermal
protection, and housekeeping improvements appeared to have reduced the
risk of sensitization among workers at the plant, even though airborne
beryllium levels in some areas of the plant had not changed
significantly since the 1998 survey.

Copper-Beryllium Alloy Processing and Distribution

Schuler et al. (2005) studied a group of 152 workers at a facility
processing copper-beryllium alloys and small quantities of
nickel-beryllium alloys, and converting semi-finished alloy strip and
wire into finished strip, wire and rod.  Production activities included
annealing, drawing, straightening, point and chamfer, rod and wire
packing, die grinding, pickling, slitting, degreasing.  Periodically in
the plant’s history, they also did salt baths, cadmium plating,
welding and deburring.  Since the late 1980s, rod and wire production
processes were physically segregated from strip metal production.
Production support jobs included mechanical maintenance, quality
assurance, shipping and receiving, inspection, and wastewater treatment.
 Administration was divided into staff primarily working within the
plant and personnel who mostly worked in office areas (Schuler, et. al.,
2005).  Workers’ respirator use was limited, mostly to occasional
tasks where high exposures were anticipated.

Following the 1999 diagnosis of a worker with CBD, the company surveyed
the workforce, offering all current employees BeLPT testing in 2000 and
offering sensitized workers clinical evaluation for CBD, including BAL
and transbronchial biopsy.  Of the facility’s 185 employees, 152
participated in the BeLPT screening. Samples were split between two
laboratories, with additional draws and testing for confirmation if
conflicting tests resulted in the initial draw.  Ten participants (7
percent) had at least two abnormal BeLPT results. The results of nine
workers who had abnormal BeLPT results from only one laboratory were not
included because the authors believed it was experiencing technical
problems with the test (Schuler et al., 2005).  CBD was diagnosed in six
workers (4 percent) on evidence of pathogenic abnormalities (e.g.,
granulomas) or evidence of clinical abnormalities consistent with CBD
based on pulmonary function testing, pulmonary exercise testing, and/or
chest radiography.  One worker diagnosed with CBD had been exposed to
beryllium during previous work at another copper-beryllium processing
facility.

measurements were below the current OSHA PEL of 2.0 μg/m3 (8-hr TWA);
93 percent were below the DOE action level of 0.2 μg/m3; and the median
value was 0.02 µg/m3.  The SD-HV BZ samples had a median value of 0.44
μg/m3, with 90 percent below the OSHA Short-Term Exposure Limit (STEL)
of 5.0 μg/m3.  The highest levels of beryllium were found in rod and
wire production, particularly in wire annealing and pickling, the only
production job with a median personal sample measurement greater than
0.1 µg/m3 (median 0.12 µg/m3; range 0.01 - 7.8 μg/m3) (Schuler et
al., Table 4).  These concentrations were significantly higher than the
exposure levels in the strip metal area (median 0.02, range 0.01 - 0.72
μg/m3), in production support jobs (median 0.02, range < 0.01 - 0.33
μg/m3), plant administration (median 0.02, range < 0.01 - 0.11 μg/m3),
and office administration jobs (median 0.01, range < 0.01 - 0.06
μg/m3).

The authors reported that eight of the ten sensitized employees,
including all six CBD cases, had worked in both major production areas
during their tenure with the plant.  The 7 percent prevalence (6 of 81
workers) of CBD among employees who had ever worked in rod and wire was
statistically significantly elevated compared with employees who had
never worked in rod and wire (p < 0.05), while the 6 percent prevalence
(6 of 94 workers) among those who had worked in strip metal was not
significantly elevated compared to non-strip metal workers (p > 0.1).
Based on these results, together with the higher exposure levels
reported for the rod and wire production area, Schuler et al. concluded
that work in rod and wire was a key risk factor for CBD in this
population.  Schuler et al. also found a high prevalence (13 percent) of
sensitization among workers who had been exposed to beryllium for less
than a year at the time of the screening, a rate similar to that found
by Henneberger et al. among beryllium ceramics workers exposed for one
year or less (16 percent, Henneberger et al., 2001).  All four workers
who were sensitized without disease had been exposed 5 years or less;
conversely, all six of the workers with CBD had first been exposed to
beryllium at least five years prior to the screening (Schuler et al.,
Table 2).

μg/m3).

μg/m3, and 59 percent below the limit of detection (LOD), which was
either 0.02 µg/m3 or 0.2 µg/m3 depending on the method of sample
analysis (Thomas et al. 2009, p. 116).  Median values below 0.03 were
reported for all processes except the wire annealing and pickling
process.  Samples for this process remained somewhat elevated, with a
median of 0.1 μg/m3.  In January 2002, the plant enclosed the wire
annealing and pickling process in a restricted access zone (RAZ),
requiring respiratory PPE in the RAZ and implementing stringent measures
to minimize the potential for skin contact and beryllium transfer out of
the zone.  While exposure samples collected by the facility were sparse
following the enclosure, they suggest exposure levels comparable to the
2000-01 samples in areas other than the RAZ.  Within the RAZ, required
use of powered-air purifier respirators indicates that respiratory
exposure was negligible.

To test the efficacy of the new measures in preventing sensitization and
CBD, in June 2000 the facility began an intensive BeLPT screening
program for all new workers.  The company screened workers at the time
of hire; at intervals of 3, 6, 12, 24, and 48 months; and at 3-year
intervals thereafter.  Among 82 workers hired after 1999, three (3.7
percent) cases of sensitization were found.  Two (5.4 percent) of 37
workers hired prior to enclosure of the wire annealing and pickling
process were found to be sensitized within 3 and 6 months of beginning
work at the plant.  One (2.2 percent) of 45 workers hired after the
enclosure was confirmed as sensitized.

Thomas et al. calculated a sensitization IR of 1.9 per 1,000
person-months for the workers hired after the exposure control program
was initiated in 2000 (“program workers”), using the sum of
sensitization-free months of employment among all 82 workers as the
denominator (Thomas et al., 2009).  They calculated an estimated IR of
3.8 per 1,000 person-months for 43 workers hired between 1993 and 2000
who had participated in the 2000 BeLPT screening (“legacy workers”).
 This estimated IR was based on one BeLPT screening, rather than BeLPTs
conducted throughout the legacy workers’ employment, the denominator
in this case is the total months of employment until the 2000 screening.
 Because sensitized workers may have been sensitized prior to the
screening, the denominator may overestimate sensitization-free time in
the legacy group, and the actual sensitization IR for legacy workers may
be somewhat higher than 3.8 per 1,000 person-months.  Based on
comparison of the IRs and the prevalence rates discussed previously, the
authors concluded that the combination of dermal protection, respiratory
protection, housekeeping improvements and engineering controls
implemented beginning in 2000 appeared to have reduced the risk of
sensitization among workers at the plant.  However, they noted that the
small size of the study population and the short follow-up time for the
program workers suggested that further research is needed to confirm the
program’s efficacy (Thomas et al. 2009, p. 123).

Stanton et al. (2006) conducted a study of workers in three different
copper-beryllium alloy distribution centers in the United States.  The
distribution centers, including one bulk products center established in
1963 and strip metal centers established in 1968 and 1972, sell products
received from beryllium production and finishing facilities and small
quantities of copper-beryllium, aluminum-beryllium, and nickel-beryllium
alloy materials.  Work at distribution centers does not require
large-scale heat treatment or manipulation of material typical of
beryllium processing and machining plants, but involves final processing
steps that can generate airborne beryllium.  Slitting, the main
production activity at the two strip product distribution centers,
generates low levels of airborne beryllium particles, while operations
such as tensioning and welding used more frequently at the bulk products
center can generate somewhat higher levels.  Non-production jobs at all
three centers included shipping and receiving, palletizing and wrapping,
production-area administrative work, and office-area administrative
work.

The authors estimated workers’ beryllium exposures using IH data from
company records and job history information collected through interviews
conducted by a company occupational health nurse.  Stanton et al.
evaluated airborne beryllium levels in various jobs based on 393
full-shift LP samples collected from 1996 to 2004.  Airborne beryllium
levels at the plant were generally very low, with 54 percent of all
samples at or below the LOD, which ranged from 0.02 to 0.1 μg/m3.  The
authors reported a median of 0.03 μg/m3 and an arithmetic mean of 0.05
μg/m3 for the 393 full-shift LP samples, where samples below the LOD
were assigned a value of half the applicable LOD.  Median and geometric
mean values for specific jobs ranged from 0.01 - 0.07 and 0.02 - 0.07
µg/m3, respectively.  All measurements were below the OSHA PEL of 2.0
μg/m3 and 97 percent were below the DOE action level of 0.2 μg/m3.
The paper does not report use of respiratory or skin protection.
Exposure conditions may have changed somewhat over the history of the
plant due to changes in exposure control measures, including
improvements to product and container cleaning practices instituted
during the 1990s.

Eighty-eight of the 100 workers (88 percent) employed at the three
centers at the time of the study participated in screening for BeS.
Blood samples were collected between November 2000 and March 2001 by the
company’s medical staff.  Samples collected from employees of the
strip metal centers were split and evaluated at two laboratories, while
samples from the bulk product center workers were evaluated at a single
laboratory.  Participants were considered to be “sensitized” to
beryllium if two or more BeLPT results, from two laboratories or from
repeat testing at the same laboratory, were found to be abnormal.  One
individual was found to be sensitized and was offered clinical
evaluation, including BAL and fiberoptic bronchoscopy.  He was found to
have lung granulomas and was diagnosed with CBD.

The worker diagnosed with CBD had been employed at a strip metal
distribution center from 1978 to 2000 as a shipper and receiver, loading
and unloading trucks delivering materials from a beryllium production
facility and to the distribution center’s customers.  Although the LP
samples collected for his job between 1996 and 2000 were generally low
(n = 35, median 0.01, range < 0.02 - 0.13 µg/m3), it is not clear
whether these samples adequately characterize his exposure conditions
over the course of his work history.  He reported that early in his work
history, containers of beryllium oxide powder were transported on the
trucks he entered.  While he did not recall seeing any breaks or leaks
in the beryllium oxide containers, some containers were known to have
been punctured by forklifts on trailers used by the company during the
period of his employment, and could have contaminated trucks he entered.
 With 22 years of employment at the facility, this worker had begun
beryllium-related work earlier and performed it longer than about 90
percent of the study population (Stanton et al. p. 208).

Nuclear Weapons Production Facilities and Cleanup of Former Facilities

Primary exposure from nuclear weapons production facilities comes from
beryllium metal and beryllium alloys.

A study conducted by Kreiss et al. (1989) documented beryllium BeS and
CBD among beryllium-exposed workers in the nuclear industry.  A company
medical department identified 58 workers with beryllium exposure among a
work force of 500, of whom 51 (88 percent) participated in the study.
Twenty-four workers were involved in research and development R&D),
while the remaining 27 were production workers.  The R&D workers had a
longer tenure with a mean time from first exposure of 21.2 years,
compared to a mean time since first exposure of 5 years among the
production workers.  The number of workers with abnormal BLPT readings
was 6, with 4 being diagnosed with CBD.  This resulted in an estimated
11.8 percent prevalence of beryllium BeS.

Kreiss et al. (1993) expanded the work of Kreiss et al. (1989) by
performing a cross-sectional study of 895 (current and former) beryllium
workers in the same nuclear weapons plant.  Participants were placed in
qualitative exposure groups (“no exposure,” “minimal exposure,”
“intermittent exposure,” and “consistent exposure”) based on
questionnaire responses.  The number of workers with abnormal BeLPT
totaled 18 with 12 being diagnosed with CBD.  Three additional workers
with BeS developed CBD over the next 2 years.  BeS occurred in all of
the qualitatively defined exposure groups.  Individuals who had worked
as machinists were statistically overrepresented among
beryllium-sensitized cases, compared with non-cases.  Cases were more
likely than non-cases to report having had a measured overexposure to
beryllium (p = 0.009), a factor which proved to be a significant
predictor of BeS in logistic regression analyses, as was exposure to
beryllium prior to 1970.  Beryllium sensitized cases were also
significantly more likely to report having had cuts that were delayed in
healing (p = 0.02).  The authors concluded that individual variability
and susceptibility along with exposure circumstances are important
factors in developing beryllium BeS and CBD.

In 1991, the Beryllium Health Surveillance Program (BHSP) was
established at the Rocky Flats Nuclear Weapons Facility to offer BLPT
screening to current and former employees who may have been exposed to
beryllium (Stange et al., 1996).  Participants received an initial
BeLPT and follow-ups at one and three years.  Based on histologic
evidence of pulmonary granulomas and a positive BAL-BeLPT Stange et al.
published a study of 4,397 BHSP participants tested from June 1991 to
March 1995, including current employees (42.8 percent) and former
employees (57.2 percent).  Twenty-nine cases of CBD and 76 cases of BeS
were identified.  The sensitization rate for the population was 2.43
percent.  Available exposure data included FAH exposure samples
collected between 1970 and 1988 (mean concentration 0.016 µg/m3) and
personal samples collected between 1984 and 1987 (mean concentration
1.04 µg/m3).  Cases of CBD and BeS were noted in individuals in all
jobs classifications, including those believed to involve minimal
exposure to beryllium.  The authors recommended ongoing surveillance for
workers in all jobs with potential for beryllium exposure.

Stange et al. (2001) extended the previous study, evaluating 5,173
participants in the Rocky Flats BHSP who were tested between June 1991
and December 1997.  Three-year serial testing was offered to employees
who had not been tested for three years or more and did not show BeS
during the previous study.  This resulted in 2,891 employees being
tested.  Of the 5,173 workers participating in the study, 172 were
found to have abnormal BeLPT.  Ninety-eight (3.33 percent) of the
workers were found to be sensitized (confirmed abnormal BeLPT results)
in the initial screening, conducted in 1991.  Of these workers 74 were
diagnosed with CBD (history of beryllium exposure, evidence of
noncaseating granulomas or mononuclear cell infiltrates on lung biopsy,
and a positive BeLPT or BAL-BeLPT).  A follow-up screening of 2,891
workers three years later identified an additional 56 sensitized workers
and an additional seven cases of CBD.  BeS and CBD rates were analyzed
with respect to gender, building work locations, and length of
employment.  Historical employee data included hire date, termination
date, leave of absences, and job title changes.  Exposure to beryllium
was determined by job categories and building or work area codes.
Personal beryllium air monitoring results were used, when available,
from employees with the same job title or similar job.  However, no
quantitative information was presented in the study.  The authors
conclude that for some individuals, exposure to beryllium at levels less
that the OSHA PEL could cause BeS and CBD.

Viet et al. (2001) conducted a case-control study of the Rocky Flats
worker population studied by Stange et al. to examine the relationship
between estimated beryllium exposure level and risk of BeS or CBD.  The
worker population included 74 beryllium-sensitized workers and 50
workers diagnosed with CBD.  Beryllium exposure levels were estimated
based on FAH airhead samples from one building, the beryllium machine
shop.  These were collected away from the BZ of the machine operator
and likely underestimated exposure.  To estimate levels in other
locations, these air sample concentrations were used to construct a job
exposure matrix that included the determination of the Building 444
exposure estimates for a 30-year period; each subject’s work history
by job location, task, and time period; and assignment of exposure
estimates to each combination of job location, task, and time period as
compared to Building 444 machinists.  The authors adjusted the levels
observed in the machine shop by factors based on interviews with former
workers.  Workers’ estimated mean exposure concentrations ranged from
0.083 µg/m3 to 0.622 µg/m3.  Estimated maximum air concentrations
ranged from 0.54 µg/m3 to 36.8 µg/m3.  Cases were matched to controls
of the same age, race, gender, and smoking status (Viet et al. 2000).

Estimated mean and cumulative exposure levels and duration of employment
were found to be significantly higher for CBD cases than for controls.
Estimated mean exposure levels were significantly higher for BeS cases
than for controls.  No significant difference was observed for estimated
cumulative exposure or duration of exposure.  Similar results were
found using logistic regression analysis, which identified statistically
significant relationships between CBD and both cumulative and mean
estimated exposure, but did not find significant relationships between
estimated exposure levels and BeS without CBD.  Comparing CBD with BeS
cases, Viet et al. found that workers with CBD had significantly higher
estimated cumulative and mean beryllium exposure levels than workers who
were sensitized, but did not have CBD.

Animal Models of CBD

This section reviews the relevant animal studies supporting the
mechanisms outlined above.  Researchers have attempted to identify
animal models with which to further investigate the mechanisms
underlying the development of CBD.  A suitable animal model should
exhibit major characteristics of CBD, including the formation of immune
granulomas following inhalation exposure to beryllium, the demonstration
of a beryllium-specific immune response, and mimicking the progressive
nature of the human disease.  While exposure to beryllium has been shown
to cause chronic granulomatous inflammation of the lung in animal
studies using a variety of species, most of the granulomatous lesions
were formed by foreign-body reactions, which result from persistent
irritation and consist predominantly of macrophages and monocytes, and
small numbers of lymphocytes.  Foreign-body granulomas are distinct from
the immune granulomas of CBD, which are caused by antigenic stimulation
of the immune system and contain large numbers of lymphocytes.  Animal
studies have been useful in identifying the specific mechanistic pieces
of action for beryllium disease, however, no single model has completely
mimicked the disease process as it progresses in humans.  The following
is a discussion of the most relevant animal studies regarding the
mechanisms of BeS and CBD development in humans.

Harmesen et al. performed a study to assess whether the beagle dog could
provide an adequate model for the study of beryllium induced lung
diseases (Harmesen et al., 1985).  One group of dogs served as a control
group (air inhalation only) and four other groups received high
(approximately 50 μg/kg) and low (approximately 20 μg/kg) doses of
beryllium oxide calcined at 500° C or 1,000° C, administered as
aerosols.  As discussed above, calcining temperature controls the
solubility and SSA of beryllium particles.  Those particles calcined at
higher temperatures (e.g., 1,000° C) are less soluble and have lower
SSA than particles calcined at lower temperatures (e.g., 500°C).
Solubility and SSA are factors in determining the toxic potential of
beryllium compounds or materials.

Cells were collected from the dogs by BAL at 30, 60, 90, 180, and 210
days after exposure, and the percentages of neutrophils and lymphocytes
were determined.  In addition, the mitogenic responses of blood
lymphocytes and lavage cells collected at 210 days were determined with
either phytohemagglutinin or beryllium sulfate as mitogen.  The
percentage of neutrophils in the lavage fluid was significantly elevated
only at 30 days with exposure to either dose of 500° C beryllium oxide.
 The percentage of lymphocytes in the fluid was significantly elevated
in samples across all times with exposure to the high dose of this
beryllium oxide form.  Beryllium oxide calcined at 1,000° C elevated
lavage lymphocytes only in high dose at 30 days.  No significant effect
of 1,000° C beryllium oxide exposure on mitogenic response of any
lymphocytes was seen.  In contrast, peripheral blood lymphocytes from
the 500° C beryllium oxide exposed groups were significantly stimulated
by beryllium sulfate compared with the phytohemagglutinin exposed cells.
 The investigators in this study were able to replicate some of the same
findings as those observed in human studies – specifically, that
beryllium in soluble and insoluble forms can be mitogenic to immune
cells, an important finding for progression of BeS and proliferation of
immune cells to developing full-blown CBD.

In another beagle study Haley et al. also found that the beagle dog
appears to model some aspects of human CBD (Haley et al., 1989).  The
authors monitored lung pathologic effects, particle clearance, and
immune sensitization of peripheral blood leukocytes following a single
exposure to beryllium oxide aerosol generated from beryllium oxide
calcined at 500° C or 1,000° C.  The aerosol was administered to the
dogs perinasally to attain initial lung burdens of 6 or 18 μg
beryllium/kg body weight.  Granulomatous lesions and lung lymphocyte
responses consistent with those observed in humans with CBD were
observed, including perivascular and peribronchiolar infiltrates of
lymphocytes and macrophages, progressing to microgranulomas with areas
of granulomatous pneumonia and interstitial fibrosis.  Beryllium
specificity of the immune response was demonstrated by positive results
in the BeLPT, although there was considerable inter-animal variation.
The lesions declined in severity after 64 days post-exposure.  Thus,
while this model was able to mimic the formation of Be-specific immune
granulomas, it was not able to mimic the progressive nature of disease.

This study also provided an opportunity to compare the effects of
beryllium oxide calcination temperature on granulomatous disease in the
beagle respiratory system.  Haley et al. found that the percentage and
numbers of lymphocytes in BAL fluid was increased at 3 month
postexposure in dogs exposed to either dose of beryllium oxide calcined
at 500° C, but not in dogs exposed to the material calcined at the
higher temperature.  Although there was considerable inter-animal
variation, lesions were generally more severe in the dogs exposed to
material calcined at 500° C.  Positive BeLPT results were observed with
BAL lymphocytes only in the group with a high initial lung burden of the
material calcined at 500° C, but positive results with peripheral blood
lymphocytes were observed at both doses with material calcined at both
temperatures.

The histologic and immunologic responses of canine lungs to aerosolized
beryllium oxide were investigated in another Haley et al. (1989) study.
Beagle-dogs were exposed to high dose (50 µg/kg of body weight) or low
dose (l7 µg/kg) levels of beryllium oxide calcined at either 500° or
1000° C.  One group of dogs was examined up to 365 days after exposure
for lung histology and biochemical assay to determine the fate of
inhaled beryllium oxide.  A second group underwent BAL for lung
lymphocyte analysis for up to 22 months after exposure.  Histopathologic
examination revealed peribronchiolar and perivascular lymphocytic
histiocytic inflammation, peaking at 64 days after beryllium oxide
exposure.  Lymphocytes were initially well differentiated, but
progressed to lymphoblastic cells and aggregated in lymphofollicular
nodules or microgranulomas over time.  Alveolar macrophages were large,
and filled with intracytoplasmic material.  Cortical and paracortical
lymphoid hyperplasia of the tracheobronchial nodes was found.  Lung
lymphocyte concentrations were increased at 3 months and returned to
normal in both dose groups given 500° C treated beryllium chloride.  No
significant elevations in lymphocyte concentrations were found on dogs
given 1,000°C treated beryllium oxide.  Lung retention was higher in
the 500° C treated beryllium oxide group.  The lesions found in dog
lungs closely resembled those found in humans with CBD: severe
granulomas, lymphoblast transformation, increased pulmonary lymphocyte
concentrations and variation in beryllium sensitivity.  It was concluded
that the canine model for berylliosis may provide insight into this
disease.

4,380 μg Be/m3 as beryllium oxide calcined at 1,400° C for 30 min,
once per month for 3 months.  Because the dogs were sacrificed 2 years
post-exposure, the long time period between exposure and response may
have allowed for the reversal of any beryllium-induced changes (EPA,
1998).

A 1994 study by Haley et al. showed that intra-bronchiolar installation
of beryllium can induce immune granulomas and BeS in monkeys.  Haley et
al. (1994) exposed male cynomolgus monkeys to either beryllium metal or
beryllium oxide calcined at 500° C by intrabronchiolar instillation as
a saline suspension.  Lymphocyte counts in BAL fluid were observed, and
were found to be significantly increased in monkeys exposed to beryllium
metal on post-exposure days 14 to 90, and on post-exposure day 60 in
monkeys exposed to beryllium oxide.  The lungs of monkeys exposed to
beryllium metal had lesions characterized by interstitial fibrosis, Type
II cell hyperplasia, and lymphocyte infiltration.  Some monkeys also
exhibited immune granulomas.  Similar lesions were observed in monkeys
exposed to beryllium oxide, but the incidence and severity were much
less.  BAL lymphocytes from monkeys exposed to Be metal, but not from
monkeys exposed to beryllium oxide, proliferated in response to
beryllium sulfate in the BeLPT (EPA, 1998).

In an experiment similar to the one conducted with dogs, Conradi et al.
(1971) found no effect in monkeys (Macaca irus) exposed via whole-body
inhalation for three 30-min monthly exposures to a range of 3,300-4,380
μg Be/m3 as beryllium oxide calcined at 1,400° C.  The lack of effect
may have been related to the long period (2 years) between exposure and
sacrifice, or to low toxicity of beryllium oxide calcined at such a high
temperature.

As discussed earlier in the health effects subsection, at the cellular
level, beryllium dissolution must occur for the macrophage to present
beryllium as an antigen to induce the cell-mediated CBD immune reactions
(Stefaniak et al. 2006).  Several studies have shown that low-fired
beryllium oxide, which is predominantly made up of poorly crystallized
small particles, is more immunologically reactive than beryllium oxide
calcined at higher firing temperatures that result in less reactivity
due to increasing crystal size.  As discussed previously, Haley et al.
(1989a) found more severe lung lesions and a stronger immune response in
beagle dogs receiving a single inhalation exposure to beryllium oxide
calcined at 500° C than in dogs receiving an equivalent initial lung
burden of beryllium oxide calcined at 1,000° C.  Haley et al. found
that beryllium oxide calcined at 1,000°C elicited little local
pulmonary immune response, whereas the much more soluble beryllium oxide
calcined at 500°C produced a beryllium-specific, cell-mediated immune
response in dogs (Haley, 1991).

In a later study, beryllium metal appeared to induce a greater toxic
response than beryllium oxide following intrabronchiolar instillation in
cynomolgus monkeys, as evidenced by more severe lung lesions, a larger
effect on BAL lymphocyte counts, and a positive response in the BeLT
with BAL lymphocytes only after exposure to beryllium metal (Haley et
al., 1994).  Because an oxide layer may form on beryllium-metal surfaces
after exposure to air (Mueller and Adolphson, 1979; Harmsen et al.,
1984) dissolution of small amounts of poorly soluble beryllium compounds
in the lungs might be sufficient to allow persistent low-level beryllium
presentation to the immune system (NAS, 2008).

Preliminary Beryllium Sensitization and CBD Conclusions

It is well-established that beryllium exposure, either via inhalation or
skin, may lead to BeS, and, with inhalation exposure, may lead to the
onset and progression of CBD.  This is supported by extensive animal and
human studies.  The mechanism by which this occurs has been clearly laid
out in the previous sections.  Sensitization is a necessary first step
to the onset of CBD.  Sensitization is a change to the function of the
immune system such that a person can now develop CBD with a substantial
proportion of sensitized people progressing to this disease state.  OSHA
has made a preliminary determination to consider BeS and CBD to be
adverse events along the pathological continuum for beryllium disease,
with BeS being the necessary first step in the progression to CBD.

The epidemiological evidence presented in this section demonstrates that
BeS and CBD are continuing to occur from present-day exposures below
OSHA’s PEL.  The available literature discussed above shows that
disease prevalence can be reduced by reducing inhalation exposure.
However, the available epidemiological studies also indicate that it may
be necessary to minimize skin exposure to further reduce the incidence
of BeS.  The preliminary risk assessment also discusses the
effectiveness of interventions to reduce beryllium exposures and the
risk of BeS and CBD.

In general, the studies demonstrate that there is substantial prevalence
of BeS and CBD in modern facilities with exposure levels below the
current PEL, that risk of BeS and CBD appears to vary across industries
and processes, and that efforts to reduce exposure have succeeded in
reducing the frequency of BeS and CBD.

Of workers who were found to be sensitized and underwent clinical
evaluation, 36-100 percent was diagnosed with CBD (Kreiss et al., 1993;
Newman, 1996, 2005 and 2007).  Overall prevalence of CBD in
cross-sectional screenings ranges from 0.6 to 8 percent (Kreiss et al.,
2007).  It has been estimated from ongoing surveillance of sensitized
individuals, with an average follow-up time of 4.5 years, that 37
percent of beryllium-exposed employees were estimated to progress to CBD
(Newman, 2005).  A study of nuclear weapons facility employees enrolled
in an ongoing medical surveillance program found that only about 20
percent of sensitized individuals employed less than five years
eventually were diagnosed with CBD, while 40 percent of sensitized
employees employed ten years or more developed CBD (Stange et al.,
2001).

BERYLLIUM LUNG CANCER SECTION

Beryllium exposure has been associated with a variety of adverse health
effects including lung cancer.  The potential for beryllium and its
compounds to cause cancer has been previously assessed by various other
agencies (EPA, ATSDR, NAS, NIEHS, and NIOSH).  In addition, the
International Agency for Research on Cancer (IARC) did an extensive
evaluation in 1993 and reevaluated in April 2009 (EHP, 2009).  In brief,
IARC determined beryllium and its compounds to be carcinogenic to humans
(Group 1 category), while EPA considers beryllium to be probable human
carcinogens (EPA, 1998), and the National Toxicology Program (NTP) has
determined beryllium and its compounds are reasonably expected to be
carcinogens (NTP, 1999, 2005).  OSHA has conducted an independent
evaluation of the carcinogenic potential of beryllium and these
compounds as well.  The following is a summary of the studies used to
support the Agency findings.

Genotoxicity Studies

Genotoxicity can be an important indicator for screening the potential
of a material to induce cancer and an important mechanism leading to
tumor formation and carcinogenesis.  In a review conducted by the
National Academy of Science, beryllium and its compounds have tested
positively in nearly 50 percent of the genotoxicity studies conducted
without exogenous metabolic activity, however, they were found to be
non-genotoxic in most bacterial assays (NAS, 2008).

Gene mutations have been observed in mammalian cells cultured with
beryllium chloride in a limited number of studies (EPA, 1998; ATSDR,
2002; Gordon and Bowser, 2003).  Culturing mammalian cells with
beryllium chloride, beryllium sulfate, or beryllium nitrate has resulted
in clastogenic alterations.  However, most studies have found that
beryllium chloride, beryllium nitrate, beryllium sulfate, and beryllium
oxide did not induce gene mutations in bacterial assays with or without
metabolic activation. In the case of beryllium sulfate, all mutagenicity
studies (Ames (Simmon, 1979; Dunkel et al., 1984; Arlauskas et al.,
1985; Ashby et al., 1990); E. coli pol A (Rosenkranz and Poirer, 1979);
E. coli WP2 uvr A (Dunkel et al., 1984)) and Saccharomyces cerevisiae
(Simmon, 1979) were negative with the exception of results reported for
Bacillus subtilis rec assay (Kada et al., 1980; Kanematsu et al., 1980).
(EPA, 1998)   eryllium sulfate did not induce unscheduled DNA synthesis
in primary rat hepatocytes and was not mutagenic when injected
intraperitoneally in adult mice in a host-mediated assay using
Salmonella typhimurium (Williams et al., 1982).

Beryllium nitrate was negative in the Ames assay (Tso and Fung, 1981;
Kuroda et al., 1991) but positive in a Bacillus subtilis rec assay