Investigators have also attempted to determine how biological
fluids can dissolve beryllium materials. In two studies, 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 (PSF) 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. A follow-up study by the same
investigational team (Duling et al., 2012) confirmed dissolution of
beryllium oxide by PSF and determined the release rate was biphasic
(initial rapid diffusion followed by a latter slower surface reaction-
driven release). During the latter phase, dissolution half-times were
1,400 to 2,000 days. The authors speculated this indicated bertrandite
was persistent in the lung (Duling et al., 2012).
    In a recent study investigating the dissolution and release of
beryllium ions for 17 beryllium-containing materials (ore, hydroxide,
metal, oxide, alloys, and processing intermediates) using artificial
human airway epithelial lining fluid, Stefaniak et al., (2011) found
release of beryllium ions within 7 days (beryl ore melter dust). The
authors calculated dissolution half-times ranging from 30 days
(reduction furnace material) to 74,000 days (hydroxide). Stefaniak et
al., (2011) speculated that despite the rapid mechanical clearance,
billions of beryllium ions could be released in the respiratory tract
via dissolution in airway lining fluid (ALF). Under this scenario
beryllium-containing particles depositing in the respiratory tract
dissolving in ALF could provide beryllium ions for absorption in the
lung and interact with immune cells in the respiratory tract (Stefaniak
et al., 2011).
    Huang et al., (2011) investigated the effect of simulated lung
fluid (SLF) on dissolution and nanoparticle generation and beryllium-
containing materials. Bertrandite-containing ore, beryl-containing ore,
frit (a processing intermediate), beryllium hydroxide (a processing
intermediate) and silica (used as a control), were equilibrated in SLF
at two pH values (4.5 and 7.2) to reflect inter- and intra-cellular
environments in the lung tissue. Concentrations of beryllium, aluminum,
and silica ions increased linearly during the first 20 days in SLF,
rose slowly thereafter, reaching equilibrium over time. The study also
found nanoparticle formation (in the size range of 10-100 nm) for all
materials (Huang et al., 2011).
    In an in vitro skin model, Sutton et al., (2003) demonstrated the
dissolution of beryllium compounds (insoluble beryllium hydroxide,
soluble beryllium phosphate) in a simulated sweat fluid. This model
showed beryllium can be dissolved in biological fluids and be available
for cellular uptake in the skin. Duling et al., (2012) confirmed
dissolution and release of ions from bertrandite ore in an artificial
sweat model (pH 5.3 and pH 6.5).
b. Particle Size
    The toxicity of beryllium as exemplified by beryllium oxide also is
dependent, in part, on the particle size, with smaller particles (<10
[mu]m) able to penetrate beyond the larynx (Stefaniak et al., 2008).
Most inhalation studies and occupational exposures involve quite small
(<1-2 [mu]m) beryllium oxide particles that can penetrate to the
pulmonary regions of the lung (Stefaniak et al., 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 [mu]m.
    The temperature at which beryllium oxide is calcined influences its
particle size, surface area, solubility, and ultimately its toxicity
(Delic, 1992). Low-fired (500 [deg]C) beryllium oxide is predominantly
made up of poorly crystallized small particles, while higher firing
temperatures (1000--1750 [deg]C) result in larger particle sizes
(Delic, 1992).
    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 sensitization or CBD.
    Numerous studies have been conducted evaluating the particle size
generated during basic industrial and machining operations. In a study
by Cohen et al., (1983), a multi-cyclone sampler was utilized to
measure the size mass distribution of the beryllium aerosol at a
beryllium-copper alloy casting operation. Briefly, Cohen et al., (1983)
found variable particle size generation based on the operations being
sampled with particle size ranging from 3 to 16 [mu]m. Hoover et al.,
(1990) also found variable particle sizes being generated based on
operations. In general, Hoover et al., (1990) found that milling
operations generated smaller particle sizes than sawing operations.
Hoover et al., (1990) also found that beryllium metal generated higher
concentrations than metal alloys. Martyny et al., (2000) characterized
generation of particle size during precision beryllium machining
processes. The study found that more than 50 percent of the beryllium
machining particles collected in the breathing zone of machinists were
less than 10 [mu]m in aerodynamic diameter with 30 percent of that
fraction being particles of less than 0.6 [mu]m. 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 [mu]m. Kent et al.,
(2001) measured airborne beryllium using size-selective samplers in
five furnace areas at a beryllium processing facility. A statistically
significant linear trend was reported between the above alveolar-
deposited particle mass concentration and prevalence of CBD and
sensitization in the furnace production areas. The study authors
suggested that the concentration of alveolar-deposited particles (e.g.,
<3.5 [mu]m) may be a better predictor of sensitization and CBD than the
total mass concentration of airborne beryllium.
    A recent study by Virji et al. (2011) evaluated particle size
distribution, chemistry and solubility in areas with historically
elevated risk of sensitization and CBD at a beryllium metal powder,
beryllium oxide, and alloy production facility. The investigators
observed that historically, exposure-response relationships have been
inconsistent when using mass concentration to identify process-related
risk, possibly due to incomplete particle characterization. Two
separate exposure surveys were conducted in March 1999 and June-August
1999 using multi-stage personal impactor samplers (to determine
particle size distribution) and personal 37 mm closed face cassette
(CFC) samplers, both located in workers' breathing zones. One hundred
and ninety eight time-weighted-average (TWA) personal impactor samples
were analyzed for representative jobs and processes. A total of 4,026
CFC samples were collected over the 5-month collection period and
analyzed for mass concentration, particle size, chemical content and
solubility and compared to process areas with high risk of
sensitization and CBD. The investigators found that total beryllium
concentration varied greatly between workers and among process areas.
Analysis of chemical form and solubility also revealed wide variability
among process areas, but high risk process areas had exposures to both
soluble and insoluble forms of beryllium. Analysis of particle size
revealed most process areas had particles ranging from 5-14 [micro]m
mass median aerodynamic diameter (MMAD). Rank order correlating jobs to
particle size showed high overall consistency (Spearman r=0.84) but
moderate correlation (Pearson r=0.43). The investigators concluded that
consideration of relevant aspects of exposure such as particle size

distribution, chemical form, and solubility will likely improve
exposure assessments (Virji et al., 2011)
c. Particle Surface Area.
    Particle 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, 1995; Oberdorster et al., 1996). 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 al., 2005; Carter et al., 2006; Refsne et al.,
2006).
    Finch et al., (1988) found that beryllium oxide calcined at 500
[deg]C had 3.3 times greater specific surface area (SSA) than beryllium
oxide calcined at 1000 [deg]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 [deg]C.
As discussed above, a later study by Delic (1992) found calcining
temperatures had an effect on SSA as well as 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 [deg]C has been found to
have stronger pathogenic effects than material calcined at 1,000
[deg]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., 1988; 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 [deg]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 [deg]C beryllium oxide was
greater than that of 1,000 [deg]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, in which
SSA decreases with increasing surface diameter. In contrast, the alloys
and oxides consisted of small primary particles in clusters, in which
the SSA remains fairly constant with particle size. SSA for the metal
powders varied based on production and manufacturing process with
variations among samples as high as a factor of 37. Stefaniak 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.

B. 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.
 1. Exposure via the Respiratory System
    The respiratory tract, especially the lung, is the primary target
of inhalation exposure in workers. Inhaled beryllium particles are
deposited along the respiratory tract in a size dependent manner. In
general, particles larger than 10 [mu]m tend to deposit in the upper
respiratory tract or nasal region and do not appreciably penetrate
lower in the tracheobronchial or pulmonary regions (Figure 1).
Particles less than 10 [mu]m increasingly penetrate and deposit in the
tracheobronchial and pulmonary regions with peak deposition in the
pulmonary region occurring below 5 [mu]m in particle diameter. The CBD
pathology of concern is found in the pulmonary region. For particles
below 1 [mu]m, regional deposition changes dramatically. Ultrafine
particles (generally considered to be 100 nm or lower) have a higher
rate of deposition along the entire respiratory system (ICRP model,
1994). Those particles depositing in the lung and along the entire
respiratory tract may encounter immunologic cells or may move into the
vascular system where they are free to leave the lung and can
contribute to systemic beryllium concentrations.
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    Beryllium is removed from the respiratory tract by various
clearance mechanisms. Soluble beryllium is removed from the respiratory
tract via absorption. Sparingly soluble or insoluble beryllium may
remain in the lungs for many years after exposure, as has been observed
in workers (Schepers, 1962). Clearance mechanisms for sparingly soluble
or insoluble beryllium particles include: In the nasal passage,
sneezing, mucociliary transport to the throat, or dissolution; in the
tracheobronchial region, mucociliary transport, coughing, phagocytosis,
or dissolution; in the pulmonary or alveolar region, phagocytosis,
movement through the interstitium (translocation), or dissolution
(Schlesinger, 1997).
    Clearance mechanisms may occur slowly in humans, which is
consistent with some animal studies. For example, subjects in the
Beryllium Case Registry (BCR), which identifies and tracks cases of
acute and chronic beryllium diseases, had elevated concentrations of
beryllium in lung tissue (e.g., 3.1 [mu]g/g of dried lung tissue and
8.5 [mu]g/g in a mediastinal node) more than 20 years after termination
of short-term (generally between 2 and 5 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. As reviewed in a WHO Report (2001), 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 of 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).
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; WHO, 2001).
Confirmatory studies in rats have shown the half-time for the rapid
phase between 1-60 days, while the slow phase 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. (WHO, 2001; 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 [micro]g. These exposure levels resulted in an estimated
clearance half-life ranging

from 250-380 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-
[mu]g lung burden groups) or 360-400 days (for 12- and 34-[mu]g 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 is mainly
distributed to the tracheobronchial lymph nodes via the lymph system,
bloodstream, and 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; WHO, 2001). 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; WHO, 2001).
    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 for beryllium that may later be reabsorbed by the
circulatory system, making beryllium available to the immunological
system.
2. Dermal Exposure
    Beryllium compounds have been shown to cause skin irritation and
sensitization in humans and certain animal models (Van Orstrand et al.,
1945; de Nardi et al., 1953; Nishimura 1966; Epstein 1990; Belman,
1969; Tinkle et al., 2003; Delic, 1992). The Agency for Toxic
Substances and Disease Registry (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 et
al., 2001; Toledo et al., 2011). 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 <= 1[mu]m, as confirmed
by scanning electron microscopy. Using confocal microscopy, Tinkle et
al. demonstrated that surrogate fluorescent particles up to 1 [mu]m in
size could penetrate the mouse epidermis and dermis layers in a 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. As earlier summarized, insoluble
forms of beryllium can be solubilized in biological fluids (e.g.,
sweat) making them available for absorption through intact skin (Sutton
et al., 2003; Stefaniak et al., 2011; Duling et al., 2012).
    Although its precise role remains to be elucidated, there is
evidence to indicate that dermal exposure can contribute to beryllium
sensitization. As early as the 1940s it was recognized that dermatitis
experienced by workers in primary beryllium production facilities was
linked to exposures to the soluble beryllium salts. Except in cases of
wound contamination, dermatitis was rare in workers whose exposures
were restricted to exposure to poorly soluble beryllium-containing
particles (Van Ordstrand et al., 1945). Further investigation by McCord
in 1951 indicated that direct skin contact with soluble beryllium
compounds, but not beryllium hydroxide or beryllium metal, caused
dermal lesions (reddened, elevated, or fluid-filled lesions on exposed
body surfaces) in susceptible persons. Curtis, in 1951, demonstrated
skin sensitization to beryllium with patch testing using soluble and
insoluble forms of beryllium in beryllium-na[iuml]ve subjects. These
subjects later developed granulomatous skin lesions with the classical
delayed-type contact dermatitis following repeat challenge (Curtis,
1951). These lesions appeared after a latent period of 1-2 weeks,
suggesting a delayed allergic reaction. The dermal reaction occurred
more rapidly and in response to smaller amounts of beryllium in those
individuals previously sensitized (Van Ordstrand et al., 1945).
Contamination of cuts and scrapes with beryllium can result in the
beryllium becoming embedded within the skin causing a granuloma to
develop in the skin (Epstein, 1991). Introduction of soluble or
insoluble beryllium compounds into or under the skin as a result of
abrasions or cuts at work has 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 the 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 (WHO, 2001).
    A study by Deubner et al., (2001) concluded that exposure across
damaged skin can contribute as much systemic loading of beryllium as
inhalation (Deubner et al., 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
assumed a dermal loading rate for beryllium on skin of 0.43 [mu]g/
cm\2\, 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 that 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 (EPA, 1998).
    A study conducted by Day et al. (2007) evaluated the effectiveness
of a dermal protection program implemented in a beryllium alloy
facility in 2002. The investigators evaluated levels of beryllium in
air, on workplace surfaces, on cotton gloves worn over nitrile gloves,
and on the necks and faces of workers over a six day period. The
investigators found a good correlation between air samples and work
surface contamination at this facility. The investigators also found
measurable levels of beryllium on the skin of workers as a result of
work processes even from workplace areas

promoted as ``visually clean'' by the company housekeeping policy.
Importantly, the investigators found that the beryllium contamination
could be transferred from body region to body region (e.g., hand to
face, neck to face). The investigators demonstrated multiple pathways
of exposure which could lead to sensitization, increasing risk for
developing CBD (Day, et al., 2007).
    The same group of investigators (Armstrong et al., 2014) extended
their work on investigating multiple exposure pathways contributing to
sensitization and CBD. The investigators evaluated four different
beryllium manufacturing and processing facilities to assess the
contribution of various exposure pathways on worker exposure. Airborne,
work surface and cotton glove beryllium concentrations were evaluated.
The investigators found strong correlations between air-surface
concentrations, glove-surface concentrations, and air-glove
concentrations at this facility. This work confirms findings from Day
et al. (2007) demonstrating the importance of airborne beryllium
concentrations to surface contamination and dermal exposure even at
exposures below the current OSHA PEL (Armstrong et al., 2014).
3. Oral and Gastrointestinal Exposure
    According to the WHO Report (2001), gastrointestinal absorption of
beryllium can occur by both the inhalation and oral routes of exposure.
Through inhalation exposure, a fraction 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 (WHO, 2001). 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 (Schlesinger, 1997). Animal studies have shown oral
administration of beryllium compounds to result in very limited
absorption and storage (as reviewed by U.S. EPA, 1998). 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; WHO,
2001).
    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; WHO, 2001). 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 x 10-5 percent of the dose
administered by intratracheal instillation in baboons and 3.1 x
10-5 percent in rats (Andre et al., 1987).
4. 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 an
acidic environment and by myeloperoxidases (Leonard and Lauwerys, 1987;
Lansdown, 1995; WHO, 2001), 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).
5. Preliminary Conclusion for Particle Characterization and Kinetics of
Beryllium
    The forms and concentrations of beryllium across the workplace vary
substantially based upon location, process, production and work task.
Many factors influence the potency of beryllium including
concentration, composition, structure, size and surface area of the
particle.
    Studies have demonstrated that beryllium sensitization can occur
via the skin or inhalation from soluble or poorly soluble beryllium
particles. Beryllium must be presented to a cell in a soluble form for
activation of the immune system (NAS, 2008), and this will be discussed
in more detail in the section to follow. Poorly soluble beryllium can
be solubilized via intracellular fluid, lung fluid and sweat (Sutton et
al., 2003; Stefaniak et al., 2011). For beryllium to persist in the
lung it needs to be insoluble. However, soluble beryllium has been
shown to precipitate in the lung to form insoluble beryllium (Reeves
and Vorwald, 1967).
    Some animal and epidemiological studies suggest that the form of
beryllium may affect the rate of development of BeS and CBD. Beryllium
in an inhalable form (either as soluble or insoluble particles or mist)
can deposit in the respiratory tract and interact with immune cells
located along the entire respiratory tract (Scheslinger, 1997).
However, more study is needed to precisely determine the physiochemical
characteristics of beryllium that influence toxicity and
immunogenicity.

C. Acute Beryllium Diseases

    Acute beryllium disease (ABD) is a relatively rapid onset
inflammatory reaction resulting from breathing high airborne
concentrations of beryllium. It was first reported in workers
extracting beryllium oxide (Van Ordstrand et al., 1943). Since the
Atomic Energy Commission's adoption of occupational exposure limits for
beryllium beginning in 1949, cases of ABD have been rare. According to
the World Health Organization (2001), ABD is generally associated with
exposure to beryllium levels at or above 100 [mu]g/m\3\ and may be
fatal in 10 percent of cases. However, cases have been reported with
beryllium exposures below 100 [micro]g/m\3\ (Cummings et al., 2009).
The disease involves an inflammatory reaction that may include the
entire respiratory tract, involving the nasal passages, pharynx,
bronchial airways and alveoli. Other tissues including skin and
conjunctivae may be affected as well. The clinical features of

ABD include a nonproductive cough, chest pain, cyanosis, shortness of
breath, low-grade fever and a sharp drop in functional parameters of
the lungs. Pathological features of ABD include 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 to 72 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; DeNardi et al., 1953; Newman and
Kreiss, 1992). Evidence of a dose-response relationship to the
concentration of beryllium is limited (Eisenbud et al., 1948;
Stokinger, 1950; Sterner and Eisenbud, 1951). 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 have been documented
cases of progression to CBD (ACCP, 1965; Hall, 1950) suggesting the
possibility of an immune component to this disease (Cummings et al.,
2009) as well. 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 1970-1972 (OSHA, 1971; ACGIH, 1971;
ANSI, 1970) and 1974 (EPA, 1974).

D. Chronic Beryllium Disease

    This section provides an overview of 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 beryllium
sensitization and CBD.
    Chronic beryllium disease (CBD), formerly known as ``berylliosis''
or ``chronic berylliosis,'' is a granulomatous disorder primarily
affecting the lungs. CBD was first described in the literature by Hardy
and Tabershaw (1946) as a chronic granulomatous pneumonitis. It was
proposed as early as 1951 that CBD could be a chronic disease resulting
from an immune sensitization to beryllium (Sterner and Eisenbud, 1951;
Curtis, 1959; Nishimura, 1966). However, for a time, there remained
some controversy as to whether CBD was a delayed-onset hypersensitivity
disease or a toxicant-induced disease (NAS, 2008). Wide acceptance of
CBD as a hypersensitivity lung disease did not occur until bronchoscopy
studies and bronchoalveolar lavage (BAL) studies were performed
demonstrating that BAL cells from CBD patients responded to beryllium
challenge (Epstein et al., 1982; Rossman et al., 1988; Saltini et al.,
1989).
    CBD shares many clinical and histopathological features with
pulmonary sarcoidosis, a granulomatous lung disease of unknown
etiology. This includes such debilitating effects as airway
obstruction, diminishment of physical capacity associated with reduced
lung function, possible depression associated with decreased physical
capacity, and 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
Kreiber, 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; Cherry et al., 2015).
    Clinical signs and symptoms of CBD may include, but are not limited
to, a simple cough, shortness of breath or dypsnea, fever, weight loss
or anorexia, skin lesions, clubbing of fingers, cyanosis, night sweats,
cor pulmonale, tachycardia, edema, chest pain and arthralgia. Changes
or loss of pulmonary function also occur with CBD such as decrease in
vital capacity, reduced diffusing capacity, and 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). Besides
these listed symptoms from CBD patients, there have been reported cases
of CBD that remained asymptomatic (Muller-Querheim, 2005; NAS, 2008).
    Unlike ABD, CBD can result from inhalation exposure to beryllium at
levels below the current OSHA PEL, can take months to years after
initial beryllium exposure before signs and symptoms of CBD occur
(Newman 1996, 2005 and 2007; Henneberger, 2001; Seidler et al., 2012;
Schuler et al., 2012), and may continue to progress following removal
from beryllium exposure (Newman, 2005; Sawyer et al., 2005; Seidler et
al., 2012). 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., 1996; Newman et al.,
2005). The NAS report (2008) noted the general lack of published
studies on progression of CBD from an early asymptomatic stage to
functionally significant lung disease (NAS, 2008). The report
emphasized that risk factors and time course for clinical disease have
not been fully delineated. However, for people now under surveillance,
clinical progression from immunological sensitization and early
pathological lesions (i.e., granulomatous inflammation) prior to onset
of symptoms to symptomatic disease appears to be slow, although more
follow-up is needed (NAS, 2008). A study by Newman (1996) emphasized
the need for prospective studies to determine the natural history and
time course from BeS and asymptomatic CBD to full-blown disease
(Newman, 1996). Drawing from his own clinical experience, Newman was
able to identify the sequence of events for those with symptomatic
disease as follows: Initial determination of beryllium sensitization;
gradual emergence of chronic inflammation of the lung; pathologic
alterations with measurable physiologic changes (e.g., pulmonary
function and gas exchange); progression to a more severe lung disease
(with extrapulmonary effects such as clubbing and cor pulmonale in some
cases); and finally death in some cases (reported between 5.8 to 38
percent) (NAS, 2008; Newman, 1996).
    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; NAS 2008; Sood, 2009).
Management of CBD is generally modeled after sarcoidosis treatment.
Oral corticosteroid treatment can be initiated in patients 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 other
anti-inflammatory agents (NAS, 2008; Maier et al., 2012; Salvator et
al., 2013) as well. 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). Alternative treatments such as azathiopurine and
infliximab, while successful at treating symptoms of CBD, have been
demonstrated to have side-effects as well (Pallavicino et al., 2013;
Freeman, 2012).
1. Development of Beryllium Sensitization
    Sensitization to beryllium is an essential step for worker
development of CBD. Sensitization to beryllium can result from
inhalation exposure to beryllium (Newman et al., 2005; NAS, 2008), as
well as from skin exposure to beryllium (Curtis, 1951; Newman et al.,
1996; Tinkle et al., 2003). Sensitization is currently detected using a
laboratory blood test described in Appendix A. Although there may be no
clinical symptoms associated with BeS, a sensitized worker's immune
system has been activated to react to beryllium exposures such that
subsequent exposure to beryllium can progress to 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). Various factors, including
genetic susceptibility, have been shown to influence risk of developing
sensitization and CBD (NAS 2008) and will be discussed later in this
section.
    While various mechanisms or pathways may exist for beryllium
sensitization, the most plausible mechanisms supported by the best
available and most current science are discussed below. Sensitization
occurs via the formation of a beryllium-protein complex (an antigen)
that causes an immunological response. In some instances, onset of
sensitization has been observed in individuals exposed to beryllium for
only a few months (Kelleher et al., 2001; Henneberger et al., 2001).
This suggests the possibility that relatively brief, short-term
beryllium exposures may be sufficient to trigger the immune
hypersensitivity reaction. Several studies (Newman et al., 2001;
Henneberger et al., 2001; Rossman, 2001; Schuler et al., 2005; Donovan
et al., 2007, Schuler et al., 2012) have detected a higher prevalence
of sensitization among workers with less than one year of employment
compared to some cross-sectional studies which, due to lack of
information regarding initial exposure, cannot determine time of
sensitization (Kreiss et al., 1996; Kreiss et al., 1997). 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). Figure 2
delineates the major steps required for progression from beryllium
contact to sensitization to CBD.
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    Beryllium presentation to the immune system is believed to occur
either by direct presentation or by antigen processing. It has been
postulated that beryllium must be presented to the immune system in an
ionic form for cell-mediated immune activation to occur (Kreiss et al.,
2007). Some soluble forms of beryllium are readily presented, since the
soluble beryllium form disassociates into its ionic components.
However, for insoluble forms, dissolution may need to occur. A study by
Harmsen et al. (1986) suggested that a sufficient rate of dissolution
of small amounts of poorly soluble beryllium compounds might occur in
the lungs to allow persistent low-level beryllium presentation to the
immune system. Stefaniak et al. (2005 and 2012) reported that insoluble
beryllium particles phagocytized by macrophages were dissolved in
phagolysomal fluid (Stefaniak et al., 2005; Stefaniak et al., 2012) and
that the dissolution rate stimulated by phagolysomal fluid was
different for various forms of beryllium (Stefaniak et al., 2006;
Duling et al., 2012). Several studies have demonstrated that macrophage
uptake of beryllium can induce aberrant apoptotic processes leading to
the continued release of beryllium ions which will continually
stimulate T-cell activation (Sawyer et al., 2000; Sawyer et al., 2004;
Kittle et al., 2002). Antigen processing can be mediated by antigen-
presenting cells (APC). These may include macrophages, dendritic cells,
or other antigen-presenting cells, although this has not been well
defined in most studies (NAS, 2008).
    Because of their strong positive charge, beryllium ions have the
ability to haptenate and alter the structure of peptides occupying the
antigen-binding cleft of major histocompatibility complex (MHC) class
II on antigen-presenting cells (APC). The MHC class II antigen-binding
molecule for beryllium is the human leukocyte antigen (HLA) with
specific alleles (e.g.,

HLA-DP, HLA-DR, HLA-DQ) associated with the progression to CBD (NAS,
2008; Yucesoy and Johnson, 2011). Several studies have also
demonstrated that the electrostatic charge of HLA may be a factor in
binding beryllium (Snyder et al., 2003; Bill et al., 2005; Dai et al.,
2010). The strong positive ionic charge of the beryllium ion would have
a strong attraction for the negatively charged patches of certain HLA
alleles (Snyder et al., 2008; Dai et al., 2010). Alternatively,
beryllium oxide has been demonstrated to bind to the MHC class II
receptor in a neutral pH. The six carboxylates in the amino acid
sequence of the binding pocket provide a stable bond with the Be-O-Be
molecule when the pH of the substrate is neutral (Keizer et al., 2005).
The direct binding of BeO may eliminate the biological requirement for
antigen processing or dissolution of beryllium oxide to activate an
immune response.
    Next in sequence is the beryllium-MHC-APC complex binding to a T-
cell receptor (TCR) on a na[iuml]ve T-cell which stimulates the
proliferation and accumulation of beryllium-specific CD4\+\ (cluster of
differentiation 4\+\) T-cells (Saltini et al., 1989 and 1990; Martin et
al., 2011) as depicted in Figure 3. Fontenot et al. (1999) demonstrated
that diversely different variants of TCR were expressed by CD4\+\ T-
cells in peripheral blood cells of CBD patients. However, the CD4\+\ T-
cells from the lung were more homologous in expression of TCR variants
in CBD patients, suggesting clonal expansion of a subset of T-cells in
the lung (Fontenot et al., 1999). This may also indicate a pathogenic
potential for subsets of T-cell clones expressing this homologous TCR
(NAS, 2008). Fontenot et al. (2006) reported beryllium self-
presentation by HLA-DP expressing BAL CD4\+\ T-cells. Self-presentation
by BAL T-cells in the lung granuloma may result in activation-induced
cell death, which may then lead to oligoclonality of the T-cell
population characteristic of CBD (NAS, 2008).
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    As CD4\+\ T-cells proliferate, clonal expansion of various subsets
of the CD4\+\ beryllium specific T-cells occurs (Figure 3). In the
peripheral blood, the beryllium-specific CD4\+\ T cells require co-
stimulation with a co-stimulant CD28 (cluster of differentiation 28).
During the proliferation and differentiation process CD4\+\ T-cells
secrete pro-inflammatory cytokines that may influence this process
(Sawyer et al., 2004; Kimber et al., 2011).
2. Development of CBD
    The continued persistence of residual beryllium in the lung leads
to a T-cell maturation process. A large portion of beryllium-specific
CD4\+\ T cells were shown to cease expression of CD28 mRNA and protein,
indicating these cells no longer required co-stimulation with the CD28
ligand (Fontenot et al., 2003). This change in phenotype correlated
with lung inflammation (Fontenot et al., 2003). The CD4\+\ independent
cells continued to secrete cytokines necessary for additional
recruitment of inflammatory and immunological cells; however, they were
less proliferative and less susceptible to cell death compared to the
CD28 dependent cells (Fontenot et al., 2005; Mack et al., 2008). These
beryllium-specific CD4\+\ independent cells are considered to be mature
memory effector cells (Ndejembi et al., 2006; Bian et al., 2005).
Repeat exposure to beryllium in the lung resulting in a mature
population of T cell development independent of co-stimulation by CD28
and development of a population of T effector memory cells
(Tem cells) may be one of the mechanisms that lead to the
more severe reactions observed specifically in the lung (Fontenot et
al., 2005).
    CD4\+\ T cells created in the sensitization process recognize the
beryllium antigen, and respond by proliferating and secreting cytokines
and inflammatory mediators, including IL-2, IFN-[gamma], and TNF-
[alpha] (Tinkle et al., 1997a and b; Fontenot et al., 2002) and MIP-
1[alpha] and GRO-1 (Hong-Geller, 2006). This also results in the
accumulation of various types of inflammatory cells including
mononuclear cells (mostly CD4\+\ T cells) in the bronchoalveolar lavage
fluid (BAL fluid) (Saltini et al., 1989, 1990).
    The development of granulomatous inflammation in the lung of CBD
patients has been associated with the accumulation of beryllium
responsive CD4\+\ Tem cells in BAL fluid (NAS, 2008). The
subsequent release of pro-inflammatory cytokines, chemokines and
reactive oxygen species by these cells may lead to migration of
additional inflammatory/immune cells and the development of a
microenvironment that contributes to the development of CBD (Sawyer et
al., 2005; Tinkle et al., 1996; Hong-Geller et al., 2006; NAS, 2008).
    The cascade of events described above results in the formation of a
noncaseating granulomatous lesion.

Release of cytokines by the accumulating T cells leads to the formation
of granulomatous lesions that are characterized by an outer ring of
histiocytes surrounding non-necrotic tissue with embedded multi-
nucleated giant cells (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). 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 have been experienced in certain patients 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 (ATSDR, 2002).
    As previously mentioned, the uptake of beryllium may lead to an
aberrant apoptotic process with rerelease of beryllium ions and
continual stimulation of beryllium-responsive CD4+ cells in
the lung (Sawyer et al., 2000; Kittle et al., 2002; Sawyer et al.,
2004). Several research studies suggest apoptosis may be one mechanism
that enhances inflammatory cell recruitment, cytokine production and
inflammation, thus creating a scenario for progressive granulomatous
inflammation (Palmer et al., 2008; Rana, 2008). Macrophages and
neutrophils can phagocytize beryllium particles in an attempt to remove
the beryllium from the lung (Ding, et al., 2009). Multiple studies
(Sawyer et al., 2004; Kittle 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-
[alpha] (one of many cytokines produced in response to beryllium), and
that production of TNF-[alpha] 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). However, other factors may influence the development of
CBD and are outlined in the following section.
3. Genetic and Other Susceptibility Factors
    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. Early occupational studies proposed that CBD was
an immune reaction 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). Recent
studies have confirmed genetic susceptibility to CBD involves either
HLA variants, T-cell receptor clonality, tumor necrosis factor (TNF-
[alpha]) polymorphisms and/or transforming growth factor-beta (TGF-
[beta]) polymorphisms (Fontenot et al., 2000; Amicosante et al., 2005;
Tinkle et al., 1996; Gaede et al., 2005; Van Dyke et al., 2011;
Silveira et al., 2012).
    Single Nucleotide Polymorphisms (SNPs) have been studied with
regard to genetic variations associated with increased risk of
developing CBD. SNPs are the most abundant type of human genetic
variation. Polymorphisms in MHC class II and pro-inflammatory genes
have been shown to contribute to variations in immune responses
contributing to the susceptibility and resistance in many diseases
including auto-immunity, and beryllium sensitization and CBD (McClesky
et al., 2009). Specific SNPs have been evaluated as a factor in Glu69
variant from the HLA-DPB1 locus (Richeldi et al., 1993; Cai et al.,
2000; Saltini et al., 2001; Silviera et al., 2012; Dai et al., 2013),
HLA-DRPhe[beta]47 (Amicosante et al., 2005).
    HLA-DPB1 with a glutamic acid at amino position 69 (Glu 69) has
been shown to confer increased risk of beryllium sensitization and CBD
(Richeldi et al., 1993; Saltini et al., 2001; Amicosante et al., 2005;
Van Dyke et al., 2011; Silveira et al., 2012). Fontenot et al. (2000)
demonstrated that beryllium presentation by certain alleles of the
class II human leukocyte 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
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. The more common allele of the HLA-DP 1 variant is negatively
charged at this site and could directly interact with the positively
charged 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).
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 glutamate-69
allele was present in 86 percent of sensitized subjects, but in only 48
percent of beryllium-exposed, non-sensitized subjects. Some variants of
the HLA-DPB1 allele convey higher risk of BeS and CBD than others. For
example, HLA-DPB1*0201 yielded an approximately 3-fold increase in
disease outcome relative to controls; HLA-DPB1*1901 yielded an
approximately 5-fold increase, and HLA-DPB1*1701 an approximately 10-
fold increase (Weston et al., 2005; Snyder et al., 2008). 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
beryllium sensitization and CBD. This confirms the importance of
beryllium charge as a key factor in haptogenic potential.
    In contrast, the HLA-DRB1 allele, which lacks Glu 69, has also been
shown to increase the risk of developing sensitization and CBD
(Amicosante et al., 2005; Maier et al., 2003). Bill et al. (2005) found
that HLA-DR has a glutamic acid at position 71 of the [beta] chain,
functionally equivalent to the Glu 69 of HLA-DP (Bill et al., 2005).
Associations with BeS and CBD have also been reported with the HLA-DQ
markers (Amicosante et al., 2005; Maier et al., 2003). 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 beryllium
sensitization or CBD among individuals without the genetic risk factor.
While there remains uncertainty as to which 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 (Amicosante et al., 2002).
In addition, antibody blocking experiments revealed that anti-HLA-DP
strongly reduced proliferation responses and cytokine secretion by BAL
CD4 T cells (Chou et al., 2005). In the study by Chou (2005), anti-HLA-
DR ligand antibodies mainly affected beryllium-induced proliferation
responses with little impact on cytokines other than IL-2, thus
implying that nonproliferating BAL CD4 T cells may still contribute to
inflammation leading to the progression of CBD (Chou et al., 2005).
    TNF alpha (TNF-[alpha]) polymorphisms and TGF beta (TGF-[beta])
polymorphisms have also been shown to confer a genetic susceptibility
for developing CBD in certain individuals. TNF-[alpha] is a pro-
inflammatory cytokine associated with a more severe pulmonary disease
in CBD (NAS, 2008). Beryllium exposure has been shown to upregulate
transcription factors AP-1 and NF-[kappa]B (Sawyer et al., 2007)
inducing an inflammatory response by stimulating production of pro-
inflammatory cytokines such as TNF-[alpha] by inflammatory cells.
Polymorphisms in the 308 position of the TNF-[alpha] gene have been
demonstrated to increase production of the cytokine and increase
severity of disease (Maier et al., 2001; Saltini et al., 2001; Dotti et
al., 2004). While a study by McCanlies et al. (2007) found no
relationship between TNF-[alpha] polymorphism and BeS or CBD, the
inconsistency may be due to misclassification, exposure differences or
statistical power (NAS, 2008).
    Other genetic variations have been shown to be associated with
increased risk of beryllium sensitization and CBD (NAS, 2008). These
include TGF-[beta] (Gaede et al., 2005), angiotensin-1 converting
enzyme (ACE) (Newman et al., 1992; Maier et al., 1999) and an enzyme
involved in glutathione synthesis (glutamate cysteine ligase) (Bekris
et al., 2006). McCanlies et al. (2010) evaluated the association
between polymorphisms in a select group of interleukin genes (IL-1A;
IL-1B, IL-1RN, IL-2, IL-9, IL-9R) due to their role in immune and
inflammatory processes. The study evaluated SNPs in three groups of
workers from large beryllium manufacturing facilities in OH and AZ. The
investigators found a significant association between variants IL-1A-
1142, IL-1A-3769 and IL-1A-4697 and CBD but not with beryllium
sensitization. However, these still require confirmation in larger
studies (NAS, 2008).
    In addition to the genetic factors which may contribute to the
susceptibility and severity of disease, other factors such as smoking
and gender may play a role in the development of CBD (NAS, 2008). A
recent longitudinal cohort study by Mroz et al. (2009) of 229
individuals identified with beryllium sensitization or CBD through
workplace medical surveillance found that the prevalence of CBD among
ever smokers was significantly lower than among never smokers (38.1
percent versus 49.4 percent, p=0.025). BeS subjects that never smoked
were found to be more likely to develop CBD over the course of the
study compared to current smokers (12.6 percent versus 6.4 percent,
p=0.10). The authors suggested smoking may confer a protective effect
against development of lung granulomas as has been demonstrated with
hypersensitivity pneumonitis (Mroz et al., 2009).
4. Beryllium Sensitization 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 referred to as the LTT
(Lymphocyte Transformation Test) or BeLT (Beryllium Lymphocyte
Transformation Test). In this test, lymphocytes obtained from either
bronchoalveolar lavage fluid (the BAL BeLPT) or from peripheral blood
(the blood BeLPT) are cultured in vitro and exposed to beryllium
sulfate to stimulate lymphocyte proliferation. The observation of
beryllium-specific proliferation indicates beryllium sensitization.
Hereafter, ``BeLPT'' generally refers to the blood BeLPT, which is
typically used in screening for beryllium sensitization. This test is
described in more detail in subsection D.5.b.
    CBD can be detected at an asymptomatic 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 flexible fiberoptic
instrument known as a bronchoscope, removing the fluid and analyzing
the content for the inclusion of immune cells reactive to 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, 31-49
percent of them were diagnosed with CBD (Kreiss et al., 1993; Newman et
al., 1996, 2005, 2007; Mroz, 2009), however some estimate that with
increased surveillance the percent could be much higher (Newman, 2005;
Mroz, 2009). It has been estimated from ongoing surveillance studies of
sensitized individuals with an average follow-up time of 4.5 years that
31 percent of beryllium-sensitized 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 employed 10 years or more developed CBD (Stange et al., 2001).
One limitation for all these studies is lack of long-term follow-up. It
may be necessary to continue to monitor these workers in order to
determine whether all BeS workers will develop CBD (Newman et al.,
2005).
    CBD has a clinical spectrum ranging from evidence of beryllium
sensitization and granulomas in the lung with little symptomatology 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 are the standard treatment (NAS,
2008). No comprehensive studies have been published measuring the
overall effect of removal of workers from beryllium exposure on
sensitization and CBD (NAS, 2008) although this has been suggested as
part of an overall treatment regime for CBD (Mapel et al., 2002; Sood
et al., 2004; Maier et al., 2006; Sood, 2009; Maier et al., 2012). Sood
et al. reported that cessation of exposure can sometimes have
beneficial effects on lung function (Sood et al., 2004). However, this
was based on anecdotal evidence from six patients with CBD, so more
research is needed to better determine the relationship between

exposure duration and disease progression
5. Human Epidemiological Studies
    This section describes the human epidemiological data supporting
the mechanistic overview of beryllium-induced disease in workers. It
has been 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 beryllium sensitization
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 has been further divided by manufacturing
processes that may have similar exposure profiles. Table A.1 in the
Appendix summarizes the prevalence of beryllium sensitization and CBD,
range of exposure measurements, and other salient information from the
key epidemiological studies.
    It has been well-established that beryllium exposure, either via
inhalation or skin, may lead to beryllium sensitization, or, with
inhalation exposure, may lead to the onset and progression of CBD. The
available published epidemiological literature discussed below provides
strong evidence of beryllium sensitization and CBD in workers exposed
to airborne beryllium well below the current OSHA PEL of 2 [mu]g/m\3\.
Several studies demonstrate the prevalence of sensitization 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), 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 beryllium sensitization also may be related to
dermal exposure. An increased risk of CBD has been reported in workers
with skin lesions, potentially increasing the uptake of beryllium
(Curtis, 1951; Johnson et al., 2001; Schuler et al., 2005). Three
studies describe comprehensive preventive programs, which included
expanded respiratory protection, dermal protection, and improved
control of beryllium dust migration, that substantially reduced the
rate of beryllium sensitization among new hires (Cummings et al., 2007;
Thomas et al., 2009; Bailey et al., 2010; Schuler et al., 2012).
    Some of the epidemiological studies presented in this review suffer
from challenges common to many published epidemiological studies:
Limitations in study design (particularly cross-sectional); small
sample size; lack of personal and/or short-term exposure data,
particularly those published before the late 1990s; and incomplete
information regarding specific chemical form and/or particle
characterization. Challenges that are specific to beryllium
epidemiological studies include: uncertainty regarding the contribution
of dermal exposure; use of various BeLPT protocols; a variety of case
definitions for determining CBD; and use of various exposure sampling/
assessment methods (e.g., daily weighted average (DWA), lapel
sampling). Even with these limitations, the epidemiological evidence
presented in this section clearly demonstrates that beryllium
sensitization and CBD are continuing to occur from present-day
exposures below OSHA's PEL. The available literature also indicates
that the rate of BeS can be substantially lowered by reducing
inhalation exposure and minimizing dermal contact.
a. 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 non-occupational 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.
Patient entry into the BCR required 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); or any
three of the six criteria listed below (Hasan and Kazemi, 1974).
Patients identified using the above criteria were registered and added
to the BCR from 1952 through 1983 (Eisenbud and Lisson, 1983).
    The BCR listed the following criteria for diagnosing CBD (Eisenbud
and Lisson, 1983):
    (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.
    Prevalence of CBD in workers during the time period between the
1940s and 1950s was estimated to be between 1-10% (Eisenbud and Lisson,
1983). In a 1969 study, Stoeckle et al. presented 60 case histories
with a selective literature review utilizing the above criteria except
that urinary beryllium was substituted for lung beryllium to
demonstrate beryllium exposure. Stoeckle et al. (1969) were able to
demonstrate corticosteroids as a successful treatment option in one
case of confirmed CBD. This study also presented a 28 percent mortality
rate from complications of CBD at the time of publication. However,
even with the improved methodology for determining CBD based on the BCR
criteria, these studies suffered from lack of well-defined cohorts,
modern diagnostic techniques or adequate follow-up.
b. Criteria for Beryllium Sensitization and CBD Case Definition
Following the Development of the BeLPT
    The criteria for diagnosis of CBD have evolved over time as more
advanced

diagnostic technology, such as the (blood) BeLPT and BAL BeLPT, 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 beryllium sensitization. The
BeLPT measures the degree to which beryllium stimulates lymphocyte
proliferation 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 (Haley et al., 1994).
    Screenings for beryllium sensitization 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.,
confirmed positive) if the abnormal result was repeated.
    There has been criticism regarding the reliability and specificity
of the BeLPT as a screening tool (Borak et al., 2006). Stange et al.
(2004) studied the reliability and laboratory variability of the BeLPT
by splitting blood samples and sending samples to two laboratories
simultaneously for BeLPT analysis. Stange et al. found the range of
agreement on abnormal (positive BeLPT) results was 26.2--61.8 percent
depending upon the labs tested (Stange et al., 2004). Borak et al.
(2006) contended that the positive predictive value (PPV) (PPV is the
portion of patients with positive test result correctly diagnosed) is
not high enough to meet the criteria of a good screening tool.
Middleton et al. (2008) used the data from the Stange et al. (2004)
study to estimate the PPV and determined that the PPV of the BeLPT
could be improved from 0.383 to 0.968 when an abnormal BeLPT result is
confirmed with a second abnormal result (Middleton et al., 2008).
However, an apparent false positive can occur in people not
occupationally exposed to beryllium (NAS, 2008). An analysis of survey
data from the general workforce and new employees at a beryllium
manufacturer was performed to assess the reliability of the BeLPT
(Donovan et al. 2007). Donovan et al. analyzed more than 10,000 test
results from nearly 2400 participants over a 12-year period. Donovan et
al. found that approximately 2 percent of new employees had at least
one positive BeLPT at the time of hire and 1 percent of new hires with
no known occupational exposure were confirmed positive at the time of
hire with two BeLPTs. Since there are currently no alternatives to the
BeLPT in a screening program many programs rely on a second test to
confirm a positive result (NAS, 2008).
    The epidemiological studies presented in this section utilized the
BeLPT as either a surveillance tool or a screening tool for determining
sensitization status and/or sensitization/CBD prevalence in workers for
inclusion in the published studies. Most epidemiological studies have
reported rates of sensitization 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
sensitization over several years (Newman et al., 2001, Stange et al.,
2001). OSHA regards the BeLPT as a reliable medical surveillance tool.
The BeLPT is discussed in more detail in Non-Mandatory Appendix A to
the proposed standard, Immunological Testing for the Determination of
Beryllium Sensitization.
c. 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, beryllium hydroxide (NAS 2008) or
beryllium oxide (Stefaniak et al., 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 surveyed for sensitization with the BeLPT,
three were identified as sensitized by an abnormal BeLPT result. One of
those found to be sensitized was diagnosed with CBD. Exposures at the
facility included primarily beryllium ore and salts. 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 [mu]g/m\3\.
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. A study by Stefaniak et al. (2008)
demonstrated that beryllium was present at the mill in three forms:
mineral, poorly crystalline oxide, and hydroxide.
    There was no sensitization 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.
d. 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.
    The authors characterized exposures at the plant using industrial
hygiene (IH) samples collected between 1980 and 1993. The exposure
samples and the plant's formulas for estimating workers' DWA exposures
were used, together with study participants' work histories, to
estimate their cumulative and average beryllium exposure levels.
Exposure concentrations reflected the high exposures found historically
in beryllium production and processing. Short-term BZ measurements had
a median of 1.4, with 18.5 percent of samples exceeding OSHA's STEL of
5.0 [mu]g/m\3\. Particularly high beryllium concentrations were
reported in the areas of beryllium powder production, laundry, alloy
arc furnace (approximately 40 percent of DWA estimates over 2.0 [mu]g/
m\3\) and furnace rebuild (28.6 percent of short-term BZ samples over
the OSHA STEL of 5 [mu]g/m\3\). LP samples (n = 179), which were
available from 1990 to 1992, had a median value of 1 [mu]g/m\3\.
    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 of the 50 initial workers with
abnormal results declined to participate), 24 workers were diagnosed
with CBD based on evidence of granulomas on lung biopsy (20 workers) or
on other findings consistent with CBD (4 workers) (Kreiss et al.,
1997). 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 sensitization
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 [mu]m in diameter as defined by the authors) and
alveolar-deposited (e.g., particles <1 [mu]m in diameter as defined by
the authors) 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
sensitization 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 sensitization than the
total mass concentration of airborne beryllium.
    Bailey et al. (2010) evaluated the effectiveness of a workplace
preventive program in lowering BeS at the beryllium metal, oxide, and
alloy production plant studied by Kreiss et al. (1997). The preventive
program included use of administrative and PPE controls (e.g., improved
training, skin protection and other PPE, half-mask or air-purified
respirators, medical surveillance, improved housekeeping standards,
clean uniforms) as well as engineering controls (e.g., migration
controls, physical separation of administrative offices from production
facilities) implemented over the course of five years.
    In a cross-sectional/longitudinal hybrid study, Bailey et al.
compared rates of sensitization in pre-program workers to those hired
after the preventive program began. Pre-program workers were surveyed
cross-sectionally in 1993-1994, and again in 1999 using the BeLPT to
determine sensitization and CBD prevalence rates. The 1999 cross-
sectional survey was conducted to determine if improvements in
engineering and administrative controls were successful, however,
results indicated no improvement in reducing rates of sensitization or
CBD.
    An enhanced preventive program including particle migration
control, respiratory and dermal protection, and process enclosure was
implemented in 2000, with continuing improvements made to the program
in 2001, 2002-2004, and 2005. Workers hired during this period were
longitudinally surveyed for sensitization using the BeLPT. Both the
pre-program and program survey of worker sensitization status utilized
split-sample testing to verify positive test results using the BeLPT.
Of the total 660 workers employed at the production plant, 258 workers
participated from the pre-program group while 290 participated from the
program group (206 partial program, 84 full program). Prevalence
comparisons of the pre-program and

program groups (partial and full) were performed by calculating
prevalence ratios. A 95 percent confidence interval (95 percent CI) was
derived using a cohort study method that accounted for the variance in
survey techniques (cross-sectional versus longitudinal) (Bailey et al.,
2010). The sensitization prevalence of the pre-program group was 3.8
times higher (95 percent CI, 1.5-9.3) than the program group, 4.0 times
higher (95 percent CI, 1.4-11.6) than the partial program subgroup, and
3.3 times higher (95 percent CI, 0.8-13.7) than the full program
subgroup indicating that a comprehensive preventive program can reduce,
but not eliminate, occurrence of sensitization among non-sensitized
workers (Bailey et al., 2010).
    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 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.
    Rosenman et al. used the plant's DWA formulas to assess workers'
full-shift exposure levels, based on IH data collected between 1957-
1962 and 1971-1976, to calculate exposure metrics including cumulative,
average, and peak for each worker in the study. The DWA was calculated
based on air monitoring that consisted of GA and short-term task-based
BZ samples. Workers' exposures to specific chemical and physical forms
of beryllium were assessed, including insoluble beryllium (metal and
oxide), soluble beryllium (fluoride and hydroxide), mixed soluble and
insoluble beryllium, beryllium dust (metal, hydroxide, or oxide), fume
(fluoride), and mixed dust and fume. Use of respiratory or dermal
protection by workers was not reported. Exposures in the plant were
high overall. Representative task-based IH samples ranged from 0.9 [mu]
g/m\3\ to 84 [mu] g/m\3\ in the 1960s, falling to a range of 0.5-16.7
[mu] g/m\3\ in the 1970s. A large number of workers' mean DWA estimates
(25 percent) were above the OSHA PEL of 2.0 [mu] g/m\3\, while most
workers had mean DWA exposures between 0.2 and 2.0 [mu] g/m\3\ (74
percent) or below 0.02 [mu] g/m\3\ (1 percent) (Rosenman et al., Table
11; revised erratum April, 2006).
    Blood samples for the BeLPT were collected from the former workers
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-BeLPT or
confirmed positive BeLPT and radiographic 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.
    The authors reported a total prevalence of 14.5 percent for CBD
(definite and probable) and sensitization. This rate, considerably
higher than the overall prevalence of sensitization and disease in
several other worker cohorts as described earlier in this section,
reflects in part the very high exposures experienced by many workers
during the plant's operation in the 1950s, 1960s and 1970s. A total of
115 workers had mean DWAs above the OSHA PEL of 2 [mu] g/m\3\. Of
those, 7 (6.0 percent) had definite or probable CBD and another 13 (11
percent) were classified as sensitized without disease. The true
prevalence of 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,
sensitization and CBD also were observed within the small subgroup of
participants believed to have relatively low beryllium exposures.
Thirty-three cases of CBD and 24 additional cases of sensitization
occurred among 339 workers with mean DWA exposures below OSHA's PEL of
2.0 [mu] g/m\3\ (Rosenman et al., Table 11, erratum 2006). Ten cases of
sensitization and five cases of CBD were found among office and
clerical workers, who were believed to have low exposures (levels not
reported).
    Follow-up time for sensitization screening of 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, sensitization only, and no disease or sensitization
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 sensitization to CBD is related to the level or
extent of exposure a worker experiences. The risk of developing CBD
following sensitization 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 sensitization 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 sensitization 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.
    A follow-up was conducted of the cross-sectional study of a
population of workers first evaluated by Kreiss et al. (1997) and
Rosenman et al. (2005) at a beryllium production and processing
facility in eastern Pennsylvania by Schuler et al. (2012), and in a
companion study by Virji et al. (2012). Schuler et al. evaluated the
worker population employed in 1999 with six years or less work tenure
in a cross-sectional study. The investigators evaluated the worker
population by administering a work history questionnaire with a follow-
up examination for sensitization and CBD. A job-exposure matrix (JEM)
was combined with work histories to create individual estimates of
average, cumulative, and highest-job-related exposure for total,
respirable, and sub-micron beryllium mass concentration. Of the 291
eligible workers, 90.7 percent (264) participated in the study.
Sensitization prevalence was 9.8 percent (26/264) with CBD prevalence
of 2.3 percent (6/264). The investigators found a general pattern of
increasing sensitization prevalence as the exposure quartile increased
indicating an exposure-response relationship. The investigators found
positive associations with both total and respirable mass concentration
with sensitization (average and highest job) and CBD (cumulative).
Increased sensitization prevalence was observed with metal oxide
production alloy melting and casting, and maintenance. CBD was
associated with melting and casting. The investigators summarized that
both total and respirable mass concentration were relevant predictors
of risk (Schuler et al., 2012).
    In the companion study by Virji et al. (2012), the investigators
reconstructed historical exposure from 1994 to 1999 utilizing the
personal sampling data collected in 1999 as baseline exposure estimates
(BEE). The study evaluated techniques for reconstructing historical
data to evaluate exposure-response relationships for epidemiological
studies. The investigators constructed JEMs using the BEE and estimates
of annual changes in exposure for 25 different process areas. The
investigators concluded these reconstructed JEMs could be used to
evaluate a range of exposure parameters from total, respirable and
submicron mass concentration including cumulative, average, and highest
exposure. These two studies demonstrate that high-quality exposure
estimates can be developed both for total mass and respirable mass
concentrations.
e. 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 et
al., 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 beryllium
sensitization 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 sensititization 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 two-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).
    Kelleher et al. performed a nested case-control study of the 235
workers evaluated in Newman et al. (2001) to evaluate the relationship
between beryllium exposure levels and risk of sensitization and CBD
(Kelleher et al., 2001). The authors evaluated exposures at the plant
using IH samples they had collected between 1996 and 1999, using
personal cascade impactors designed to measure the mass of beryllium
particles less than 6 [mu] m, particles less than 1 [mu]m in diameter,
and total mass. The great majority of workers' exposures were below the
OSHA PEL of 2 [mu] g/m\3\. However, a few higher levels were observed
in machining jobs including deburring, lathing, 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.
    Twenty workers with beryllium sensitization or CBD (cases) were
compared to 206 workers (controls) for the case-control analysis from
the study evaluating workers originally conducted by Newman et al.
Thirteen 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, thus twenty composing the case
group. Nine of the remaining 215 workers first identified in original
study (Newman et al., 2001) were

excluded due to incomplete job history information, leaving 206 workers
in the control group.
    Kelleher et al.'s analysis included comparisons of the case and
control groups' median exposure levels; calculation of odds ratios for
workers in high, medium, and low exposure groups; and logistic
regression testing of the association of sensitization or CBD with
exposure level and other variables. Median cumulative exposures for
total mass, particles <6 [mu] m, and particles <1 [mu]m 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 sensitization
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 sensitization or disease risk.
    Citing an 11.5 percent prevalence of beryllium sensitization or CBD
among machinists as compared with 2.9 percent prevalence among workers
with no machinist work history, the authors concluded that the risk of
sensitization and CBD is increased among workers who machine beryllium.
Although differences between cases and controls in median cumulative
exposure did not achieve conventional thresholds for statistical
significance, the authors noted that cumulative exposures were
consistently higher among cases than controls for all categories of
exposure estimates and for all particle sizes, suggesting an effect of
cumulative exposure on risk. The levels at which workers developed CBD
and sensitization were predominantly below OSHA's current PEL of 2 [mu]
g/m\3\, and no cases of sensitization or CBD were observed among
workers with LTW exposure <0.02 [mu]g/m\3\. Twelve (60 percent) of the
20 sensitized workers had LTW exposures > 0.20 [mu] g/m\3\.
    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.
    Based on their estimates of workers' upper level exposures, Madl et
al. concluded that workers with sensitization or CBD were likely to
have been exposed to airborne beryllium levels greater than 0.2 [mu]g/
m\3\ as an 8-hour TWA at some point in their history of employment in
the plant. They also concluded that most sensitization and CBD cases
were likely to have been exposed to levels greater than 0.4 [mu]g/m\3\
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
sensitization 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). Because CBD is an
immunological disease and beryllium sensitization 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 sensitization 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).
f. 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 had not
previously been 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;
these workers were also 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 screening population) 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.
    Kreiss et al. later published a study of workers at a second
ceramics plant located in Tucson, AZ (Kreiss et al., 1996), which since
1980 had produced beryllium ceramics from beryllium oxide powder
manufactured elsewhere. IH measurements collected between 1981 and
1992, primarily GA or short-term BZ samples and a few (<100) LP
samples, were available from the plant. Airborne beryllium exposures
were generally low. The majority of area samples were below the
analytical detection limit of 0.1 [mu]g/m\3\, while LP and short-term
BZ samples had medians of 0.3 [mu]g/m\3\. However, 3.6 percent of
short-term BZ samples and 0.7 percent of GA samples exceeded 5.0 [mu]g/
mg\3\, while LP samples ranged from 0.1 to 1.8 [mu]g/m\3\. 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 [mu]g/m\3\ vs. 0.3 [mu]g/mg\3\, 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/m\3\ and the
median average exposure was 0.35 [mu]g/m\3\.
    One hundred thirty-six of the 139 workers employed at the plant at
the time of the Kreiss et al. (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 sensitization 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 sensitization 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
study of the same ceramics plant 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 [mu]g/m\3\ (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 et
al.), or who had participated and were not found to have sensitization
or disease (``long-term workers''--77 of those studied by Henneberger
et al.).
    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 [mu]g/m\3\;
mean--14.9 [mu]g/m\3\) than the short-term workers, who were hired
after 1992 (median 0.28 [mu]g/m\3\, mean 6.1 [mu]g/m\3\).
    Fifteen cases of sensitization 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 non-sensitized long-term worker
and one sensitized long-term worker declined clinical examination.
    Henneberger et al. reported a higher prevalence of sensitization
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 sensitization (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.
    The cumulative incidence of sensitization and CBD was investigated
in a cohort of 136 workers at the beryllium ceramics plant previously
studied by the Kreiss and Henneberger groups (Schuler et al., 2008).
The study cohort consisted of those who participated in the plant-wide
BeLPT screening in 1992. Both current and former workers from this
group were invited to participate in follow-up BeLPT screenings in
1998, 2000, and 2002-03. A total of 106 of the 128 non-sensitized
individuals in 1992 participated in the 11-year follow-up.
Sensitization was defined as a confirmed abnormal BeLPT based on the
split blood sample-dual laboratory protocol described earlier. CBD was
diagnosed in sensitized individuals based on pathological findings from
transbronchial biopsy and BAL fluid analysis. The 11-year crude
cumulative incidence of sensitization and CBD was 13 percent (14 of
106) and 8 percent (9 of 106) respectively. The cumulative prevalence
was about triple the point prevalences determined in the initial 1992
cross-sectional survey. The corrected cumulative prevalences for those
that ever worked in machining were nearly twice that for non-
machinists. The data illustrate the value of longitudinal medical
screening over time to obtain a more accurate estimate of the
occurrence of sensitization and CBD among an exposed working
population.
    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 [mu]g/m\3\, 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 estimated an incidence rate (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.
g. 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, and 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.
    Schuler et al. evaluated airborne beryllium levels at the plant
using IH samples collected between 1969 and 2000, including 4,524 GA
samples, 650 LP samples and 815 short-duration (3-5 min) high volume
(SD-HV) BZ task-specific samples. Occupational exposures to airborne
beryllium were generally low. Ninety-nine percent of all LP
measurements were below the current OSHA PEL of 2.0 [mu]g/m\3\ (8-hr
TWA); 93 percent were below the DOE action level of 0.2 [mu]g/m\3\; and
the median value was 0.02 [mu]g/m\3\. The SD-HV BZ samples had a median
value of 0.44 [mu]g/m\3\, with 90 percent below the OSHA Short-Term
Exposure Limit (STEL) of 5.0 [mu]g/m\3\. 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 [mu]g/m\3\ (median 0.12 [mu]g/m\3\;
range 0.01-7.8 [mu]g/m\3\) (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 [mu]g/m\3\), in
production support jobs (median 0.02, range <0.01-0.33 [mu]g/m\3\),
plant administration (median 0.02, range <0.01-0.11 [mu]g/m\3\), and
office administration jobs (median 0.01, range <0.01-0.06 [mu]g/m\3\).
    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;