mist at the impact point where material is broken and crushed.
Jackhammers retrofitted with a focused water mist aimed at the tip of
the blade offer a dramatic decrease in silica exposure. Although water-
fed jackhammers are not commercially available, it is neither expensive
nor difficult to retrofit equipment. Studies suggest that a water flow
rate of \1/8\ to \1/4\ gallon per minute is best for silica dust
control. At this rate, about 7.5 to 15 gallons of water per hour would
be applied to (i.e., sprayed on) the work area. It is unclear whether
this quantity of water applied to a moveable work area at a constant
rate would produce a runoff. If the work were in sufficient proximity
to a storm drain or surface water, the contractor might need to use a
simple barrier to prevent the water from entering the drain, or filter
it. Because the volume of water is relatively small, the costs for such
barriers are likely insubstantial. However, because this type of runoff
could happen occasionally, OSHA has added costs for barriers in costing
silica controls for this task.
    As a result of this review, OSHA has made a determination that the
silica proposal would have little potential impact on air, water, or
soil quality; plant or animal life; the use of land; or aspects of the
external environment. As described above in this section, effective
abatement measures are available where the potential for environmental
impacts exist. Therefore, OSHA preliminarily concludes that the
proposed standard would have no significant environmental impacts.
However, while the Agency does not believe that the proposed rule would
create significant costs, or otherwise pose a significant challenge,
for employers to comply with existing environmental rules, OSHA
welcomes comment on this or any other environmentally related issues,
or potential conflicts with other agency rules.

XV. Public Participation

    OSHA encourages members of the public to participate in this
rulemaking by submitting comments on the proposal and by providing oral
testimony and documentary evidence at the informal public hearings that
the Agency will convene after the comment period ends. The Agency
invites interested persons having knowledge of, or experience with,
occupational exposure to silica and the issues raised by the proposed
rule to participate in this process, and welcomes any

pertinent data and information that will provide it with the best
available evidence on which to develop the final regulatory
requirements.
    The Agency has scheduled time during the informal rulemaking
hearing in Washington, DC, for participants to testify on the Health
Effects Literature Review and Preliminary Quantitative Risk Assessment
in the presence of peer reviewers. Peer reviewers will subsequently be
able to submit amended final comments to the record. As described in
OSHA's peer review agenda, peer reviewers have reviewed OSHA's draft
Health Effects Literature Review and Preliminary Quantitative Risk
Assessment and have submitted written reports that the Agency has
considered prior to publication of the proposed rule. The open comment
period and informal hearing will provide the public an opportunity to
submit information to the record that it believes will benefit the peer
review, and to testify in the presence of the reviewers. This section
describes the procedures the public must use to submit their comments
to the docket in a timely manner, and to schedule an opportunity to
deliver oral testimony and provide documentary evidence at informal
public hearings on the proposal. Comments, notices of intention to
appear, hearing testimony and documentary evidence will be available
for inspection and copying at the OSHA Docket Office. You also should
read the sections above titled DATES and ADDRESSES for additional
information on submitting comments, documents, the presence of peer
reviewers at the hearings, and requests to the Agency for consideration
in this rulemaking.
    Written Comments. OSHA invites interested persons to submit written
data, views, and arguments concerning this proposal. In particular,
OSHA encourages interested persons to comment on the issues raised in
Section I of this preamble. When submitting comments, persons must
follow the procedures specified above in the sections titled DATES and
ADDRESSES. The comments must clearly identify the provision of the
proposal you are addressing, the position taken with respect to each
issue, and the basis for that position. Comments, along with supporting
data and references, received by the end of the specified comment
period will become part of the record and will be available for public
inspection and copying at the OSHA Docket Office as well as online at
www.regulations.gov (Docket Number OSHA-2010-0034).
    Informal Public Hearings. Pursuant to section 6(b)(3) of the Act,
members of the public will have an opportunity to provide oral
testimony concerning the issues raised in this proposal at informal
public hearings. The legislative history of section 6 of the OSH Act,
as well as OSHA's regulation governing public hearings (29 CFR
1911.15), establish the purpose and procedures of informal public
hearings. Although the presiding officer of the hearing is an
administrative law judge (ALJ) and questioning of witnesses is allowed
on crucial issues, the proceeding is largely informal and essentially
legislative in purpose. Therefore, the hearing provides interested
persons with an opportunity to make oral presentations in the absence
of procedural restraints or rigid procedures that could impede or
protract the rulemaking process. The hearing is not an adjudicative
proceeding subject to the technical rules of evidence. Instead, it is
an informal administrative proceeding convened for the purpose of
gathering and clarifying information. The regulations that govern the
hearings and the prehearing guidelines issued for the hearing will
ensure that participants are treated fairly and provided due process.
This approach will facilitate the development of a clear, accurate, and
complete record. Accordingly, application of these rules and guidelines
will be such that questions of relevance, procedure, and participation
generally will be resolved in favor of developing a clear, accurate,
and complete record. Conduct of the hearing will conform to 29 CFR
1911.15. In addition, the Assistant Secretary may, on reasonable
notice, issue additional or alternative procedures to expedite the
proceedings, to provide greater procedural protections to interested
persons or to further any other good cause consistent with applicable
law (29 CFR 1911.4).
    Although the ALJ presiding over the hearing makes no decision or
recommendation on the merits of the proposal, the ALJ has the
responsibility and authority necessary to ensure the hearing progresses
at a reasonable pace and in an orderly manner. To ensure that
interested persons receive a full and fair hearing, the ALJ has the
power to regulate the course of the proceedings; dispose of procedural
requests, objections, and comparable matters; confine presentations to
matters pertinent to the issues the proposed rule raises; use
appropriate means to regulate the conduct of persons present at the
hearing; question witnesses and permit others to do so; limit the time
for such questioning; and leave the record open for a reasonable time
after the hearing for the submission of additional data, evidence,
comments and arguments (29 CFR 1911.16).
    At the close of the hearing the ALJ will establish a post-hearing
comment period for interested persons who filed a timely notice of
intention to appear at the hearing. During the first part of the post-
hearing period, those persons may submit additional data and
information to OSHA. During the second part they may submit final
briefs, arguments, and summations.
    Notice of Intention to Appear to Provide Testimony at the Informal
Public Hearing. Interested persons who intend to provide oral testimony
at the informal public hearing must file a notice of intention to
appear by using the procedures specified above in the sections titled
DATES and ADDRESSES. This notice must provide the following
information:
    Name, address, email address, and telephone number of each
individual who will give oral testimony;
    Name of the establishment or organization each individual
represents, if any;
    Occupational title and position of each individual testifying;
    Approximate amount of time required for each individual's
testimony;
    If the individual requests to present testimony related to the
Health Effects Literature Review and Preliminary Quantitative Risk
Assessment, the notice should specify if the submitter requests this
testimony be provided in the presence of peer reviewers;
    A brief statement of the position each individual will take with
respect to the issues raised by the proposed rule; and
    A brief summary of documentary evidence each individual intends to
present.
    Participants who need projectors and other special equipment for
their testimony must contact Frank Meilinger at OSHA's Office of
Communications, telephone<PHONE_NUMBER>, no later than one week before
the hearing begins.
    OSHA emphasizes that the hearings are open to the public; however,
only individuals who file a notice of intention to appear may question
witnesses and participate fully at the hearing. If time permits, and at
the discretion of the ALJ, an individual who did not file a notice of
intention to appear may be allowed to testify at the hearing, but for
no more than 10 minutes.
    Hearing testimony and documentary evidence. Individuals who request
more than 10 minutes to present their oral testimony at the hearing or
who will submit documentary evidence at the

hearing must submit (transmit, send, postmark, deliver) the full text
of their testimony and all documentary evidence no later than December
11, 2013.
    The Agency will review each submission and determine if the
information it contains warrants the amount of time the individual
requested for the presentation. If OSHA believes the requested time is
excessive, the Agency will allocate an appropriate amount of time for
the presentation. The Agency also may limit to 10 minutes the
presentation of any participant who fails to comply substantially with
these procedural requirements, and may request that the participant
return for questioning at a later time. Before the hearing, OSHA will
notify participants of the time the Agency will allow for their
presentation and, if less than requested, the reasons for its decision.
In addition, before the hearing OSHA will provide the pre-hearing
guidelines and hearing schedule to each participant.
    Certification of the hearing record and Agency final determination.
Following the close of the hearing and the post-hearing comment
periods, the ALJ will certify the record to the Assistant Secretary of
Labor for Occupational Safety and Health. The record will consist of
all of the written comments, oral testimony and documentary evidence
received during the proceeding. The ALJ, however, will not make or
recommend any decisions as to the content of the final standard.
Following certification of the record, OSHA will review all the
evidence received into the record and will issue the final rule based
on the record as a whole.

XVI. Summary and Explanation of the Standards

(a) Scope and application

    OSHA is proposing to issue one standard addressing respirable
crystalline silica exposure in general industry and maritime and a
separate standard addressing exposure in the construction industry. The
scope provisions are contained in paragraph (a) of the proposed
standards. The proposed standard for the construction industry is
similar to the proposed standard for general industry and maritime, and
the standards are intended to provide equivalent protection for all
workers while accounting for the different work activities, anticipated
exposures, and other conditions in these sectors. The limited
differences between the proposed construction and general industry/
maritime standards exist because OSHA believes, based on the record
developed to date, that certain activities in construction are
different enough to warrant modified requirements.
    The proposed standards do not cover the agricultural sector, due to
limited data on exposures and control measures in this sector. OSHA's
authority is also restricted in this area; since 1976, an annual rider
in the Agency's Congressional appropriations bill has limited OSHA's
use of funds with respect to farming operations that employ fewer than
ten workers. Consolidated Appropriations Act, 1976, Public Law 94-439,
90 Stat. 1420, 1421 (1976) (and subsequent appropriations acts).
However, some evidence indicates that certain agricultural operations
may result in exposures to respirable silica in excess of the proposed
PEL. A literature review conducted by Swanepoel et al. (2010)
identified studies that examined respirable quartz exposure and
associated diseases in agricultural settings. Three of the exposure
studies measured respirable quartz in the personal breathing zone of
workers (Popendorf et al. 1982; Archer et al. 2002; Lee et al. 2004).
Popendorf et al. (1982) investigated exposures among citrus, peach, and
grape harvesters; Archer et al. (2002) reported on farmworkers in
eastern North Carolina; and Lee et al. (2004) examined citrus and grape
harvesters in California. Each of these studies identified instances
where exposures exceeded the proposed PEL. In particular, Archer et al.
(2002) reported respirable quartz concentrations as high as 3910 [mu]g/
m\3\ among farmworkers during sweet potato transplanting. Area samples
reported in two other studies support the belief that agricultural
operations can generate high levels of respirable quartz. Gustafsson et
al. (1978) reported average respirable quartz concentrations of 2000
[mu]g/m\3\ in open tractor cabs, while Lawson et al. (1995) reported
respirable quartz concentrations ranging from 20-90 [mu]g/m\3\ during
rice farming operations. Little evidence was reported in the literature
regarding diseases associated with respirable crystalline silica
exposure in agricultural workers (Swanepoel et al., 2010). OSHA is
interested in additional evidence relating to exposures to respirable
crystalline silica that occur in agriculture and to associated control
measures, as well as information related to the development of
respirable crystalline silica-related diseases among workers in the
agricultural sector, and is requesting such information in the
``Issues'' section (Section I) of this preamble.
    In paragraph (b) (definition of ``respirable crystalline silica''),
OSHA proposes to cover quartz, cristobalite, and tridymite under the
standard. The Agency believes the evidence supports this approach. OSHA
currently has different permissible exposure limits (PELs) for
different forms of crystalline silica. The current general industry
PELs for cristobalite and tridymite are one half of the general
industry PEL for quartz. This difference was based on the fact that
early animal studies appeared to suggest that cristobalite and
tridymite were more toxic to the lung than quartz. However, as
discussed in OSHA's Review of Health Effects Literature and summarized
in Section V of this preamble, reviews of more recent studies have led
OSHA to preliminarily conclude that cristobalite and tridymite are
comparable to quartz in their toxicities. Also, a difference in
toxicity between cristobalite and quartz has not been observed in
epidemiologic studies. Exposure to tridymite has not been the subject
of epidemiologic study.
    OSHA's preliminary conclusion that quartz, cristobalite, and
tridymite should be addressed under a single standard and subject to
the same PEL is consistent with the recommendation of the National
Institute for Occupational Safety and Health (NIOSH), which has a
single Recommended Exposure Limit (REL) covering all forms of
respirable crystalline silica. In addition, the American Conference of
Governmental Industrial Hygienists (ACGIH) has issued a single
Threshold Limit Value (TLV) for quartz and cristobalite.
    In 2003, OSHA presented respirable crystalline silica draft
standards for both general industry and construction to the Small
Business Regulatory Enforcement Fairness Act (SBREFA) review panel. The
general industry scope has remained unchanged, while the SBREFA
construction draft standard included two alternative scope provisions.
The first option, which is included in the proposal, stated that the
rule applied to all construction operations covered by 29 CFR part
1926. The second option was more restrictive, indicating the rule would
apply only to abrasive blasting and other specified operations
(cutting, sanding, drilling, crushing, grinding, milling, sawing,
scabbling, scrapping, mixing, jack hammering, excavating, or disturbing
materials that contain crystalline silica). The SBREFA panel
recommended that OSHA continue to evaluate and consider modifications
to the second option that could serve to limit the scope of the
standard.

    OSHA is proposing to cover all occupational exposures to respirable
crystalline silica in construction work, as defined in 29 CFR
1910.12(b) and covered under 29 CFR part 1926, because the Agency wants
to ensure that all activities are covered by the standard if they
involve exposures that present a significant risk to workers. The
second scope option in the SBREFA draft included activities that are
typically associated with higher worker exposures to crystalline
silica, but would not cover all operations that present a significant
risk.
    Collectively, the proposed standards apply to occupational exposure
in which respirable crystalline silica is present in an occupationally
related context. Exposure of employees to the ambient environment,
which may contain small concentrations of respirable crystalline silica
unrelated to occupational activities, is not subject to the proposed
standards.

(b) Definitions

    ``Action level'' is defined as an airborne concentration of
respirable crystalline silica of 25 micrograms per cubic meter of air
(25 [mu]g/m\3\) calculated as an eight-hour time-weighted average
(TWA). The action level triggers requirements for periodic exposure
monitoring. In this proposal, as in other standards, the action level
has been set at one-half of the PEL.
    Because of the variable nature of employee exposures to airborne
concentrations of respirable crystalline silica, maintaining exposures
below the action level provides reasonable assurance that employees
will not be exposed to respirable crystalline silica at levels above
the PEL on days when no exposure measurements are made. Even when all
measurements on a given day fall below the PEL but are above the action
level, there is a reasonable chance that on another day, when exposures
are not measured, the employee's actual exposure may exceed the PEL.
Previous standards have recognized a statistical basis for using an
action level of one-half the PEL (e.g., acrylonitrile, 29 CFR
1910.1045; ethylene oxide, 29 CFR 1910.1047). In brief, OSHA previously
determined (based in part on research conducted by Leidel et al.) that
where exposure measurements are above one-half the PEL, the employer
cannot be reasonably confident that the employee is not exposed above
the PEL on days when no measurements are taken (Leidel, et al., 1975).
Therefore, requiring periodic exposure measurements when the action
level is exceeded provides employers with additional assurance that
employees are being protected from exposures above the PEL.
    As exposures are lowered, the risk of adverse health effects among
workers decreases. In addition, there is an economic benefit to
employers who reduce exposure levels below the action level: They can
avoid the costs associated with periodic exposure monitoring
requirements. Some employers will be able to reduce exposures below the
action level in all work areas, and other employers in some work areas.
    OSHA's preliminary risk assessment indicates that significant risk
remains at the proposed PEL of 50 [mu]g/m\3\. At least one court has
held that OSHA has a duty to impose additional requirements on
employers to eliminate remaining significant risk when those
requirements will afford benefits to workers and are feasible. Building
and Construction Trades Department, AFL-CIO v. Brock, 838 F.2d 1258,
1269 (D.C. Cir 1988). OSHA's preliminary conclusion is that the action
level will result in a very real and necessary further reduction in
risk beyond that provided by the PEL alone. OSHA's decision to propose
an action level of one-half of the PEL is based, in part, on the
Agency's successful experience with other standards, including those
for inorganic arsenic (29 CFR 1910.1018), ethylene oxide (29 CFR
1910.1047), benzene (29 CFR 1910.1028), and methylene chloride (29 CFR
1910.1052).
    ``Competent person'' means one who is capable of identifying
existing and predictable respirable crystalline silica hazards in the
surroundings or working conditions and who has authorization to take
prompt corrective measures to eliminate them. The competent person
concept has been broadly used in OSHA construction standards,
particularly in safety standards. In OSHA shipyard standards, a defined
role for the competent person focuses on confined space hazards, hot
work, and explosive environments. Competent person requirements also
apply to powder actuated tools. It is not the intent of this proposal
to modify the existing competent person requirements in shipyard
standards.
    As explained below in section (e) (Regulated areas and access
control), employers have the option to develop a written access control
plan in lieu of establishing regulated areas to minimize exposures to
employees not directly involved in operations that generate respirable
crystalline silica in excess of the PEL. The access control plan would
require that a competent person identify areas where respirable
crystalline silica exposures are, or can reasonably be expected to be,
in excess of the PEL.
    The proposed standard does not specify particular training
requirements for competent persons. Rather, the requirement for a
competent person is performance-based; the competent person must be
capable of effectively performing the duties assigned under the
standard. Therefore, the competent person must have the knowledge and
experience necessary to identify in advance tasks or operations during
which exposures are reasonably expected to exceed the PEL, so that
affected employees can be notified of the presence and location of
areas where such exposures may occur, and the employer can take steps
to limit access to these areas and provide appropriate respiratory
protection.
    OSHA included more extensive competent person requirements in both
the draft general industry/maritime and construction standards
presented for review to the Small Business Regulatory Enforcement
Fairness Act (SBREFA) review panel. The SBREFA draft standards included
requirements for a competent person at each worksite to ensure
compliance with the provisions of the standard. Specifically, the
SBREFA draft standards required that the competent person: Evaluate
workplace exposures and the effectiveness of controls, and implement
corrective measures to ensure that employees are not exposed in excess
of the PEL; establish regulated areas wherever the airborne
concentration of respirable crystalline silica exceeds or can
reasonably be expected to exceed the PEL, taking into consideration
factors that could affect exposures such as wind direction, changes in
work processes, and proximity to other workplace operations; and check
the regulated area daily to ensure the boundary is maintained. The
SBREFA draft standards also required the employer to ensure that the
competent person inspect abrasive blasting activities as necessary to
ensure that controls are being properly used and remain effective;
participate in the evaluation of alternative blast media; and
communicate with other employers to inform them of the boundaries of
regulated areas established around abrasive blasting operations.
    Many small entity representatives (SERs) from the construction
industry who reviewed the SBREFA draft standard found the requirements
for a competent person hard to understand (OSHA, 2003). Many believed
that the competent person required a high skill level, while others
thought that a large proportion of their employees would

need to be trained. SERs thought that the requirements would be
difficult to comply with and costly. These concerns may have been due
to the specific regulatory language used in the SBREFA draft, rather
than the general concept of competent person requirements. OSHA's
Advisory Committee on Construction Safety and Health recommended that
the Agency retain the requirement and responsibilities for a competent
person in the proposed rule (ACCSH, 2009). The Building and
Construction Trades Department, AFL-CIO has also consistently
recommended including competent person requirements in a proposed
silica standard.
    OSHA has proposed limited competent person requirements because the
Agency has preliminarily concluded that the provisions of the proposed
standard will generally be effective without the involvement of an
individual specifically designated as a competent person. For example,
the proposed standard requires that the employer use engineering and
work practice controls to reduce and maintain employee exposure to
respirable crystalline silica to or below the PEL. OSHA believes that
this provision adequately communicates this requirement to employers,
and that an additional requirement for a ``competent person'' to
evaluate the effectiveness of these controls and implement corrective
measures in this standard is not necessary. However, the Agency is
aware that competent person requirements have been included in other
health and safety standards, and that some parties believe such
requirements would be useful in the silica standard. OSHA is interested
in information and comment on the appropriate role of a competent
person in the respirable crystalline silica standard, and has included
this topic in the ``Issues'' section (Section I) of this preamble.
    ``Employee exposure'' means exposure to airborne respirable
crystalline silica that would occur if the employee were not using a
respirator. This definition is included to clarify the requirement that
employee exposure be measured as if no respiratory protection were
being worn. It is consistent with OSHA's previous use of the term in
other standards.
    ``Objective data'' means information, such as air monitoring data
from industry-wide surveys or calculations based on the composition or
chemical and physical properties of a substance, demonstrating employee
exposure to respirable crystalline silica associated with a particular
product, material, process, operation, or activity. The data must
reflect workplace conditions closely resembling the processes, types of
material, control methods, work practices, and environmental conditions
in the employer's current operations. Objective data is further
discussed below in section (d) (Exposure Assessment).
    ``Physician or other licensed health care professional (PLHCP)''
means an individual whose legally permitted scope of practice (i.e.,
license, registration, or certification) allows him or her to
independently provide or be delegated the responsibility to provide
some or all of the particular health care services required by
paragraph (h) of this section. This definition is included because the
proposed standard requires that all medical examinations and procedures
be performed by or under the supervision of a PLHCP.
    Any PLHCP may perform the medical examinations and procedures
required under the standard when they are licensed, registered, or
certified by state law to do so. The Agency recognizes that this means
that the personnel qualified to provide the required medical
examinations and procedures may vary from state to state, depending on
state licensing or certification laws. This provision of the proposed
rule grants the employer the flexibility to retain the services of a
variety of qualified licensed health care professionals, provided that
these individuals are licensed to perform, or be delegated the
responsibility to perform, the specified service. OSHA believes that
this flexibility will reduce cost and compliance burdens for employers
and increase convenience for employees. The approach taken in this
proposed standard is consistent with the approach OSHA has taken in
other recent standards, such as chromium (VI) (29 CFR 1910.1026),
bloodborne pathogens (29 CFR 1910.1030), and respiratory protection (29
CFR 1910.134).
    ``Regulated area'' means an area, demarcated by the employer, where
an employee's exposure to airborne concentrations of respirable
crystalline silica exceeds, or can reasonably be expected to exceed,
the PEL. This definition is consistent with the use of the term in
other standards, including those for chromium (VI) (29 CFR 1910.1026),
1,3-butadiene (29 CFR 1910.1051), and methylene chloride (29 CFR
1910.1052).
    ``Respirable crystalline silica'' means airborne particles that
contain quartz, cristobalite, and/or tridymite and whose measurement is
determined by a sampling device designed to meet the characteristics
for respirable-particle-size-selective samplers specified in the
International Organization for Standardization (ISO) 7708:1995: Air
Quality--Particle Size Fraction Definitions for Health-Related
Sampling.
    The Agency's proposed definition for respirable crystalline silica
seeks to harmonize the Agency's practice with current aerosol science
and the ISO definition of respirable particulate mass. Thus, the
proposed definition would encompass the polymorphs of silica covered
under current OSHA standards and would be consistent with the
international consensus that the ISO definition of respirable
particulate mass represents. The American Conference of Governmental
Industrial Hygienists (ACGIH) and the European Committee for
Standardization (CEN) have adopted the ISO definition of respirable
particulate mass. The National Institute for Occupational Safety and
Health (NIOSH) has also adopted the ISO definition of respirable
particulate mass in its Manual of Sampling and Analytical Methods.
Adoption of this definition by OSHA would allow for workplace sampling
for respirable crystalline silica exposures to be conducted using any
particulate sampling device that conforms to the ISO definition (i.e.,
that collects dust according to the particle collection efficiency
curve specified in the ISO standard). OSHA's current respirable
crystalline silica PELs are measured according to a particle collection
efficiency curve formerly specified by ACGIH, which is now obsolete.
The relationship between the ISO definition of respirable particulate
mass and the ACGIH criteria is discussed in greater detail in the
Technological Feasibility chapter of the Preliminary Economic Analysis,
and is summarized in section VIII of this preamble.
    The definitions for ``Assistant Secretary,'' ``Director,'' ``High-
efficiency particulate air [HEPA] filter,'' and ``This section'' are
consistent with OSHA's previous use of these terms in other health
standards.

(c) Permissible Exposure Limit (PEL)

    In paragraph (c), OSHA proposes to set an 8-hour time-weighted
average (TWA) exposure limit of 50 micrograms of respirable crystalline
silica per cubic meter of air (50 [mu]g/m\3\). This limit means that
over the course of any 8-hour work shift, the average exposure to
respirable crystalline silica cannot exceed 50 [mu]g/m\3\. The proposed
PEL is

the same for both general industry/maritime \38\ and construction.
---------------------------------------------------------------------------

    \38\ OSHA regulates silica exposure in three maritime-related
activities: Shipyards (29 CFR 1915.1000, Table Z), Marine Terminals
(29 CFR 1917.1(a)(2)(xiii)), and Longshoring (29 CFR 1918.1(b)(9)).
Marine Terminals and Longshoring incorporate by reference the toxic
and hazardous substance requirements in subpart Z of the general
industry standard, which includes both a particle-counting formula
and a mass formula for the silica PEL (29 CFR 1910.1000, Table Z-3).
Shipyards has its own subpart Z, which uses the particle-counting
formula for the silica PEL. Thus, under the current scheme, Marine
Terminals and Longshoring use two alternative PEL formulas, while
Shipyards uses a single PEL formula. The proposal eliminates this
discrepancy by adopting a single PEL (50 [mu]g/m\3\) for all three
maritime sectors, in addition to construction and general industry.
    In this section, the Agency distinguishes between the proposed
maritime PEL (50 [mu]g/m\3\ for all three maritime sectors) and the
current shipyard PEL (the particle-counting formula required for
shipyards and construction).
---------------------------------------------------------------------------

    OSHA currently expresses the general industry PEL for respirable
crystalline silica in the form of quartz in two ways. The first, which
is based on gravimetric measurement, is derived from the formula (PEL =
(10 mg/m\3\)/(% quartz + 2) as respirable dust). This is approximately
equivalent to 100 [mu]g/m\3\ of respirable crystalline silica. The
current general industry PELs for the polymorphs cristobalite and
tridymite are one-half of the value calculated from this formula, or
approximately 50 [mu]g/m\3\ of respirable crystalline silica. The
proposed PEL is thus approximately equivalent to the current general
industry PELs for cristobalite and tridymite. In cases where exposures
to quartz, cristobalite, and/or tridymite occur at the same time, the
PEL is calculated following the procedure specified in 29 CFR
1910.1000(d)(2) for exposures to mixtures of substances having an
additive effect on the body or target organ system.
    The second way OSHA expresses the general industry PEL for
respirable crystalline silica in the form of quartz is based on a now-
obsolete particle count sampling method, and is presented in terms of
millions of particles per cubic foot (mppcf). This PEL is based on the
formula (PELmppcf = 250/(% quartz + 5) as respirable dust).
The current general industry PELs for cristobalite and tridymite are
one-half of the value calculated from this formula. These two parallel
PELs in general industry were originally believed to be equivalent
values (Ayer, 1995). However, as discussed below, the values are now
considered to differ substantially.
    The current PEL for crystalline silica in the form of quartz in
construction and shipyards (PELmppcf = 250/(% quartz + 5) as
respirable dust) is expressed only in terms of mppcf. This is the same
formula as the parallel PEL for respirable crystalline silica in the
form of quartz in general industry that is expressed in mppcf. The
Mineral Dusts tables that contain the silica PELs for construction and
shipyards do not clearly express PELs for cristobalite and tridymite.
29 CFR 1926.55; 29 CFR 1915.1000. This lack of textual clarity likely
results from a transcription error during the codification of these
rules. OSHA's current proposal provides the same PEL for quartz,
cristobalite, and tridymite, in general industry, construction, and
shipyards.
    The current PELs in general industry, construction, and shipyards
are 8-hour TWA exposure limits. Both formulas express the PEL in terms
of a permissible level of exposure to respirable dust, rather than a
permissible level of exposure to respirable crystalline silica. The
higher the percentage of crystalline silica in the sample, the lower
the level of respirable dust allowed.
    The current PELs for construction and shipyards (and the parallel
PEL presented for general industry) are based on a particle count
method long rendered obsolete by gravimetric respirable mass sampling,
which yields results reported in milligrams or micrograms per cubic
meter of air (mg/m\3\or [mu]g/m\3\). Gravimetric sampling methods are
the only methods currently available to OSHA compliance personnel.
Since the current construction and shipyard PELs are expressed only in
terms of mppcf, the results of the gravimetric sampling must be
converted to an equivalent mppcf value.
    In order to determine a formula for converting from mg/m\3\ to
mppcf, OSHA requested assistance from the National Institute for
Occupational Safety and Health (NIOSH). Based on its review of
published studies comparing the particle count and gravimetric methods,
NIOSH recommended a conversion factor of 0.1 mg/m\3\ respirable dust to
1 mppcf. OSHA has determined that this conversion factor should be
applied to silica sampling results used to characterize exposures in
construction and shipyard operations. Appendix E to CPL 03-00-007,
OSHA's National Emphasis Program for Crystalline Silica, illustrates
how the conversion factor is applied to enforce the current PEL for
crystalline silica in the construction and shipyard industries.
Applying the conversion factor to a sample consisting of pure (i.e.,
100%) crystalline silica indicates that the current PEL for
construction and shipyards is approximately equivalent to 250 [mu]g/
m\3\ of respirable crystalline silica.
    OSHA's current PELs for respirable crystalline silica are expressed
as respirable dust, or respirable particulate mass. The proposed PEL is
expressed as respirable crystalline silica, or the amount of
crystalline silica that is present as respirable particulate mass.
Respirable particulate mass refers to airborne particulate matter that
is capable of entering the gas-exchange region of the lung, where
crystalline silica particles cause pathological damage. Only very small
particles (particles of about 10 [mu]g/m or less) are able to penetrate
into the gas-exchange region of the lung. As particle size decreases,
the relative proportion of particles that is expected to reach the gas-
exchange region of the lung increases.
    Under the proposed definition of respirable crystalline silica in
paragraph (b), respirable crystalline silica means airborne particles
that contain quartz, cristobalite, and tridymite and whose measurement
is determined by a sampling device designed to meet the characteristics
for particle-size-selective samplers specified in International
Organization for Standardization (ISO) 7708:1995: Air Quality--Particle
Size Fraction Definitions for Health-Related Sampling. This definition
of respirable particulate mass is intended to correspond with airborne
particulate matter that is capable of entering the gas-exchange region
of the lung. It provides a formula for determining the respirable
fraction based on the aerodynamic diameter of the particles, and
represents an international consensus that has been adopted by the
American Conference of Governmental Industrial Hygienists (ACGIH) and
the European Committee for Standardization (CEN). The ISO definition is
also used by the National Institute for Occupational Safety and Health
(NIOSH) in its Manual of Sampling and Analytical Methods. The ISO
definition of respirable particulate mass is discussed in greater
detail in the Technological Feasibility chapter of the Preliminary
Economic Analysis.
    OSHA currently has a PEL for exposure to total quartz dust (PEL =
(30 mg/m\3\)/(% quartz + 2) as total dust) in general industry. As with
the PEL for respirable dust, the PELs for cristobalite and tridymite
are one-half of the value calculated from this formula. The Agency does
not have a PEL for exposure to total quartz dust for construction or
shipyards. OSHA proposes to delete the PELs for exposure to total
crystalline silica dust, because the Review of Health Effects
Literature and Preliminary Quantitative Risk Assessment clearly relates
development

of crystalline silica-related disease to respirable, rather than total,
dust exposure. This view is consistent with ACGIH, which no longer has
a TLV for total crystalline silica dust. NIOSH does not have a
Recommended Exposure Level for total crystalline silica exposure, and
neither the National Toxicology Program nor the International Agency
for Research on Cancer has linked exposure to total crystalline silica
dust exposure to cancer, as they have with respirable crystalline
silica exposure.
    OSHA proposes a new PEL of 50 [mu]g/m\3\ because the Agency has
preliminarily determined that occupational exposure to respirable
crystalline silica at the current PEL results in a significant risk of
material health impairment among exposed workers, and that compliance
with the proposed standard will substantially reduce that risk. OSHA's
Preliminary Quantitative Risk Assessment, summarized in Section VI of
this preamble, indicates that a 45-year exposure to respirable
crystalline silica at the current general industry PEL would lead to
between 13 and 60 excess deaths from lung cancer, 9 deaths from
silicosis, 83 deaths from all forms of non-malignant respiratory
disease (including silicosis), and 39 deaths from renal disease per
1000 workers. Exposures at the current construction and shipyard PEL
would result in even higher levels of risk. As discussed in Section VII
of this preamble, these results clearly represent a risk of material
impairment of health that is significant within the context of the
``Benzene'' decision. Indus. Union Dep't, AFL-CIO v. Am. Petroleum
Inst., 448 U.S. 607 (1980). OSHA believes that lowering the PEL to 50
[mu]g/m\3\ would reduce the lifetime excess risk of death per 1000
workers to between 6 and 26 deaths from lung cancer, 7 deaths from
silicosis, 43 deaths from all forms of non-malignant respiratory
disease (including silicosis), and 32 deaths from renal disease.
    OSHA considers the level of risk remaining at the proposed PEL to
be significant. However, the proposed PEL is set at the lowest level
that the Agency believes to be technologically feasible. As discussed
in the Technological Feasibility chapter of the Preliminary Economic
Analysis and summarized in section VIII of this preamble, OSHA's
analysis indicates that exposures at the proposed PEL can be measured
with a reasonable degree of precision and accuracy. In addition, the
analysis presented in the Technological Feasibility chapter of the
Preliminary Economic Analysis makes clear that many industries and
operations could not achieve an alternative PEL of 25 [mu]g/m\3\ with
engineering and work practice controls alone. As guided by the 1988
``Asbestos'' decision (Bldg & Constr. Trades Dep't v. Brock, 838 F.2d
1258, 1266 (DC Cir. 1988)), OSHA is proposing additional requirements
to further reduce the remaining risk. OSHA anticipates that the
ancillary provisions in the proposed standard, including requirements
for regulated areas and medical surveillance, will further reduce the
risk beyond the reduction that would be achieved by the proposed PEL
alone. OSHA also believes that a new PEL, expressed as a gravimetric
measurement of respirable crystalline silica, will improve compliance
because the PEL is simple and relatively easy to understand. In
comparison, the existing PELs require application of a formula to
account for the crystalline silica content of the dust sampled and, in
the case of the construction and shipyard PELs, a conversion of mppcf
to mg/m\3\ as well.
    OSHA believes that it is appropriate to establish a single PEL that
applies to respirable quartz, cristobalite, and tridymite. As explained
in the Review of Health Effects Literature and Preliminary Quantitative
Risk Assessment (see sections V and VI of this preamble for summaries),
research indicates that certain physical factors may affect the
toxicologic potency of crystalline silica. These factors include
particle surface characteristics, the age of fractured surfaces of the
crystal particle, the presence of impurities on particle surfaces, and
coating of the particle. These factors may vary among different
workplace settings, suggesting that the risk to workers exposed to a
given level of respirable crystalline silica may not be equivalent in
different work environments. The Agency's Quantitative Risk Assessment,
summarized in section VI of this preamble, relies on studies involving
a range of work environments; from study to study, workers' exposures
to respirable crystalline silica varied in terms of particle age,
surface impurities, and particle coatings. While the risk estimates
that OSHA derived using data from different work environments are
somewhat dissimilar, and these differences may be due in part to
variations in particle toxicity, all of OSHA's risk estimates indicate
significant risk above the proposed PEL of 50 [mu]g/m\3\. Thus, while
the available evidence is not sufficient to establish precise
quantitative differences in risk based on these physical factors, the
Agency's findings of significant risk are representative of a wide
range of workplaces reflecting differences in the form of silica
present, surface properties, and impurities. OSHA is therefore
proposing a single PEL for respirable quartz, cristobalite, and
tridymite.
    OSHA currently has separate entries in 29 CFR 1910.1000 Table Z-1
for cristobalite, quartz, tripoli (as quartz), and tridymite. The
proposal would present a single entry for crystalline silica, as
respirable dust, with a cross reference to the new standard. As
discussed above, the proposed PEL applies to quartz, cristobalite, and
tridymite. Tripoli, which is extremely fine-grained crystalline silica,
is covered under the proposed PEL as quartz. Comparable revisions would
be made to 29 CFR 1915.1000 Table Z and 29 CFR 1926.55 Appendix A.

(d) Exposure Assessment

    Paragraph (d) of the proposed standard sets forth requirements for
assessing employee exposures to respirable crystalline silica. The
requirements are issued pursuant to section 6(b)(7) of the OSH Act,
which mandates that any standard promulgated under section 6(b) shall,
where appropriate, ``provide for monitoring or measuring employee
exposure at such locations and intervals, and in such manner as may be
necessary for the protection of employees.'' 29 U.S.C. 655(b)(7).
    As a general matter, monitoring of employee exposure to toxic
substances is a well-recognized and accepted risk management tool. The
purposes of requiring an assessment of employee exposures to respirable
crystalline silica include: determination of the extent and degree of
exposure at the worksite; identification and prevention of employee
overexposure; identification of the sources of exposure; collection of
exposure data so that the employer can select the proper control
methods to be used; and evaluation of the effectiveness of those
selected methods. Assessment enables employers to meet their legal
obligation to ensure that their employees are not exposed in excess of
the permissible exposure level and to ensure employees have access to
accurate information about their exposure levels, as required by
section 8(c)(3) of the Act. 29 U.S.C. 657(c)(3). In addition, the
availability of exposure data enables PLHCPs performing medical
examinations to be informed of the extent of occupational exposures.
    Paragraph (d)(1) contains proposed general requirements for
exposure assessment. The general requirements for assessing exposure to
respirable

crystalline silica in the proposed standard are similar to the
requirements contained in previous OSHA substance-specific health
standards. Except as provided for in the construction standard under
paragraph (d)(8), paragraph (d)(1)(i) requires each employer to assess
the exposure of any employees who are exposed, or may reasonably be
expected to be exposed, to respirable crystalline silica at or above
the action level. Under paragraph (d)(1)(ii), monitoring to determine
employee exposures must represent the employee's time-weighted average
exposure to airborne respirable crystalline silica over an 8-hour
workday. Samples must be taken within the employee's breathing zone
(i.e., ``personal breathing zone samples'' or ``personal samples''),
and must represent the employee's exposure without regard to the use of
respiratory protection.
    Employers must accurately characterize the exposure of each
employee to respirable crystalline silica. In some cases, this will
entail monitoring all exposed employees. In other cases, as set out in
proposed paragraph (d)(1)(iii), monitoring of ``representative''
employees is sufficient. Representative exposure sampling is permitted
when a number of employees perform essentially the same job on the same
shift and under the same conditions. For employees engaged in similar
work, it may be sufficient to monitor a fraction of these employees in
order to obtain data that are ``representative'' of the remaining
employees. Under the proposed standard, a representative sample must
include employee(s) reasonably expected to have the highest exposures.
For example, this may involve monitoring the exposure of the employee
closest to an exposure source. This exposure result may then be
attributed to the remaining employees in the group.
    Representative exposure monitoring must include at least one full-
shift sample taken for each job function in each job classification, in
each work area, for each shift. These samples must consist of either a
single sample characteristic of the entire shift or consecutive samples
taken over the length of the shift. In many cases, full-shift samples
on two or more days may be necessary to adequately characterize
exposure and obtain results that are representative of employees with
the highest exposure for each job classification. Where employees are
not performing the same job under the same conditions, representative
sampling will not adequately characterize actual exposures, and
individual monitoring is necessary.
    Paragraph (d)(2)(i) of the proposed standard requires employers to
conduct an initial exposure assessment by performing initial monitoring
of any employees who are exposed, or may reasonably be expected to be
exposed, to respirable crystalline silica at or above the action level.
Further obligations under the standard are based on the results of this
initial assessment. These may include obligations for periodic
monitoring, establishment of regulated areas, implementation of control
measures, and provision of medical surveillance.
    The proposed standard, paragraph (d)(2)(ii), provides two
exceptions to the requirement to conduct initial exposure monitoring.
First, under paragraph (d)(2)(ii)(A), employers may rely on existing
monitoring data to satisfy the requirement for an initial exposure
assessment if employee exposures have been monitored within 12 months
prior to the effective date of the standard under conditions that
closely resemble those currently prevailing, and if that monitoring was
conducted using one of the sampling and analytical methods specified in
paragraph (d)(5)(i). This provision is intended to make it clear that
employers who have recently performed appropriate employee monitoring
will not be required to conduct additional monitoring to satisfy the
requirement for ``initial'' monitoring. OSHA anticipates that this
provision will reduce the compliance burden on employers who have
already assessed exposure levels, since ``initial'' monitoring would
not be required. The Agency believes the use of data obtained no more
than 12 months prior to the effective date is appropriate, since
samples taken more than 12 months before the effective date may not
adequately represent current workplace conditions. The 12 month limit
is consistent with the methylene chloride standard, 29 CFR 1910.1052.
    Second, to meet the requirement for an initial exposure assessment,
the employer may, under paragraph (d)(2)(ii)(B), use objective data
that demonstrate that respirable crystalline silica will not be
released in airborne concentrations at or above the action level under
any expected conditions of processing, use, or handling. Objective data
must demonstrate that the work operation or the product may not
reasonably be foreseen to release respirable crystalline silica in
concentrations at or above the action level under any expected
conditions of use. OSHA has allowed employers to use objective data in
lieu of initial monitoring in other standards, such as formaldehyde (29
CFR 1910.1048) and asbestos (29 CFR 1910.1001). Any existing air
monitoring data or objective data used in lieu of conducting initial
monitoring must be maintained in accordance with the recordkeeping
requirements in paragraph (j) of this standard.
    Paragraph (d)(3) of the proposed standard requires the employer to
assess employee exposure to respirable crystalline silica on a periodic
basis for employees exposed at or above the action level. If initial
monitoring indicates that employee exposures are below the action
level, the employer may discontinue monitoring for those employees
whose exposures are represented by such monitoring. If the initial
monitoring indicates employee exposure are at or above the action
level, then the employer has the choice of following either a fixed
schedule option or a performance option for periodic exposure
assessments.
    The fixed schedule option in paragraph (d)(3)(i) specifies the
frequency of monitoring based on the results of the initial and
subsequent monitoring. If the initial monitoring indicates employee
exposures to be at or above the action level but at or below the PEL,
the employer must perform periodic monitoring at least every six
months. If the initial or subsequent monitoring reveals employee
exposures to be above the PEL, the employer must repeat monitoring at
least every three months. If periodic monitoring results indicate that
employee exposures have fallen below the action level, and those
results are confirmed by a second measurement taken consecutively at
least seven days afterwards, the employer may discontinue monitoring
for those employees whose exposures are represented by such monitoring
unless, under paragraph (d)(4), changes in the workplace result in new
or additional exposures.
    OSHA recognizes that exposures in the workplace may fluctuate.
Periodic monitoring provides the employer with assurance that employees
are not experiencing exposures that are higher than expected and
require the use of additional control measures. In addition, periodic
monitoring reminds employees and employers of the continued need to
protect against the hazards associated with exposure to respirable
crystalline silica.
    Because of the fluctuation in exposures, OSHA believes that when
initial monitoring results equal or exceed the action level, but are at
or below the PEL, employers should continue to monitor employees to

ensure that exposures remain at or below the PEL. Likewise, when
initial monitoring results exceed the PEL, periodic monitoring allows
the employer to maintain an accurate profile of employee exposures. If
the employer installs or upgrades controls, periodic monitoring will
demonstrate whether or not controls are working properly. Selection of
appropriate respiratory protection also depends on adequate knowledge
of employee exposures.
    In general, the more frequently periodic monitoring is performed,
the more accurate the employee exposure profile. Selecting an
appropriate interval between measurements is a matter of judgment. OSHA
believes that the proposed frequencies of six months for subsequent
periodic monitoring for exposures at or above the action level but at
or below the PEL, and three months for exposures above the PEL, provide
intervals that are both practical for employers and protective for
employees. This belief is supported by OSHA's experience with
comparable monitoring intervals in other standards, including those for
cadmium (29 CFR 1910.1027), methylenedianiline (29 CFR 1910.1050),
methylene chloride (29 CFR 1910.1052), and formaldehyde (29 CFR
1910.1048).
    OSHA recognizes that monitoring can be a time-consuming, expensive
endeavor and therefore offers employers the incentive of discontinuing
monitoring for employees whose sampling results indicate exposures are
below the action level. Periodic monitoring for a specific worker or
representative group of workers can be discontinued when at least two
consecutive measurements taken at least seven days apart are below the
action level, because this indicates a low probability that under the
prevailing conditions exposure levels exceed the PEL. Therefore the
final rule provides an incentive for employers to control their
employees' exposures to respirable crystalline silica to below the
action level to minimize their exposure monitoring obligations while
maximizing the protection of employees' health.
    The performance option described in paragraph (d)(3)(ii) of the
proposed standard provides employers flexibility to assess 8-hour TWA
exposures on the basis of any combination of air monitoring data or
objective data sufficient to accurately characterize employee exposures
to respirable crystalline silica. OSHA recognizes that exposure
monitoring may present challenges in certain instances, particularly
when operations are of short duration or performed under varying
environmental conditions. The performance option is intended to allow
employers flexibility in performing periodic exposure assessments.
Where the employer elects this option, the employer must conduct the
exposure assessment prior to the time the work operation commences, and
must demonstrate that employee exposures have been accurately
characterized.
    Previous OSHA substance-specific health standards have usually
allowed employers to use objective data to characterize employee
exposures, but have generally limited its use to demonstrating that
exposures would be below the action level (e.g., cadmium, 29 CFR
1910.1027(d)(2)(iii)). In this instance, OSHA proposes to allow
reliance on the use of objective data for periodic exposure
assessments, even where exposures may exceed the action level or PEL.
However, the burden is on the employer to show that the exposure
assessment is sufficient to accurately characterize employee exposures
to respirable crystalline silica. For example, where an employer has a
substantial body of data (from previous monitoring, industry-wide
surveys, or other sources) indicating that worker exposures in a given
operation exceed the PEL, but do not exceed 10 times the PEL under any
expected conditions, the employer may choose to rely on that data to
determine his or her compliance obligations (e.g., implementation of
feasible engineering and work practice controls, respiratory
protection, medical surveillance). OSHA's intent is to allow employers
flexibility in methods used to assess employee exposures to respirable
crystalline silica, but to ensure that the methods used are accurate in
characterizing employee exposures. Any objective data relied upon must
be maintained and made available in accordance with the recordkeeping
requirements in paragraph (j)(2) of the proposed standard.
    Under paragraph (d)(4), the employer is required to reevaluate
employee exposures whenever there has been a change in the production,
process, control equipment, personnel, or work practices that may
reasonably be expected to result in new or additional exposures to
respirable crystalline silica at or above the action level. For
example, if an employer has conducted monitoring during an operation
while using local exhaust ventilation, and the flow rate of the
ventilation system is decreased, then additional monitoring would be
necessary to assess employee exposures under the modified conditions.
In addition, there may be other situations which can result in new or
additional exposures to respirable crystalline silica which are unique
to an employee's work situation. For instance, a worker may move from
an open, outdoor location to an enclosed or confined space. Even though
the task performed and materials used may remain constant, the changed
environment could reasonably be expected to result in higher exposures
to respirable crystalline silica. In order to cover those special
situations, OSHA requires the employer to conduct an additional
exposure assessment whenever a change may result in new or additional
exposures at or above the action level. This reevaluation is necessary
to ensure that the exposure assessment accurately represents existing
exposure conditions. The exposure information gained from such
assessments will enable the employer to take appropriate action to
protect exposed employees, such as instituting additional engineering
controls or providing appropriate respiratory protection. On the other
hand, additional monitoring is not required simply because a change has
been made, if the change is not reasonably expected to result in new or
additional exposures to respirable crystalline silica at or above the
action level.
    Paragraph (d)(5) of the proposed standard contains specifications
for the methods to be used for sampling and analysis of respirable
crystalline silica samples. OSHA has typically included specifications
for the accuracy of exposure monitoring methods in substance specific
standards, but not the specific analytical methods to be used or the
qualifications of the laboratory that analyzes the samples. The
proposed standard includes details regarding the specific sampling and
analytical methods to be used, as well as the qualifications of the
laboratories at which the samples are analyzed. As discussed in greater
detail in the Technological Feasibility section of the Preliminary
Economic Analysis, the Agency has preliminarily determined that these
provisions are needed to ensure that monitoring can be relied upon to
accurately measure employee exposures.
    Under proposed paragraph (d)(5)(i), all samples taken to satisfy
the monitoring requirements of this section must be evaluated using the
procedures specified in one of the following analytical methods: OSHA
ID-142; NMAM 7500, NMAM 7602; NMAM 7603; MSHA P-2; or MSHA P-7. OSHA
has determined based on inter-laboratory comparisons that laboratory
analysis by either X-ray diffraction (XRD) or infrared (IR)
spectroscopy is

required to ensure the accuracy of the monitoring results in
environments subject to the Agency's jurisdiction. The specified
analytical methods are the XRD or IR methods for analysis of respirable
crystalline silica that have been established by OSHA, NIOSH, or MSHA.
    To ensure the accuracy of air sampling data relied on by employers
to achieve compliance with standard, the standard requires that air
samples are to be analyzed only at accredited laboratories that meet
six requirements listed in paragraphs (d)(5)(ii)(A-F). The requirements
were developed based on procedures implemented at laboratories that
have achieved acceptable levels of accuracy and precision during a
study of inter-laboratory variability. An employer who engages an
independent laboratory to analyze respirable crystalline silica samples
could rely on an assurance from that laboratory that the specified
requirements were met. For example, the laboratory could include a
statement that it complied with the requirements of the standard along
with the sampling results provided to the employer.
    Paragraph (d)(5)(ii)(A) requires employers to ensure that samples
taken to monitor employee exposures are analyzed by a laboratory that
is accredited to ANS/ISO/IEC Standard 17025 ``General requirements for
the competence of testing and calibration laboratories'' (EN ISO/IEC
17025:2005) by an accrediting organization that can demonstrate
compliance with the requirements of ISO/IEC 17011 ``Conformity
assessment--General requirements for accreditation bodies accrediting
conformity assessment bodies'' (EN ISO/IEC 17011:2004). ANS/ISO/IEC
17025 is a consensus standard that was developed by the International
Organization for Standardization and the International Electrotechnical
Commission (ISO/IEC) and approved by the American Society for Testing
and Materials (ASTM). This standard establishes criteria by which
laboratories can demonstrate proficiency in conducting laboratory
analysis through the implementation of quality control measures. To
demonstrate competence, laboratories must implement a quality control
(QC) program that evaluates analytical uncertainty and provides
employers with estimates of sampling and analytical error (SAE) when
reporting samples. ISO/IEC 17011 establishes criteria for organizations
that accredit laboratories under ISO/IEC 17025. For example, the AIHA
accredits laboratories for proficiency in the analysis of crystalline
silica using criteria based on the ISO 17025 and other criteria
appropriate for the scope of the accreditation.
    Paragraphs (d)(5)(ii)(B)-(F) contain additional requirements for
laboratories that have been demonstrated to improve accuracy and
reliability through inter-laboratory comparisons. The laboratory must
participate in a round robin testing program with at least two other
independent laboratories at least every six months. An example of a
testing program that satisfies this requirement, as it is currently
implemented, is the program established by AIHA Proficiency Analytical
Testing Programs, LLC. The laboratory must use the most current
National Institute of Standards and Technology (NIST) or NIST traceable
standards for instrument calibration or instrument calibration
verification. The laboratory must have an internal quality control (QC)
program that evaluates analytical uncertainty and provides employers
with estimates of sampling and analytical error. The laboratory must
characterize the sample material by identifying polymorphs of
respirable crystalline silica present, identifying the presence of any
interfering compounds that might affect the analysis, and making the
corrections necessary in order to obtain accurate sample analysis. The
laboratory must analyze quantitatively for respirable crystalline
silica only after confirming that the sample matrix is free of
uncorrectable analytical interferences, and corrects for analytical
interferences. The laboratory must perform routine calibration checks
with standards that bracket the sample concentrations using five or
more calibration standard levels to prepare calibration curves, and use
instruments optimized to obtain a quantitative limit of detection that
represents a value no higher than 25 percent of the PEL.
    Under paragraph (d)(6) of the proposed rule, employers covered by
the general industry standard must notify each affected employee within
15 working days of completing an exposure assessment. Notification is
required whenever an exposure assessment has been conducted regardless
of whether or not employee exposure exceeds the action level or PEL. In
construction, employers must notify each affected employee not more
than five working days after the exposure assessment has been
completed. A shorter time period for notification is provided in
construction in recognition of the often short duration of operations
and employment in particular locations in this sector. The time allowed
for notification is consistent with the harmonized notification times
established for certain health standards applicable to general industry
and construction in Phase II of OSHA's Standards Improvement Project.
70 FR 1112; January 5, 2005. Where the employer follows the scheduled
monitoring option provided for in paragraph (d)(3)(i), the 15 (or five)
day period for notification commences when monitoring results are
received by the employer. For employers following the performance-
oriented option under paragraph (d)(3)(ii), the period commences when
the employer makes a determination of the exposure levels and the need
for corresponding control measures (i.e., prior to the time the work
operation commences, and whenever exposures are re-evaluated).
    The notification requirements in this provision apply to all
employees for which an exposure assessment has been conducted, either
individually or as part of a representative monitoring strategy. It
includes employees who were subject to personal monitoring, as well as
employees whose exposure was assessed based on other employees who were
sampled, and employees whose exposures have been assessed on the basis
of objective data. The employer shall either notify each affected
employee in writing or post the monitoring results in an appropriate
location accessible to all affected employees. In addition, paragraph
(d)(6)(ii) requires that whenever the PEL has been exceeded, the
written notification must contain a description of the corrective
action(s) being taken by the employer to reduce employee exposures to
or below the PEL. The requirement to inform employees of the corrective
actions the employer is taking to reduce the exposure level to or below
the PEL is necessary to assure employees that the employer is making
efforts to furnish them with a safe and healthful work environment, and
is required under section 8(c)(3) of the OSH Act. 29 U.S.C. 657(c)(3).
    Notifying employees of their exposures provides them with knowledge
that can permit and encourage them to be more proactive in working to
control their own exposures through better and safer work practices and
more active participation in safety programs. As OSHA noted with
respect to its Hazard Communication Standard: ``Workers provided the
necessary hazard information will more fully participate in, and
support, the protective measures instituted in their workplaces.'' 59
FR 6126, 6127; Feb. 9, 1994. Exposures to respirable crystalline silica
below the PEL may still be hazardous, and making employees aware of
such exposures may encourage them to take whatever steps

they can, as individuals, to reduce their exposures as much as
possible.
    Paragraph (d)(7) requires the employer to provide affected
employees or their designated representatives an opportunity to observe
any air monitoring of employee exposure to respirable crystalline
silica, whether the employer uses the fixed schedule option or the
performance option. When observation of monitoring requires entry into
an area where the use of protective clothing or equipment is required,
the employer must provide the observer with that protective clothing or
equipment, and assure that the observer uses such clothing or
equipment.
    The requirement for employers to provide employees or their
representatives the opportunity to observe monitoring is consistent
with the OSH Act. Section 8(c)(3) of the OSH Act mandates that
regulations developed under section 6 of the Act provide employees or
their representatives with the opportunity to observe monitoring or
measurements. 29 U.S.C. 657(c)(3). Also, section 6(b)(7) of the OSH Act
states that, where appropriate, OSHA standards are to prescribe
suitable protective equipment to be used in dealing with hazards. 29
U.S.C. 655(b)(7). The provision for observation of monitoring and
protection of the observers is also consistent with OSHA's other
substance-specific health standards such as those for cadmium (29 CFR
1910.1027) and methylene chloride (29 CFR 1910.1052).
    Table 1 in paragraph (f) of the proposed construction standard
lists exposure control methods for selected construction operations. As
discussed with regard to paragraph (f), OSHA has preliminarily
determined that the engineering controls, work practices, and
respiratory protection specified for each operation in Table 1
represent appropriate and effective controls for those operations.
Therefore, paragraph (d)(8) of the proposed construction standard makes
an exception to the general requirement for exposure assessment where
employees perform operations in Table 1 and the employer has fully
implemented the controls specified for that operation. This relieves
the employer of the burden of performing exposure monitoring in these
situations.
    Where the employer elects to implement the control measures
specified in Table 1 for a given construction operation, paragraph
(d)(8)(ii) requires that the employer presume that each employee
performing an operation listed in Table 1 that requires a respirator is
exposed above the PEL, unless the employer can demonstrate otherwise in
accordance with paragraph (d) of the proposed rule. So, for example, if
an employer elects to implement the controls specified in Table 1 for a
given construction operation that requires a respirator and does not
conduct an exposure assessment to demonstrate that exposures are below
the PEL, the employer would be required to provide each employee
performing that operation for 30 or more days per year with medical
surveillance in accordance with paragraph (h) of the proposed rule.

(e) Regulated Areas and Access Control

    Under paragraph (e)(1) in the standards, employers have two options
wherever an employee's exposure to airborne concentrations of
respirable silica is, or can reasonably be expected to be, in excess of
the PEL: (1) the establishment of regulated areas in accordance with
paragraph (e)(2); or (2) the implementation of a written access control
plan in accordance with paragraph (e)(3).
    The purpose of a regulated area is to ensure that the employer
makes employees aware of the presence of respirable crystalline silica
at levels above the PEL, and to limit exposure to as few employees as
possible. The establishment of a regulated area is an effective means
of minimizing exposure to employees not directly involved in operations
that generate respirable crystalline silica and limiting the risk of
exposure to a substance known to cause adverse health effects. Because
of the potentially serious results of exposure and the need for persons
entering the area to be properly protected, the number of persons given
access to the area should be limited to those employees needed to
perform the job. Limiting access to regulated areas also has the
benefit of reducing the employer's obligation to implement other
provisions of this proposed standard to as few employees as possible.
    Under paragraph (e)(2)(ii), regulated areas are to be demarcated
from the rest of the workplace in any manner that adequately
establishes and alerts employees to the boundary of the regulated area,
and minimizes the number of employees exposed to respirable crystalline
silica within the regulated area. OSHA has not specified how employers
are to demarcate regulated areas. Signs, barricades, lines, or textured
flooring may each be effective means of demarcating the boundaries of
regulated areas. Permitting employers to choose how best to identify
and limit access to regulated areas is consistent with OSHA's belief
that employers are in the best position to make such determinations,
based on their knowledge of the specific conditions of their
workplaces. Whatever methods are chosen to establish a regulated area,
the demarcation must effectively warn employees not to enter the area
unless they are authorized, and then only if they are using the proper
personal protective equipment. Allowing employers to demarcate and
limit access to the regulated areas as they choose is consistent with
recent OSHA substance-specific health standards, such as chromium (VI)
(29 CFR 1910.1026) and 1,3-butadiene (29 CFR 1910.1051).
    Paragraph (e)(2)(iii) describes who may enter regulated areas. In
both standards, access to regulated areas is restricted to persons
required by their job duties to be present in the area, as authorized
by the employer. In addition, designated employee representatives
exercising the right to observe monitoring procedures are allowed to
enter regulated areas. For example, employees in some workplaces may
designate a union representative to observe monitoring; this person
would be allowed to enter the regulated area. Persons authorized under
the OSH Act, such as OSHA compliance officers, are also allowed access
to regulated areas.
    Under paragraph (e)(2)(iv), employers must provide each employee
and designated representative who enters a regulated area with an
appropriate respirator in accordance with paragraph (g), and require
that the employee or designated representative uses the respirator
while in the regulated area. The boundary of the regulated area
indicates where respirators must be donned prior to entering, and where
respirators can be doffed, or removed, upon exiting the regulated area.
This provision is intended to establish a clear and consistent
requirement for respirator use for all employees who enter a regulated
area, regardless of the duration of their presence in the regulated
area. OSHA believes this proposed requirement is simple to administer
and enforce, protective of employee health, and consistent with general
practice in management of regulated areas.
    OSHA has proposed a requirement for use of protective clothing or
other measures to limit contamination of clothing for employees working
in regulated areas. Paragraph (e)(2)(v) requires that, where there is
the potential for employees' work clothing to become grossly
contaminated with finely divided material containing crystalline
silica, the employer must

either provide appropriate protective clothing such as coveralls or
similar full-bodied clothing, or else provide a means to remove
excessive silica dust from contaminated clothing when exiting the
regulated area. This provision is intended to limit additional
respirable crystalline exposures to employees in regulated areas that
could result from disturbing the dust that has accumulated on their
clothing. It is also intended to protect employees in adjacent areas
from exposures that could occur if employees with grossly contaminated
clothing were to carry crystalline silica dust to other areas of the
workplace. The purpose of this provision is not, however, to protect
employees from dermal exposure to crystalline silica, as discussed
further below.
    In paragraph (e)(2)(v)(A), the proposal refers to ``finely divided
materials.'' When using this term, the proposed standard refers to
particles with very small diameters (i.e., <= 10 [mu]m) such that, once
airborne, the particles would be considered respirable dust. ``Gross
contamination'' refers to a substantial accumulation of dust on
clothing worn by an employee working in a regulated area such that
movement by the individual results in the release of dust from the
clothing. The provision is not intended to cover any contamination of
clothing, but rather those limited circumstances where significant
quantities of dust are deposited on workers' clothing. Where such
conditions exist, OSHA anticipates that the dust present on workers'
clothing or the release of dust from the clothing would be plainly
visible.
    Under paragraphs (e)(2)(v)(A)(1)-(2), the employer would have the
option of providing either appropriate protective clothing, such as
coveralls that can be removed upon exiting the regulated area, or any
other means of removing excessive silica dust from contaminated
clothing that minimizes employee exposure to respirable crystalline
silica. The employer may choose the approach that works best in the
circumstances found in a particular workplace. The employer may choose,
for example, to provide HEPA vacuums for removal of dust from clothing.
It should be noted, however, that paragraph (f)(3)(ii)
(paragraph(f)(4)(ii) of the standard for construction) prohibits the
use of compressed air, dry sweeping, and dry brushing to clean clothing
or surfaces contaminated with crystalline silica where such activities
could contribute to employee exposure to respirable crystalline silica
that exceeds the PEL. Paragraph (e)(2)(v) requires contaminated
clothing to be either cleaned or removed upon exiting the regulated
area, in order to ensure that other areas of the workplace do not
become contaminated. Cleaning or removal of contaminated clothing must
take place prior to removal of respiratory protection in order to
ensure that any exposure to dust released from contaminated clothing is
minimized.
    In other substance-specific chemical standards, OSHA has typically
included requirements for provision of protective clothing, as well as
associated provisions addressing removal, storage, cleaning, and
replacement of protective clothing. The proposed provisions for this
respirable crystalline standard are more limited than other OSHA
standards, in that the requirements only apply in regulated areas, and
then only when there is the potential for clothing to become grossly
contaminated. The employer is also given the option of providing other
means to remove dust from contaminated clothing, an alternative not
generally available in other OSHA standards. OSHA has proposed these
more limited provisions because the Agency has made a preliminary
determination that the proposed provisions will serve to reduce
employee exposures, and that additional requirements for protective
clothing are not reasonably necessary and appropriate.
    Most other chemicals regulated under OSHA substance-specific
standards either have direct dermal effects or can contribute to
overall exposures through dermal absorption. OSHA is not aware of any
evidence that dermal exposure is a concern for respirable crystalline
silica. Moreover, dusts containing crystalline silica are ubiquitous in
many of the work environments covered by this proposed standard.
Therefore, the proposed silica standard focuses on those situations
where contamination of clothing has the potential to contribute
significantly to employee inhalation exposures. OSHA recognizes that
the ASTM standards addressing occupational exposure to respirable
crystalline silica do not include requirements for protective clothing.
However, the Agency believes that the proposed provisions will serve to
limit employee exposures in those situations where contamination of
clothing contributes to inhalation exposures. OSHA also notes that the
Agency's Advisory Committee on Construction Safety and Health
recommended that OSHA maintain the language on protective clothing that
was included in the draft provided for review under the Small Business
Regulatory Enforcement Fairness Act (SBREFA). The SBREFA draft language
would have required protective clothing or a means to vacuum
contaminated clothing for all employees exposed above the PEL. The
Agency seeks comment on the proposed provisions for protective clothing
and has included this topic in the ``Issues'' section of this preamble.
    OSHA's standard addressing sanitation in general industry (29 CFR
1910.141) requires that whenever employees are required by a particular
standard to wear protective clothing because of the possibility of
contamination with toxic materials, change rooms equipped with storage
facilities for street clothes and separate storage facilities for
protective clothing shall be provided (29 CFR 1910.141(e)). The
sanitation standard also includes provisions for lavatories with
running water (29 CFR 1910.141(d)(2)), and prohibits storage or
consumption of food or beverages in any area exposed to a toxic
material (29 CFR 1910.141(g)(2)). Similar provisions are in place for
construction (29 CFR 1926.51). OSHA expects that employers will comply
with the provisions of the sanitation standard when required. Thus, no
additional requirements for hygiene practices are included in the
proposed silica standards.
    The proposed standard provides two options for employers to choose
between for minimizing exposure to employees not directly involved in
operations that generate respirable crystalline silica. The
establishment of regulated areas under paragraph (e)(2), as described
above, is the first option for exposure control in workplaces, and when
fully implemented will satisfy this requirement. However, OSHA
recognizes that establishing regulated areas in some workplaces can be
difficult. For example, in the SBREFA review process, the question was
raised as to how a regulated area could be established for a highway
project, where the source of exposure could be constantly moving. Some
activities covered by the general industry/maritime standard may
present similar difficulties, such as hydraulic fracturing operations
where exposures may occur over a large area. In recognition of the
practical problems that may be encountered in such circumstances, the
proposed standard includes an option in paragraph (e)(3) for
establishing and implementing a written access control plan in lieu of
a regulated area.
    Paragraph (e)(3)(ii) in the standard sets out the requirements for
a written access control plan. The plan must contain provisions for a
competent person to identify the presence and location of any areas
where respirable crystalline silica exposures are, or can

reasonably be expected to be, in excess of the PEL. It must describe
how employees will be notified of the presence and location of areas
where exposures are, or can reasonably be expected to be, in excess of
the PEL, and how these areas will be demarcated from the rest of the
workplace. For multi-employer workplaces, the plan must identify the
methods that will be used to inform other employers of the presence and
the location of areas where respirable crystalline silica exposures
are, or can reasonably be expected to be, in excess of the PEL, and any
precautionary measures that need to be taken to protect employees. The
written plan must contain provisions for limiting access to these
areas, in order to minimize the number of employees exposed and the
level of employee exposure. The plan must also describe procedures for
providing each employee working in areas where respirable crystalline
silica exposures are, or can reasonably be expected to be, in excess of
the PEL with an appropriate respirator in accordance with paragraph (g)
of this section. Where there is the potential for employees' work
clothing to become grossly contaminated with finely divided material
containing crystalline silica, the access control plan must include
provisions for the employer to provide either appropriate protective
clothing, or a means to remove excessive silica dust from contaminated
clothing that minimizes employee exposure to respirable crystalline
silica. The access control plan must also include provisions for
removal or cleaning of such clothing.
    The employer must review and evaluate the effectiveness of the
written access control plan at least annually and update it as
necessary. The written access control plan must be available for
examination and copying, upon request, to employees, their designated
representatives, the Assistant Secretary and the Director.
    The intent of the provision for establishing written access control
plans in lieu of regulated areas is to provide employers with
flexibility to adapt to the particular circumstances of their worksites
while maintaining equivalent protection for employees. The Agency seeks
comment on this proposed approach and has included this topic in the
``Issues'' section of this preamble.

(f) Methods of Compliance

    Paragraph (f)(1) of the proposed rule establishes a hierarchy of
controls which employers must use to reduce and maintain exposures to
respirable crystalline silica to or below the permissible exposure
limit (PEL). The proposed rule requires employers to implement
engineering and work practice controls as the primary means to reduce
exposure to the PEL or to the lowest feasible level above the PEL. In
situations where engineering and work practice controls are not
sufficient to reduce exposures to or below the PEL, employers are
required to supplement these controls with respiratory protection,
according to the requirements of paragraph (g) of the proposed rule.
OSHA proposes to require primary reliance on engineering controls and
work practices because reliance on these methods is consistent with
good industrial hygiene practice, with the Agency's experience in
ensuring that workers have a healthy workplace, and with the Agency's
traditional adherence to a hierarchy of preferred controls.
    OSHA requires adherence to this hierarchy of controls in a number
of current standards, including the Air Contaminants (29 CFR 1910.1000)
and Respiratory Protection (29 CFR 1910.134) standards, as well as
previous substance-specific standards. The Agency's adherence to the
hierarchy of controls has been successfully upheld by the courts (see
AFL-CIO v. Marshall, 617 F.2d 636 (D.C. Cir. 1979) (cotton dust
standard); United Steelworkers v. Marshall, 647 F.2d 1189 (DC Cir.
1980), cert. denied, 453 U.S. 913 (1981) (lead standard); ASARCO v.
OSHA, 746 F.2d 483 (9th Cir. 1984) (arsenic standard); Am. Iron & Steel
v. OSHA, 182 F.3d 1261 (11th Cir. 1999) (respiratory protection
standard); Pub. Citizen v. U.S. Dep't of Labor, 557 F.3d 165 (3rd Cir.
2009) (hexavalent chromium standard)).
    The Agency understands that engineering controls: (1) Control
crystalline silica-containing dust particles at the source; (2) are
reliable, predictable, and provide consistent levels of protection to a
large number of workers; (3) can be monitored continually and
relatively easily; and (4) are not as susceptible to human error as is
the use of personal protective equipment. The use of engineering
controls to prevent the release of silica-containing dust particles at
the source also minimizes the silica exposure of other employees in
surrounding work areas, especially at construction sites, who are not
directly involved in the task that is generating the dust, and may not
be wearing respirators.
    Respirators are another important means of protecting workers from
exposure to air contaminants. However, to be effective, respirators
must be individually selected; fitted and periodically refitted;
conscientiously and properly worn; regularly maintained; and replaced
as necessary. In many workplaces, these conditions for effective
respirator use are difficult to achieve. The absence of any one of
these conditions can reduce or eliminate the protection the respirator
provides to some or all of the employees. For example, certain types of
respirators require the user to be clean shaven to achieve an effective
seal where the respirator contacts the worker's skin. Failure to ensure
a tight seal due to the presence of facial hair compromises the
effectiveness of the respirator.
    Respirator effectiveness ultimately relies on the good work
practices of individual employees. In contrast, the effectiveness of
engineering controls does not rely so heavily on actions of individual
employees. Engineering and work practice controls are capable of
reducing or eliminating a hazard from the workplace as a whole, while
respirators protect only the employees who are wearing them correctly.
Furthermore, engineering and work practice controls permit the employer
to evaluate their effectiveness directly through air monitoring and
other means. It is considerably more difficult to directly measure the
effectiveness of respirators on a regular basis to ensure that
employees are not unknowingly being overexposed. OSHA therefore
considers the use of respirators to be the least satisfactory approach
to exposure control.
    In addition, use of respirators in the workplace presents other
safety and health concerns. Respirators can impose substantial
physiological burdens on employees, including the burden imposed by the
weight of the respirator; increased breathing resistance during
operation; limitations on auditory, visual, and odor sensations; and
isolation from the workplace environment. Job and workplace factors
such as the level of physical work effort, the use of protective
clothing, and temperature extremes or high humidity can also impose
physiological burdens on workers wearing respirators. These stressors
may interact with respirator use to increase the physiological strain
experienced by employees.
    Certain medical conditions can compromise an employee's ability to
tolerate the physiological burdens imposed by respirator use, thereby
placing the employee wearing the respirator at an increased risk of
illness, injury, and even death. These medical conditions include
cardiovascular and respiratory diseases (e.g., a history of high blood
pressure, angina, heart attack, cardiac arrhythmias, stroke, asthma,
chronic bronchitis,

emphysema), reduced pulmonary function caused by other factors (e.g.,
smoking or prior exposure to respiratory hazards), neurological or
musculoskeletal disorders (e.g., epilepsy, lower back pain), and
impaired sensory function (e.g., a perforated ear drum, reduced
olfactory function). Psychological conditions, such as claustrophobia,
can also impair the effective use of respirators by employees and may
also cause, independent of physiological burdens, significant
elevations in heart rate, blood pressure, and respiratory rate that can
jeopardize the health of employees who are at high risk for
cardiopulmonary disease.
    These concerns about the burdens placed on workers by the use of
respirators were acknowledged in OSHA's revision of its Respiratory
Protection standard, and are the basis for the requirement that
employers provide a medical evaluation to determine the employee's
ability to wear a respirator before the employee is fit tested or
required to use a respirator in the workplace (63 FR 1152, Jan. 8,
1998). Although experience in industry shows that most healthy workers
do not have physiological problems wearing properly chosen and fitted
respirators, nonetheless common health problems can cause difficulty in
breathing while an employee is wearing a respirator.
    In addition, safety problems created by respirators that limit
vision and communication must always be considered. In some difficult
or dangerous jobs, effective vision or communication is vital. Voice
transmission through a respirator can be difficult, annoying, and
fatiguing. In addition, movement of the jaw in speaking can cause
leakage, thereby reducing the efficiency of the respirator and
decreasing the protection afforded the employee. Skin irritation can
result from wearing a respirator in hot, humid conditions. Such
irritation can cause considerable distress to workers and can cause
workers to refrain from wearing the respirator, thereby rendering it
ineffective.
    While OSHA acknowledges that certain types of respirators may
lessen problems associated with breathing resistance and skin
discomfort, OSHA does not believe that respirators provide employees
with a level of protection that is equivalent to engineering controls,
regardless of the type of respirator used. It is well-recognized that
certain types of respirators are superior to other types of respirators
with regard to the level of protection offered, or impart other
advantages. OSHA has evaluated the level of protection offered by
different types of respirators in the Agency's Assigned Protection
Factors rulemaking (68 FR 34036, June 6, 2003). Even in situations
where engineering controls are not sufficiently effective to reduce
exposure levels to or below the PEL, the reduction in exposure levels
benefits workers by reducing the required protection factor of the
respirator, which provides a wider range of options in the type of
respirators that can be used. For example, for situations in which dust
concentrations are reduced through use of engineering controls to
levels that are less than ten times the PEL, employers would have the
option of providing approved half-mask respirators that may be lighter
and easier to use when compared with full-facepiece respirators.
    In summary, engineering and work practice controls are capable of
reducing or eliminating a hazard from the workplace; respirators
protect only the employees who are wearing them. In addition, the
effectiveness of respiratory protection always depends on the actions
of employees, while the efficacy of engineering controls is generally
independent of the individual. OSHA believes that engineering controls
offer more reliable and consistent protection to a greater number of
workers, and are therefore preferable to respiratory protection.
Engineering controls. The engineering controls presented in this
proposal can be grouped into these main categories: (1) Substitution,
(2) isolation, (3) ventilation, and (4) dust suppression. Depending on
the sources of crystalline silica dust and the operations conducted, a
combination of control methods may reduce silica exposure levels more
effectively than a single method. Substitution. Substitution refers to
the replacement of a toxic material with another material that reduces
or eliminates the harmful exposure. OSHA considers substitution to be
an ideal control measure if it replaces a toxic material in the work
environment with a non-toxic material, thus eliminating the risk of
adverse health effects.
    The technological feasibility study (PEA, Chapter 4) indicates that
employers use substitutes for crystalline silica in a variety of
operations. For example, some employers use substitutes in abrasive
blasting operations, repair and replacement of refractory materials,
operations performed in foundries, and in the railroad transportation
industry. If substitutes for crystalline silica are being used in any
operation not considered in the feasibility study, OSHA is requesting
relevant information that contains data supporting the effectiveness,
in reducing exposure to crystalline silica, of substitutes currently
being used.
    Before replacing a toxic material with a substitute, it is
important that employers evaluate the toxicity of the substitute
materials relative to the toxicity of the original material. Substitute
materials that pose significant new or additional risks to workers are
not a desirable means of control. Additionally, employers must comply
with Section 5(a)(1) of the OSH Act, which prohibits occupational
exposure to ``recognized hazards that are causing or are likely to
cause death or serious physical harm.'' 29 U.S.C. 654(a)(1). Employers
must also comply with applicable standards. 29 U.S.C. 654(a)(2). For
example, with respect to chemical hazards, OSHA's Hazard Communication
standard imposes specific requirements for employee training, material
safety data sheets, and labeling. 29 CFR 1910.1200.
    While the Agency's technological feasibility analysis includes
information about materials that some employers use as alternatives to
silica or silica-containing materials, the Agency recognizes that these
substitute materials may present health risks. OSHA does not intend to
imply that any particular material is an appropriate or safe substitute
for silica. Isolation. Isolation, by means of a process enclosure, is
another effective engineering control employed to reduce exposures to
crystalline silica. It refers to a physical barrier normally
surrounding the source of exposure and installed to contain a toxic
substance within the barrier. Isolating the source of a hazard within
an enclosure restricts respirable dust from spreading throughout a
workplace and exposing workers who are not directly involved in dust-
generating operations.
    Due to the shift from manually operated to automated processes,
enclosures have become more practicable. For example, forming line
operators in structural clay products manufacturing can use automation
for transfer of materials, allowing conveyors and milling areas to be
enclosed (OSHA SEP Inspection Report 300523396). Another example can be
observed in automated refractory demolition and installation methods. A
``pusher'' system installed in coreless induction furnaces allows
refractory linings to be automatically pressed out by push plates
installed in furnace bottoms. A representative of Foundry Products
Supplier B (2000a) estimated that total worker exposure using a pusher
system would be roughly half that of traditional

chipping refractory removal methods and possibly as much as 80 percent
less if an enclosure (tarp) was used over the end of the furnace from
which the lining is extruded. At a pottery facility, the exposure for a
material handler monitoring automated equipment that is adding silica-
containing raw materials to a mixer was about 66 percent lower than the
exposure of a material handler manually adding the material to the
mixer (OSHA SEP Inspection Report 300384435). At a structural clay
industry facility inspected by OSHA, an 86-percent reduction in
respirable quartz exposure readings occurred after management installed
an enclosed, automated sand transfer system, despite not having
optimally sealed components (PEA, Chapter 4).
    Workers can also be isolated from a hazardous source when they
operate heavy machinery equipped with enclosed cabs. In such cases, a
cab that is well sealed and equipped with ventilation and a high-
efficiency particulate air (HEPA) filter can minimize the potential for
exposure from the dust created outside the cab.
    MSHA (1997) recommended the following controls to maximize the
effectiveness of an enclosed cab: keeping the cab interior's horizontal
and vertical surfaces and areas clean and free of debris; inspecting
door seals and closing mechanisms to ensure they work properly;
ensuring that seals around windows, power line entries, and joints in
the walls and floors of the cab are tightly sealed; ensuring that air
conditioners are designed so that air comes in from the outdoors to
create positive pressure and passes first through a pre-filter (those
with an American Society of Heating, Refrigeration and Air-Conditioning
Engineers efficiency rating of 90 percent are common) and then through
a HEPA filter; and ensuring that HEPA filters are changed when they
reach the manufacturer's final resistance value (MSHA, 1997).
    Tractors, front-end loaders, and other mobile material-handling
equipment equipped with properly enclosed, sealed, and ventilated
operator cabs (i.e., no leaks, positive pressure, and effective air
filtration) can substantially reduce silica exposures associated with
the use of such equipment. Direct-reading instruments show that fine
particle (0.3 micron ([mu]m) in size) concentrations inside operator
cabs can be reduced by an average of 96 percent when cabs are clean,
sealed, and have a functionally adequate filtration and pressurization
system. Gravimetric sampling instruments found an average cab
efficiency of about 93 percent when comparing dust levels outside and
inside the cab (Cecala et al., 2005). Similarly, NIOSH investigators
reported respirable dust exposure reductions of 97 and 98 percent,
respectively, inside the cabin of a modified railroad ballast dumper in
the railroad transportation industry (NIOSH HHE 92-0311, 2001). Other
researchers have reported particle reductions inside the operator cab
greater than 90 percent (Hall et al., 2002).
    The Agency recognizes that although enclosed cabs have been proven
to be an effective control method, they do not control exposures at the
source. In many circumstances, machine operators work alongside
employees who are outside the enclosed cabs and are not protected by
them. As such, OSHA expects employers to apply all other feasible
controls to protect those employees.
    In certain situations, a process enclosure can enhance the benefits
of other control methods when used simultaneously, such as when an
enclosure is equipped with local exhaust ventilation (LEV). When the
enclosure contains the crystalline-silica-containing dust cloud, the
ventilation system is able to remove that contaminant in a more
effective and timely fashion, as opposed to having it dissipate out of
the ventilation system's exhaust range where there is no enclosure.
    In the asphalt roofing manufacturing industry, the capture of
process emissions (including dust) at the coater station is best
achieved by using LEV in conjunction with an enclosure. When using a
full enclosure with LEV, NIOSH recommends several practices that
improve the capture efficiency of the ventilation system. OSHA believes
these recommendations are beneficial whenever this control method is
used in a production line. The recommendations are: (1) When process
enclosures are used, the number and size of openings in the enclosure
must be minimized to prevent a reduction in the capture efficiency of
the ventilation system; (2) all doors should be adequately sealed and
closed during operation of the line; (3) the size of the opening where
the product enters and leaves the process equipment should be minimized
to ensure an inward flow of air by the negative pressure within the
enclosure; and (4) negative pressure must be maintained inside the
enclosure to prevent leakage of process emissions into the workplace.
    In the foundry industry, shakeout operators are responsible for
monitoring equipment that separates the casting being produced from the
molding material. This process generally involves shaking the casting,
which creates dust exposure associated with respirable crystalline
silica levels above the PEL. OSHA has determined that employers using
this process should enclose the shakeout operations, and the most
effective method to reduce exposure is installing efficient ventilation
(PEA, Chapter 4).
    Another example occurs in the masonry industry, when stationary
saws are placed inside ventilated enclosures, and the set-up permits
the operator to stand outside the enclosure. A 78-percent reduction in
respirable quartz exposure was observed (from 354 [mu]g/m\3\ to 78
[mu]g/m\3\) when workers used a site-built ventilated booth outdoors as
opposed to cutting with no booth (ERG-C, 2008).
    Ventilation. Ventilation is another engineering control method used
to minimize airborne concentrations of a contaminant by supplying or
exhausting air. Two types of systems are commonly used: LEV and
dilution ventilation. LEV is used to remove an air contaminant by
capturing it at or near the source of emission, before the contaminant
spreads throughout the workplace. Dilution ventilation allows the
contaminant to spread over the work area but dilutes it by circulating
large quantities of air into and out of the area. Consistent with past
recommendations such as those included in the Hexavalent Chromium Rule,
OSHA prefers the use of LEV systems to control airborne toxics because,
if designed properly, they efficiently remove contaminants and provide
for cleaner and safer work environments.
    The use of effective exhaust ventilation in controlling worker
exposures to crystalline silica can be illustrated by an example in the
mineral processing industry. Here, the highest exposure levels obtained
by OSHA were associated with bag dumping and disposal operations at a
pottery clay manufacturing company (OSHA SEP Inspection Report
116178096). After the facility installed ventilated bag disposal
hoppers, HEPA filters, and an enhanced LEV system, the exposure of the
production workers was reduced by about 80 percent (from 221 [mu]g/m\3\
to 44 [mu]g/m\3\). A Canadian study of a rock-crushing plant also shows
the effectiveness of LEV systems (Grenier, 1987); the plant, originally
equipped with a general exhaust ventilation system with fabric dust
collectors, processed rock containing as much as 60 percent crystalline
silica. Operation of the LEV system was associated with reductions of
respirable crystalline silica levels ranging from 20 to 79 percent.

    LEV can be adapted to diverse sources of emissions. For workers who
empty bags or mix powders that contain crystalline silica material, a
portable exhaust trunk positioned near the bag-dumping hopper can
capture a portion of the dust released during that activity. Additional
crystalline silica exposure can occur when workers compress empty bags,
an activity that can also be performed with LEV control (PEA, Chapter
4).
    LEV can also be applied to operations involving portable tools. The
benefits of tool-mounted LEV systems for controlling crystalline silica
have been demonstrated by two NIOSH evaluations. In one evaluation,
NIOSH tested two tool-mounted LEV shrouds for hand-held pneumatic
chipping equipment (impact drills): one custom built, the other a
commercially available model. Comparing multiple short-term exposure
samples, NIOSH found that the shrouds reduced personal breathing zone
(PBZ) respirable dust by 48 to 60 percent (NIOSH, 2003-EPHB 282-11a).
In a separate evaluation, NIOSH collected short-term PBZ samples while
workers used 25- or 30-pound jackhammers to chip concrete from inside
concrete mixer truck drums. During 90- to 120-minute periods of active
chipping, mean respirable silica levels decreased by 69 percent when
the workers used a tool-mounted LEV shroud in these enclosed spaces
(NIOSH, 2001-EPHB 247-19).
    In the railroad transportation industry, dust control kits that
incorporate LEV are designed to reduce the amount of ballast dust
released by activities of heavy equipment during maintenance. These
kits can be used with brooming equipment (mechanical sweepers) and
present an alternative to relying on cab modification. Workers that
operate brooming equipment have the greatest potential for elevated
exposures among workers in this industry, and the Agency believes that
kits would be a better control measure than cab modification because
they reduce exposures at the source. Unfortunately, information
regarding the effectiveness of these kits in reducing worker exposure
to crystalline silica is not available from the manufacturer. OSHA is
therefore requesting any relevant information that would aid the Agency
in determining the potential impact of dust control kits in the
railroad transportation industry (HTT, 2003; ERG-GI, 2008).
    Based on the information presented in OSHA's technological
feasibility analysis, many exposures in the workplace have occurred, in
part, due to faulty ventilation systems and improper work practices
that minimize their efficiency. In many cases, exposures can be reduced
with the proper use and maintenance of ventilation systems (PEA,
Chapter 4).
    Dust suppression. Dust suppression methods are generally effective
in controlling respirable crystalline silica dust, and they can be
applied to many different operations such as material handling, rock
crushing, abrasive blasting, and operation of heavy equipment (Smandych
et al., 1998). Dust suppression can be accomplished by one of three
systems: (1) wet dust suppression, in which a liquid or foam is applied
to the surface of the dust-generating material; (2) airborne capture,
in which moisture is dispensed into a dust cloud, collides with
particles, and causes them to drop from the air; and (3) stabilization,
which holds down dust particles by physical or chemical means
(lignosulfonate, calcium chloride, and magnesium chloride are examples
of stabilizers).
    The most common dust suppression controls encountered during the
technological feasibility review correspond to wet methods (PEA,
Chapter 4). Water is generally an inexpensive and readily available
resource and has been proven an efficient engineering control method to
reduce exposures to airborne crystalline silica-containing dust. Dust,
when wet, is less able to become or remain airborne.
    In its analysis of technological feasibility, OSHA demonstrated
that wet methods are effective in a wide variety of operations. For
example, respirable quartz exposures for masonry cutters using
stationary saws were substantially lower when wet cutting was performed
instead of dry cutting (mean levels of 42 [mu]g/m\3\ versus 345 [mu]g/
m\3\). Also, the exposure level for fabricators in the stone and stone
products industry, who produce finished stone products from slabs, can
be reduced substantially by applying wet method controls. Simcox et al.
(1999) shows that exposures of fabricators at granite-handling
facilities were reduced by 88 percent (490 [mu]g/m\3\ to 60 [mu]g/m\3\)
when all dry-grinding tools used on granite were either replaced or
modified to be water-fed.
    Regarding the application of wet methods to operations involving
portable equipment, recent studies show that using wet methods to
control respirable dust released during chipping with hand-held
equipment can reduce worker exposure substantially. NIOSH (2003-EPHB
282-11a) investigated a water-spray dust control used by construction
workers breaking concrete with 60- and 90-pound jackhammers. A spray
nozzle was fitted to the body of the chipping tool, and a fine mist was
directed at the breaking point. Compared with uncontrolled pavement
breaking, PBZ respirable dust concentrations were between 72 and 90
percent lower when the water spray was used. Williams and Sam (1999)
also reported that a water-spray nozzle mounted on a hand-held
pneumatic chipper decreased respirable dust by approximately 70 percent
in the worker's breathing zone.
    Washing aggregate also reduces the amount of fine particulate
matter generated during subsequent use or handling. Burgess (1995)
reports that the use of washed sand, from which a substantial portion
of the fine particles have been removed, results in respirable
crystalline silica exposures that are generally lower than when sand is
not pre-washed. Plinke et al. (1992) also report that increasing
moisture content decreases the amount of dust generated and state that
it is often most efficient to apply water sprays to material before it
reaches a transfer point so that the dust has time to absorb water
before being disturbed.
    For the railroad transportation industry, OSHA is recommending that
ballast be washed before it is loaded into hopper cars. Ballast wetted
at the supplier's site might dry prior to reaching the dumping site
(NIOSH HETA-92-0311, 2001). In this circumstance, applying an
additional layer of blanketing foam or other sealing chemical
suppressant on top of the rail car can reduce water evaporation and
provide an additional type of dust suppression (ECS, 2007). Work
practice controls. Work practice controls systematically modify how
workers perform an operation, and often involve workers' use of
engineering controls. For crystalline silica exposures, OSHA's
technological feasibility analysis shows that work practice controls
are generally applied complementary to engineering controls, to adjust
the way a task is performed. For work practice controls to be most
effective, it is essential that workers and supervisors are fully aware
of the exposures generated by relevant workplace activities and the
impact of the engineering controls installed. Work practice controls
are preferred over the use of personal protective equipment since work
practice controls can address the exposure of silica at the source of
emissions, thus protecting nearby workers.
    Work practice controls can enhance the effects of engineering
controls. For example, to ensure that LEV is working effectively, a
worker would position it so that it captures the full range of dust

created, thus minimizing silica exposures.
    A good example of adequate work practice controls can be found in
ready-mixed concrete operations. Exposure data available to OSHA
indicate that all truck drivers or other workers who remove residual
concrete inside ready-mixed truck mixer drums have silica exposures
greater than the proposed PEL, with some exposures approaching 10,000
[mu]g/m\3\. The Agency recommends wet methods and ventilation as
appropriate engineering controls and also gives priority to performing
a particular work practice that can reduce exposures. Specifically,
this work practice involves the timely rinsing of drum mixers. One
report (Williams and Sam, 1999) concluded that heavy build-up of
concrete inside truck mixer drums results in higher concentrations of
worker exposure to crystalline silica during cleaning because a greater
amount of time is required to remove the build-up. Rinsing the drum
with water immediately after each load helps minimize build-up and the
resulting dust exposure. The same cleaning methods are used, such as
water pressure and scraping, independently of how often rinsing is
performed. However, by rinsing the tanks with more frequency, the
employer is modifying the nature of the cleaning operation because less
concrete will be present, and thus less respirable dust created, during
each cleaning.
    Another example of good work practices can be observed in the
porcelain enameling industry. One facility stated that porcelain
applicators can ensure that they are making optimal use of LEV by
avoiding positioning themselves between the enamel spray and the
ventilation system. For large items, workers can use a turntable
support to rotate the item so that it can be sprayed on all sides while
the worker maintains the spray direction pointing into the ventilated
booth (Porcelain Industries, 2004a).
    Combined control methods. Exposure documentation obtained by the
Agency demonstrates that for many operations, a combination of
engineering and work practice controls reduces silica exposure levels
more effectively than a single control method. The following examples
represent preliminary feasibility conclusions for several industries.
    In the dental equipment and supplies industry, OSHA has found that
employers can limit the exposure of most workers to 50 [mu]g/m\3\ or
less by implementing a combination of engineering controls, including
improving ventilation systems (at bag-dumping stations, weighing and
mixing equipment, and packaging machinery) and designing workstations
to minimize spills, and encouraging work practices that maximize the
effect of engineering controls. One facility that implemented these
controls reduced median exposure levels by 80 percent, from 160 [mu]g/
m\3\ to 32 [mu]g/m\3\ (OSHA SEP Inspection Report 122252281).
    Based on the exposure profile for the rock and concrete drilling
industry, construction sites have already achieved compliance with the
proposed PEL for about half of the workers operating drilling rigs
through a combination of controls, including wet dust suppression
methods, shrouds, and hoods connected to dust extraction equipment, and
management of dust collection dump points (PEA, Chapter 4).
    An example from a routine cupola relining in the ferrous foundry
industry also demonstrates the benefit of a combination of controls.
Samples taken before and after additional controls were installed
reflect a 90-percent reduction of the median worker exposures (OSHA SEP
Inspection Report 122209679). The modifications included using
refractory material with reduced silica and greater moisture content,
improving equipment and materials to reduce malfunction and task
duration, wetting refractory material before removal, and assigning a
consistent team of trained workers to the task.
    Burmeister (2001) also reported on the benefits of multiple
controls on another refractory relining activity. Initially, a full-
shift crystalline silica result of 2.74 times the current calculated
PEL was obtained while a worker chipped away the old refractory lining
and then mixed the replacement refractory material. The foundry
responded by holding a training meeting and seeking worker input on
abatement actions, implementing a water control system to reduce dust
generated during the pneumatic chipping process, purchasing chisel
retainers that eliminated the need for workers to reach into the ladle
during chipping, and purchasing a vacuum to remove dust and chipped
material from the ladle. With these changes in place, a consultant
found that exposure was reduced to 87 percent of the calculated PEL,
representing a 70-percent reduction in worker exposure.
    These examples illustrate the importance and value of maintaining
an effective set of engineering controls alongside work practice
controls to optimize silica exposure reduction. The proposed
requirements are consistent with ASTM E 1132-06 and ASTM E 2625-09, the
national consensus standards for controlling occupational exposure to
respirable crystalline silica in general industry and in construction,
respectively. Each of these standards has explicit requirements for
methods of compliance. These requirements include use of properly
designed engineering controls such as ventilation or other dust
suppression methods and enclosed workstations such as control booths
and equipment cabs; requirements for maintenance and evaluation of
engineering controls; and implementation of certain work practices such
as not working in areas where visible dust is generated from respirable
crystalline silica containing materials without use of respiratory
protection. OSHA has elected to propose a performance standard for
general industry in which particular engineering and work practice
controls are not specified. Instead, the standard requires that
employers use engineering and work practice controls to achieve the
PEL. In this case the use of properly designed, maintained, and
regularly inspected engineering controls is implied by the ongoing
ability of the employer to achieve the PEL. The national consensus
standard for construction (ASTM E 2625-09) includes task-based control
strategies for situations where exposures are known from empirical
data. This approach is consistent with the alternative approach for
construction operations in paragraph (f)(2) described below.
    Paragraph (f)(2) of the proposed rule provides an alternative
approach to achieve compliance with paragraph (f), Methods of
Compliance, for construction operations. Under this paragraph,
employers that implement the specific engineering controls, work
practices, and, if required, respiratory protection described in Table
1 (please refer to paragraph (f) of the proposed rule) are considered
to be in compliance with the requirements for engineering and work
practice controls in paragraph (f)(1) of the proposed rule. An
advantage of complying with Table 1 is that the employer need not make
a determination of the hierarchy of controls, because the table
incorporates that determination for each job operation listed.
Furthermore, proposed paragraph (d)(8)(i) specifies that if an employer
chooses to follow Table 1, the employer need not conduct exposure
assessments required by paragraph (d) of the proposed rule. Rather, for
those operations in Table 1 where respirator use is required, proposed
paragraph (d)(8)(ii) requires employers to presume that workers engaged
in those operations are exposed above the PEL; in those cases, the
employer would be

required to comply with all provisions of the standard that apply to
exposures above the PEL except for monitoring. For instance, when Table
1 requires workers to use respirators, the employer relying on Table 1
must: establish a regulated area or access control plan pursuant to
proposed paragraph (e); comply with the cleaning methods provisions in
proposed paragraph (f)(4); comply with the prohibition of employee
rotation as specified in proposed paragraph (f)(5); establish a
respiratory protection program pursuant to proposed paragraph (g)(2);
and provide medical surveillance pursuant to paragraph (h) if workers
are exposed for 30 or more days per year.
    Table 1 was developed using recommendations made by small entity
representatives through the Small Business Regulatory Enforcement
Fairness Act (SBREFA) process. The SBREFA panel asked OSHA to develop a
provision that detailed what specific controls to use for each
construction operation covered by the rule in order to achieve
compliance with paragraph (f)(1). Additionally, the Advisory Committee
for Construction Safety and Health (ACCSH) has recommended that OSHA
proceed with the development of Table 1. The table provides a list of
13 construction operations that expose workers to respirable
crystalline silica as well as control strategies (engineering controls,
work practices, and respirators) that reduce those exposures.
    In developing control strategies for each of the 13 construction
operations in Table 1, OSHA relied upon information from a variety of
sources including scientific literature, NIOSH reports, OSHA site
visits, and compliance case files (SEP reports). For several of the
listed operations and controls, the Agency requests additional
information from the public that will allow the Agency to determine
whether the operations, corresponding control strategies, and
conditions of use should be modified or removed from Table 1. OSHA also
requests comment on the degree of specificity used for engineering and
work practice controls for tasks identified in Table 1, including
maintenance requirements.
    Table 1 implements a novel approach for OSHA. The Agency believes
that the table will provide significant benefits to workers and
employers by ensuring that workers are adequately protected, providing
specific approaches for complying with paragraph (f) requirements, and
reducing the monitoring and sampling burden.
    The table divides operations according to duration into ``less than
or equal to'' four-hours-per-day tasks and ``greater than'' four-hours-
per-day tasks. The Agency recognizes that some activities do not last a
full work shift, and often some activities are performed for half-
shifts or less. The duration of a task influences the extent of worker
exposure and the selection of appropriate control strategies. OSHA
followed its hierarchy of controls to develop these control strategies.
Respiratory protection has been included in Table 1 for operations in
which the specified engineering and work practice controls may not
maintain worker exposures at or below the proposed PEL for all workers