(1995) did find significant pulmonary decrements among a subset of
granite workers (termed ``dropouts'') who left work and consequently
did not voluntarily participate in the last of a series of annual
pulmonary function tests. This group of workers experienced steeper
declines in FEV1 compared to the subset of workers who
remained at work and participated in all tests (termed ``survivors''),
and these declines were significantly related to dust exposure. Thus,
in this study, workers who had left work had exposure-related declines
in pulmonary function to a greater extent than did workers who remained
on the job, clearly demonstrating a survivor effect among the active
workers. Exposure-related changes in lung function were also reported
in a 12-year study of granite workers (Malmberg et al., 1993), in two
5-year studies of South African miners (Hnizdo, 1992; Cowie, 1998), and
in a study of foundry workers whose lung function was assessed between
1978 and 1992 (Hertzberg et al., 2002).
    Each of these studies reported their findings in terms of rates of
decline in any of several pulmonary function measures, such as FVC,
FEV1, and FEV1/FVC. To put these declines in
perspective, Eisen et al. (1995), reported that the rate of decline in
FEV1 seen among the dropout subgroup of Vermont granite
workers was 4 ml per mg/m\3\-year of exposure to respirable granite
dust; by comparison, FEV1 declines at a rate of 10 ml/year
from smoking one pack of cigarettes daily. From their study of foundry
workers, Hertzberg et al., (2002) reported finding a 1.1 ml/year
decline in FEV1 and a 1.6 ml/year decline in FVC for each
mg/m\3\-year of respirable silica exposure after controlling for
ethnicity and smoking. From these rates of decline, they estimated that
exposure to the current OSHA quartz standard of 0.1 mg/m\3\ for 40
years would result in a total loss of FEV1 and FVC that is
less than but still comparable to smoking a pack of cigarettes daily
for 40 years. Hertzberg et al. (2002) also estimated that exposure to
the current standard for 40 years would increase the risk of developing
abnormal FEV1 or FVC by factors of 1.68 and 1.42,
respectively. OSHA believes that this magnitude of reduced pulmonary
function, as well as the increased morbidity and mortality from non-
malignant respiratory disease that has been documented in the studies
summarized above, constitute material impairments of health and loss of
functional respiratory capacity.
d. Renal and Autoimmune Effects
    OSHA's review of the literature summarized in Section V, Health
Effects Summary, reflects substantial evidence that exposure to
crystalline silica increases the risk of renal and autoimmune diseases.
Epidemiologic studies have found statistically significant associations
between occupational exposure to silica dust and chronic renal disease
(e.g., Calvert et al., 1997), subclinical renal changes including
proteinurea and elevated serum creatinine (e.g., Ng et al., 1992c;
Rosenman et al., 2000; Hotz et al., 1995), end-stage renal disease
morbidity (e.g., Steenland et al., 1990), chronic renal disease
mortality (Steenland et al., 2001b, 2002a), and Wegener's
granulomatosis (Nuyts et al., 1995), the latter of which represents
severe injury to the glomeruli that, if untreated, rapidly leads to
renal failure. Possible mechanisms suggested for silica-induced renal
disease include a direct toxic effect on the kidney, deposition in the
kidney of immune complexes (IgA) following silica-related pulmonary
inflammation, or an autoimmune mechanism (Calvert et al., 1997;
Gregorini et al., 1993). Steenland et al. (2002a) demonstrated a
positive exposure-response relationship between exposure to respirable
crystalline silica and end-stage renal disease mortality.
    In addition, there are a number of studies that show exposure to be
related to increased risks of autoimmune disease, including scleroderma
(e.g., Sluis-Cremer et al., 1985), rheumatoid arthritis (e.g. Klockars
et al., 1987; Rosenman and Zhu, 1995), and systemic lupus erythematosus
(e.g., Brown et al., 1997). Scleroderma is a degenerative disorder that
leads to over-production of collagen in connective tissue that can
cause a wide variety of symptoms including skin discoloration and
ulceration, joint pain, swelling and discomfort in the extremities,
breathing problems, and digestive problems. Rheumatoid arthritis is
characterized by joint pain and tenderness, fatigue, fever, and weight
loss. Systemic lupus erythematosus is a chronic disease of connective
tissue that can present a wide range of symptoms including skin rash,
fever, malaise, joint pain, and, in many cases, anemia and iron
deficiency. OSHA believes that chronic renal disease, end-stage renal
disease mortality, Wegener's granulomatosis, scleroderma, rheumatoid
arthritis, and systemic lupus erythematosus clearly represent material
impairments of health.
2. Significance of Risk
    To evaluate the significance of the health risks that result from
exposure to hazardous chemical agents, OSHA relies on toxicological,
epidemiological, and experimental data, as well as statistical methods.
The Agency uses these data and methods to characterize the risk of
disease resulting from workers' exposure to a given hazard over a
working lifetime at levels of exposure reflecting both compliance with
current standards and compliance with the new standard being proposed.
In the case of crystalline silica, the current general industry,
construction, and shipyard PELs are formulas that limit 8-hour TWA
exposures to respirable dust; the limit on exposure decreases with
increasing crystalline silica content of the dust. OSHA's current
general industry PEL for respirable quartz is expressed both in terms
of a particle count as well as a gravimetric concentration, while the
current construction and shipyard employment PELs for respirable quartz
are only expressed in terms of a particle count formula. For general
industry, the gravimetric formula PEL for quartz approaches 0.1 mg/m\3\
(100 [mu]g/m\3\) of respirable crystalline silica when the quartz
content of the dust is about 10 percent or greater. For the
construction and shipyard industries, the current PEL is a formula that
is based on concentration of respirable particles in the air; on a mass
concentration basis, it is believed by OSHA to lie within a range of
between about 0.25 mg/m\3\ (250 [mu]g/m\3\) to 0.5 mg/m\3\ (500 [mu]g/
m\3\) expressed as respirable quartz (see Section VI). In general
industry, the current PELs for cristobalite and tridymite are one-half
the PEL for quartz.
    OSHA is proposing to revise the current PELs for general industry,
construction, and shipyards to 0.05 mg/m\3\ (50 [mu]g/m\3\) of
respirable crystalline silica. OSHA is also proposing an action level
of 0.025 mg/m\3\ (25 [mu]g/m\3\). In the Summary of the Preliminary
Quantitative Risk Assessment (Section VI of the preamble), OSHA
presents estimates of health risks associated with 45 years of exposure
to 0.025, 0.05, and 0.1 mg/m\3\ respirable crystalline silica to
represent the risks associated with exposure over a working lifetime to
the proposed action level, proposed PEL, and current general industry
PEL, respectively. OSHA also presents estimates associated with
exposure to 0.25 and 0.5 mg/m\3\ to represent a range of risks likely
to be associated with exposure to the current construction and shipyard
PELs. Risk estimates are

presented for mortality due to lung cancer, silicosis and other non-
malignant lung disease, and end-stage renal disease, as well as
silicosis morbidity. The preliminary findings from this assessment are
summarized below.
a. Summary of Excess Risk Estimates for Excess Lung Cancer Mortality
    For preliminary estimates of lung cancer risk from crystalline
silica exposure, OSHA has relied upon studies of exposure-response
relationships presented in a pooled analysis of 10 cohort studies
(Steenland, et al. 2001a; Toxichemica, Inc., 2004) as well as on
individual studies of granite (Attfield and Costello, 2004),
diatomaceous earth (Rice et al., 2001), and industrial sand (Hughes et
al., 2001) worker cohorts, and a study of coal miners exposed to
respirable quartz (Miller et al., 2007; Miller and MacCalman, 2009).
OSHA believes these studies are suitable for use to quantitatively
characterize health risks to exposed workers because (1) study
populations were of sufficient size to provide adequate power to detect
low levels of risk, (2) sufficient quantitative exposure data were
available to characterize cumulative exposures of cohort members to
respirable crystalline silica, (3) the studies either adjusted for or
otherwise adequately addressed confounding factors such as smoking and
exposure to other carcinogens, and (4) investigators developed
quantitative assessments of exposure-response relationships using
appropriate statistical models or otherwise provided sufficient
information that permits OSHA to do so. Where investigators estimated
excess lung cancer risks associated with exposure to the current PEL or
NIOSH recommended exposure limit, OSHA provided these estimates in its
Preliminary Quantitative Risk Assessment. However, OSHA implemented all
risk models in its own life table analysis so that the use of
background lung cancer rates and assumptions regarding length of
exposure and lifetime were constant across each of the models, and so
OSHA could estimate lung cancer risks associated with exposure to
specific levels of silica of interest to the Agency.
    The Steenland et al. (2001a) study consisted of a pooled exposure-
response analysis and risk assessment based on raw data obtained for
ten cohorts of silica-exposed workers (65,980 workers, 1,072 lung
cancer deaths). The cohorts in this pooled analysis include U.S. gold
miners (Steenland and Brown, 1995a), U.S. diatomaceous earth workers
(Checkoway et al., 1997), Australian gold miners (deKlerk and Musk,
1998), Finnish granite workers (Koskela et al., 1994), South African
gold miners (Hnizdo et al., 1997), U.S. industrial sand employees
(Steenland et al., 2001b), Vermont granite workers (Costello and
Graham, 1988), and Chinese pottery workers, tin miners, and tungsten
miners (Chen et al., 1992). The investigators used a nested case-
control design with cases and controls matched for race, sex, age
(within five years) and study; 100 controls were matched for each case.
An extensive exposure assessment for this pooled analysis was developed
and published by Mannetje et al. (2002a). Exposure measurement data
were available for all 10 cohorts and included measurements of particle
counts, total dust mass, respirable dust mass, and, for one cohort,
respirable quartz. Cohort-specific conversion factors were used to
estimate cumulative exposures to respirable crystalline silica. A case-
control analysis of silicosis mortality (Mannetje et al., 2002b) showed
a strong positive exposure-response trend, indicating that cumulative
exposure estimates for the cohorts were not subject to random
misclassification errors of such a magnitude so as to obscure observing
an exposure-response relationship between silica and silicosis despite
the variety of dust measurement metrics relied upon and the need to
make assumptions to convert the data to a single exposure metric (i.e.,
mass concentration of respirable crystalline silica). In effect, the
known relationship between exposure to respirable silica and silicosis
served as a positive control to assess the validity of exposure
estimates. Quantitative assessment of lung cancer risks were based on
use of a log-linear model (log RR = [beta]x, where x represents the
exposure variable and [beta] the coefficient to be estimated) with a
15-year exposure lag providing the best fit. Models based on
untransformed or log-transformed cumulative dose metrics provided an
acceptable fit to the pooled data, with the model using untransformed
cumulative dose providing a slightly better fit. However, there was
substantial heterogeneity among the exposure-response coefficients
derived from the individual cohorts when untransformed cumulative dose
was used, which could result in one or a few of the cohorts unduly
influencing the pooled exposure-response coefficient. For this reason,
the authors preferred the use of log-transformed cumulative exposure in
the model to derive the pooled coefficient since heterogeneity was
substantially reduced.
    OSHA's implementation of this model is based on a re-analysis
conducted by Steenland and Bartow (Toxichemica, 2004), which corrected
small errors in the assignment of exposure estimates in the original
analysis. In addition, subsequent to the Toxichemica report, and in
response to suggestions made by external peer reviewers, Steenland and
Bartow conducted additional analyses based on use of a linear relative
risk model having the general form RR = 1 + [beta]x, as well as a
categorical analysis (personal communication, Steenland 2010). The
linear model was implemented with both untransformed and log-
transformed cumulative exposure metrics, and was also implemented as a
2-piece spline model.
    The categorical analysis indicates that, for the pooled data set,
lung cancer relative risks increase steeply at low exposures, after
which the rate of increase in relative risk declines and the exposure-
response curve becomes flat (see Figure II-2 of the Preliminary
Quantitative Risk Assessment). Use of either the linear relative risk
or log-linear relative risk model with untransformed cumulative
exposure (with or without a 15-year lag) failed to capture this initial
steep slope, resulting in an underestimate of the relative risk
compared to that suggested by the categorical analysis. In contrast,
use of log-transformed cumulative exposure with the linear or log-
linear model, and use of the 2-piece linear spline model with
untransformed exposure, better reflected the initial rise and
subsequent leveling out of the exposure-response curve, with the spline
model fitting somewhat better than either the linear or log-linear
models (all models incorporated a 15-year exposure lag). Of the three
models that best reflect the shape of the underlying exposure-response
curve suggested by the categorical analysis, there is no clear
rationale to prefer one over the other. Use of log-transformed
cumulative exposure in either the linear or log-linear models has the
advantage of reducing heterogeneity among the 10 pooled studies,
lessening the likelihood that the pooled coefficient would be overtly
influenced by outliers; however, use of a log-transformed exposure
metric complicates comparing results with those from other risk
analyses considered by OSHA that are based on untransformed exposure
metrics. Since all three of these models yield comparable estimates of
risk the choice of model is not critical for the purpose of assessing
significance of the risk, and therefore OSHA believes that the risk
estimates derived from the pooled study

are best represented as a range of estimates based on all three of
these models.
    From these models, the estimated lung cancer risk associated with
45 years of exposure to 0.1 mg/m\3\ (about equal to the current general
industry PEL) is between 22 and 29 deaths per 1,000 workers. The
estimated risk associated with exposure to silica concentrations in the
range of 0.25 and 0.5 mg/m\3\ (about equal to the current construction
and shipyard PELs) is between 27 and 38 deaths per 1,000. At the
proposed PEL of 0.05 mg/m\3\, the estimated excess risk ranges from 18
to 26 deaths per 1,000, and, at the proposed action level of 0.025 mg/
m\3\, from 9 to 23 deaths per 1,000.
    As previously discussed, the exposure-response coefficients derived
from each of the 10 cohorts exhibited significant heterogeneity; risk
estimates based on the coefficients derived from the individual studies
for untransformed cumulative exposure varied by almost two orders of
magnitude, with estimated risks associated with exposure over a working
lifetime to the current general industry PEL ranging from a low of 0.8
deaths per 1,000 (from the Chinese pottery worker study) to a high of
69 deaths per 1,000 (from the South African miner study). It is
possible that the differences seen in the slopes of the exposure-
response relationships reflect physical differences in the nature of
crystalline silica particles generated in these workplaces and/or the
presence of different substances on the crystal surfaces that could
mitigate or enhance their toxicity (see Section V, Health Effects
Summary). It may also be that exposure estimates for some cohorts were
subject to systematic misclassification errors resulting in under- or
over-estimation of exposures due to the use of assumptions and
conversion factors that were necessary to estimate mass respirable
crystalline silica concentrations from exposure samples analyzed as
particle counts or total and respirable dust mass. OSHA believes that,
given the wide range of risk estimates derived from these 10 studies,
use of log-transformed cumulative exposure or the 2-piece spline model
is a reasonable approach for deriving a single summary statistic that
represents the lung cancer risk across the range of workplaces and
exposure conditions represented by the studies. However, use of these
approaches results in a non-linear exposure-response and suggests that
the relative risk of silica-related lung cancer begins to attenuate at
cumulative exposures in the range of those represented by the current
PELs. Although such exposure-response relationships have been described
for some carcinogens (for example, from metabolic saturation or a
healthy worker survivor effect, see Staynor et al., 2003), OSHA is not
aware of any specific evidence that would suggest that such a result is
biologically plausible for silica, except perhaps the possibility that
lung cancer risks increase more slowly with increasing exposure because
of competing risks from other silica-related diseases. Attenuation of
the exposure-response can also result from misclassification of
exposure estimates for the more highly-exposed cohort members (Staynor
et al., 2003). OSHA's evaluation of individual cohort studies discussed
below indicates that, with the exception of the Vermont granite cohort,
attenuation of exposure-related lung cancer response has not been
directly observed.
    In addition to the pooled cohort study, OSHA's Preliminary
Quantitative Risk Assessment presents risk estimates derived from four
individual studies where investigators presented either lung cancer
risk estimates or exposure-response coefficients. Two of these studies,
one on diatomaceous earth workers (Rice et al., 2001) and one on
Vermont granite workers (Attfield and Costello, 2004), were included in
the 10-cohort pooled study (Steenland et al., 2001a; Toxichemica,
2004). The other two were of British coal miners (Miller et al., 2007;
Miller and MacCalman, 2010) and North American industrial sand workers
(Hughes et al., 2001).
    Rice et al. (2001) presents an exposure-response analysis of the
diatomaceous worker cohort studied by Checkoway et al. (1993, 1996,
1997), who found a significant relationship between exposure to
respirable cristobalite and increased lung cancer mortality. The cohort
consisted of 2,342 white males employed for at least one year between
1942 and 1987 in a California diatomaceous earth mining and processing
plant. The cohort was followed until 1994, and included 77 lung cancer
deaths. The risk analysis relied on an extensive job-specific exposure
assessment developed by Sexias et al. (1997), which included use of
over 6,000 samples taken during the period 1948 through 1988. The mean
cumulative exposure for the cohort was 2.16 mg/m\3\-years for
respirable crystalline silica dust. Rice et al. (2001) evaluated
several model forms for the exposure-response analysis and found
exposure to respirable cristobalite to be a significant predictor of
lung cancer mortality with the best-fitting model being a linear
relative risk model (with a 15-year exposure lag). From this model, the
estimates of the excess risk of lung cancer mortality are 34, 17, and 9
deaths per 1,000 workers for 45-years of exposure to 0.1, 0.05, and
0.025 mg/m\3\, respectively. For exposures in the range of the current
construction and shipyard PELs over 45 years, estimated risks lie in a
range between 81 and 152 deaths per 1,000 workers.
    Somewhat higher risk estimates are derived from the analysis
presented by Attfield and Costello (2004) of Vermont granite workers.
This study involved a cohort of 5,414 male granite workers who were
employed in the Vermont granite industry between 1950 and 1982 and who
were followed through 1994. Workers' cumulative exposures were
estimated by Davis et al. (1983) based on historical exposure data
collected in six environmental surveys conducted between 1924 and 1977.
A categorical analysis showed an increasing trend of lung cancer risk
ratios with increasing exposure, and Poisson regression was used to
evaluate several exposure-response models with varying exposure lags
and use of either untransformed or log-transformed exposure metrics.
The best-fitting model was based on use of a 15-year lag, use of
untransformed cumulative exposure, and omission of the highest exposure
group. The investigators believed that the omission of the highest
exposure group was appropriate since: (1) The underlying exposure data
for the high-exposure group was weaker than for the others; (2) there
was a greater likelihood that competing causes of death and
misdiagnoses of causes of death attenuated the lung cancer death rate
in the highest exposure group; (3) all of the remaining groups
comprised 85 percent of the deaths in the cohort and showed a strong
linear increase in lung cancer mortality with increasing exposure; and
(4) the exposure-response relationship seen in the lower exposure
groups was more relevant given that the exposures of these groups were
within the range of current occupational standards. OSHA's use of the
exposure coefficient from this analysis in a log-linear relative risk
model yielded a risk estimate of 60 deaths per 1,000 workers for 45
years of exposure to the current general industry PEL of 0.1 mg/m\3\,
25 deaths per 1,000 for 45 years of exposure to the proposed PEL of
0.05 mg/m\3\, and 11 deaths per 1,000 for 45 years of exposure at the
proposed action level of 0.025 mg/m\3\. Estimated risks associated with
45 years of exposure at the current construction PEL range from 250 to
653 deaths per 1,000.
    Hughes et al. (2001) conducted a nested case-control study of 95
lung cancer deaths from a cohort of 2,670

industrial sand workers in the U.S. and Canada studied by McDonald et
al. (2001). (This cohort overlaps with the cohort studied by Steenland
and Sanderson (2001), which was included in the 10-cohort pooled study
by Steenland et al., 2001a). Both categorical analyses and conditional
logistic regression were used to examine relationships with cumulative
exposure, log of cumulative exposure, and average exposure. Exposure
levels over time were estimated via a job-exposure matrix developed for
this study (Rando et al., 2001). The 50th percentile (median) exposure
level of cases and controls for lung cancer were 0.149 and 0.110 mg/
m\3\ respirable crystalline silica, respectively, slightly above the
current OSHA general industry standard. There did not appear to be
substantial misclassification of exposures, as evidenced by silicosis
mortality showing a positive exposure-response trend with cumulative
exposure and average exposure concentration. Statistically significant
positive exposure-response trends for lung cancer were found for both
cumulative exposure (lagged 15 years) and average exposure
concentration, but not for duration of employment, after controlling
for smoking. There was no indication of an interaction effect of
smoking and cumulative silica exposure. Hughes et al. (2001) reported
the exposure coefficients for both lagged and unlagged cumulative
exposure; there was no significant difference between the two (0.13 per
mg/m\3\-year for lagged vs. 0.14 per mg/m\3\-year for unlagged). Use of
the coefficient from Hughes et al. (2001) that incorporated a 15-year
lag generates estimated cancer risks of 34, 15, and 7 deaths per 1,000
for 45 years exposure to the current general industry PEL of 0.1, the
proposed PEL of 0.05 mg/m\3\, and the proposed action level of 0.025
mg/m\3\ respirable silica, respectively. For 45 years of exposure to
the construction PEL, estimated risks range from 120 to 387 deaths per
1,000 workers.
    Miller and MacCalman (2010, also reported in Miller et al., 2007)
extended the follow-up of a previously published cohort mortality study
(Miller and Buchanan, 1997). The follow-up study included 17,800 miners
from 10 coal mines in the U.K. who were followed through the end of
2005; observation in the original study began in 1970. By 2005, there
were 516,431 person years of observation, an average of 29 years per
miner, with 10,698 deaths from all causes. Exposure estimates of cohort
members were not updated from the earlier study since the mines closed
in the 1980s; however, some of these men might have had additional
exposure at other mines or facilities. An analysis of cause-specific
mortality was performed using external controls; it demonstrated that
lung cancer mortality was statistically significantly elevated for coal
miners exposed to silica. An analysis using internal controls was
performed via Cox proportional hazards regression methods, which
allowed for each individual miner's measurements of age and smoking
status, as well as the individual's detailed dust and quartz time-
dependent exposure measurements. From the Cox regression, Miller and
MacCalman (2009) estimated that cumulative exposure of 5 g-h/m\3\
respirable quartz (incorporating a 15-year lag) was associated with a
relative risk of 1.14 for lung cancer. This cumulative exposure is
about equivalent to 45 years of exposure to 0.055 mg/m\3\ respirable
quartz, or a cumulative exposure of 2.25 mg/m\3\-yr, assuming 2,000
hours of exposure per year. OSHA applied this slope factor in a log-
relative risk model and estimated the lifetime lung cancer mortality
risk to be 13 per 1,000 for 45 years of exposure to 0.1 mg/m\3\
respirable crystalline silica. For the proposed PEL of 0.05 mg/m\3\ and
proposed action level of 0.025 mg/m\3\, the lifetime risks are
estimated to be 6 and 3 deaths per 1,000, respectively. The range of
risks estimated to result from 45 years of exposure to the current
construction and shipyard PELs is from 37 to 95 deaths per 1,000
workers.
    The analysis from the Miller and MacCalman (2009) study yields risk
estimates that are lower than those obtained from the other cohort
studies described above. Possible explanations for this include: (1)
Unlike the studies on diatomaceous earth workers and granite workers,
the mortality analysis of the coal miners was adjusted for smoking; (2)
lung cancer risks might have been lower among the coal miners due to
high competing mortality risks observed in the cohort (mortality was
significantly increased for several diseases, including tuberculosis,
chronic bronchitis, and non-malignant respiratory disease); and (3) the
lower risk estimates derived from the coal miner study could reflect an
actual difference in the cancer potency of the quartz dust in the coal
mines compared to that present in the work environments studied
elsewhere. OSHA believes that the risk estimates derived from this
study are credible. In terms of design, the cohort was based on union
rolls with very good participation rates and good reporting. The study
group was the largest of any of the individual cohort studies reviewed
here (over 17,000 workers) and there was an average of nearly 30 years
of follow-up, with about 60 percent of the cohort having died by the
end of follow-up. Just as important were the high quality and detail of
the exposure measurements, both of total dust and quartz.
b. Summary of Risk Estimates for Silicosis and Other Chronic Lung
Disease Mortality
    OSHA based its quantitative assessment of silicosis mortality risks
on a pooled analysis conducted by Mannetje et al. (2002b) of data from
six of the ten epidemiological studies in the Steenland et al. (2001a)
pooled analysis of lung cancer mortality. Cohorts included in the
silicosis study were U.S. diatomaceous earth workers (Checkoway et al.,
1997); Finnish granite workers (Koskela et al., 1994); U.S. granite
workers (Costello and Graham, 1988); U.S. industrial sand workers
(Steenland and Sanderson, 2001); U.S. gold miners (Steenland and Brown,
1995b); and Australian gold miners (deKlerk and Musk, 1998). These six
cohorts contained 18,634 subjects and 170 silicosis deaths, where
silicosis mortality was defined as death from silicosis (ICD-9 502,
n=150) or from unspecified pneumoconiosis (ICD-9 505, n = 20). Analysis
of exposure-response was performed in a categorical analysis where the
cohort was divided into cumulative exposure deciles and Poisson
regression was used to estimate silicosis rate ratios for each
category, adjusted for age, calendar period, and study. Exposure-
response was examined in more detail using a nested case-control design
and logistic regression. Although Mannetje et al. (2002b) estimated
silicosis risks at the current OSHA PEL from the Poisson regression, a
subsequent analysis based on the case-control design was conducted by
Steenland and Bartow (Toxichemica, 2004), which resulted in slightly
lower estimates of risk. Based on the Toxichemica analysis, OSHA
estimates that the lifetime risk (over 85 years) of silicosis mortality
associated with 45 years of exposure to the current general industry
PEL of 0.1 mg/m\3\ is 11 deaths per 1,000 workers. Exposure for 45
years to the proposed PEL of 0.05 mg/m\3\ and action level of 0.025 mg/
m\3\ results in an estimated 7 and 4 silicosis deaths per 1,000,
respectively. Lifetime risks associated with exposure at the current
construction and shipyard PELs range from 17 to 22 deaths per 1,000
workers.
    To study non-malignant respiratory diseases, of which silicosis is
one, Park et al. (2002) analyzed the California

diatomaceous earth cohort data originally studied by Checkoway et al.
(1997), consisting of 2,570 diatomaceous earth workers employed for 12
months or more from 1942 to 1994. The authors quantified the
relationship between exposure to cristobalite and mortality from
chronic lung disease other than cancer (LDOC). Diseases in this
category included pneumoconiosis (which included silicosis), chronic
bronchitis, and emphysema, but excluded pneumonia and other infectious
diseases. Less than 25 percent of the LDOC deaths in the analysis were
coded as silicosis or other pneumoconiosis (15 of 67). As noted by Park
et al. (2002), it is likely that silicosis as a cause of death is often
misclassified as emphysema or chronic bronchitis. Exposure-response
relationships were explored using both Poisson regression models and
Cox's proportional hazards models fit to the same series of relative
rate exposure-response models that were evaluated by Rice et al. (2001)
for lung cancer (i.e., log-linear, log-square root, log-quadratic,
linear relative rate, a power function, and a shape function). Relative
or excess rates were modeled using internal controls and adjusting for
age, calendar time, ethnicity (Hispanic versus white), and time since
first entry into the cohort, or using age- and calendar time-adjusted
external standardization to U.S. population mortality rates. There were
no LDOC deaths recorded among workers having cumulative exposures above
32 mg/m\3\-years, causing the response to level off or decline in the
highest exposure range; possible explanations considered included
survivor selection, depletion of susceptible populations in high dust
areas, and/or a higher degree of misclassification of exposures in the
earlier years where exposure data were lacking and when exposures were
presumably the highest. Therefore, Park et al. (2002) performed
exposure-response analyses that restricted the dataset to observations
where cumulative exposures were below 10 mg/m\3\-years, a level more
than four times higher than that resulting from 45 years of exposure to
the current general industry PEL for cristobalite (which is about 0.05
mg/m\3\), as well as analyses using the full dataset. Among the models
based on the restricted dataset, the best-fitting model with a single
exposure term was the linear relative rate model using external
adjustment.
    OSHA's estimates of the lifetime chronic lung disease mortality
risk based on this model are substantially higher than those that OSHA
derived from the Mannetje et al. (2002b) silicosis analysis. For the
current general industry PEL of 0.1 mg/m\3\, exposure for 45 years is
estimated to result in 83 deaths per 1,000 workers. At the proposed PEL
of 0.05 mg/m\3\ and action level of 0.025 mg/m\3\, OSHA estimates the
lifetime risk from 45 years of exposure to be 43 and 22 deaths per
1,000, respectively. The range of risks associated with exposure at the
construction and shipyard PELs over a working lifetime is from 188 to
321 deaths per 1,000 workers. It should be noted that the Mannetje
study (2002b) was not adjusted for smoking while the Park study (2002)
had data on smoking habits for about one-third of the workers who died
from LDOC and about half of the entire cohort. The Poisson regression
on which the risk model is based was partially stratified on smoking.
Furthermore, analyses without adjustment for smoking suggested to the
authors that smoking was acting as a negative confounder.
c. Summary of Risk Estimates for Renal Disease Mortality
    OSHA's analysis of the health effects literature included several
studies that have demonstrated that exposure to crystalline silica
increases the risk of renal and autoimmune disease (see Section V,
Health Effects Summary). Studies have found statistically significant
associations between occupational exposure to silica dust and chronic
renal disease, sub-clinical renal changes, end-stage renal disease
morbidity, chronic renal disease mortality, and Wegener's
granulomatosis. A strong exposure-response association for renal
disease mortality and silica exposure has also been demonstrated.
    OSHA's assessment of the renal disease risks that result from
exposure to respirable crystalline silica are based on an analysis of
pooled data from three cohort studies (Steenland et al., 2002a). The
combined cohort for the pooled analysis (Steenland et al., 2002a)
consisted of 13,382 workers and included industrial sand workers
(Steenland et al., 2001b), U.S. gold miners (Steenland and Brown,
1995a), and Vermont granite workers (Costello and Graham, 1998).
Exposure data were available for 12,783 workers and analyses conducted
by the original investigators demonstrated monotonically increasing
exposure-response trends for silicosis, indicating that exposure
estimates were not likely subject to significant random
misclassification. The mean duration of exposure, cumulative exposure,
and concentration of respirable silica for the combined cohort were
13.6 years, 1.2 mg/m\3\-years, and 0.07 mg/m\3\, respectively. There
were highly statistically significant trends for increasing renal
disease mortality with increasing cumulative exposure for both multiple
cause analysis of mortality (p<0.000001) and underlying cause analysis
(p = 0.0007). Exposure-response analysis was also conducted as part of
a nested case-control study, which showed statistically significant
monotonic trends of increasing risk with increasing exposure again for
both multiple cause (p = 0.004 linear trend, 0.0002 log trend) and
underlying cause (p = 0.21 linear trend, 0.03 log trend) analysis. The
authors found that use of log-cumulative dose in a log relative risk
model fit the pooled data better than cumulative exposure, average
exposure, or lagged exposure. OSHA's estimates of renal disease
mortality risk, which are based on the log relative risk model with log
cumulative exposure, are 39 deaths per 1,000 for 45 years of exposure
at the current general industry PEL of 0.1 mg/m\3\, 32 deaths per 1,000
for exposure at the proposed PEL of 0.05 mg/m\3\, and 25 deaths per
1,000 at the proposed action level of 0.025 mg/m\3\. OSHA also
estimates that 45 years of exposure at the current construction and
shipyard PELs would result in a renal disease mortality risk ranging
from 52 to 63 deaths per 1,000 workers.
d. Summary of Risk Estimates for Silicosis Morbidity
    OSHA's Preliminary Quantitative Risk Assessment reviewed several
cross-sectional studies designed to characterize relationships between
exposure to respirable crystalline silica and development of silicosis
as determined by chest radiography. Several of these studies could not
provide information on exposure or length of employment prior to
disease onset. Others did have access to sufficient historical medical
data to retrospectively determine time of disease onset but included
medical examination at follow up of primarily active workers with
little or no post-employment follow-up. Although OSHA presents
silicosis risk estimates that were reported by the investigators of
these studies, OSHA believes that such estimates are likely to
understate lifetime risk of developing radiological silicosis; in fact,
the risk estimates reported in these studies are generally lower than
those derived from studies that included retired workers in follow up
medical examinations.
    Therefore, OSHA believes that the most useful studies for
characterizing lifetime risk of silicosis morbidity are retrospective
cohort studies that

included a large proportion of retired workers in the cohort and that
were able to evaluate disease status over time, including post-
retirement. OSHA identified studies of six cohorts for which the
inclusion of retirees was deemed sufficient to adequately characterize
silicosis morbidity risks well past employment (Hnizdo and Sluis-
Cremer, 1993; Steenland and Brown, 1995b; Miller et al., 1998; Buchanan
et al., 2003; Chen et al., 2001; Chen et al., 2005). Study populations
included five mining cohorts and a Chinese pottery worker cohort.
Except for the Chinese studies (Chen et al., 2001; Chen et al., 2005),
chest radiographs were interpreted in accordance with the ILO system
described earlier in this section, and x-ray films were read by panels
of B-readers. In the Chinese studies, films were evaluated using a
Chinese system of classification that is analogous to the ILO system.
In addition, the Steenland and Brown (1995b) study of U.S. gold miners
included silicosis mortality as well as morbidity in its analysis.
OSHA's estimates of silicosis morbidity risks are based on implementing
the various exposure-response models reported by the investigators;
these are considered to be cumulative risk models in the sense that
they represent the risk observed in the cohort at the time of the last
medical evaluation and do not reflect all of the risk that may become
manifest over a lifetime. With the exception of a coal miner study
(Buchanan et al., 2003), risk estimates reflect the risk that a worker
will acquire an abnormal chest x-ray classified as ILO major category 1
or greater; the coal miner study evaluated the risk of acquiring an
abnormal chest x-ray classified as major category 2 or higher.
    For miners exposed to freshly cut crystalline silica, the estimated
risk of developing lesions consistent with an ILO classification of
category 1 or greater is estimated to range from 120 to 773 cases per
1,000 workers exposed at the current general industry PEL of 0.1 mg/
m\3\ for 45 years. For 45 years of exposure to the proposed PEL of 0.05
mg/m\3\, the range in estimated risk is from 20 to 170 cases per 1,000
workers. The risk predicted from exposure to the proposed action level
of 0.025 mg/m\3\ ranges from 5 to 40 cases per 1,000. From the coal
miner study of Buchanan et al. (2003), the estimated risks of acquiring
an abnormal chest x-ray classified as ILO category 2 or higher are 301,
55, and 21 cases per 1,000 workers exposed for 45 years to 0.1, 0.05,
and 0.025 mg/m\3\, respectively. These estimates are within the range
of risks obtained from the other mining studies. At exposures at or
above 0.25 mg/m\3\ for 45 years (equivalent to the current construction
and shipyard PELs), the risk of acquiring an abnormal chest x-ray
approaches unity. Risk estimates based on the pottery cohort are 60,
20, and 5 cases per 1,000 workers exposed for 45 years to 0.1, 0.05,
and 0.025 mg/m\3\, respectively, which is generally below the range of
risks estimated from the other studies and may reflect a lower toxicity
of quartz particles in that work environment due to the presence of
alumino-silicates on the particle surfaces. According to Chen et al.
(2005), adjustment of the exposure metric to reflect the unoccluded
surface area of silica particles resulted in an exposure-response of
pottery workers that was similar to the mining cohorts. The finding of
a reduced silicosis risk among pottery workers is consistent with other
studies of clay and brick industries that have reported finding a lower
prevalence of silicosis compared to that experienced in other industry
sectors (Love et al., 1999; Hessel, 2006; Miller and Soutar, 2007) as
well as a lower silicosis risk per unit of cumulative exposure (Love et
al., 1999; Miller and Soutar, 2007).
3. Significance of Risk and Risk Reduction
    The Supreme Court's benzene decision of 1980, discussed above in
this section, states that ``before he can promulgate any permanent
health or safety standard, the Secretary [of Labor] is required to make
a threshold finding that a place of employment is unsafe--in the sense
that significant risks are present and can be eliminated or lessened by
a change in practices.'' Benzene, 448 U.S. at 642. While making it
clear that it is up to the Agency to determine what constitutes a
significant risk, the Court offered general guidance on the level of
risk OSHA might determine to be significant.

    It is the Agency's responsibility to determine in the first
instance what it considers to be a ``significant'' risk. Some risks
are plainly acceptable and others are plainly unacceptable. If, for
example, the odds are one in a billion that a person will die from
cancer by taking a drink of chlorinated water, the risk clearly
could not be considered significant. On the other hand, if the odds
are one in a thousand that regular inhalation of gasoline vapors
that are 2% benzene will be fatal, a reasonable person might well
consider the risk significant and take appropriate steps to decrease
or eliminate it.

Benzene, 448 U.S. at 655. The Court further stated that the
determination of significant risk is not a mathematical straitjacket
and that ``the Agency has no duty to calculate the exact probability of
harm.'' Id.
    In this section, OSHA presents its preliminary findings with
respect to the significance of the risks summarized above, and the
potential of the proposed standard to reduce those risks. Findings
related to mortality risk will be presented first, followed by
silicosis morbidity risks.
a. Mortality Risks
    OSHA's Preliminary Quantitative Risk Assessment (and the Summary of
the Preliminary Quantitative Risk Assessment in section VI) presents
risk estimates for four causes of excess mortality: Lung cancer,
silicosis, non-malignant respiratory disease (including silicosis and
COPD), and renal disease. Table VII-2 presents the estimated excess
lifetime risks (i.e., to age 85) of these fatal diseases associated
with various levels of crystalline silica exposure allowed under the
current rule, based on OSHA's risk assessment and assuming 45 years of
occupational exposure to crystalline silica.

                              Table VII-2--Expected Excess Deaths per 1,000 Workers
----------------------------------------------------------------------------------------------------------------
                                                                                Current
                                                             Current general    construction/
                   Fatal health outcome                       industry PEL      shipyard PEL      Proposed PEL
                                                              (0.1 mg/m\3\)     (0.25-0.5 mg/    (0.05 mg/m\3\)
                                                                                m\3\)
----------------------------------------------------------------------------------------------------------------
Lung Cancer:
    10-cohort pooled analysis.............................             22-29             27-38             18-26
    Single cohort study-lowest estimate...................                13             37-95                 6
    Single cohort study-highest estimate..................                60           250-653                25
Silicosis.................................................                11             17-22                 7
Non-Malignant Respiratory Disease (including silicosis)...                83           188-321                43

Renal Disease.............................................                39             52-63                32
----------------------------------------------------------------------------------------------------------------

    The purpose of the OSH Act, as stated in Section 6(b), is to ensure
``that no employee will suffer material impairment of health or
functional capacity even if such employee has regular exposure to the
hazard . . . for the period of his working life.'' 29 U.S.C. 655(b)(5).
Assuming a 45-year working life, as OSHA has done in significant risk
determinations for previous standards, the Agency preliminarily finds
that the excess risk of disease mortality related to exposure to
respirable crystalline silica at levels permitted by current OSHA
standards is clearly significant. The Agency's estimate of such risk
falls well above the level of risk the Supreme Court indicated a
reasonable person might consider unacceptable. Benzene, 448 U.S. at
655. For lung cancer, OSHA estimates the range of risk at the current
general industry PEL to be between 13 and 60 deaths per 1,000 workers.
The estimated risk for silicosis mortality is lower, at 11 deaths per
1,000 workers; however, the estimated lifetime risk for non-malignant
respiratory disease mortality, including silicosis, is about 8-fold
higher than that for silicosis alone, at 83 deaths per 1,000. OSHA
believes that the estimate for non-malignant respiratory disease
mortality is better than the estimate for silicosis mortality at
capturing the total respiratory disease burden associated with exposure
to crystalline silica dust. The former captures deaths related to COPD,
for which there is strong evidence of a causal relationship with
exposure to silica, and is also more likely to capture those deaths
where silicosis was a contributing factor but where the cause of death
was misclassified. Finally, there is an estimated lifetime risk of
renal disease mortality of 39 deaths per 1,000. Exposure for 45 years
at levels of respirable crystalline silica in the range of the current
limits for construction and shipyards result in even higher risk
estimates, as presented in Table VII-2.
    To further demonstrate significant risk, OSHA compares the risk
from currently permissible crystalline silica exposures to risks found
across a broad variety of occupations. The Agency has used similar
occupational risk comparisons in the significant risk determination for
substance-specific standards promulgated since the benzene decision.
This approach is supported by evidence in the legislative record, with
regard to Section 6(b)(5) of the Act (29 U.S.C. 655(b)(5)), that
Congress intended the Agency to regulate unacceptably severe
occupational hazards, and not ``to establish a utopia free from any
hazards'' or to address risks comparable to those that exist in
virtually any occupation or workplace. 116 Cong. Rec. 37614 (1970),
Leg. Hist. 480-82. It is also consistent with Section 6(g) of the OSH
Act, which states: ``In determining the priority for establishing
standards under this section, the Secretary shall give due regard to
the urgency of the need for mandatory safety and health standards for
particular industries, trades, crafts, occupations, businesses,
workplaces or work environments.'' 29 U.S.C. 655(g).
    Fatal injury rates for most U.S. industries and occupations may be
obtained from data collected by the Bureau of Labor Statistics. Table
VII-3 shows annual fatality rates per 1,000 employees for several
industries for 2007, as well as projected fatalities per 1,000
employees assuming exposure to workplace hazards for 45 years based on
these annual rates (BLS, 2010). While it is difficult to meaningfully
compare aggregate industry fatality rates to the risks estimated in the
quantitative risk assessment for crystalline silica, which address one
specific hazard (inhalation exposure to respirable crystalline silica)
and several health outcomes (lung cancer, silicosis, NMRD, renal
disease mortality), these rates provide a useful frame of reference for
considering risk from inhalation exposure to crystalline silica. For
example, OSHA's estimated range of 6-60 excess lung cancer deaths per
1,000 workers from regular occupational exposure to respirable
crystalline silica in the range of 0.05--0.1 mg/m\3\ is roughly
comparable to, or higher than, the expected risk of fatal injuries over
a working life in high-risk occupations such as mining and construction
(see Table VII-3). Regular exposures at higher levels, including the
current construction and shipyard PELs for respirable crystalline
silica, are expected to cause substantially more deaths per 1,000
workers from lung cancer (ranging from 37 to 653 per 1,000) than result
from occupational injuries in most private industry. At the proposed
PEL of 0.05 mg/m\3\ respirable crystalline silica, the Agency's
estimate of excess lung cancer mortality, from 6 to 26 deaths per 1,000
workers, is still 3- to10-fold or more higher than private industry's
average fatal injury rate, given the same employment time, and
substantially exceeds those rates found in lower-risk industries such
as finance and educational and health services.

  Table VII-3--Fatal Injuries per 1000 Employees, by Industry or Sector
------------------------------------------------------------------------
                                            Over 1 year    Over 45 years
------------------------------------------------------------------------
All Private Industry....................           0.043             1.9
Mining (General)........................           0.214             9.6
Construction............................           0.108             4.8
Manufacturing...........................           0.024             1.1
Wholesale Trade.........................           0.045             2.0
Transportation and Warehousing..........           0.165             7.4
Financial Activities....................           0.012             0.5
Educational and Health Services.........           0.008             0.4
------------------------------------------------------------------------
Source: BLS (2010).

    Because there is little available information on the incidence of
occupational cancer across all industries, risk from crystalline silica
exposure cannot be compared with overall risk from other workplace
carcinogens. However, OSHA's previous risk assessments provide
estimates of risk from exposure to certain carcinogens. These risk
assessments, as with the current assessment for crystalline silica,
were based on animal or human data of reasonable or high quality and
used the best information then available. Table VII-4 shows the
Agency's best estimates of cancer risk from 45 years of occupational
exposure to several carcinogens, as published in the preambles to final
rules promulgated since the benzene decision in 1980. These risks were
judged by the Agency to be significant.

                      Table VII-4--Selected OSHA Risk Estimates for Prior and Current PELs
                                        [Excess Cancers per 1000 workers]
----------------------------------------------------------------------------------------------------------------
             Standard                Risk at prior PEL    Risk at current PEL        Federal Register date
----------------------------------------------------------------------------------------------------------------
Ethylene Oxide...................  63-109 per 1000.....  1.2-2.3 per 1000....  June 22, 1984.
Asbestos.........................  64 per 1000.........  6.7 per 1000........  June 20, 1986.
Benzene..........................  95 per 1000.........  10 per 1000.........  September 11, 1987.
Formaldehyde.....................  0.4-6.2 per 1000....  0.0056 per 1000.....  December 4, 1987.
Methylenedianiline...............  *6-30 per 1000......  0.8 per 1000........  August 10, 1992.
Cadmium..........................  58-157 per 1000.....  3-15 per 1000.......  September 14, 1992.
1,3-Butadiene....................  11.2-59.4 per 1000..  1.3-8.1 per 1000....  November 4, 1996.
Methylene Chloride...............  126 per 1000........  3.6 per 1000........  January 10, 1997.
Chromium VI......................  101-351 per 1000....  10-45 per 1000......  February 28, 2006
Crystalline Silica:
    General Industry PEL.........  **13-60 per 1000....  ***6-26 per 1000....  N/A
    Construction/Shipyard PEL....  **27-653 per 1000...  ***6-26 per 1000....  .................................
----------------------------------------------------------------------------------------------------------------
* no prior standard; reported risk is based on estimated exposures at the time of the rulemaking
** estimated excess lung cancer risks at the current PEL
*** estimated excess lung cancer risks at the proposed new PEL

    The estimated excess lung cancer risks associated with respirable
crystalline silica at the current general industry PEL, 13-60 deaths
per 1,000 workers, are comparable to, and in some cases higher than,
the estimated excess cancer risks for many other workplace carcinogens
for which OSHA made a determination of significant risk (see Table VII-
4, ``Selected OSHA Risk Estimates for Prior and Current PELs''). The
estimated excess lung cancer risks associated with exposure to the
current construction and shipyard PELs are even higher. The estimated
risk from lifetime occupational exposure to respirable crystalline
silica at the proposed PEL is 6-26 excess lung cancer deaths per 1,000
workers, a range still higher than the risks from exposure to many
other carcinogens regulated by OSHA (see Table VII-4, ``Selected OSHA
Risk Estimates for Prior and Current PELs'').
    OSHA's preliminary risk assessment also shows that reduction of the
current PELs to the proposed level of 0.05 mg/m\3\ will result in
substantial reduction in risk, although quantification of that
reduction is subject to model uncertainty. Risk models that reflect
attenuation of the risk with increasing exposure, such as those
relating risk to a log transformation of cumulative exposure, will
result in lower estimates of risk reduction compared to linear risk
models. Thus, for lung cancer risks, the assessment based on the 10-
cohort pooled analysis by Steenland et al. (2001; also Toxichemica,
2004; Steenland 2010) suggests risk will be reduced by about 14 percent
from the current general industry PEL and by 28-41 percent from the
current construction/shipyard PEL (based on the midpoint of the ranges
of estimated risk derived from the three models used for the pooled
cohort data). These risk reduction estimates, however, are much lower
than those derived from the single cohort studies (Rice et al., 2001;
Attfield and Costello, 2004; Hughes et al., 2001; Miller and MacCalman,
2009), which used linear or log-linear relative risk models with
untransformed cumulative exposure as the dose metric. These single
cohort studies suggest that reducing the current PELs to the proposed
PEL will reduce lung cancer risk by more than 50 percent in general
industry and by more than 80 percent in construction and shipyards.
    For silicosis mortality, OSHA's assessment indicates that risk will
be reduced by 36 percent and by 58-68 percent as a result of reducing
the current general industry and construction/shipyard PELs,
respectively. Non-malignant respiratory disease mortality risks will be
reduced by 48 percent and by 77-87 percent from reducing the general
industry and construction/shipyard PELs, respectively, to the proposed
PEL. There is also a substantial reduction in renal disease mortality
risks; an 18-percent reduction associated with reducing the general
industry PEL and a 38- to 49-percent reduction associated with reducing
the construction/shipyard PEL.
    Thus, OSHA believes that the proposed PEL of 0.05 mg/m\3\
respirable crystalline silica will substantially reduce the risk of
material health impairments associated with exposure to silica.
However, even at the proposed PEL, as well as the action level of 0.025
mg/m\3\, the risk posed to workers with 45 years of regular exposure to
respirable crystalline silica is greater than 1 per 1,000 workers and
is still clearly significant.
b. Silicosis Morbidity Risks
    OSHA's Preliminary Risk Assessment characterizes the risk of
developing lung fibrosis as detected by chest x-ray. For 45 years of
exposure at the current general industry PEL, OSHA estimates that the
risk of developing lung fibrosis consistent with an ILO category 1+
degree of small opacity profusion ranges from 60 to 773 cases per
1,000. For exposure at the construction and shipyard PELs, the risk
approaches unity. The wide range of risk estimates derived from the
underlying studies relied on for the risk assessment may reflect
differences in the relative toxicity of quartz particles in different
workplaces; nevertheless, OSHA believes that each of these risk
estimates clearly represent a significant risk of developing fibrotic
lesions in the lung. Exposure to the proposed PEL of 0.05 mg/m\3\
respirable crystalline silica for 45 years yields an estimated risk of

between 20 and 170 cases per 1,000 for developing fibrotic lesions
consistent with an ILO category of 1+. These risk estimates indicate
that promulgation of the proposed PEL would result in a reduction in
risk by about two-thirds or more, which the Agency believes is a
substantial reduction of the risk of developing abnormal chest x-ray
findings consistent with silicosis.
    One study of coal miners also permitted the agency to evaluate the
risk of developing lung fibrosis consistent with an ILO category 2+
degree of profusion of small opacities (Buchanan et al., 2003). This
level of profusion has been shown to be associated with a higher
prevalence of lung function decrement and an increased rate of early
mortality (Ng et al., 1987a; Begin et al., 1998; Moore et al., 1988; Ng
et al., 1992a; Infante-Rivard et al., 1991). From this study, OSHA
estimates that the risk associated with 45 years of exposure to the
current general industry PEL is 301 cases per 1,000 workers, again a
clearly significant risk. Exposure to the proposed PEL of 0.05 mg/m\3\
respirable crystalline silica for 45 years yields an estimated risk of
55 cases per 1,000 for developing lesions consistent with an ILO
category 2+ degree of small opacity profusion. This represents a
reduction in risk of over 80 percent, again a clearly substantial
reduction of the risk of developing radiologic silicosis consistent
with ILO category 2+ degree of small opacity profusion.
    As is the case for other health effects addressed in the
preliminary risk assessment (i.e., lung cancer, silicosis morbidity
defined as ILO 1+ level of profusion), there is some evidence that this
risk will vary according to the nature of quartz particles present in
different workplaces. In particular, risk may vary depending on whether
quartz is freshly fractured during work operations and the co-existence
of other minerals and substances that could alter the biological
activity of quartz. Using medical and exposure data taken from a cohort
of heavy clay workers first studied by Love et al. (1999), Miller and
Soutar (2007) compared the silicosis prevalence within the cohort to
that predicted by the exposure-response model derived by Buchanan et
al. (2003) and used by OSHA to estimate the risk of radiologic
silicosis with a classification of ILO 2+. They found that the model
predicted about a 4-fold higher prevalence of workers having an
abnormal x-ray than was actually seen in the clay cohort (31 cases
predicted vs. 8 observed). Unlike the coal miner study, the clay worker
cohort included only active workers and not retirees (Love et al.,
1999); however, Miller and Soutar believed this could not explain the
magnitude of the difference between the model prediction and observed
silicosis prevalence in the clay worker cohort. OSHA believes that the
result obtained by Miller and Soutar (2007) likely does reflect
differences in the toxic potency of quartz particles in different work
settings. Nevertheless, even if the risk estimates predicted by the
model derived from the coal worker study were reduced substantially,
even by more than a factor of 10, the resulting risk estimate would
still reflect the presence of a significant risk.
    The Preliminary Quantitative Risk Assessment also discusses the
question of a threshold exposure level for silicosis. There is little
quantitative data available with which to estimate a threshold exposure
level for silicosis or any of the other silica-related diseases
addressed in the risk assessment. The risk assessment discussed one
study that perhaps provides the best information. This is an analysis
by Kuempel et al. (2001) who used a rat-based toxicokinetic/
toxicodynamic model along with a human lung deposition/clearance model
to estimate a minimum lung burden necessary to cause the initial
inflammatory events that can lead to lung fibrosis and an indirect
genotoxic cause of lung cancer. They estimated that the threshold
effect level of lung burden associated with this inflammation
(Mcrit) is the equivalent of exposure to 0.036 mg/m\3\ for
45 years; thus, exposures below this level would presumably not lead to
an excess lung cancer risk (based on an indirect genotoxic mechanism)
nor to silicosis, at least in the ``average individual.'' This might
suggest that exposures to a concentration of silica at the proposed
action level would not be associated with a risk of silicosis, and
possibly not of lung cancer. However, OSHA does not believe that the
analysis by Kuemple et al. is definitive with respect to a threshold
for silica-related disease. First, since the critical quartz burden is
a mean value derived from the model, the authors estimated that a 45-
year exposure to a concentration as low as 0.005 mg/m\3\, or 5 times
below the proposed action level, would result in a lung quartz burden
that was equal to the 95-percent lower confidence limit on
Mcrit. Due to the statistical uncertainty in Kuemple et
al.'s estimate of critical lung burden, OSHA cannot rule out the
existence of a threshold lung burden that is below that resulting from
exposure to the proposed action level. In addition, with respect to
silica-related lung cancer, if at least some of the risk is from a
direct genotoxic mechanism (see section II.F of the Health Effects
Literature Review), then this threshold value is not relevant to the
risk of lung cancer. Supporting evidence comes from Steenland and
Deddens (2002), who found that, for the 10-cohort pooled data set, a
risk model that incorporated a threshold did fit better than a no-
threshold model, but the estimated threshold was very low, 0.010 mg/
m\3\ (10 [mu]g/m\3\). OSHA acknowledges that a threshold exposure level
might lie within the range of the proposed action level, as suggested
by the work of Kuempel et al. (2001) and that this possibility adds
uncertainty to the estimated risks associated with exposure to the
action level. However, OSHA believes that available information cannot
firmly establish a threshold exposure level for silica-related effects,
and there is no empirical evidence that a threshold exists at or above
the proposed PEL of 0.05 mg/m\3\ for respirable crystalline silica.

VIII. Summary of the Preliminary Economic Analysis and Initial
Regulatory Flexibility Analysis

A. Introduction and Summary

    OSHA's Preliminary Economic Analysis and Initial Regulatory
Flexibility Analysis (PEA) addresses issues related to the costs,
benefits, technological and economic feasibility, and the economic
impacts (including impacts on small entities) of this proposed
respirable crystalline silica rule and evaluates regulatory
alternatives to the proposed rule. Executive Orders 13563 and 12866
direct agencies to assess all costs and benefits of available
regulatory alternatives and, if regulation is necessary, to select
regulatory approaches that maximize net benefits (including potential
economic, environmental, and public health and safety effects;
distributive impacts; and equity). Executive Order 13563 emphasized the
importance of quantifying both costs and benefits, of reducing costs,
of harmonizing rules, and of promoting flexibility. The full PEA has
been placed in OSHA rulemaking docket OSHA-2010-0034. This rule is an
economically significant regulatory action under Sec. 3(f)(1) of
Executive Order 12866 and has been reviewed by the Office of
Information and Regulatory Affairs in the Office of Management and
Budget, as required by executive order.
    The purpose of the PEA is to:
     Identify the establishments and industries potentially
affected by the proposed rule;

     Estimate current exposures and the technologically
feasible methods of controlling these exposures;
     Estimate the benefits resulting from employers coming into
compliance with the proposed rule in terms of reductions in cases of
silicosis, lung cancer, other forms of chronic obstructive pulmonary
disease, and renal failure;
     Evaluate the costs and economic impacts that
establishments in the regulated community will incur to achieve
compliance with the proposed rule;
     Assess the economic feasibility of the proposed rule for
affected industries; and
     Assess the impact of the proposed rule on small entities
through an Initial Regulatory Flexibility Analysis (IRFA), to include
an evaluation of significant regulatory alternatives to the proposed
rule that OSHA has considered.
    The Preliminary Economic Analysis contains the following chapters:

Chapter I. Introduction
Chapter II. Assessing the Need for Regulation
Chapter III. Profile of Affected Industries
Chapter IV. Technological Feasibility
Chapter V. Costs of Compliance
Chapter VI. Economic Impacts
Chapter VII. Benefits and Net Benefits
Chapter VIII. Regulatory Alternatives
Chapter IX. Initial Regulatory Flexibility Analysis
Chapter X. Environmental Impacts

    Key findings of these chapters are summarized below and in sections
VIII.B through VIII.I of this PEA summary.
Profile of Affected Industries
    The proposed rule would affect employers and employees in many
different industries across the economy. As described in Section VIII.C
and reported in Table VIII-3 of this preamble, OSHA estimates that a
total of 2.1 million employees in 550,000 establishments and 533,000
firms (entities) are potentially at risk from exposure to respirable
crystalline silica. This total includes 1.8 million employees in
477,000 establishments and 486,000 firms in the construction industry
and 295,000 employees in 56,000 establishments and 47,000 firms in
general industry and maritime.
Technological Feasibility
    As described in more detail in Section VIII.D of this preamble and
in Chapter IV of the PEA, OSHA assessed, for all affected sectors, the
current exposures and the technological feasibility of the proposed PEL
of 50 [micro]g/m\3\ and, for analytic purposes, an alternative PEL of
25 [micro]g/m\3\.
    Tables VIII-6 and VIII-7 in section VIII.D of this preamble
summarize all the industry sectors and construction activities studied
in the technological feasibility analysis and show how many operations
within each can achieve levels of 50 [mu]g/m\3\ through the
implementation of engineering and work practice controls. The table
also summarizes the overall feasibility finding for each industry
sector or construction activity based on the number of feasible versus
infeasible operations. For the general industry sector, OSHA has
preliminarily concluded that the proposed PEL of 50 [mu]g/m\3\ is
technologically feasible for all affected industries. For the
construction activities, OSHA has determined that the proposed PEL of
50 [mu]g/m\3\ is feasible in 10 out of 12 of the affected activities.
Thus, OSHA preliminarily concludes that engineering and work practices
will be sufficient to reduce and maintain silica exposures to the
proposed PEL of 50 [mu]g/m\3\ or below in most operations most of the
time in the affected industries. For those few operations within an
industry or activity where the proposed PEL is not technologically
feasible even when workers use recommended engineering and work
practice controls (seven out of 108 operations, see Tables VIII-6 and
VIII-7), employers can supplement controls with respirators to achieve
exposure levels at or below the proposed PEL.
    Based on the information presented in the technological feasibility
analysis, the Agency believes that 50 [mu]g/m\3\ is the lowest feasible
PEL. An alternative PEL of 25 [mu]g/m\3\ would not be feasible because
the engineering and work practice controls identified to date will not
be sufficient to consistently reduce exposures to levels below 25
[mu]g/m\3\ in most operations most of the time. OSHA believes that an
alternative PEL of 25 [mu]g/m\3\ would not be feasible for many
industries, and that the use of respiratory protection would be
necessary in most operations most of the time to achieve compliance.
Additionally, the current methods of sampling analysis create higher
errors and lower precision in measurement as concentrations of silica
lower than the proposed PEL are analyzed. However, the Agency
preliminarily concludes that these sampling and analytical methods are
adequate to permit employers to comply with all applicable requirements
triggered by the proposed action level and PEL.
Costs of Compliance
    As described in more detail in Section VIII.E and reported by
industry in Table VIII-8 of this preamble, the total annualized cost of
compliance with the proposed standard is estimated to be about $658
million. The major cost elements associated with the revisions to the
standard are costs for engineering controls, including controls for
abrasive blasting ($344 million); medical surveillance ($79 million);
exposure monitoring ($74 million); respiratory protection ($91
million); training ($50 million) and regulated areas or access control
($19 million). Of the total cost, $511 million would be borne by firms
in the construction industry and $147 million would be borne by firms
in general industry and maritime.
    The compliance costs are expressed as annualized costs in order to
evaluate economic impacts against annual revenue and annual profits, to
be able to compare the economic impact of the rulemaking with other
OSHA regulatory actions, and to be able to add and track Federal
regulatory compliance costs and economic impacts in a consistent
manner. Annualized costs also represent a better measure for assessing
the longer-term potential impacts of the rulemaking. The annualized
costs were calculated by annualizing the one-time costs over a period
of 10 years and applying discount rates of 7 and 3 percent as
appropriate.
    The estimated costs for the proposed silica standard rule include
the additional costs necessary for employers to achieve full
compliance. They do not include costs associated with current
compliance that has already been achieved with regard to the new
requirements or costs necessary to achieve compliance with existing
silica requirements, to the extent that some employers may currently
not be fully complying with applicable regulatory requirements.
    OSHA's exposure profile represents the Agency's best estimate of
current exposures (i.e., baseline exposures). OSHA did not attempt to
determine the extent to which current exposures in compliance with the
current silica PELs are the result of baseline engineering controls or
the result of circumstances leading to low exposures. This information
is not needed to estimate the costs of (additional) engineering
controls needed to comply with the proposed standard.
    Because of the severe health hazards involved, the Agency expects
that the estimated 15,446 abrasive blasters in the construction sector
and the estimated 4,550 abrasive blasters in the maritime sector are
currently wearing respirators in compliance with OSHA's abrasive
blasting provisions. Furthermore, for the construction baseline, an
estimated 241,269 workers, including abrasive blasters, will need to
use respirators to achieve compliance with the proposed

rule, and, based on the NIOSH/BLS respirator use survey (NIOSH/BLS,
2003), an estimated 56 percent of construction employers currently
require such respiratory use and have respirator programs that meet
OSHA's respirator standard. OSHA has not taken any costs for employers
and their workers currently in compliance with the respiratory
provisions in the proposed rule.
    In addition, under both the general industry and construction
baselines, an estimated 50 percent of employers have pre-existing
training programs that address silica-related risks (as required under
OSHA's hazard communication standard) and partially satisfy the
proposed rule's training requirements (for costing purposes, estimated
to satisfy 50 percent of the training requirements in the proposed
rule). These employers will need fewer resources to achieve full
compliance with the proposed rule than those employers without pre-
existing training programs that address silica-related risks.
    Other than respiratory protection and worker training concerning
silica-related risks, OSHA did not assume baseline compliance with any
ancillary provisions, even though some employers have reported that
they do currently monitor silica exposure and some employers have
reported conducting medical surveillance.
Economic Impacts
    To assess the nature and magnitude of the economic impacts
associated with compliance with the proposed rule, OSHA developed
quantitative estimates of the potential economic impact of the new
requirements on entities in each of the affected industry sectors. The
estimated compliance costs were compared with industry revenues and
profits to provide an assessment of the economic feasibility of
complying with the revised standard and an evaluation of the potential
economic impacts.
    As described in greater detail in Section VIII.F of this preamble,
the costs of compliance with the proposed rulemaking are not large in
relation to the corresponding annual financial flows associated with
each of the affected industry sectors. The estimated annualized costs
of compliance represent about 0.02 percent of annual revenues and about
0.5 percent of annual profits, on average, across all firms in general
industry and maritime, and about 0.05 percent of annual revenues and
about 1.0 percent of annual profits, on average, across all firms in
construction. Compliance costs do not represent more than 0.39 percent
of revenues or more than 8.8 percent of profits in any affected
industry in general industry or maritime, or more than 0.13 percent of
revenues or more than 3 percent of profits in any affected industry in
construction.
    Based on its analysis of international trade effects, OSHA
concluded that most or all costs arising from this proposed silica rule
would be passed on in higher prices rather than absorbed in lost
profits and that any price increases would result in minimal loss of
business to foreign competition.
    Given the minimal potential impact on prices or profits in the
affected industries, OSHA has preliminarily concluded that compliance
with the requirements of the proposed rulemaking would be economically
feasible in every affected industry sector.
    In addition, OSHA directed Inforum--a not-for-profit corporation
with over 40 years of experience in the design and application of
macroeconomic models--to run its LIFT (Long-term Interindustry
Forecasting Tool) model of the U.S. economy to estimate the industry
and aggregate employment effects of the proposed silica rule. Inforum
developed estimates of the employment impacts over the ten-year period
from 2014-2023 by feeding OSHA's year-by-year and industry-by-industry
estimates of the compliance costs of the proposed rule into its LIFT
model. The most important Inforum result is that the proposed silica
rule would have a negligible--albeit slightly positive--net effect on
aggregate U.S. employment.
    Based on its analysis of the costs and economic impacts associated
with this rulemaking and on Inforum's estimates of associated
employment and other macroeconomic impacts, OSHA preliminarily
concludes that the effect of the proposed standard on employment,
wages, and economic growth for the United States would be negligible.
Benefits, Net Benefits, and Cost-Effectiveness
    As described in more detail in Section VIII.G of this preamble,
OSHA estimated the benefits, net benefits, and incremental benefits of
the proposed silica rule. That section also contains a sensitivity
analysis to show how robust the estimates of net benefits are to
changes in various cost and benefit parameters. A full explanation of
the derivation of the estimates presented there is provided in Chapter
VII of the PEA for the proposed rule. OSHA invites comments on any
aspect of its estimation of the benefits and net benefits of the
proposed rule.
    OSHA estimated the benefits associated with the proposed PEL of 50
[mu]g/m\3\ and, for analytical purposes to comply with OMB Circular A-
4, with an alternative PEL of 100 [mu]g/m\3\ for respirable crystalline
silica by applying the dose-response relationship developed in the
Agency's quantitative risk assessment--summarized in Section VI of this
preamble--to current exposure levels. OSHA determined current exposure
levels by first developing an exposure profile (presented in Chapter IV
of the PEA) for industries with workers exposed to respirable
crystalline silica, using OSHA inspection and site-visit data, and then
applying this exposure profile to the total current worker population.
The industry-by-industry exposure profile is summarized in Table VIII-5
in Section VIII.C of this preamble.
    By applying the dose-response relationship to estimates of current
exposure levels across industries, it is possible to project the number
of cases of the following diseases expected to occur in the worker
population given current exposure levels (the ``baseline''):
     Fatal cases of lung cancer,
     fatal cases of non-malignant respiratory disease
(including silicosis),
     fatal cases of end-stage renal disease, and
     cases of silicosis morbidity.
    Table VIII-1 provides a summary of OSHA's best estimate of the
costs and benefits of the proposed rule using a discount rate of 3
percent. As shown, the proposed rule is estimated to prevent 688
fatalities and 1,585 silica-related illnesses annually once it is fully
effective, and the estimated cost of the rule is $637 million annually.
Also as shown in Table VIII-1, the discounted monetized benefits of the
proposed rule are estimated to be $5.3 billion annually, and the
proposed rule is estimated to generate net benefits of $4.6 billion
annually. Table VIII-1 also presents the estimated costs and benefits
of the proposed rule using a discount rate of 7 percent. The estimated
costs and benefits of the proposed rule, disaggregated by industry
sector, were previously presented in Table SI-3 in this preamble.

  Table VIII-1--Annualized Benefits, Costs and Net Benefits of OSHA's Proposed Silica Standard of 50 [mu]g/m\3\
----------------------------------------------------------------------------------------------------------------
                       Discount rate                                                 3%                7%
----------------------------------------------------------------------------------------------------------------
Annualized Costs
    Engineering Controls (includes Abrasive Blasting).....                        $329,994,068      $343,818,700
    Respirators...........................................                          90,573,449        90,918,741
    Exposure Assessment...................................                          72,504,999        74,421,757
    Medical Surveillance..................................                          76,233,932        79,069,527
    Training..............................................                          48,779,433        50,266,744
    Regulated Area or Access Control......................                          19,243,500        19,396,743
                                                           -----------------------------------------------------
        Total Annualized Costs (point estimate)...........                         637,329,380       657,892,211
Annual Benefits: Number of Cases Prevented
    Fatal Lung Cancers (midpoint estimate)................               162
    Fatal Silicosis & other Non-Malignant Respiratory                    375
     Diseases.............................................
    Fatal Renal Disease...................................               151
                                                           ------------------
    Silica-Related Mortality..............................               688     3,203,485,869     2,101,980,475
    Silicosis Morbidity...................................             1,585     1,986,214,921     1,363,727,104
                                                                             -----------------------------------
        Monetized Annual Benefits (midpoint estimate).....                       5,189,700,790     3,465,707,579
        Net Benefits......................................                       4,552,371,410     2,807,815,368
----------------------------------------------------------------------------------------------------------------

Initial Regulatory Flexibility Analysis
    OSHA has prepared an Initial Regulatory Flexibility Analysis (IRFA)
in accordance with the requirements of the Regulatory Flexibility Act,
as amended in 1996. Among the contents of the IRFA are an analysis of
the potential impact of the proposed rule on small entities and a
description and discussion of significant alternatives to the proposed
rule that OSHA has considered. The IRFA is presented in its entirety
both in Chapter IX of the PEA and in Section VIII.I of this preamble.
    The remainder of this section (Section VIII) of the preamble is
organized as follows:

B. The Need for Regulation
C. Profile of Affected Industry
D. Technological Feasibility
E. Costs of Compliance
F. Economic Feasibility Analysis and Regulatory Flexibility
Determination
G. Benefits and Net Benefits
H. Regulatory Alternatives
I. Initial Regulatory Flexibility Analysis.

B. Need for Regulation

    Employees in work environments addressed by the proposed silica
rule are exposed to a variety of significant hazards that can and do
cause serious injury and death. As described in Chapter II of the PEA
in support of the proposed rule, the risks to employees are excessively
large due to the existence of various types of market failure, and
existing and alternative methods of overcoming these negative
consequences--such as workers' compensation systems, tort liability
options, and information dissemination programs--have been shown to
provide insufficient worker protection.
    After carefully weighing the various potential advantages and
disadvantages of using a regulatory approach to improve upon the
current situation, OSHA concludes that, in the case of silica exposure,
the proposed mandatory standards represent the best choice for reducing
the risks to employees. In addition, rulemaking is necessary in this
case in order to replace older existing standards with updated, clear,
and consistent health standards.

C. Profile of Affected Industries

1. Introduction
    Chapter III of the PEA presents profile data for industries
potentially affected by the proposed silica rule. The discussion below
summarizes the findings in that chapter. As a first step, OSHA
identifies the North American Industrial Classification System (NAICS)
industries, both in general industry and maritime and in the
construction sector, with potential worker exposure to silica. Next,
OSHA provides summary statistics for the affected industries, including
the number of affected entities and establishments, the number of at-
risk workers, and the average revenue for affected entities and
establishments. \3\ Finally, OSHA presents silica exposure profiles for
at-risk workers. These data are presented by sector and job category.
Summary data are also provided for the number of workers in each
affected industry who are currently exposed above the proposed silica
PEL of 50 [mu]g/m\3\, as well as above an alternative PEL of 100 [mu]g/
m\3\ for economic analysis purposes.
---------------------------------------------------------------------------

    \3\ An establishment is a single physical location at which
business is conducted or services or industrial operations are
performed. An entity is an aggregation of all establishments owned
by a parent company within an industry with some annual payroll.
---------------------------------------------------------------------------

    The methodological basis for the industry and at-risk worker data
presented here comes from ERG (2007a, 2007b, 2008a, and 2008b). The
actual data presented here comes from the technological feasibility
analyses presented in Chapter IV of the PEA and from ERG (2013), which
updated ERG's earlier spreadsheets to reflect the most recent industry
data available. The technological feasibility analyses identified the
job categories with potential worker exposure to silica. ERG (2007a,
2007b) matched the BLS Occupational Employment Survey (OES)
occupational titles in NAICS industries with the at-risk job categories
and then calculated the percentages of production employment
represented by each at-risk job title.\4\ These percentages were then
used to project the number of employees in the at-risk job categories
by NAICS industry. OSHA welcomes additional information and data that
might help improve the accuracy and usefulness of the industry profile
presented here and in Chapter III of the PEA.
---------------------------------------------------------------------------

    \4\ Production employment includes workers in building and
grounds maintenance; forestry, fishing, and farming; installation
and maintenance; construction; production; and material handling
occupations.
---------------------------------------------------------------------------

2. Selection of NAICS Industries for Analysis
    The technological feasibility analyses presented in Chapter IV of
the PEA identify the general industry and maritime sectors and the
construction activities potentially affected by the proposed silica
standard.

a. General Industry and Maritime
    Employees engaged in various activities in general industry and
maritime routinely encounter crystalline silica as a molding material,
as an inert mineral additive, as a refractory material, as a
sandblasting abrasive, or as a natural component of the base materials
with which they work. Some industries use various forms of silica for
multiple purposes. As a result, employers are challenged to limit
worker exposure to silica in dozens of job categories throughout the
general industry and maritime sectors.
    Job categories in general industry and maritime were selected for
analysis based on data from the technical industrial hygiene
literature, evidence from OSHA Special Emphasis Program (SEP) results,
and, in several cases, information from ERG site visit reports. These
data sources provided evidence of silica exposures in numerous sectors.
While the available data are not entirely comprehensive, OSHA believes
that silica exposures in other sectors are quite limited.
    The 25 industry subsectors in the overall general industry and
maritime sectors that OSHA identified as being potentially affected by
the proposed silica standard are as follows:

 Asphalt Paving Products
 Asphalt Roofing Materials
 Industries with Captive Foundries
 Concrete Products
 Cut Stone
 Dental Equipment and Supplies
 Dental Laboratories
 Flat Glass
 Iron Foundries
 Jewelry
 Mineral Processing
 Mineral Wool
 Nonferrous Sand Casting Foundries
 Non-Sand Casting Foundries
 Other Ferrous Sand Casting Foundries
 Other Glass Products
 Paint and Coatings
 Porcelain Enameling
 Pottery
 Railroads
 Ready-Mix Concrete
 Refractories
 Refractory Repair
 Shipyards
 Structural Clay

    In some cases, affected industries presented in the technological
feasibility analysis have been disaggregated to facilitate the cost and
economic impact analysis. In particular, flat glass, mineral wool, and
other glass products are subsectors of the glass industry described in
Chapter IV of the PEA, and captive foundries,\5\ iron foundries,
nonferrous sand casting foundries, non-sand cast foundries, and other
ferrous sand casting foundries are subsectors of the overall foundries
industry presented in Chapter IV of the PEA.
---------------------------------------------------------------------------

    \5\ Captive foundries include establishments in other industries
with foundry processes incidental to the primary products
manufactured. ERG (2008b) provides a discussion of the
methodological issues involved in estimating the number of captive
foundries and in identifying the industries in which they are found.
---------------------------------------------------------------------------

    As described in ERG (2008b), OSHA identified the six-digit NAICS
codes for these subsectors to develop a list of industries potentially
affected by the proposed silica standard. Table VIII-2 presents the
sectors listed above with their corresponding six-digit NAICS
industries.
BILLING CODE 4510-26-P

[GRAPHIC] [TIFF OMITTED] TP12SE13.004

[GRAPHIC] [TIFF OMITTED] TP12SE13.005

BILLING CODE 4510-26-C

b. Construction
    The construction sector is an integral part of the nation's
economy, accounting for almost 6 percent of total employment.
Establishments in this industry are involved in a wide variety of
activities, including land development and subdivision, homebuilding,
construction of nonresidential buildings and other structures, heavy
construction work (including roadways and bridges), and a myriad of
special trades such as plumbing, roofing, electrical, excavation, and
demolition work.
    Construction activities were selected for analysis based on
historical data of recorded samples of construction worker exposures
from the OSHA Integrated Management Information System (IMIS) and the
National Institute for Occupational Safety and Health (NIOSH). In
addition, OSHA reviewed the industrial hygiene literature across the
full range of construction activities, and focused on dusty operations
where silica sand was most likely to be fractured or abraded by work
operations. These physical processes have been found to cause the
silica exposures that pose the greatest risk of silicosis for workers.
    The 12 construction activities, by job category, that OSHA
identified as being potentially affected by the proposed silica
standard are as follows:

 Abrasive Blasters
 Drywall Finishers
 Heavy Equipment Operators
 Hole Drillers Using Hand-Held Drills
 Jackhammer and Impact Drillers
 Masonry Cutters Using Portable Saws
 Masonry Cutters Using Stationary Saws
 Millers Using Portable or Mobile Machines
 Rock and Concrete Drillers
 Rock-Crushing Machine Operators and Tenders
 Tuckpointers and Grinders
 Underground Construction Workers

    As shown in ERG (2008a) and in Chapter IV of the PEA, these
construction activities occur in the following construction industries,
accompanied by their four-digit NAICS codes: \6\ \7\
---------------------------------------------------------------------------

    \6\ ERG and OSHA used the four-digit NAICS codes for the
construction sector both because the BLS's Occupational Employment
Statistics survey only provides data at this level of detail and
because, unlike the case in general industry and maritime, job
categories in the construction sector are task-specific, not
industry-specific. Furthermore, as far as economic impacts are
concerned, IRS data on profitability are reported only at the four-
digit NAICS code level of detail.
    \7\ In addition, some public employees in state and local
governments are exposed to elevated levels of respirable crystalline
silica. These exposures are included in the construction sector
because they are the result of construction activities.

 2361 Residential Building Construction
 2362 Nonresidential Building Construction
 2371 Utility System Construction
 2372 Land Subdivision
 2373 Highway, Street, and Bridge Construction
 2379 Other Heavy and Civil Engineering Construction
 2381 Foundation, Structure, and Building Exterior Contractors
 2382 Building Equipment Contractors
 2383 Building Finishing Contractors
 2389 Other Specialty Trade Contractors
Characteristics of Affected Industries
    Table VIII-3 provides an overview of the industries and estimated
number of workers affected by the proposed rule. Included in Table
VIII-3 are summary statistics for each of the affected industries,
subtotals for construction and for general industry and maritime, and
grand totals for all affected industries combined.
    The first five columns in Table VIII-3 identify each industry in
which workers are routinely exposed to respirable crystalline silica
(preceded by the industry's NAICS code) and the total number of
entities, establishments, and employees for that industry. Note that
not all entities, establishments, and employees in these affected
industries necessarily engage in activities involving silica exposure.
    The next three columns in Table VIII-3 show, for each affected
industry, OSHA's estimate of the number of affected entities,
establishments, and workers--that is, the number of entities and
establishments in which workers are actually exposed to silica and the
total number of workers exposed to silica. Based on ERG (2007a, 2007b),
OSHA's methodology focused on estimation of the number of affected
workers. The number of affected establishments was set equal to the
total number of establishments in an industry (based on Census data)
unless the number of affected establishments would exceed the number of
affected employees in the industry. In that case, the number of
affected establishments in the industry was set equal to the number of
affected employees, and the number of affected entities in the industry
was reduced so as to maintain the same ratio of entities to
establishments in the industry.\8\
---------------------------------------------------------------------------

    \8\ OSHA determined that removing this assumption would have a
negligible impact on total costs and would reduce the cost and
economic impact on the average affected establishment or entity.

                                            Table VIII-3--Characteristics of Industries Affected by OSHA's Proposed Standard for Silica--All Entities
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                      Total                                      Total affected                     Total FTE
    NAICS          Industry      Total entities    establish-         Total      Total affected  establishments  Total affected     affected      Total revenues   Revenues per    Revenues per
                                       \a\          ments \a\    employment \a\   entities \b\         \b\       employment \b\   employees \b\    ($1,000) \c\       entity       establishment
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Construction
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
236100.......  Residential              197,600         198,912         966,198          54,973          55,338          55,338          27,669     $374,724,410      $1,896,379      $1,883,870
                Building
                Construction.
236200.......  Nonresidential            43,634          44,702         741,978          43,634          44,702         173,939          34,788      313,592,140       7,186,876       7,015,170
                Building
                Construction.
237100.......  Utility System            20,236          21,232         496,628          20,236          21,232         217,070          96,181       98,129,343       4,849,246       4,621,766
                Construction.
237200.......  Land Subdivision          12,383          12,469          77,406           6,466           6,511           6,511           3,255       24,449,519       1,974,442       1,960,824
237300.......  Highway, Street,          11,081          11,860         325,182          11,081          11,860         204,899          66,916       96,655,241       8,722,610       8,149,683
                and Bridge
                Construction.
237900.......  Other Heavy and            5,326           5,561          90,167           5,326           5,561          46,813          18,835       19,456,230       3,653,066       3,498,693
                Civil
                Engineering
                Construction.
238100.......  Foundation,              116,836         117,456       1,167,986         116,836         117,456         559,729         111,946      157,513,197       1,348,156       1,341,040
                Structure, and
                Building
                Exterior
                Contractors.
238200.......  Building                 179,051         182,368       1,940,281          19,988          20,358          20,358          10,179      267,537,377       1,494,196       1,467,019
                Equipment
                Contractors.
238300.......  Building                 132,219         133,343         975,335         119,000         120,012         120,012          60,006      112,005,298         847,120         839,979
                Finishing
                Contractors.
238900.......  Other Specialty           73,922          74,446         557,638          73,922          74,446         274,439         137,219       84,184,953       1,138,835       1,130,819
                Trade
                Contractors.
999000.......  State and local           14,397             N/A       5,762,939          14,397              NA         170,068          85,034              N/A             N/A             N/A
                governments \d\.
                                ----------------------------------------------------------------------------------------------------------------------------------------------------------------
                  Subtotals--Co         806,685         802,349      13,101,738         485,859         477,476       1,849,175         652,029    1,548,247,709       1,954,148       1,929,644
                   nstruction.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                General Industry and Maritime
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
324121.......  Asphalt paving               480           1,431          14,471             480           1,431           5,043  ..............        8,909,030      18,560,480       6,225,737
                mixture and
                block
                manufacturing.
324122.......  Asphalt shingle              121             224          12,631             121             224           4,395  ..............        7,168,591      59,244,556      32,002,640
                and roofing
                materials.
325510.......  Paint and                  1,093           1,344          46,209           1,093           1,344           3,285  ..............       24,113,682      22,061,923      17,941,728
                coating
                manufacturing
                \e\.
327111.......  Vitreous china                31              41           5,854              31              41           2,802  ..............          818,725      26,410,479      19,968,899
                plumbing
                fixtures &
                bathroom
                accessories
                manufacturing.
327112.......  Vitreous china,              728             731           9,178             728             731           4,394  ..............          827,296       1,136,395       1,131,731
                fine
                earthenware, &
                other pottery
                product
                manufacturing.
327113.......  Porcelain                    110             125           6,168             110             125           2,953  ..............          951,475       8,649,776       7,611,802
                electrical
                supply mfg.
327121.......  Brick and                    104             204          13,509             104             204           5,132  ..............        2,195,641      21,111,931      10,762,945
                structural clay
                mfg.
327122.......  Ceramic wall and             180             193           7,094             180             193           2,695  ..............        1,217,597       6,764,429       6,308,794
                floor tile mfg.
327123.......  Other structural              45              49           1,603              45              49             609  ..............          227,406       5,053,461       4,640,933
                clay product
                mfg.
327124.......  Clay refractory              108             129           4,475             108             129           1,646  ..............          955,377       8,846,082       7,406,022
                manufacturing.
327125.......  Nonclay                       81             105           5,640              81             105           2,075  ..............        1,453,869      17,948,999      13,846,371
                refractory
                manufacturing.
327211.......  Flat glass                    56              83          11,003              56              83             271  ..............        3,421,674      61,101,328      41,224,993
                manufacturing.
327212.......  Other pressed                457             499          20,625             457             499           1,034  ..............        3,395,635       7,430,274       6,804,880
                and blown glass
                and glassware
                manufacturing.
327213.......  Glass container               32              72          14,392              32              72             722  ..............        4,365,673     136,427,289      60,634,351
                manufacturing.
327320.......  Ready-mixed                2,470           6,064         107,190           2,470           6,064          43,920  ..............       27,904,708      11,297,453       4,601,700
                concrete
                manufacturing.
327331.......  Concrete block               599             951          22,738             599             951          10,962  ..............        5,127,518       8,560,131       5,391,712
                and brick mfg.
327332.......  Concrete pipe                194             385          14,077             194             385           6,787  ..............        2,861,038      14,747,620       7,431,268
                mfg.
327390.......  Other concrete             1,934           2,281          66,095           1,934           2,281          31,865  ..............       10,336,178       5,344,456       4,531,424
                product mfg.
327991.......  Cut stone and              1,885           1,943          30,633           1,885           1,943          12,085  ..............        3,507,209       1,860,588       1,805,048
                stone product
                manufacturing.
327992.......  Ground or                    171             271           6,629             171             271           5,051  ..............        2,205,910      12,900,061       8,139,891
                treated mineral
                and earth
                manufacturing.
327993.......  Mineral wool                 195             321          19,241             195             321           1,090  ..............        5,734,226      29,406,287      17,863,633
                manufacturing.
327999.......  All other misc.              350             465          10,028             350             465           4,835  ..............        2,538,560       7,253,028       5,459,268
                nonmetallic
                mineral product
                mfg.
331111.......  Iron and steel               686             805         108,592             523             614             614  ..............       53,496,748      77,983,597      66,455,587
                mills.
331112.......  Electrometallurg              22              22           2,198              12              12              12  ..............        1,027,769      46,716,774      46,716,774
                ical ferroalloy
                product
                manufacturing.
331210.......  Iron and steel               186             240          21,543              94             122             122  ..............        7,014,894      37,714,484      29,228,725
                pipe and tube
                manufacturing
                from purchased
                steel.
331221.......  Rolled steel                 150             170          10,857              54              61              61  ..............        4,494,254      29,961,696      26,436,790
                shape
                manufacturing.
331222.......  Steel wire                   232             288          14,669              67              83              83  ..............        3,496,143      15,069,584      12,139,387
                drawing.
331314.......  Secondary                    119             150           7,381              33              42              42  ..............        4,139,263      34,783,724      27,595,088
                smelting and
                alloying of
                aluminum.
331423.......  Secondary                     29              31           1,278               7               7               7  ..............          765,196      26,386,082      24,683,755
                smelting,
                refining, and
                alloying of
                copper.
331492.......  Secondary                    195             217           9,383              48              53              53  ..............        3,012,985      15,451,203      13,884,721
                smelting,
                refining, and
                alloying of
                nonferrous
                metal (except
                cu & al).
331511.......  Iron foundries..             457             527          59,209             457             527          22,111  ..............        9,753,093      21,341,560      18,506,818
331512.......  Steel investment             115             132          16,429             115             132           5,934  ..............        2,290,472      19,917,147      17,352,060
                foundries.
331513.......  Steel foundries              208             222          17,722             208             222           6,618  ..............        3,640,441      17,502,121      16,398,383
                (except
                investment).
331524.......  Aluminum                     441             466          26,565             441             466           9,633  ..............        3,614,233       8,195,541       7,755,866
                foundries
                (except die-
                casting).
331525.......  Copper foundries             251             256           6,120             251             256           2,219  ..............          747,437       2,977,835       2,919,674
                (except die-
                casting).
331528.......  Other nonferrous             119             124           4,710             119             124           1,708  ..............          821,327       6,901,910       6,623,607
                foundries
                (except die-
                casting).
332111.......  Iron and steel               358             398          26,596             135             150             150  ..............        5,702,872      15,929,811      14,328,825
                forging.
332112.......  Nonferrous                    67              77           8,814              43              50              50  ..............        2,080,000      31,044,783      27,012,993
                forging.
332115.......  Crown and                     50              59           3,243              15              18              18  ..............          905,206      18,104,119      15,342,473
                closure
                manufacturing.
332116.......  Metal stamping..           1,556           1,641          64,724             347             366             366  ..............       10,418,233       6,695,523       6,348,710
332117.......  Powder                       111             129           8,362              41              47              47  ..............        1,178,698      10,618,900       9,137,193
                metallurgy part
                manufacturing.
332211.......  Cutlery and                  138             141           5,779              32              33              33  ..............        1,198,675       8,686,049       8,501,240
                flatware
                (except
                precious)
                manufacturing.
332212.......  Hand and edge              1,056           1,155          36,622             189             207             207  ..............        6,382,593       6,044,123       5,526,055
                tool
                manufacturing.
332213.......  Saw blade and                127             136           7,304              39              41              41  ..............        1,450,781      11,423,474      10,667,509
                handsaw
                manufacturing.
332214.......  Kitchen utensil,              64              70           3,928              20              22              22  ..............        1,226,230      19,159,850      17,517,577
                pot, and pan
                manufacturing.
332323.......  Ornamental and             2,408           2,450          39,947              53              54              54  ..............        6,402,565       2,658,873       2,613,292
                architectural
                metal work.
332439.......  Other metal                  364             401          15,195              78              86              86  ..............        2,817,120       7,739,340       7,025,236
                container
                manufacturing.

332510.......  Hardware                     734             828          45,282             227             256             256  ..............        9,268,800      12,627,793      11,194,203
                manufacturing.
332611.......  Spring (heavy                109             113           4,059              22              23              23  ..............          825,444       7,572,882       7,304,815
                gauge)
                manufacturing.
332612.......  Spring (light                270             340          15,336              69              87              87  ..............        2,618,283       9,697,344       7,700,832
                gauge)
                manufacturing.
332618.......  Other fabricated           1,103           1,198          36,364             189             205             205  ..............        5,770,701       5,231,823       4,816,946
                wire product
                manufacturing.
332710.......  Machine shops...          21,135          21,356         266,597           1,490           1,506           1,506  ..............       32,643,382       1,544,518       1,528,534
332812.......  Metal coating              2,363           2,599          56,978           2,363           2,599           4,695  ..............       11,010,624       4,659,595       4,236,485
                and allied
                services.
332911.......  Industrial valve             394             488          38,330             175             216             216  ..............        8,446,768      21,438,497      17,308,951
                manufacturing.
332912.......  Fluid power                  306             381          35,519             161             201             201  ..............        8,044,008      26,287,608      21,112,882
                valve and hose
                fitting
                manufacturing.
332913.......  Plumbing fixture             126             144          11,513              57              65              65  ..............        3,276,413      26,003,281      22,752,871
                fitting and
                trim
                manufacturing.
332919.......  Other metal                  240             268          18,112              91             102             102  ..............        3,787,626      15,781,773      14,132,931
                valve and pipe
                fitting
                manufacturing.
332991.......  Ball and roller              107             180          27,197              91             154             154  ..............        6,198,871      57,933,374      34,438,172
                bearing
                manufacturing.
332996.......  Fabricated pipe              711             765          27,201             143             154             154  ..............        4,879,023       6,862,198       6,377,808
                and pipe
                fitting
                manufacturing.
332997.......  Industrial                   459             461           5,281              30              30              30  ..............          486,947       1,060,887       1,056,285
                pattern
                manufacturing.
332998.......  Enameled iron                 72              76           5,655              72              76              96  ..............        1,036,508      14,395,940      13,638,259
                and metal
                sanitary ware
                manufacturing.
332999.......  All other                  3,043           3,123          72,201             397             408             408  ..............       12,944,345       4,253,811       4,144,843
                miscellaneous
                fabricated
                metal product
                manufacturing.
333319.......  Other commercial           1,253           1,349          53,012             278             299             299  ..............       12,744,730      10,171,373       9,447,539
                and service
                industry
                machinery
                manufacturing.
333411.......  Air purification             303             351          14,883              72              84              84  ..............        2,428,159       8,013,727       6,917,833
                equipment
                manufacturing.
333412.......  Industrial and               142             163          10,506              52              59              59  ..............        1,962,040      13,817,181      12,037,053
                commercial fan
                and blower
                manufacturing.
333414.......  Heating                      377             407          20,577             108             116             116  ..............        4,266,536      11,317,071      10,482,888
                equipment
                (except warm
                air furnaces)
                manufacturing.
333511.......  Industrial mold            2,084           2,126          39,917             221             226             226  ..............        4,963,915       2,381,917       2,334,861
                manufacturing.
333512.......  Machine tool                 514             530          17,220              94              97              97  ..............        3,675,264       7,150,320       6,934,461
                (metal cutting
                types)
                manufacturing.
333513.......  Machine tool                 274             285           8,556              46              48              48  ..............        1,398,993       5,105,812       4,908,746
                (metal forming
                types)
                manufacturing.
333514.......  Special die and            3,172           3,232          57,576             319             325             325  ..............        7,232,706       2,280,172       2,237,842
                tool, die set,
                jig, and
                fixture
                manufacturing.
333515.......  Cutting tool and           1,482           1,552          34,922             188             197             197  ..............        4,941,932       3,334,637       3,184,235
                machine tool
                accessory
                manufacturing.
333516.......  Rolling mill                  70              73           3,020              17              17              17  ..............          652,141       9,316,299       8,933,437
                machinery and
                equipment
                manufacturing.
333518.......  Other                        362             383          12,470              67              70              70  ..............        2,605,582       7,197,740       6,803,086
                metalworking
                machinery
                manufacturing.
333612.......  Speed changer,               197             226          12,374              61              70              70  ..............        2,280,825      11,577,790      10,092,145
                industrial high-
                speed drive,
                and gear
                manufacturing.
333613.......  Mechanical power             196             231          15,645              75              88              88  ..............        3,256,010      16,612,294      14,095,280
                transmission
                equipment
                manufacturing.
333911.......  Pump and pumping             413             490          30,764             147             174             174  ..............        7,872,517      19,061,785      16,066,362
                equipment
                manufacturing.
333912.......  Air and gas                  272             318          21,417             104             121             121  ..............        6,305,944      23,183,616      19,830,011
                compressor
                manufacturing.
333991.......  Power-driven                 137             150           8,714              45              49              49  ..............        3,115,514      22,740,979      20,770,094
                handtool
                manufacturing.
333992.......  Welding and                  250             275          15,853              82              90              90  ..............        4,257,678      17,030,713      15,482,466
                soldering
                equipment
                manufacturing.
333993.......  Packaging                    583             619          21,179             113             120             120  ..............        4,294,579       7,366,345       6,937,931
                machinery
                manufacturing.
333994.......  Industrial                   312             335          10,720              56              61              61  ..............        1,759,938       5,640,828       5,253,548
                process furnace
                and oven
                manufacturing.
333995.......  Fluid power                  269             319          19,887              95             112             112  ..............        3,991,832      14,839,523      12,513,579
                cylinder and
                actuator
                manufacturing.
333996.......  Fluid power pump             146             178          13,631              63              77              77  ..............        3,019,188      20,679,367      16,961,728
                and motor
                manufacturing.
333997.......  Scale and                     95             102           3,748              20              21              21  ..............          694,419       7,309,671       6,808,027
                balance (except
                laboratory)
                manufacturing.
333999.......  All other                  1,630           1,725          52,454             280             296             296  ..............        9,791,511       6,007,062       5,676,238
                miscellaneous
                general purpose
                machinery
                manufacturing.
334518.......  Watch, clock,                104             106           2,188              12              12              12  ..............          491,114       4,722,250       4,633,151
                and part
                manufacturing.
335211.......  Electric                      99             105           7,425              20              22              22  ..............        2,175,398      21,973,717      20,718,076
                housewares and
                household fans.
335221.......  Household                    116             125          16,033              43              47              47  ..............        4,461,008      38,456,968      35,688,066
                cooking
                appliance
                manufacturing.
335222.......  Household                     18              26          17,121              18              26              50  ..............        4,601,594     255,644,105     176,984,380
                refrigerator
                and home
                freezer
                manufacturing.
335224.......  Household                     17              23          16,269              17              23              47  ..............        4,792,444     281,908,445     208,367,112
                laundry
                equipment
                manufacturing.
335228.......  Other major                   39              45          12,806              32              37              37  ..............        4,549,859     116,663,058     101,107,984
                household
                appliance
                manufacturing.
336111.......  Automobile                   167             181          75,225             167             181             425  ..............       87,308,106     522,803,033     482,365,229
                manufacturing.
336112.......  Light truck and               63              94         103,815              63              94             587  ..............      139,827,543   2,219,484,812   1,487,527,055
                utility vehicle
                manufacturing.
336120.......  Heavy duty truck              77              95          32,122              77              95             181  ..............       17,387,065     225,806,042     183,021,739
                manufacturing.
336211.......  Motor vehicle                728             820          47,566             239             269             269  ..............       11,581,029      15,908,007      14,123,206
                body
                manufacturing.
336212.......  Truck trailer                353             394          32,260             163             182             182  ..............        6,313,133      17,884,229      16,023,179
                manufacturing.
336213.......  Motor home                    79              91          21,533              79              91             122  ..............        5,600,569      70,893,283      61,544,718
                manufacturing.
336311.......  Carburetor,                  102             116          10,537              52              60              60  ..............        2,327,226      22,815,945      20,062,296
                piston, piston
                ring, and valve
                manufacturing.