NIOSH
HAZARD REVIEW
Health
Effects of Occupational Exposure
to
Respirable Crystalline Silica
|
Table
12. Predicted incidence or prevalence of silicosis following exposure
to selected concentrations of respirable quartz dust—based
on modeling of cumulative exposure over a 45-year working lifetime
|
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|
Study
and cohort
|
Selected
mean
concentration of respirable quartz dust (mg/m3) |
Mean
time since first quartz exposure
(yr) |
Maximum
time since first quartz exposure
(yr) |
Predicted
incidence or prevalence of silicosis,
ILO category > 1/1 (cases/100 workers) |
| Hnizdo and Sluis-Cremer [1993], 2,235 South African gold miners |
0.05
0.10 |
36*
— |
50*
— |
13†
70‡ |
| Hughes et al. [1998], 2,342 U.S. workers in a diatomaceous earth mining and processing facility |
0.05
0.10 |
11.5
— |
46
— |
1.5§–4‡,**
4§–17‡,** |
| Kreiss and Zhen [1996], 100 U.S. hardrock miners and 34 community controls |
0.05
0.10 |
41.6*
33.5‡‡ |
66*
68‡‡ |
30‡,††
90‡,†† |
| Muir et al. [1989a,b] and Muir [1991], 2,109 Canadian gold and uranium miners |
0.05
|
18
|
38*
|
0.09–0.62§§
|
| Ng and Chan [1994], 338 Hong Kong granite workers |
0.045‡,***
|
—†††
|
—†††
|
6
|
| Rosenman et al. [1996], 1,072 U.S. gray iron foundry workers |
0.05
0.10 |
28
— |
>30
— |
2‡‡‡
3‡‡‡ |
| Steenland and Brown [1995a], 3,330 U.S. gold miners |
0.05
0.09 |
37
— |
73§§§
— |
10****
47**** |
|
*Silicotic miners. †Estimate reported in Rice and Stayner [1995]. ‡Approximate. §Primarily cristobalite dust. Cumulative risk of small opacities >ILO category 1/0 and/or large opacities. For 1,452 workers with an average crystalline silica exposure <0.50 mg/m3; 1,138 (78%) of these workers were hired in 1950 or later. **Primarily cristobalite dust. Cumulative risk of small opacities ILO category 1/0 and/or large opacities. For 357 workers with an average crystalline silica exposure >0.50 mg/m3; 319 (89%) of these workers were hired before 1950. ††Based on cumulative silica exposure model with 10 yr of post-employment followup. ‡‡Nonsilicotic miners. §§No post-employment followup and no retired miners included. The range includes five estimates (one for each reader). Estimate reported in Rice and Stayner [1995]. ***Based on a 50-year-old worker with cumulative silica exposure of 2 mg/m3 yr. †††Not reported. Mean duration of employment was 17 yr for all workers and 27.5 yr for workers in the highest category of cumulative silica exposure. ‡‡‡ILO category >1/0. Based on a 40-yr working lifetime and controlling for pack-years of cigarette smoking, race, and silica exposure other than in the foundry under study. §§§Steenland [1998]. ****Includes 141 cases documented on death certificate only. Estimated risk not adjusted for age or calendar time [Steenland 1997]. |
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