Table
12. Predicted incidence or prevalence of silicosis following exposure
to selected concentrations of respirable quartz dustbased
on modeling of cumulative exposure over a 45-year working lifetime
|
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*
|
0.090.62§§
|
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]. |