NIOSH
HAZARD REVIEW
Health
Effects of Occupational Exposure
to
Respirable Crystalline Silica
|
Table
18. Epidemiologic studies of emphysema in workers exposed to silica
dust
|
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|
Reference
and country
|
Study
design, cohort, and followup
|
Subgroup
|
Number
of emphysema deaths or cases in subgroup
|
Risk
measure
|
95%
CI*
|
Adjusted
for smoking
|
Comments
|
| Becklake et al. [1987], South Africa |
Unmatched
case-control study of 44 autopsied white gold miners with emphysema > grade 2.0 (i.e., moderate or marked emphysema) and 42 controls without emphysema. Miners and controls were aged 51–70 at death (1980–1981). |
Miners
who smoked 20 cigarettes/day before 1960 |
—† |
30.3‡ |
7.0–141.0 |
Yes |
The
presence of emphysema at autopsy was not associated with the presence
of silicosis.
Deaths during 1980–1981 may not be typical of deaths in the total cohort of South African gold miners. |
| Miners aged 70 at death |
— |
26.8‡ |
2.0–327.0 |
No |
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| Miners who worked 20 yr in occupations with "high" dust exposure |
|
|
|
|
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| Chatgidakis [1963], South Africa | Prevalence study of 800 consecutive autopsies of white gold miners conducted between January 1957 and October 1962. | Miners with silicosis and emphysema |
297 |
44.58§ |
—** |
No |
Degree of emphysema was not related to years of service. Pulmonary diffuse emphysema increased significantly with incidence and degree of silicosis and with age. |
| Cowie et al. [1993], South Africa |
Random
sample of 70 black underground gold miners selected for computed tomography lung examination from 1,197 participants in a cross-sectional study conducted in 1984–1985. |
Miners
by emphysema grade:
|
Yes
|
Presence
and grade of emphysema were associated with silicosis (P<0.002;
P=0.006 ) and smoking (P<0.02; P=0.01) but were not associated with years of underground mining. Low agreement (i.e., 37/70) between computed tomographic and radiologic assessments of silicotic nodule profusion categories. |
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| Grade 0 (no evidence) |
22 |
— |
— |
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| Grade 1 (<25% of lung affected) |
38 |
— |
— |
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| Grade 2 (25%–50% of lung affected) |
10 |
— |
— |
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| Hnizdo et al. [1991], South Africa |
Retrospective cohort study of the relationship of emphysema with lung function changes in 1,553 white gold miners aged >40 with autopsy examination between 1974 and 1987 and panacinar, centriacinar, or a mixed type of emphysema. | Miners who worked 20 yr in occupations with "high" dust exposure up to age 45 |
— |
3.5‡ |
1.7–6.6 |
Yes
(in some analyses)
|
Logistic
regression model showed significant association between
Possible misclassification of emphysema type. |
| Hnizdo et al. [1994], South Africa |
Retrospective cohort study of relationship of emphysema with lung function in 242 white gold miners who were life-long nonsmokers, were aged >45 at death, and had an autopsy examination during 1974–1990. | Nonsmoking miners with moderate emphysema |
4 |
— |
— |
Yes
(all study subjects were nonsmokers) |
For nonsmokers, degree of emphysema at autopsy was not associated (i.e., P>0.05 in multiple regression model) with years of gold mining, cumulative dust exposure, parenchymal silicosis, or lung function impairment after adjusting for age at death. |
| *Abbreviations:
CI=confidence interval; OR=odds ratio. †Dash indicates not reported. ‡OR for emphysema > grade 2 at autopsy. §Chi-square value (comparing silicotic miners with emphysema to silicotic miners without emphysema). **P<0.00001. |
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