Table
15. IARC*-reviewed epidemiologic studies having the least
confounded investigations of an association between occupational
exposure to crystalline silica and lung cancer
|
Reference
and country
|
Study
design, cohort, and followup
|
Subgroup
|
Number
of lung cancer deaths or cases
|
Risk
measure
|
CI
|
Smoking
information available and analyzed
|
Comments
|
Amandus
et al. [1991], United States |
Mortality
study of 714 male, North Carolina dusty trades workers diagnosed with
silicosis between 1940 and 1983 and compared with the 19401983
lung cancer mortality rates for U.S. males. |
Whites
|
33
|
2.6
|
1.83.6
|
Yes
|
The
age- and smoking-adjusted rate ratio for white silicotics with lung
cancer was 3.9 (95% CI= 2.46.4) compared with a referent group
of metal miners.
"Exposure
to respirable silica dust" was defined as working in a dusty
trade and having radio-graphic silicosis.
No
quantitative exposure data were available.
|
Nonwhites |
1
|
0.7
|
Not
reported
|
White
silicotics:
|
Diagnosed
while employed
|
28
|
2.5
|
1.73.7
|
Employed
in jobs with silica exposure only§
|
26
|
2.3
|
1.53.4
|
Past
or current smokers
|
18
|
3.4
|
2.05.3
|
Silicotics,
never smoked
|
5
|
1.7
|
0.53.9
|
Amandus
et al. [1992], United States |
Mortality
study of subgroup of 306 white males from Amandus et al. [1991] cohort
of silicotics diagnosed and traced from 1940 through 1983. 143 of
the subgroup were reclassified as silicotics, and 96 were reclassified
as having a normal radiograph. 10 deaths from lung cancer occurred
in the reclassified group. |
Silicotics |
8
|
2.5
|
1.14.9
|
Yes
|
"Exposure
to respirable silica dust" was defined as working in a dusty
trade and having radiographic silicosis.
No
quantitative exposure data were available.
|
Nonsilicotics** |
2
|
1.0
|
0.13.5
|
Smokers: |
Silicotics |
5
|
3.4
|
1.17.9
|
Nonsilicotics** |
1
|
1.3
|
0.037.1
|
Burgess
et al. [1997],
Cherry
et al. [1997], McDonald et al. [1997], United Kingdom |
Nested
case-control study of lung cancer deaths within Cherry et al. [1995],
including duration and intensity of exposure, smoking, and radiological
changes. Cases were employed as pottery workers for >10
yr. Each death was matched with
3 or 4 controls on date of birth and date of first expo-sure. |
Cumulative
exposure to respirable crystalline silica dust
>4,000 µg/m3 yr |
52
|
0.60
|
0.261.41
|
Yes
|
ORs
were adjusted for smoking and radio-graphic changes.
This
was the only epidemiologic study of peak exposure effects and lung
cancer. Results support significant lung cancer risk for high-intensity
silica exposures.
Silica
dust exposures 400 µg/m3 occurred in firing and
post-firing operations. Exposures to cristobalite were possible.
|
Duration
of employment
>20 yr |
|
0.48
|
0.211.09
|
Mean
intensity of silica dust exposure
>200 µg/m3 |
|
1.68
|
0.933.03
|
Maximum
silica dust exposure >400 µg/m3 |
|
2.07
|
1.044.14
|
Checkoway
et al. [1993; 1996],
United States |
Mortality
study of 2,570 male workers at diatomaceous earth plants employed
>1 yr and worked >1 day between 1942 and 1987.
Cohort mortality traced for that period. |
|
59
|
1.43
|
1.091.84
|
Limited
to comparisons of smoking prevalence.
|
Estimated
relative risks for lung cancer (not shown) were adjusted for age,
calendar year, duration of followup, and ethnicity. The risks increased
significantly (P<0.05 for trend) with duration of
employment and cumulative exposure to crystalline silica [Checkoway
et al. 1993]. Checkoway et al. [1996] also adjusted for asbestos exposure. |
Checkoway
et al. [1996] reanalyzed 2,266 workers (a subset of the orig-inal
cohort). Mortality traced from 1942 through 1987. |
|
52
|
1.41
|
1.051.85
|
Cherry
et al. [1995], United Kingdom |
Mortality
study of 5,115 pottery workers, excluding exposure to asbestos, foundry,
and other dusts; with mortality followup to June 30, 1992. |
|
68
|
1.28
|
1.041.57
|
No
|
Lung
cancer rates in pottery workers were compared with local mortality
rates. |
Costello
and Graham [1988],
United States |
Mortality
study of 5,414 white male workers in Vermont granite sheds and quarries
employed between 1950 and 1982 with at least one radiologic examination
in the worker surveillance program. |
Quarry
workers |
20
|
0.82
|
Not
reported
|
No
|
Dust
exposure data were not included, limiting conclusions about exposure-response.
Cohort overlaps with cohort of Davis et al. [1983].
CIs
reported by IARC [1997].
|
Shed
workers: |
98
|
1.27
|
Not
reported§§
|
Started
before 1940, latency period >40
yr, tenure >30 yr |
47
|
1.81
|
1.332.41***
|
Started
after 1940, latency period >25 yr,
tenure >10 yr |
17
|
1.73
|
1.012.77
|
Costello
et al. [1995],
United States |
Mortality
study of 3,246 male workers employed >1 yr between 1940
and 1980 at 20 U.S. crushed stone (i.e., granite, limestone, traprock,
or sandstone) operations. |
Whites |
40
|
1.2
|
0.91.6
|
No
|
|
Nonwhites |
11
|
1.9
|
0.93.3
|
Workers
in granite facilities with >20-yr latency period and >10-yr
tenure |
7
|
3.5
|
1.47.3
|
Workers
in limestone facilities |
23
|
1.5
|
1.02.3
|
Workers
in traprock facilities |
3
|
0.6
|
0.11.8
|
Dong
et al. [1995], China |
Mortality
study of lung cancer in 6,266 male silicotic and nonsilicotic refractory
brick workers employed before 1962 and followed for mortality from
1963 to 1985. 11,470 nonsilicotic male steel workers used as controls. |
Silicotics |
35
|
2.1
|
Not
reported***
|
Yes
|
Twofold
excess lung cancer mortality occurred in both smokers and nonsmokers.
Exposure-response trends were found for years since first employment
and lung cancer mortality, and for severity of silicosis and lung
cancer mortality. |
Silicotics
in Chinese radiological category: |
I |
21
|
2.0
|
Not
reported***
|
II |
10
|
2.3
|
Not
reported§§
|
III |
4
|
2.6
|
Not
reported§§
|
Nonsilicotics |
30
|
1.1
|
Not
reported***
|
Guénel
et al. [1989], Denmark |
Cohort
study of 2,175 Danish stone workers who met the following criteria:
- were
alive on Jan. 1, 1943, or were born later, and
- were
aged <65 when first identified in one of 6 data sources.
The
cohort included 2,071 cancer cases identified in the Danish cancer
registry between 1943 and 1984.
|
Lung
cancer cases |
44
|
2.00
|
1.492.69
|
Yes
|
Adjusted
for regional differences in smoking. Lung cancer mortality highest
among Copenhagen sandstone cutters hired before 1940 prior to ventilation
improvements.
|
McDonald
et al. [1995], United Kingdom |
Preliminary
report of proportionate mortality study of 7,020 pottery workers born
between 1916 and 1945 with mortality followup to June 30, 1992. Preliminary
nested case-control study of 75 lung cancer cases and
75 controls. |
Lung
cancer deaths in pottery workers not exposed to asbestos |
112
|
1.22§§§
|
1.041.43
|
No
|
Preliminary
results
(final results in Cherry et al. [1995]).
Lung
cancer rates in pottery workers were compared with local mortality
rates.
|
Smokers
and nonsmokers with >10 yr of silica exposure |
75
|
1.4
|
0.72.7
|
Smokers
with >10 yr of silica exposure |
47
|
2.8
|
1.17.5
|
McLaughlin
et al. [1992], China |
Nested
case-control study of 62 pottery factory workers employed between
1972 and 1974 who died from lung can-cer before 1990;
238 controls matched by decade of birth and factory. |
Cumulative
respirable silica dust exposure (µg/m3-yr): |
Yes
|
ORs
were adjusted for age and smoking. Test for exposure-response trend
was not statistically significant (P>0.05) for cumulative
exposure to dust or respirable silica. High OR (7.4; CI and number
of deaths not reported) for lung cancer in workers who smoked >20
cigarettes per day. CIs reported in IARC monograph [1997]. |
None |
11
|
1.0
|
|
Low
(0.18.69) |
17
|
1.8
|
1.042.87
|
Medium
(8.7026.2) |
27
|
1.5
|
0.992.18
|
High
( 26.3) |
7
|
2.1
|
0.804.12
|
Merlo
et al. [1991], Italy |
1,022
male refractory brick workers employed at least 6 months between 1954
and 1977. Retrospective cohort study of mortality through 1986. |
All
brick workers |
28
|
1.51
|
1.002.18
|
Yes
|
Smoking
habits of cohort comparable with the national population (includes
the men in Puntoni et al. [1988]). |
Brick
workers: |
<19
yr since 1st exposure and employed <19
yr |
7
|
1.05
|
0.422.16
|
>19
yr since 1st exposure and employed <19
yr |
8
|
1.75
|
0.753.46
|
>19
yr since 1st exposure and employed >19
yr |
13
|
2.01
|
1.073.44
|
Partanen
et al. [1994],
Finland |
Cohort
study of
811 male silicotics, compensated and not compensated, who were diagnosed
between 1936 and 1977 in Finland. Cancer incidence for 19531991
was obtained from the Finnish Cancer Registry. |
Length
of followup from date of silicosis diagnosis: |
Yes
|
Update
of Kurppa et al. [1986].
No
evidence of confounding by tobacco smoking.
|
<2
yr |
1
|
0.4
|
0.012.3
|
29
yr |
32
|
2.7
|
1.93.9
|
>10
yr |
168
|
3.3
|
2.54.1
|
Histology
of lung cancers: |
Adenocarcinoma
|
5
|
2.0
|
0.64.6
|
Squamous-cell |
34
|
3.2
|
2.34.5
|
Small-cell |
9
|
2.1
|
0.93.9
|
Other/unknown |
53
|
3.0
|
2.23.9
|
Industry: |
Mining/quarrying
(excluding granite) |
38
|
3.7
|
2.65.0
|
Granite |
13
|
2.9
|
1.65.0
|
Glass/ceramic |
10
|
3.3
|
1.66.1
|
Grinding/
sharpening |
3
|
3.0
|
.68.7
|
Casting/
founding |
22
|
1.8
|
1.12.6
|
Construction |
2
|
10
|
1.337
|
Excavation/
foundation |
9
|
5.8
|
2.711.1
|
Steenland
and Brown [1995b],
United States |
Cohort
study of 3,328 white male gold miners employed underground >1
yr between 1940 and 1965 and followed for mortality from 1977 to 1990.
Mortality rates of U.S. males used for comparison. |
|
115
|
1.13
|
0.941.36
|
Yes
|
High
historical exposures. No exposure-response trend by cumulative dust
exposure.
Low
radon and arsenic exposures.
|
Source:
IARC [1997].
*Abbreviations: CI=confidence interval; IARC=International
Agency for Research on Cancer; PMR=proportional mortality ratio; OR=odds
ratio; SIR=standardized incidence ratio; SMR=standardized mortality
ratio; SRR=standardized rate ratio
SMR unless otherwise noted.
95% CI unless otherwise noted.
§Workers who had no known exposure to other occupational
carcinogens such as asbestos manufacturing, insulation work, olivine
mining, talc, and foundry work.
**Nonsilicotics are subjects with normal radiographs.
OR.
90% CI.
§§P <0.05.
***P <0.01.
Values in this study are SRRs.
Values in this study are SIRs.
§§§PMR. |