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up period. The final cohort included those hired after 1925 and employed 6 months or longer in
production areas of the plant during the period 1940-1969. The cause-specific death rates were
adjusted by the indirect method to yield standardized mortality ratios (SMRs) and by the direct method
to yield standardized rate ratios (SRRs). The SMR for lung cancer in the overall cohort was 147, while
for those with 2 or more years of employment it was 229, with a 95% confidence interval of (131,371).
Exposure data that had been collected since the 1940's allowed evaluation of the lung cancer SMR by
dose. Industrial hygiene measurements for departments and job sites with potential cadmium exposure
were available (Smith et al. 1980). These were combined with individual work histories for each
member of the cohort in order to assign an exposure level to each work day. Interruptions of
employment were taken into account and exposure levels were adjusted to reflect respirator usage in
departments where these were worn. A cumulative exposure in mg-years/m 3 was then assigned to each
person-year of follow-up for each worker. The range of cumulative exposures was divided into three
categories and both SMRs and SRRs were calculated for each category. The results are shown in
Table 2 using US white males as the comparison population, and in Table 3 using Colorado white males
as the comparison population. (Thun presented the analysis using Colorado white males as the control
group at the Fifth International Cadmium Conference, February 1986, in San Francisco. This analysis
assumes that pre-1950 lung cancer rates equaled those in 1950, since cause-specific rates were not
tabulated in that state before 1950.)
Table 2:
Lung Cancer (ICD 162-163) Mortality By Cumulative Exposure White Male Cadmium
Workers Hired on or After 1/1/26 Compared to U.S. Death Rates (Adapted from
Thun et al. (1986), Table 7)
Exposure
(cumulative mg/m 3 )
Range Median Person years at
risk
Deaths SMR SRR
≤384 184.1 7005 2 53 0.48
385-1920 795.6 5825 7 (6) * 152 (130) * 1.55 (l.33) *
≥1921 2761.6 2214 7 280 3.45
U.S. WHITE MALES 100 1.00
* Numbers in parentheses exclude one lung cancer death which was originally
miscoded as being due to another cause.
The data indicate a clear dose-response relationship between cumulative cadmium exposure and the
risk of death due to lung cancer. Using the US population as the comparison group, both the SMR and
the SRR rise from about 1/2 the expected at "low" cumulative exposure to about 3 times the expected
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