Our analyses suggest that high TCDD exposure results in an excess of all cancers combined, without any marked specificity. However, excess cancer was limited to the highest exposed workers, with exposures that were likely to have been 100-1000 times higher than those experienced by the general population and similar to the TCDD levels used in animal studies.

This study of mortality among workers with occupational exposure to TCDD does not confirm the high relative risks reported for many cancers in previous studies. Conclusions about an increase in the risk of soft-tissue sarcoma are limited by small numbers and misclassification on death certificates. Excess mortality from all cancers combined, cancers of the respiratory tract, and soft-tissue sarcoma may result from exposure to TCDD, although we cannot exclude the possible contribution of factors such as smoking and occupational exposure to other chemicals.

The International Agency for Research on Cancer (Lyon, France) recently concluded that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a human carcinogen. There have been few human studies and risk assessments with quantitative exposure data. The authors previously conducted exposure-response analyses based on estimated external TCDD exposure for 3,538 US male chemical workers and found a positive trend for all cancer with increasing cumulative exposure. In the present study, 1988 data from 170 workers with both estimated external exposure and known serum TCDD levels were used to derive the relation between the two. This derived relation was used to estimate serum TCDD levels over time for all 3,538 workers, and new dose-response analyses were conducted by using cumulative serum level. A positive trend (p = 0.003) was found between estimated log cumulative TCDD serum level and cancer mortality. For males, the excess lifetime (75 years) risk of dying of cancer given a TCDD intake of 1.0 pg/kg of body weight per day, twice the background intake, was an estimated 0.05-0.9% above a background lifetime risk of cancer death of 12.4%. Data from this cohort are consistent with another epidemiologic risk assessment from Germany and support recent conclusions by the US Environmental Protection Agency.

Although low back pain is a common disorder, the lifting index appears be a useful indicator for determining the risk of low back pain caused by manual lifting.