Risk assessment for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) based on anepidemiologic study

The International Agency for Research on Cancer (Lyon, France) recently con cluded that 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) is a human carcinog en. There have been few human studies and risk assessments with quantitativ e exposure data. The authors previously conducted exposure-response analyse s based on estimated external TCDD exposure for 3,538 US male chemical work ers and found a positive trend for all cancer with increasing cumulative ex posure. In the present study, 1988 data from 170 workers with both estimate d external exposure and known serum TCDD levels were used to derive the rel ation between the two. This derived relation was used to estimate serum TCD D levels over time for all 3,538 workers, and new dose-response analyses we re conducted by using cumulative serum level. A positive trend (p=0.003) wa s found between estimated log cumulative TCDD serum level and cancer mortal ity. For males, the excess lifetime (75 years) risk of dying of cancer give n a TCDD intake of 1.0 pg/kg of body weight per day, twice the background i ntake, was an estimated 0.05-0.9% above a background lifetime risk of cance r death of 12.4%. Data from this cohort are consistent with another epidemi ologic risk assessment from Germany and support recent conclusions by the U S Environmental Protection Agency.