Dioxin Exposure and Cancer Risk A 15Year Mortality Study after the “Seveso Accident”

Dioxin 2,3,7,8tetrachlorodibenzoparadioxin, or TCDD is a powerful carcinogen in experimental animals, whereas the evidence in humans is limited. We examined cancer mortality from 1976 to 1991 among residents of Seveso, Italy, which was highly contaminated after an industrial accident. The area was divided into zones with decreasing exposure to dioxin A highest, B lower, R lowest. The population of a surrounding noncontaminated area was used as a reference group. Zone A was small 11,516 personyears in that zone, we saw a moderate increase in mortality from digestive cancer among women relative risk RR 1.5 95 confidence interval CI 0.5–3.5. In zone B, we also saw excesses at digestive sites 83,610 personyears, 10 years after the accident. Women had an increased mortality from stomach cancer RR 2.4 95 CI 0.8–5.7, and men had increased mortality from rectal cancer RR 6.2 95 CI 1.7–15.9. Hematologic neoplasms were increased. The highest risks were seen in zone B for leukemia in men RR 3.1 95 CI 1.3–6.4, multiple myeloma in women RR 6.6 95 CI 1.8–16.8, and Hodgkin's disease in both genders RR 3.3 95 CI 0.4–11.9 in men and RR 6.5 95 CI 0.7–23.5 in women. Soft tissue sarcoma was elevated only among zone R males 256,408 personyears RR 2.1 95 CI 0.6–5.4. We found no increase for allcancer mortality or major specific sites for example, respiratory among males, breast among females. The specific excesses that we observed were not explained by bias or confounding, and their association with dioxin exposure is plausible. The followup is continuing.