Epidemiology of long-term health effects: a review and recent results

The long-term effects of TCDD exposure in the population involved in the IC MESA accident in 1976 in Italy have been examined by means of mortality and cancer incidence studies. The mortality study covering the 1976-1986 decad e showed an increased cardiovascular mortality in the early period after th e accident, possibly related to the stressful postdisaster experience. Canc er incidence findings suggested increased risks for hepatobiliary cancer, n eoplasm of the lymphatic and hematopoietic tissue, and soft-tissue sarcoma. The extension of the cancer incidence study is underway. We present here r esults for the extended mortality study covering the period 1976-1991. Vital status ascertainment was >99% successful. In zone A, the small size o f the population prevents sound interpretation of results. Among males in z one B, there was nearly a 3-fold significant increase recorded for rectal c ancer, and deaths due to lymphoematopoietic neoplasm were significantly in excess of expectations, particularly leukaemia. In zone R, soft-tissue sarc omas exhibited a greater than 2-fold increased risk. Among females in zone B, increased risks were recorded for lymphoemopoietic neoplasm, with a 6-fo ld elevated relative risk for Hodgkin disease and myeloma. In zone R, no ca ses of soft-tissue sarcoma were observed. Among the people of zone A, an in creased mortality from cardiovascular disease was confirmed. Results of previous experimental and epidemiological studies, along with me chanistic knowledge on dioxin toxicity, corroborate the hypothesis that the observed departures from expectations, although based on a small number of deaths, might be associated with dioxin exposure.