Seveso accident

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Seveso accident: the best-known dioxin accident in 1976 in Italy. In Seveso, 20 km north of Milan, a trichlorophenol production reactor in a chemical factory blew up and released kilogram quantities of TCDD to the environment. The cloud of chemicals spread as far as 6 km from the factory, and settled on the ground. Within 5 weeks the area was subdivided into three subareas based on soil concentrations: zone A (87 hectares, over 50 µg/m2 of TCDD), zone B (270 hectares, over 5 µg/m2), and zone R (1430 hectares, below 5 µg/m2). From zone A over 730 inhabitants were evacuated, and strict hygienic regulations were set for other zones. In a selected group of highly exposed persons, TCDD concentrations up to 56,000 ng/kg (TCDD in fat) were detected. In randomly sampled persons, the calculated median concentrations were 390 ng/kg (TCDD in fat) (zone A), 78 ng/kg (zone B) and in the reference population 5.5 ng/kg.

Chloracne was observed in a number of persons, most of them children. In 15-year follow-up studies, no increased total mortality was observed, but there was an increase of leukaemia (7 cases, 2.2 expected in zone B) in males, and myeloma (4 cases, 0.6 expected in zone B) in females. All-cancer mortality or mortality from the most common cancers were not increased (e.g. there were non-significantly less breast cancers than expected). There were no increases in zone A, but the population was too small for reliable analysis. One may conclude that, noting the relatively short period of observation, the increase of some cancers is likely to be real, but considering the high exposure, the risk is not very high (for details, see Bertazzi et al., Epidemiology 1997:8:646-652, Consonni et al., Am. J.Epid. 2008:167:847-858, [[2]]; Pesatori et al., Environ. Health 2009:8:39, [[3]]).[1]


  1. Tuomisto, Vartiainen, Tuomisto: Dioxin synopsis. Report / National Institute for Health and Welfare, ISSN 1798-0089 ; 14/2011 [1]