AT APPROXIMATELY noon on Saturday, July 10, 1976, an explosion occurred during the production of 2,4,5-trichlorophenol in a factory in Meda, about 25 km north of Milan, in the Lombardia region of Italy. A cloud of toxic material was released and included 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD). Debris from this cloud fell south-southeast of the plant on an area of about 2.8 km2 (700 acres), including parts of the towns of Seveso, Meda, Cesano Maderno, and Desio. The size of the contaminated area was estimated primarily by measuring TCDD in the soil; additional criteria included the presence of dead animals (e.g., birds, rabbits, chickens) and detection of dermal lesions among persons in the area. The contaminated area was divided into three zones (A, B, and R) depending on the concentration of TCDD in the soil (Table 1). An additional zone, Zone S, outside the contaminated area was examined as a control zone.
Preliminary Report: 2,3,7,8-Tetrachlorodibenzo-p-dioxin Exposure to Humans—Seveso, Italy. Arch Dermatol. 1989;125(3):329-330. doi:10.1001/archderm.1989.01670150019002