THE SEVESO ACCIDENT: ITS NATURE, EXTENT AND CONSEQUENCES

Abstract

The accident which occurred during the production of TCP at Seveso. Italy, was possibly caused by an unforeseeable exothermic reaction with increase of temperature, slow decomposition of the reaction mass, formation of gas and rise in pressure. The nature of the reaction is still unknown and will be investigated further. The detection and measurement of TCDD by the Company's analysts on material collected at the site of the accident have guided measures for the protection of the population and the land and for the prevention of further damage. Chloracne, the skin lesion indicating a TCDD exposure, appearing mainly in a small segment of the population, has been generally of mild degree and inclined to rapid and complete healing. Incidence or severity of adolescent acne and of the current skin pathology have not been affected. Hepatotoxicity, neurological findings or deranged porphyrin metabolism have not been observed in the chloracne cases. Pregnancy, foetal development, growth of the new-born, immunoresponse, rate of chromosome aberrations, functions of the neurological system, haematological and hepatic conditions, morbidity and mortality have been surveyed in the exposed population. So far the pathology related to these parameters has remained within the range which is current for the population of this region and could not be correlated to the exposure to TCDD. Four per cent of the domestic animals living in the contaminated zones died spontaneously, 99.64% of these being small animals. The remaining animals (77,716) were slaughtered as a preventive measure to protect the food chain. The analysis of TCDD tissue levels revealed that the rather large amount did not necessarily correspond to anatomical or functional lesions. The elimination of TCDD from the body in small as well as large animals indicated that, if TCDD is removed from the diet, all animals can be reintroduced into the food chain after a suitable recovery period. As regards the crops and the land, the deposited chemicals had practically no effect on the flora. About 80% of the TCDD adhered to foliage, grass and crops for several weeks until it was transferred to the soil by the rain. Field and greenhouse trials have shown that TCDD does not leach significantly beyond a depth of 20 cm in the soil and that its 50% breakdown in the Seveso soil takes between 9 and 12 months. Only fractions of the TCDD in the soil can be found in the vegetation and fruit growing in the contaminated area. Decontamination could have been rapidly achieved immediately after the accident either by collecting and disposing of the vegetation or by the spraying of an H donor. Today the area which is still fenced-in could be made accessible by removing the contaminated soil layers and burying them in a concrete pit. The natural course of the breakdown would take at least 6–8 yr.