[The chemical accident of the Hoechst AG facility 22 February 1993--1. Extent of environmental pollution and clean-up].

A major industrial chemical accident occurred on 22 February 1993 at Hoechst AG Frankfurt/Germany. Due to a series of errors in operational procedures approximately 11.8 tons of a chemical mixture were emitted, partly resulting in heavy contamination of a nearby housing area. The chemical mixture consisted of about 26% anorganic and 74% organic substances, mostly chlorinated nitroarenes, the most important organic contaminant being o-nitroanisol (about 27% of the total amount). Maximum earth contamination in allotment gardens was up to 8 g o-nitroanisol/m2, in the housing area 547 mg/m2. Maximum air contamination was up to 18 micrograms o-nitroanisol/m3, declining quickly during redevelopment and staying constantly below 2 micrograms/m3 from 2 March 1993 onwards. In 96% of more than 300 indoor air measurements no o-nitroanisol could be detected. Redevelopment measurements were started and completed very quickly: Removal of contaminated earth, recultivation of the gardens, cutting bushes and cutting down coniferous trees, cutting off and renewing street-surfaces, cleaning up footpaths and roofs of the houses. Four weeks after the accident, redevelopment measurements were completed, as confirmed by numerous analyses.