Guidelines for the definition of environmental action alert thresholds for polychlorodibenzodioxins and...

In July 1986, a 314-ha area surrounding the municipal solid waste incinerator of San Donnino (Florence, Italy) was subjected to hygienic and sanitary measures as polychlorodibenzodioxins (PCDDs) and polychlorodibenzofurans (PCDFs) had been detected in soil at levels higher than the "reference technical limits" adopted by the National Toxicology Commission in 1985. In this report the case of San Donnino is the starting point used to define "maximum tolerable environmental limits" for complex mixtures of PCDDs and PCDFs. Limits are expressed in "2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity equivalence" units according to a relative toxicity ranking where the toxic potency of the aforementioned chemical is considered the highest and set equal to unit. Man's exposure to PCDDs and PCDFs is estimated on the basis of experimental findings and with reference to such limits.