ABSTRACT
The presence of hexachloroxanthene in most of the Missouri dioxin sites, although at levels that vary considerably from site to site and also within the site, implicates a hexachlorophene producer as the source of dioxin. The state of Missouri has more than 40 hazardous waste sites containing the toxic compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Hexachlorophene is used as an active constituent in several cosmetics and some over the counter and prescription drugs. Pharmaceutical-grade hexachlorophene requires purification of 2,4,5-trichlorophenol prior to its reaction with formaldehyde. Since hexachlorophene production requires the intermediate production of 2,4,5-trichlorophenol, the waste materials from the hexachlorophene manufacturing process often contain two chlorinated by-products, 1,2,3,5,7,8-hexachloro-9H-xanthene (HCX) and TCDD. The high temperature, high pressure and the strongly alkaline conditions promote a continuation of the reaction, in which 2,4,5-trichlorophenol combines with itself to form 2,3,7,8-TCDD. The chapter shows the TCDD and HCX contents of soil samples from some of the other dioxin sites.
