Photochemical degradation of di- and octachlorodibenzofuran.

In the last few years, it has been shown that polychlorinated biphenyls undergo decomposition on irradiation with artificial ultraviolet light sources and sunlight (1-7). Reductive dehalogenation of one or more chlorine atoms was a major reaction, particularly in hydrocarbon solvents. In fluorocarbon solvents or thin films, small quantities of chlorobiphenyls with increased chlorine content could also be detected. Irradiation in hydroxylic solvents gave the dechlorinated species as well as photoproducts containing oxygen. In addition, chlorinated terphenyls and quaterphenyls were also detected in some instances, and on prolonged irradiation polymeric products were formed. It has been speculated for some time that chlorodibenzofurans may be formed from chlorobiphenyls under photochemical conditions which lead to oxygenated products. Although no chlorodibenzofurans could be detected in a number of chlorobiphenyl samples which had been exposed to sunlight for over 2 months (4), preliminary results indicated the formation of chlorodibenzofur-