Both Incidence, Control of Dioxin Are Highly Complex: A by-product of many industrial processes, dioxin presents big problem in waste disposal; the technology is on hand, but economic, political barriers persist

C&EN's dioxin coverage now turns to the practical world of industry. How and where, exactly, do dioxins turn up? And how can they be controlled? It's a complicated situation, in part because of the myriad of dioxin structures and reactions. So a short review of chemistry is in order before a look at commercial reactions and disposal methods. On the dioxin molecular framework— consisting of two benzene rings connected by two oxygen bridges—there are eight positions where substitutions can take place. In any or all of these eight substituent positions, hydrogen atoms can be replaced by other atoms or by organic or inorganic radicals. The number of possible combinations is almost limitless. These days, of course, when people speak of dioxins, they likely are referring to the black-sheep branch of the family, the chlorinated dioxins (CDDs), in which one to eight of the substituent positions are occupied by chlorine atoms. The arrangement allows for a ...