Emissions of polychlorinated biphenyls from combustion sources

Polychlorinated biphenyls (PCBs) have been widely used in the past as industrial chemicals, particularly as additives in electrical transformer cooling oil. Growing evidence of PCBs' role as a persistent, bioaccumulative, human carcinogen has led to the banning of the production and use of PCBs as an industrial chemical in major industrialized countries including the United States. PCBs, however, are still being released into the environment as an unwanted by-product of combustion processes, particularly those associated with chlorinated materials. A subset of PCBs, the coplanar isomers, exhibit biological activity similar to that of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs), a widely recognized by-product of combustion processes. Significant progress has been made over the last 10 years investigating the fundamental PCDD/PCDF formation mechanisms, while emissions of PCBs from combustion devices have not been extensively investigated. This paper presents background information on some of the combustion sources that generate PCBs.