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PCBs, used to manage risks from the flammability of dielectric fluids and to increase the durability of elastic sealants, had declining environmental concentrations after legislation banning new production was passed during the 1970s and 1980s in Europe and North America. To answer why PCB temporal trends are now nearly stable and if current policies will further reduce concentrations and our exposure, we estimated PCB stocks in Toronto, Canada (population of approximately 2.5 million) of 437 (282-796) tonnes, of which 97 and 3% are in closed sources and building sealants, respectively. The greatest geographic density of PCBs is downtown, specifically in commercial, electricity-intensive skyscrapers. An unknown stock is within now-buried landfills and other waste-handling facilities as well as diffuse sources such as electrical wiring and paints. Using the Multimedia Urban Model, we estimated city-wide emissions of approximately 0.14-1.4 mg m(-2) y(-1) or 35-350 mg capita(-1) y(-1) of SigmaPCB(70), which is approximately 0.01-0.3% annually of total documented stocks. Canada, as one of 159 signatories of the Stockholm Convention and the 35 parties that have reported progress toward environmentally sound management of their PCB inventories by 2028, has passed national legislation with a timetable of inventory reductions. It is unclear whether this legislation will successfully reduce concentrations and exposures, however the analysis should inform our management of other contaminants.

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Enantiomeric fractions (EFs) of chiral PCBs 95, 136, and 149 were measured in samples of topsoil and outdoor air at one urban and one rural location in the U.K. West Midlands between early 2001 and early 2002. While EFs in air were essentially racemic, those in topsoil indicated appreciable enantioenrichment of the second eluting enantiomer for PCB 95 and the (+) enantiomer for PCBs 136 and 149. This suggests (i) that essentially all atmospheric PCBs at both sites arise from racemic (i.e, primary) sources, rather than volatilization from soil and (ii) that appreciable enantioselective degradation of the monitored PCBs in topsoil occurs. This is one of only two reports of enantioselective degradation of PCBs in soil worldwide and is particularly noteworthy as it is occurring at PCB concentrations (e.g., 5.9 pg g(-1) for PCB 136) that are typical of the U.K. and other industrialized countries. The extent of enantioselective degradation in this study for PCBs 95 and 136 is consistent with those reported for soils in the Greater Toronto area (GTA). In contrast, enantioselective degradation of PCB 149 observed in this study is--while consistent with that reported for U.K. lacustrine sediments--in excess of that observed in either the GTA soil study or in U.S. lake sediments.