‘New’unintentionally produced PCBs in the Arctic

Contamination of the Arctic by legacy polychlorinated biphenyls(PCB)is well documented,but the more recent discovery of unintentionally produced(UP)PCBs in the Arctic is a cause for concern.Legacy PCBs are covered by existing international conventions and regular monitoring,and the UP congeners are covered by the Stockholm Convention and the U.S.Toxic Substances Control Act,but systematic monitoring and regulatory enforcement of UP-PCBs are lacking.Sources of UP-PCB are by-products of manufacturing(e.g.pigments)and from thermal sources(e.g.incinerators).Estimates of PCB emissions in China now show UP-PCB eclipsing emissions of legacy PCB.Here we discuss the 209 PCB-congener results from surface snow samples from Lomonosovfonna in 2010 and 2014,a glacial site on Svalbard which,in 2014,shows presence of PCB5,PCB11,and an unusually high amount of PCB52.While PCB5 and PCB11 may not be found in legacy PCB mixtures,PCB52 is in many PCB mixtures,yet dominates none of them as in the 2014 snow sample.Is it possible that these congeners are from UP-PCB processes?A search of the literature shows that PCB5,PCB11 and PCB52 are co-synthesis products of pigment production and that PCB5 and PCB11 are found in flue gas and ash from hazardous waste incineration.Of these,PCB11 has received greater attention in the literature.It has recently been consistently detected in the air,snow,soil and biota in the Arctic,evidence that PCB11 and possibly other UP-PCB congeners are global contaminants.Ice core measurements dating from 1957 to 2009 of PCBs in Svalbard reveal PCB11 presence throughout that period,indicating historic presence in the Arctic before being a focus of research elsewhere.Other UP-PCB need to be more fully investigated,especially from thermal sources.