Partial pressures of PCB-11 in air from several Great Lakes sites.

Relatively high concentrations of 3,3'-dichlorobiphenyl (PCB-11) have been reported in water and air, and it has been suggested that this compound did not come from commercial PCB products. We report here data on atmospheric partial pressures of PCB-11 and of total PCBs at five sites around the Great Lakes and demonstrate that both total PCBs and PCB-11 track human population density. In addition, we show that with the exception of Chicago, the PCB congener pattern at our sampling sites is best represented by Aroclor 1242; in Chicago, the pattern is best represented by a 1:1 mixture of Aroclors 1242 and 1254. With the possible exception of Sturgeon Point New York, the levels of PCB-11 in air have not changed between January 2004 and December 2007. The source of PCB-11 may be related to yellow pigments, to the degradation of more highly chlorinated PCB congeners, or to both.