Atmospheric Concentrations of PCB-11 Near the Great Lakes Have Not Decreased Since 2004

3,3'-Dichlorobiphenyl (PCB-11) is thought to be a byproduct of the production of yellow pigments, and thus, it has sources to the environment that differ both in type and magnitude compared to the PCBs that made up the, now banned, Aroclor commercial products. To assess these differences, the temporal trends of atmospheric concentrations of PCB-11 relative to those of 31 specific Aroclor-related congeners and relative to those of total Aroclor-PCBs at six sites near the North American Great Lakes were investigated. About 1800 atmospheric samples were collected over the period of 2004-2015 (inclusive). A multiple linear regression approach was used to isolate the variations in the atmospheric concentrations due to the human population near the sampling sites, seasonal effects, and long-term temporal changes. The atmospheric concentrations of the Aroclor-PCBs are decreasing with halving times of about 12 years, but the atmospheric concentrations of PCB-11 have not changed significantly over this time period. These results suggest that PCB-11 is still leaking into the environment, while at the same time sources of Aroclor-PCBs are coming under control. This effect is particularly notable at the most remote site on Lake Superior, where PCB-11 levels are, on average, 11% of those of total Aroclor-PCBs; this is a not insignificant abundance of a single PCB congener.