Temporal trends of PCBs and DDTs in Great Lakes fish compared to those in air

Regulations designed to lower the concentrations of PCBs and DDTs in the environment have been in place since the 1970s, but the levels of PCBs are still high enough to cause fish consumption advisories for Great Lakes fish. The levels of PCBs and DDTs have been tracked in these fish since about 1975, and the rates at which these age-adjusted concentrations have been decreasing over the period 1999-2014 have been recently been estimated. This paper compares these rates to ones estimated from the entire data set (~1975-2014) and to rates estimated from changes in atmospheric concentrations, which have been tracked since 1992. In general the halving times (9-17 years for PCBs and 7-10 years for DDTs) estimated from the full fish dataset are similar to those estimated from the atmospheric data, suggesting that the atmospheric and the fish levels are coupled. The more recent, age-adjusted rates are sometimes significantly faster than those from the full fish and atmospheric datasets, suggesting that the air-water dynamic may now be changing.