This is a result of proper operation of industrial and municipal wastewater treatment facilities. Low streamflow conditions and high temperatures contributed to these violations. Fish from an additional eight lakes and 28 river or stream segments were tested and have no restrictions. In the early 1990s, PCBs and chlordane caused most of the restrictions in Georgia. Manufacturing of these chemicals have has been banned and their use is highly restricted, so concentrations of those chemicals in fish is slowly decreasing.
More restrictions are now due to mercury contamination.
Mercury is a naturally occurring element, and has likely always been present in fish at low concentrations. The amount of mercury in most fish in Georgia has remained fairly constant since 1971.