MONITORING THE ELIMINATION OF PERSISTENT TOXIC-SUBSTANCES FROM THE GREAT-LAKES - CHEMICAL AND PHYSIOLOGICAL EVIDENCE FROM ADULT HERRING-GULLS

To assess progress towards virtual elimination of PCBs, DDE, dieldrin and Mirex and their associated physiological effects, we compared thei r concentrations in pooled livers of adult herring gulls (Larus argent atus) repeatedly sampled at 8 Great Lakes colonies and a reference col ony on the Atlantic coast between 1974 and 1993. We measured the relat ive thyroid mass and concentrations of highly carboxylated porphyrins and retinyl palmitate in the liver of each individual. PCBs, dieldrin and mirex declined in 7 of 8 colonies while DDE decreased in six. The greatest decreases occurred pre-1985. PCBs and DDE did not decrease in gulls from Middle Island in western L. Erie. Middle Island and Sagina w Bay had the highest concentrations of PCBs of 11 Great Lakes colonie s in the 1990s. Thyroids of gulls from Great Lakes colonies were sligh tly enlarged but the degree of enlargement has decreased over time. In 1991, gulls from Great Lakes colonies had slight to moderately elevat ed concentrations of highly carboxylated porphyrins. In the early 1990 s, hepatic stores of retinyl palmitate were very seriously depleted in gulls from the Detroit River, western basin of Lake Erie, and Lake On tario, reflecting decreased availability and altered storage. We concl ude that PCBs and/or other persistent toxic substances in the food of herring gulls have not been virtually eliminated.