Levels and temporal trends of toxaphene congeners in beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary, Canada

Environmentally relevant toxaphene congeners were determined in blubber samples of stranded beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary (SLE), Canada. The purpose of this study was to evaluate the levels and the temporal trends (1988-1999) of a suite of six chlorobornanes (P26, P40/41, P44, P50, and P62) in the SLE belugas. P26 and P50 mean concentrations were in the same range as those reported for animals living in the Arctic environment suggesting that the atmospheric transport represents the main input of toxaphene to the SLE. A general exponential decline of chlorobornane concentrations in belugas was observed, except for P26 and P50 in males. On average, concentrations decreased by a factor of two in 8.5 years during the 1988-1999 time period. This rate of decline is similar to the reduction of toxaphene emission from agricultural soils in the southern United States reported over the same time period. Some differences in decline rates were observed among the studied CHB congeners. For instance, P62 decreased more rapidly than P26 and P50 in both male and female belugas. Several hypotheses were advanced to explain these differences such as selective metabolism of specific chlorobornanes by SLE belugas or their prey. However, a most likely explanation is the selective degradation of the technical product in soils and atmosphere in the source region.