2,3,7,8-tetrachlorodibenzo-p-dioxin and related dioxins and furans in snapping turtle ( [formula omitted][formula omitted]) tissues from the upper St. Lawrence River

Abstract

Fat and liver samples from three snapping turtles ( Chelydra serpentina ) from the upper St. Lawrence River were analysed for tetra- up to octa-chlorinated dibenzo-p-dioxins (PCDDs) and chlorinated dibenzofurans (PCDFs) by two gas chromatography - mass spectrometry techniques and by a bioassay. The tissues contained only 2,3,7,8-chlorine substituted PCDDs and PCDFs with high levels occurring for 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). On a wet weight basis, fat levels of 2,3,7,8-TCDD were 4 to 7 times higher than liver levels with up to 500 pg/g present in turtle fat. One fat sample also contained over 3 ng/g of 2,3,4,7,8-pentachlorodibenzofuran (PnCDF) suggestive of a PCB source of contamination. The TCDD levels in the turtles are consistent with the consumption of a fish diet containing about 20 pg/g 2,3,7,8-TCDD, a level currently found in eel samples from the same region. Comparison of this limited snapping turtle data with that of other aquatic species from the same and different bodies of water suggest that the Niagara River via Lake Ontario could be a possible source of contamination of 2,3,7,8-TCDD for the St. Lawrence River. The results also show that turtles are excellent monitors for PCDD and PCDF contamination. Human consumption of turtle tissue samples containing the highest levels of 2,3,7,8-TCDD and PCDFs so far detected in wildlife samples may constitute a hazard.