Determination of human health risks related to consumption of snapping turtle tissue contaminated with polychlorinated biphenyls

In this study, twenty-five snapping turtles (Chelydra serpentina) were collected from Watts Bar Reservoir and the Clinch River, in Tennessee, to determine the concentration of polychlorinated biphenyls (PCBs) in edible tissues. Results were then used to evaluate human health risks from consumption of edible snapping turtle tissue. Muscle, fat, and eggs (if present) were analyzed for Aroclor 1016/1242, 1221, 1232, 1248, 1254, 1260, 1262. Specific analysis for the following congeners (as designated by the International Union of Pure and Applied Chemistry system) was also performed on the muscle of two of the larger turtles: IUPAC# 8, 18, 28, 44, 52, 66, 77, 81, 101, 105, 110, 118, 126, 128, 138, 153, 169, 170, 180, 187, 195, 206, and 209.

Results indicate that mean PCB concentrations in fat are significantly higher (63.83 ppm ± SE 22.38) than in muscle (0.49 ppm ± SE 0.18) or eggs (2.11 ppm ± SE 0.66). Although the fat accumulates higher concentrations of PCBs than the muscle or eggs, some turtles had concentrations in the muscle and eggs above the Food and Drug Administration Guidelines for PCBs in fish tissue (2.0 mg/kg). Even though PCBs were found at higher levels in tissue of the turtles most individuals do not consume (i.e., fat), the amount of PCBs found in edible turtle tissue is high enough to note as an important source of exposure.

A comparison of other studies evaluating concentrations of PCBs in fish tissue versus concentrations of PCBs in turtle tissues from this study, indicates that turtles concentrate PCBs at higher levels than fish from relatively the same location. Additionally, congener-specific analysis performed on muscle tissue of two of the larger turtles identified ten congeners considered "of highest concern" by the Environmental Protection Agency. A comparison of the congener-specific analysis performed on two turtles from this study with catfish from a previous study, revealed that congeners IUPAC# 153 and 180 were two of the most prominent congeners in both the turtles and the catfish. Both of these congeners are noted as high toxicity and abundance by the EPA (U. S. EPA, 1996c).

Risk assessment calculations revealed a current human health risk for both carcinogenic effects and non-carcinogenic health effects at levels of concern to individuals who consume snapping turtles from Watts Bar Reservoir and the Clinch River. However, because there are currently no toxicity values available for individual PCB congeners, uncertainty in the toxicity of PCB mixtures remains. Additionally, there is uncertainty in the toxicity values of the Aroclors used in the risk calculations, and uncertainty in the actual quantity and type of tissue consumed, which must be noted. Because of these uncertainties, the real risk could be greater or less than the calculated risk. This does not preclude a recommendation to add snapping turtles to those fishing advisories already posted for PCBs in fish and advising that fat should be discarded prior to preparation of snapping turtles for consumption.