Radiocesium in Mourning Doves: Effects of a Contaminated Reservoir Drawdown and Risk to Human Consumers

Abstract

From September 1991 through January 1995, partial drawdown of a 1,130-ha U.S. Department of Energy reactor cooling reservoir (Par Pond) in South Carolina exposed sediments contaminated by low-level radiocesium ( 137 Cs). These exposed sediments were designated as a U.S. Environmental Protection Agency (EPA) superfund site. Whole-body and muscle concentrations of 137 Cs in mourning doves (Zenaida macroura) collected from Par Pond in 1992 and 1993 were 2-3 orders of magnitude higher than in doves from nearby public dove-hunting fields located 12 and 32 km away. Only 1 of 102 Par Pond doves exceeded the European Economic Community limit of 0.60 Becquerels (Bq) 137 Cs/g for fresh meat. A human risk analysis based on consumption of doves at the observed maximum of muscle 137 Cs concentration (0.82 Bq/g wet mass) indicated no more than 41 doves could be consumed by an individual per year at that level before the EPA threshold for action on a superfund site would be exceeded (i.e., further site characterization, possible remedial action). Levels of whole-body 137 Cs in doves from Par Pond declined by >75% from 1992 through 1994. Pokeweed (Phytolacca americana) seeds, the dominant food of doves foraging on the exposed lake bed, likewise declined (>90%) in 137 Cs content over the period. We noted subtle annual changes in the diets of doves that likely contributed to reduced rates of 137 Cs ingestion as the drawdown progressed. Doves differed by age class in their food intake and selection, and immature doves showed higher levels of ingesta 137 Cs. However, age classes did not differ in whole-body 137 Cs (P = 0.156) or muscle 137 Cs (P = 0.181). Dove whole-body 137 cs was a good predictor (r2 = 0.94) of muscle 137 Cs, and thus provides the opportunity to estimate levels of 137 Cs in edible muscle without destructive sampling by simply subjecting live-captured birds to whole-body determination of 137 Cs content. The radiological consequences of a long-term drawdown or complete draining of such a reservoir are not clear.