Effects of cooking on radiocesium in fish from the Savannah River: exposure differences for the public

Understanding the factors that contribute to the risk from fish consumption is an important public health concern because of potential adverse effects of radionuclides, organochlorines, other pesticides, and mercury. Risk from consumption is normally computed on the basis of contaminant levels in fish, meal frequency, and meal size, yet cooking practices may also affect risk. This study examines the effect of deep-frying on radiocesium (137Cs) levels and risk to people fishing along the Savannah River. South Carolina and Georgia have issued consumption advisories for the Savannah River, based partly on 137Cs. 137Cs levels were significantly higher in the cooked fish compared to the raw fish on a wet weight basis. Mean 137Cs levels were 0.61 pCi/g (wet weight basis) in raw fish, 0.81 pCi/g in cooked-breaded, and 0.99 pCi/g in cooked-unbreaded fish. Deep-frying with and without breading resulted in a weight loss of 25 and 39%, while 137Cs levels increased by 32 and 62%, respectively. Therefore, the differences were due mainly to weight loss during cooking. However, the data suggest that risk assessments should be based on cooked portion size for contaminant analysis, or the risk from 137Cs in fish will be underestimated. People are likely to estimate the amounts of fish they eat based on a meal size of the cooked portion, while risk assessors determine 137Cs levels in raw fish. A conversion factor of at least two for 137Cs increase during cooking is reasonable and conservative, given the variability in 137Cs levels. The data also suggest that surveys determining consumption should specifically ask about portion size before or after cooking and state which was used in their methods.