The development of a spatially explicit model to estimate radiocaesium body burdens in raccoons (Procyon lotor) for ecological risk assessment.

A spatially explicit model of raccoon (Procyon lotor) distribution for the U.S. Department of Energy's (DOE) Savannah River Site (SRS) in west-central South Carolina was developed using data from a raccoon radio-telemetry study and visualized within a Geographic Information System (GIS). An inductive approach was employed to develop three sub-models using the ecological requirements of raccoons studied in the following habitats: (1) man-made reservoirs, (2) bottomland hardwood/riverine systems, and (3) isolated wetland systems. Logistic regression was used to derive probabilistic resource selection functions using habitat compositional data and landscape metrics. The final distribution model provides a spatially explicit probability (likelihood of being in an area) surface for male raccoons. The model is a stand-alone tool consisting of algorithms independent of the specific GIS data layers to which they were derived. The model was then used to predict contaminant burdens in raccoons inhabiting a riverine system contaminated with radiocaesium (137Cs). The predicted 137Cs burdens were less than if one would assume homogeneous use of the contaminated areas. This modelling effort provides a template for DOE managed lands and other large government facilities to establish a framework for site-specific ecological assessments that use wildlife species as endpoints.

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.

Effect of deep-frying fish on risk from mercury.

The U.S. Environmental Protection Agency (EPA) and many states have issued advisories to limit or avoid the consumption of certain fish or fish from certain waters, particularly by pregnant women and young children or even women of childbearing age. Typically, risk is calculated by multiplying contaminant concentrations in fish tissue, frequency of meals, and meal size, compared to some criterion, usually the U.S. EPA reference dose (RfD). Site-specific data on mercury concentrations, meal size, and consumption frequency by fishermen were used to determine how frying fish affected risk estimates. In consumption studies fishermen typically estimate the size of portions as they appear on the plate (i.e., cooked), yet assessors calculate risk based on contaminant levels in uncooked fish. Largemouth bass (Micropterus salmoides, n = 39) were collected from the contaminated L Lake on the Savannah River Site, South Carolina. Fillets from the opposite sides of the same fish were divided and randomly assigned to a raw or fried treatment (the commonly used local cooking method). The fried fillet was further divided in half for a breaded or nonbreaded treatment. Mercury averaged 0.44 microg/g (ppm, wet weight) in raw fish, 0.63 microg/g in fried and breaded fish, and 0.76 microg/g in fried, unbreaded fish. The maximum concentration was 1.5 microg/g in raw fish (1.9 microg/g in cooked fish). Deep-frying with and without breading resulted in weight loss of 25% and 39%, while mercury levels increased by 45% and 75%, perhaps due to the breading and absorption of oil. At the mean fish

Metal levels in fish from the Savannah River: potential hazards to fish and other receptors.

Fish are ideal indicators of heavy metal contamination in aquatic systems because they occupy different trophic levels and are different sizes and ages. In this paper, we report concentrations of arsenic, cadmium, chromium, copper, lead, manganese, strontium(88) and mercury in the muscle of 11 species of fish from the Savannah River near the Savannah River Site. We test the hypotheses that there are no locational, species, or trophic-level differences in contaminant levels. There were significant species differences for all metals; higher-trophic-level fish generally had higher levels of arsenic, chromium, and copper. There were relatively few locational differences, and where there were such differences, they were small. The relationships between body weight and contaminant levels were generally positive, except for strontium, where there was a negative correlation for bowfin (Amia cal va), bass (Micropterus salmoides), yellow perch (Perca flavescens), and shellcracker (Lepomis microlophus) and no relationship for the other species. The levels of most metals were similar to, or lower than, those for the United States generally, and the levels of metals in fish from the Savannah River do not appear to pose a health threat to the fish themselves or to higher-order consumers, based on levels known to cause effects.