A probabilistic risk assessment of the effects of methylmercury and PCBs on mink and kingfishers along East Fork Poplar Creek, Oak Ridge, Tennessee, USA

Abstract

Abstract-Over fifty years of operations, storage, and disposal of wastes from the U.S. Department of Energy (U.S. DOE) Y-12 nuclear weapons facility at Oak Ridge, Tennessee, USA, has resulted in the contamination of water, sediment, biota, and floodplain soils of East Fork Poplar Creek. A preliminary assessment revealed that methylmercury and polychlorinated biphenyls (PCBs) were the contaminants of most concern. Because these contaminants are persistent, accumulate in tissues, and biomagnify up the food chain, piscivorous wildlife are the biota at greatest risk of exposure. The objective of this study was to estimate the risks posed by methylmercury and PCBs to two piscivorous species: mink and belted kingfishers. We conducted Monte Carlo simulations to estimate total daily intakes of each contaminant by each species and then integrated the resulting distributions with their respective dose-response curves to estimate risks. The results indicate that methylmercury poses a moderate risk to female mink (24% probability of at least 15% mortality) and kingfishers (50% probability of at least a 12-28% decline in fecundity depending on location). The PCBs pose a very serious risk to mink (52% probability of at least a 50% decline in reproductive fecundity), a species known to be especially sensitive to the effects of organochlorine substances, but little risk to kingfishers (Ͻ5% probability of a decline in reproductive fecundity greater than 10% at any location).

Recommendations for the development and application of wildlife toxicity reference values

“…Receptor-specific models can be developed when sufficient data exist (e.g., Kerr and Meador 1996;Moore et al , 1999Moore et al , 2003Wayland et al 2007). In cases where data are more limited, it may be possible to combine dose and response data from different species or endpoints and use the whole data set for deriving the model.…”

“…In the first situation, there are several ''joint probability'' methods (e.g., Jacobs and Vesilind 1992;Solomon et al 2000;Suter 2007) that consider both the exposure and effects distributions to develop true risk estimates (i.e., both probability and magnitude of adverse effects). Some examples of studies where these techniques have been applied in wildlife ecological risk assessments include Moore et al ( , 1999Moore et al ( , 2003 and Wayland et al (2007). In cases where dose-response relationships were not modeled, the exposure distribution could be used to estimate the probability of exceeding one (or several) EDx values (i.e., derived using scatter plots).…”

Patterns and Interpretation of Mercury Exposure in Freshwater Avian Communities in Northeastern North America

“…The belted kingfisher is increasingly being used as an indicator for assessing Hg in riverine systems (Baron et al, 1997;Moore et al, 1999). Use of artificial nesting boxes on riverine habitat and experimental design interests for both piscivorous and insectivorous birds can be achieved with the hooded merganser and tree swallow.…”

“…Many past and even current inputs of waterborne Hg sources occur throughout North America and the Northeast. These are related to past improper waste disposal of Hg at weapons facilities (Halbrook et al, 1999), chlor-alkali plants (Fimreite, 1974;Gardner et al, 1978;Barr, 1986;Adair et al, 2003), mercury, gold, and silver mines Henny et al, 2002;Seiler et al, 2004;Weech et al, 2004) and governmental storage facilities (Moore et al, 1999) as well as current inputs from wastewater treatment plants .…”

Polychlorinated biphenyls, dioxins, furans, and organochlorine pesticides in belted kingfisher eggs from the upper Hudson River basin, New York, USA

“…Belted kingfishers (hereafter kingfishers, Ceryle alcyon) have been used as a representative fish-eating species in ecological risk assessments [18,19]. Kingfishers were selected because they breed throughout North America, are a regular resident of riparian zones of small streams, and feed almost exclusively on small fish [20].…”