Olfactory bulb uptake and determination of biotransfer factors in the California ground squirrel (Spermophilus beecheyi) exposed to manganese and cadmium in environmental habitats.

Manganese (Mn) and cadmium (Cd) profiles in olfactory bulbs of California ground squirrels (Spermophilus beecheyi) trapped at Lawrence Livermore National Laboratory's Site 300 facility in California were determined with proton induced X-ray emission (PIXE). As a reference, Mn profiles in olfactory bulbs from laboratory rats exposed via nose-only inhalation to 0.53 mg/m3 Mn in the form of MnCl2 were also determined with PIXE. Atomic absorption spectrophotometry was used to measure soil Mn and Cd contents from the trapping sites and Mn and Cd contents in ground squirrel liver and leg muscle tissues. The data from laboratory rats revealed that Mn uptake into the olfactory bulb occurs via inhalation exposure. Data from ground squirrels and knowledge of the collection sites indicate that although several routes of exposure may occur, fossorial rodent olfactory uptake affords a significant exposure route to Mn and Cd in soils. Measured biotransfer factors (ratio of leg muscle tissue metal content to soil metal content) for Cd in ground squirrels were 10(3)-fold greater than exposure modeling estimates based on oral Cd uptake data from livestock. The measurements for ground squirrel tissues show that when conducting ecological risk assessments for natural habitats considerable care should be taken in selecting transfer factors. Specifically, transfer factors derived from data pertaining to comparable exposure pathways and ecological setting should be used wherever possible.

Ecological risks to fossorial vertebrates from volatile organic compounds in soil.

The past several years has seen an increased awareness of the need to conduct ecological risk assessments (ERAs) for hazardous waste sites. One technique used in ERAs involves estimating contaminant exposure to individual animals of selected species, which is then compared to a reference dose derived from the literature. Exposure estimates are conducted on those species which are representative of the different trophic levels found at the site. In many terrestrial systems, fossorial (burrowing) vertebrates are found in both lower and upper trophic levels. As part of the ERA conducted for Site 300, Lawrence Livermore National Laboratory's high-explosive test facility, contaminant exposures were estimated for fossorial and nonfossorial vertebrates spanning two trophic levels. The results of the evaluation revealed that a significant pathway by which fossorial vertebrates could be exposed to trichloroethylene in soil was through the inhalation of contaminated subsurface burrow air. This was the first time that the importance of this ecological exposure pathway has been recognized. The results of this analysis suggest that further research into the ecological significance of subsurface burrow air contaminated with volatile organic compounds is warranted.