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 g round squirrels (Spermophilus beecheyi) trapped at Lawrence Livermore Natio nal Laboratory's Site 300 facility in California were determined with proto n induced X-ray emission (PIXE). As a reference, Mn profiles in olfactory b ulbs from laboratory rats exposed via nose-only inhalation to 0.53 mg/m(3) Mn in the form of MnCl2 were also determined with PIXE. Atomic absorption s pectrophotometry was used to measure soil Mn and Cd contents from the trapp ing sites and Mn and Cd contents in ground squirrel liver and leg muscle ti ssues. The data from laboratory rats revealed that Mn uptake into the olfac tory bulb occurs via inhalation exposure. Data from ground squirrels and kn owledge of the collection sites indicate that although several routes of ex posure may occur, fossorial rodent olfactory uptake affords a significant e xposure 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 sq uirrels were 10(3)-fold greater than exposure modeling estimates based on o ral Cd uptake data from livestock. The measurements for ground squirrel tis sues show that when conducting ecological risk assessments for natural habi tats considerable care should be taken in selecting transfer factors. Speci fically, transfer factors derived from data pertaining to comparable exposu re pathways and ecological setting should be used wherever possible.