Petrochemical waste contains inorganic contaminants that can pollute soil and pose ecological risks to wildlife. Few studies have evaluated bioaccumulation of inorganic contaminants by small mammals from soil contaminated with petrochemical waste. In this study, we determined the extent of soil contamination with inorganics, the bioaccumulation of metals and F in bone of cotton rats (Sigmodon hispidus), and the relationship between contaminants in soil and in bone of cotton rats on petrochemical waste sites. Cotton rats and soils from 12 petrochemical‐contaminated and matched reference sites were analyzed over a three‐year period. The number of petrochemical‐contaminated sites with soil contamination (in parentheses) were Zn (12), Pb (9), Cr (9), Cu (8), F (7), Ni (7), Sr (6), Ti (5), V (5), Co (3), Ba (3), and Cd (2). Lead and F were the most frequently bioaccumulated contaminants in cotton rat bones. Bone Pb of 3.8 to 63.4 mg/kg was 2‐ to 42‐fold and bone F of 830 to 3,680 mg/kg was 5‐ to 23‐fold greater than mean bone Pb and F from reference sites. Bone Pb and F showed a seasonal trend with winter greater than summer levels. Bone F was an accurate predictor of dental fluorosis when bone F was low (< 1,000 mg/kg, no fluorosis) or high (>3,000 mg/kg, fluorosis) but was inaccurate for intermediate bone F (1,000–3,000 mg/kg). The prevalence of dental fluorosis on F‐contaminated sites was 50% higher in winter than summer. Strong relationships were found between bone F and HCl‐extractable F (r = 0.70) and bone F and total content of F (r = 0.85) in F‐contaminated soils. Land disposal of petrochemical wastes should limit the amount of inorganic contaminants applied to soil.

Abstract-Total fluoride (F) content of soils, vegetation, and cotton rats (Sigmodon hispidus) was measured on a landfarm contaminated with petrochemical wastes. A potentially bioavailable form of F was determined by HCl extraction of soils and vegetation. Cotton rats from the landfarm were examined for dental lesions indicative of fluorosis. Exposure pathways including dietary ingestion of unwashed vegetation and nondietary ingestion of soil associated with grooming and burrowing were evaluated. Mean bone F (1,515 mg/kg) and mean soil total F (1,954 mg/kg) from the landfarm site were greater than bone F (121 mg/kg) and soil total F (121 mg/kg) at a reference site. The HCl-extractable F was elevated in landfarm soil (326 mg/kg) compared to the reference site (2.3 mg/kg). About 80% of the cotton rats collected from the landfarm had dental fluorosis. During winter, the dietary pathway consisted of 78.9% of the potential bioavailable exposure (HCl-extractable F) of the two exposure pathways. However, in the summer, the nondietary pathway consisted of 87.9% of the potential bioavailable exposure of the two pathways. Incidental ingestion of soil associated with grooming and burrowing is more important than consumption of unwashed vegetation for cotton rats on the landfarm site in the summer. Fluoride accumulation in the soil from landfarming of petroleum wastes may pose a risk to terrestrial vertebrates. In addition to monitoring petroleum hydrocarbons, land application of petrochemical wastes should consider F and other inorganic contaminant loadings to the soil system.

Land-treatment of petroleum wastes is a widely used industrial practice, yet there has been no comprehensive evaluation of the long-term risks to human or terrestrial ecosystems from such practices. We evaluated cotton rat (Sigmodon hispidus) populations on three sites in Oklahoma (USA) that historically used land-treatment for disposal of various petroleum wastes (July 1995-March 1997. Average concentrations of fluoride in soil from these sites ranged from 878 to 4317 mg/kg. A census of resident cotton rats on land-treatment sites revealed a high incidence (40% overall) of dental lesions compared to reference populations (Ͻ1% dental lesions). During winter there was a 34% to 65% increase compared to summer in frequency of dental lesions in cotton rats on two of the three land-treatment sites. Incidence of dental lesions on two land-treatment sites was greater (9-16%) in female cotton rats compared to males. Cotton rats from land-treatment sites had higher concentrations of fluoride in bone and greater severity of dental lesions compared to reference animals. Dental lesions were considered to be most consistent with dental fluorosis because of elevated fluoride in bone. Neither concentration of fluoride in soil nor level of fluoride in bone was a good predictor of severity of dental lesions in cotton rats on land-treatment sites.

Abstract-Petrochemical waste contains inorganic contaminants that can pollute soil and pose ecological risks to wildlife. Few studies have evaluated bioaccumulation of inorganic contaminants by small mammals from soil contaminated with petrochemical waste. In this study, we determined the extent of soil contamination with inorganics, the bioaccumulation of metals and F in bone of cotton rats (Sigmodon hispidus), and the relationship between contaminants in soil and in bone of cotton rats on petrochemical waste sites. Cotton rats and soils from 12 petrochemical-contaminated and matched reference sites were analyzed over a three-year period. The number of petrochemical-contaminated sites with soil contamination (in parentheses) were

Arsenic is a ubiquitous contaminant of many toxic waste sites around the country and experimental animal trials have indicated that arsenic may be immunotoxic to laboratory rodents. Because wild rodents such as the herbivorous cotton rat (Sigmodon hispidus) reside on many of these toxic waste sites, we explored the sensitivity of their immune systems to oral exposures of environmentally relevant concentrations of inorganic arsenic. We exposed adult male cotton rats (n = 36) to either 0 (controls), 5 (low dose), or 10 (high dose) ppm sodium arsenite in drinking water for 6 weeks. Daily food intake decreased in a dose-dependent manner, ranging from an average of 10.03 +/- 0.45 in the high-dose group to 11.27 +/- 0.42 (SE) g/animal/day in the control group. Mass of testes in the low-dose group increased significantly compared to controls, but there was no difference between the high-dose and control groups. Masses of liver, kidney, adrenals, popliteal lymph nodes, spleen, epididymides, and seminal vesicles and selected hematological parameters were unaffected by arsenic exposure. In vivo cell-mediated immunity, as measured by a phytohemagglutinin-hypersensitivity response to an intradermal challenge, was suppressed 30% in the low-dose group compared to controls; however, responses of those receiving a high dose of arsenic were similar to controls. Arsenic treatment did not have a measurable impact on lymphoproliferative responses of cultured splenocytes to the mitogens Concanavalin A and Pokeweed mitogen, or to the lymphokine interleukin-2. We also observed no impact of low-level arsenic exposure on macrophage phagocytic activity and tumoricidal activity of lymphokine-activated killer cells in vitro. It is possible that malnutrition caused by decreased food intake may eventually lead to atrophy of lymphoid organs and render animals more susceptible to environmental pathogens. However, direct effects of low-level arsenic exposure on immune function of cotton rats was minimal (a moderate depression in the in vivo cell-mediated immunity assay) and may not be clinically relevant with regard to susceptibility to disease in the wild.