Genotoxic effects of petroleum industry emissions in Richardson's Ground Squirrels (Spermophilus richardsonii)
Kallas, Melissa Mary
The petroleum industry is a major political and economic force in western Canada, and rural communities are concerned that airborne emissions from extraction and processing facilities may be adversely affecting their health and the environment. Since these emissions contain genotoxic contaminants, including polycyclic aromatic hydrocarbons and other organic compounds, the overall goal of this research was to assess whether chronic exposure to airborne emissions from petroleum field facilities is damaging to the genetic make-up of a representative small mammal, Richardson's ground squirrel (Spermophilus richardsonii). In 2002, ground squirrels were captured at 21 sites in Alberta and Saskatchewan representing a range of exposure to oil and gas field facilities. Tissue analysis included four methods (cytochrome P450 induction, the comet assay, flow cytometric DNA analysis, and histopathology) that were used to evaluate the progression of genotoxic effects, as well as two general indices of health, body condition and white blood cell (WBC) counts. The number of facilities and the total volumes of gases flared or vented within a defined radius of the trap locations were then examined for any association with measured biological outcomes. Hepatic cytochrome P4501A1 activity, as measured by the 7-ethoxyresorufin O-deethylase (EROD) assay, was increased in association with gas venting from small facilities (e.g. batteries; P < 0.0101) and the number of oil and gas wells (P < 0.0249), while cytochrome P4501A2 activity, as determined by the 7-methoxyresorufin O-deethylase (MROD) assay, was unrelated to facility exposure. The comet assay suggested evidence of primary genetic damage (DNA strand breaks) in peripheral WBCs, as comet tail ratios were significantly increased in association with flaring from gas processing plants (P < 0.0124). However, flow cytometry results provided no indication of chromosomal damage in WBCs associated with facility exposure. The incidence of lesions in the liver, but not in the lung, kidney, or heart, was significantly increased in ground squirrels exposed to gas plant flaring (P = 0.0109). Among the nonspecific health indicators, only total WBC counts and lymphocyte counts were related to petroleum facility exposure, with both outcomes being increased with exposure to large facilities (P < 0.0060 and P < 0.0096, respectively). Together, these results suggest that ground squirrels living near petroleum field facilities are experiencing a degree of genotoxic and immunotoxic stress and potentially altered liver function. Given the possible adverse consequences of these effects such as increased malignancy, impaired reproduction, and reduced resistance to toxicants and disease, further research is recommended in order to better characterize the health risks to rural residents, domestic animals, and wildlife living near these facilities. Better understanding of the effects of industry emissions on air quality is necessary to achieve sustainable exploitation of petroleum resources, both in Canada and worldwide.