Gestational exposure to volatile organic compounds (VOCs) in Northeastern British Columbia, Canada: A pilot study

Background: Northeastern British Columbia (Canada) is an area of intense hydraulic fracturing for unconventional natural gas exploitation. There have been multiple reports of air and water contamination by volatile organic compounds in the vicinity of gas wells. Although these chemicals are known developmental toxicants, no biomonitoring effort has been carried out in the region. Objective: To evaluate gestational exposure to benzene and toluene in the Peace River Valley, Northeastern British Columbia (Canada). Methods: Urine samples were collected over five consecutive days from 29 pregnant women. Metabolites of benzene (s-phenylmercapturic acid (S-PMA) and trans, trans-muconic acid (t, t-MA)) and toluene (s-benzylmercapturic acid (S-BMA)) were measured in pooled urine samples from each participant. Levels of benzene metabolites were compared to those from the general Canadian population and from a biomonitoring study of residents from an area of active gas exploitation in Pavillion, Wyoming (USA). Levels measured in participants from the two recruitment sites, and self-identifying as Indigenous or non-Indigenous, were also compared. Results: Whereas the median S-PMA level (0.18 mu g/g creatinine) in our study was similar to that in the general Canadian population, the median t, t-MA level (180 mu g/g creatinine) was approximately 3.5 times higher. Five women had t, t-MA levels above the biological exposure index (R) proposed by the American Conference of Governmental Industrial Hygienists. The median urinary S-BMA level in our pilot study was 7.00 mu g/g creatinine. Urinary metabolite levels were slightly higher in self-identifying Indigenous women, but this difference was only statistically significant for S-PMA. Discussion: Urinary t, t-MA levels, but not S-PMA levels, measured in our study are suggestive of a higher benzene exposure in participating pregnant women from the Peace River Valley than in the general Canadian population. Given the small sample size and limitations of t, t-MA measurements (e.g., non-specificity), more extensive monitoring is warranted.