Density and proximity of oil and gas wells and concentrations of trace elements in urine, hair, nails and tap water samples from pregnant individuals living in Northeastern British Columbia

Background: Oil and gas exploitation can release several contaminants in the environment, including trace elements, with potentially deleterious effects on exposed pregnant individuals and their developing fetus. Currently, there is limited data on pregnant individuals' exposure to contaminants associated with oil and gas activity. Objectives: We aimed to 1) measure concentrations of trace elements in biological and tap water samples collected from pregnant individuals participating in the EXPERIVA study; 2) compare with reference populations and health-based guidance values; 3) assess correlations across matrices; and 4) evaluate associations with the density/proximity of oil and gas wells. Methods: We collected tap water, hair, nails, and repeated urine samples from 85 pregnant individuals, and measured concentrations of 21 trace elements. We calculated oil and gas well density/proximity (Inverse Distance Weighting [IDW]) for 4 buffer sizes (2.5 km, 5 km, 10 km, no buffer). We performed Spearman's rank correlation analyses to assess the correlations across elements and matrices. We used multiple linear regression models to evaluate the associations between IDWs and concentrations. Results: Some study participants had urinary trace element concentrations exceeding the 95th percentile of reference values; 75% of participants for V, 29% for Co, 22% for Ba, and 20% for Mn. For a given trace element, correlation coefficients ranged from -0.23 to 0.65 across matrices; correlations with tap water concentrations were strongest for hair, followed by nails, and urine. Positive (e.g., Cu, Cr, Sr, U, Ga, Ba, Al, Cd) and negative (e. g., Fe) associations were observed between IDW metrics and the concentrations of certain trace elements in water, hair, and nails. Significance: Our results suggest that pregnant individuals living in an area of oil and gas activity may be more exposed to certain trace elements (e.g., Mn, Sr, Co, Ba) than the general population. Association with density/ proximity of wells remains unclear.