Exploratory evaluation of the association between oil and gas exposure metrics and urinary biomarkers of stress in the EXPERIVA study

Unconventional oil and gas (UOG) development has expanded rapidly in Northeastern British Columbia, Canada. Although residential proximity to UOG has been linked to poorer air quality and adverse mental health, little is known about its potential effects on stress during pregnancy. This exploratory study measured urinary concentrations of three stress biomarkers (adrenaline, noradrenaline, cortisol) in pooled urine samples from 84 pregnant participants in the Exposures in the Peace River Valley (EXPERIVA) study and examined associations with proximity-based oil and gas metrics. Participants provided daily urine samples over 7 days. ELISA assays quantified biomarker concentrations. Well density and inverse-distance-squared weighted measures for total and phase-specific UOG activity were calculated using three different buffer sizes around residences (5 km, 10 km and no buffer). Associations between exposure quartiles and creatinine corrected biomarkers were evaluated using multiple linear regression. In the main adjusted model, cortisol concentrations were significantly higher in the fourth exposure quartile of UOG drilling phase (β = 16.346 µg/g creatinine; 95% CI: 0.154, 32.538) compared to the first. Similar results were observed in models further adjusted for gestational week and self-reported mental health status. No additional significant associations were observed between cortisol and the other exposure metrics. No clear patterns were observed for noradrenaline and adrenaline. Results suggest that residential proximity to UOG activity during the drilling phase may be associated with elevated urinary cortisol during pregnancy. However, results should be interpreted cautiously given inconsistencies and null findings across exposure metrics, small sample size and the potential for false discovery. Larger studies are needed to confirm these associations and clarify underlying psychosocial and endocrine pathways.