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Assessing gestational exposure to trace elements in an area of unconventional oil and gas activity: comparison with reference populations and evaluation of variability



Located in Northeastern British Columbia, the Montney formation is an important area of unconventional oil and gas exploitation, which can release contaminants like trace elements. Gestational exposure to these contaminants may lead to deleterious developmental effects.


Our study aimed to (1) assess gestational exposure to trace elements in women living in this region through repeated urinary measurements; (2) compare urinary concentrations to those from North American reference populations; (3) compare urinary concentrations between Indigenous and non-Indigenous participants; and (4) evaluate inter- and intra-individual variability in urinary levels.


Eighty-five pregnant women participating in the Exposures in the Peace River Valley (EXPERIVA) study provided daily spot urine samples over 7 consecutive days. Samples were analyzed for 20 trace elements using inductively-coupled mass spectrometry (ICP-MS). Descriptive statistics were calculated, and inter- and intra-individual variability in urinary levels was evaluated through intraclass correlation coefficient (ICC) calculation for each trace element.


When compared with those from North American reference populations, median urinary levels were higher in our population for barium (~2 times), cobalt (~3 times) and strontium (~2 times). The 95th percentile of reference populations was exceeded at least 1 time by a substantial percentage of participants during the sampling week for barium (58%), cobalt (73%), copper (29%), manganese (28%), selenium (38%), strontium (60%) and vanadium (100%). We observed higher urinary manganese concentrations in self-identified Indigenous participants (median: 0.19 µg/g creatinine) compared to non-Indigenous participants (median: 0.15 µg/g of creatinine). ICCs varied from 0.288 to 0.722, indicating poor to moderate reliability depending on the trace element.


Our results suggest that pregnant women living in this region may be more exposed to certain trace elements (barium, cobalt, copper, manganese, selenium, strontium, and vanadium), and that one urine spot sample could be insufficient to adequately characterize participants’ exposure to certain trace elements.

Impact statement

Unconventional oil and gas (UOG) is an important industry in the Peace River Valley region (Northeastern British Columbia, Canada). Information on the impacts of this industry is limited, but recent literature emphasizes the risk of environmental contamination. The results presented in this paper highlight that pregnant women living near UOG wells in Northeastern British Columbia may be more exposed to some trace elements known to be related to this industry compared to reference populations. Furthermore, our results based on repeated urinary measurements show that one urine sample may be insufficient to adequately reflect long-term exposure to certain trace elements.

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Data availability

The authors declare that the data supporting the findings of this study are available within the article and its Supplementary Information files. We will not be able to make additional exposure data in EXPERIVA participants available to external investigators given restrictions in our research agreements and ethics approval.


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This research was conducted in Treaty 8, the traditional territory of the Cree, Saulteau and Dunne-Za people. This research project was funded through a Project Grant from the Canadian Institutes of Health Research (CIHR) (Application ID 390320) awarded to Marc-André Verner and Élyse Caron-Beaudoin. At the time of the EXPERIVA study recruitment, Élyse Caron-Beaudoin was supported through a CIHR postdoctoral fellowship (Funding Reference Number 159262). Marc-André Verner is the recipient of a Research Scholar J2 Award from the Fonds de recherche du Québec – Santé (FRQS). We want to thank the participants, as well as the Treaty 8 Tribal Association, the Saulteau First Nations and the West Moberly First Nations for their support and welcoming. The research team would also like to thank the staff from the medical and midwifery clinics for their assistance during the recruitment. We also thank Denis Dieme for analytical measurements of trace elements.


Project Grant from the Canadian Institutes of Health Research (156206) awarded to MAV and ECB. In 2019, ECB was supported through a CIHR postdoctoral fellowship (Funding Reference Number 159262). MAV is the recipient of a Research Scholar J2 Award from the Fonds de recherche du Québec—Santé (FRQS).

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LC contributed to data analysis, interpretation of the results and drafted the initial manuscript. MB developed the analytical methods, provided scientific support and reviewed the manuscript. LG reviewed the manuscript. DBR provided scientific support for the statistical analysis and reviewed the manuscript. NOB and WMFNCC contributed to the conceptualization of EXPERIA and reviewed the manuscript. ECB managed the recruitment and sampling. ECB and MAV were responsible for the conceptualization of EXPERIVA, developing the methodologies, funding, supervising the project, data interpretation and manuscript writing and editing. All authors contributed to the final version of the manuscript.

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Correspondence to Marc-André Verner.

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The authors declare no competing interests.

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This study received ethical approval from the Northern Health Research Review Committee and the Université de Montréal Institutional Review Board (#CERC-18-003-P).

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Claustre, L., Bouchard, M., Gasparyan, L. et al. Assessing gestational exposure to trace elements in an area of unconventional oil and gas activity: comparison with reference populations and evaluation of variability. J Expo Sci Environ Epidemiol 33, 94–101 (2023).

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  • Trace elements
  • Exposure assessment
  • Pregnant women
  • Biomonitoring
  • Inter- and intra-individual variability
  • Unconventional oil and gas


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