Tracking Fracking for Birth Outcomes

EBM Focus - Volume 17, Issue 19

Reference: JAMA Pediatr. 2022 Apr 4 early online

Fracking (hydraulic fracturing) is shorthand for the underground injection of water and chemicals into sedimentary rock, forcing out trapped natural gas. The process creates “produced water,” which is a combination of the water and chemicals injected plus previously existing groundwater and other substances that might be underground. Although there are plenty of potential problems with other parts of the process, produced water is particularly problematic, as it is often full of carcinogensheavy metalsradioactive elements and a wide variety of other toxic materials. Evidence exists associating multiple significant adverse health outcomes with people who live near fracking wells. Researchers in Alberta, Canada published a study just before Mother’s Day examining how fracking affected infants born to parents living in rural regions within 10 kilometers of fracking activity.

Between 2013 and 2018, Alberta was home to 4,871 active fracking wells, and during that time 26,193 people who lived in rural locations had a total of 34,873 pregnancies. Through use of public data source of the types and locations of wells, and also using the postal delivery points for individuals who delivered babies during that time, researchers identified the subset of 9,158 individuals who gave birth and whose postal delivery point was within 10 kilometers of at least one fracking site during preconception and/or pregnancy. Urban locations were excluded. The parents were assessed for socioeconomic status, age at delivery, comorbidities and other risk factors for adverse outcomes. The infants born from these pregnancies then had data collected and problems were noted in the first couple of months of life, including major congenital anomalies, severe morbidity/mortality, prematurity, and small for gestational age (SGA) status, defined as weight <10% of expected for gestational age.

Associations were found between proximity during preconception and pregnancy to any well for SGA (adjusted risk ratio [aRR] 1‌.12, 95% CI 1‌‌.03-1.23) and major congenital abnormalities (aRR 1.33, 95% CI 1.01-1.69). Being conceived or being pregnant within 10 km of > 100 fracking sites increased the risk of preterm labor to 1.64 (95% CI 1.04-2.60) and SGA to 1.65 (95% CI 1‌‌.1-2.48). Sensitivity analysis demonstrated that neither fracking exposure during preconception or pregnancy alone had a significant association, but exposure during both periods did, suggesting a dose response.

Observational cohorts and case studies are subject to a lot of confounding, and the tobacco industry famously thrived for decades around the sticky problem of proving causality due to an environmental exposure. The Bradford-Hill viewpoints, one of the founding documents of causal inference theory, listed temporality and dose-response as issues to consider when arguing for causation. Although there is plenty more evidence to be gathered about the likelihood of fracking causing harm, this study does its best to adjust for confounding by taking into account socioeconomic factors and significantly strengthens the case for dose-response and temporality, as pregnancy and conception are very well-defined time-sensitive phenomena compared to development of most cancers. These data support that being around more fracking wells and having a longer period of exposure both significantly increased the risk of adverse outcomes. This study provides another piece of the “evidence pie” of so-called sufficient components that suggest fracking contributes to a variety of bad health outcomes.

For more information, see the topic Risk Factors for Preterm Labor and Premature Birth in DynaMed.

DynaMed EBM Focus Editorial Team

This EBM Focus was written by Dan Randall, MD, Deputy Editor at DynaMed. Edited by Alan Ehrlich, MD, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School; Katharine DeGeorge, MD, MS, Deputy Editor at DynaMed and Associate Professor of Family Medicine at the University of Virginia; Carina Brown, MD, Assistant Professor at Cone Health Family Medicine Residency; Nicole Jensen, MD, Family Physician at WholeHealth Medical; Vincent Lemaitre, PhD, Senior Medical Writer at DynaMed; and Sarah Hill, MSc, Associate Editor at DynaMed.