Scientists Find Studies Linking Fracking to Health Impacts Poorly Designed, Inconclusive

Studies tying shale development to negative public health impacts used imprecise measures, failed to consider other possible factors, and, in some cases, were poorly designed, a committee of independent scientific experts affiliated with the Health Effects Institute concluded in a report released this week.

The in-depth analysis of 25 studies by HEI scientists – a nonprofit, independent research organization chartered to provide high-quality, impartial and relevant science on the health effects of air pollution – is a first-of-its kind review of the research that has made serious claims involving perinatal, cancer, respiratory, and cardiovascular outcomes, as well as self-reported physiological and mental health symptoms.

Even though these studies have generated headlines and are frequently referenced by anti-energy activists, the Committee’s independent, thorough analysis concluded the studies’ limitations and poor designs prevent the Committee from determining whether unconventional oil and gas development (UOGD) “contributed to the assessed health outcomes.”

“Data and study limitations prevented the Committee from determining whether exposures originating directly from UOGD contributed to the assessed health outcomes, either within individual studies or across the body of literature. The limitations include the lack of quantified exposures, the potential for residual confounding, inconsistencies in design and results across studies, and the limited number of studies for any one outcome.” (p.65)

All of the studies HEI reviewed did not directly measure exposure levels – a critically important factor.

“All studies relied on surrogate measures of exposure to UOGD, and thus the Committee could not ascribe any of the report associations to agents originating specifically from UOGD.” (p. XI)

HEI’s analysis comes on the heels of a similar, thorough review of existing epidemiologic research by the Pa. Department of Health and Colorado Department of Public Health and Environment which concluded the majority of studies claiming to link health impacts to oil and natural gas development were limited in study design and had “conflicting evidence (mixed), insufficient evidence, or in some cases, a lack of evidence of the possibility for harmful health effects.

These high-quality, independent analyses don’t support the claims repeated by anti-energy activists and the reporters behind the deeply biased Post-Gazette Human Toll series. It’s further evidence that the Physicians for Social Responsibility “compendium” (which just 2% of the 1,447 cited references are peer-reviewed, population studies) is simply a tool to achieve the group’s primary goal of banning hydraulic fracturing and killing energy jobs.

Here are key highlights of HEI’s analysis:

On studies involving perinatal – pre-birth & immediately after birth – outcomes:

“Results of studies with the same exposure-outcome pairs were inconsistent and the studies employed limited control of potential confounders, in particular strong measures of SES and lifestyle factors. The limitations of these studies prevent the Committee from concluding whether environmental exposures originating directly from UOGD did or did not contribute to the assessed perinatal outcomes.”

On studies involving cancer outcomes:

“The cancer studies lacked strong study designs, notably insufficient allowance for latency periods, and control for potential confounding. Investigators report no or weak associations between the UOGD exposure surrogates and cancer, and there were at most two studies for any one cancer outcome. The limitations of these studies prevent the Committee from concluding whether environmental exposures originating directly from UOGD did or did not contribute to the assess cancer outcomes.”

On studies involving respiratory outcomes:

“All three respiratory studies assessed asthma, but all were subject to potential confounding and lacked temporal resolution sufficient to observe acute respiratory outcomes. The Committee is therefore unable to conclude whether environmental exposures originating directly from UOGD did or did not contribute to the assessed respiratory outcomes.” 

The MSC, our members, and the tens-of-thousands of Pennsylvanians who go to work each day to produce the clean, abundant natural gas our society needs will always be guided by empirical evidence and is absolutely committed to protecting and enhancing the health and safety of our communities.


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