The Heath Implications of Unconventional Natural Gas Development in Pennsylvania

Due to technological advancements in horizontal drilling and hydraulic fracturing (fracking), natural gas trapped beneath shale formations has become more economically accessible. As shale gas plays an increasingly important role in the energy security for the U.S., the potential health risks have drawn attention from the public and regulators at various levels. Despite numerous anecdotes of adverse health effects in the media, there are few studies that examine the health risks associated with shale gas extraction activities. We are only aware of two published studies: Jemielita et al (2015) report an association between unconventional natural gas drilling and increased hospitalization rates for cardiology and neurology patients, while Casey et al (2015) find an association with preterm birth and high-risk pregnancy.

In this paper, we build on Jemielita et al (2015) and investigate the health impacts of shale gas development in Pennsylvania between 2001 and 2013. We obtained well permit data from Pennsylvania Department of Environmental Protection. These data contain detailed information on the well location, drilling commencement date, operator, output, and configuration of all wells (both conventional and unconventional) drilled in Pennsylvania. Our health outcome measures come from a database of all inpatient hospital admissions in the state (PHC4). We focus on five air-pollution-sensitive health conditions: acute myocardial infarction (AMI), chronic obstructive pulmonary disease (COPD), asthma, pneumonia, and upper respiratory infection (URI). We conduct separate analysis for four age groups: 5-19, 20-44, 45-64, and 65 above. The dependent variables in our analysis are annual county-level hospitalization rate for each condition. 

We estimate a set of county fixed-effects models where we include a binary indicator for active unconventional wells (and its lead and lag), and log of natural gas output from all active unconventional wells (and its lag). Since air pollution may come from well development activities as well as ongoing extraction activities, the well leads allow us to capture the effects of well development, while the well lags capture lagged response to development and extraction activities. We include annual county-level coal production to capture the substitution of natural gas for coal due to shale gas development. In addition, we control for the county unemployment rate, median household income, population density, and age distribution. We also include measures of patient characteristics at each county’s hospitals and use year fixed effects to account for overall secular trend in the outcomes.

We find that county-level hospitalization rates for AMI, asthma, pneumonia, and URI among young adults (aged 20-44) increased by 24 percent, 12 percent, 10 percent, and 38 percent, respectively, due to shale gas development. Hospitalizations for COPD, pneumonia, and URI also increased by 5 percent, 9 percent, and 17 percent, respectively, among the elderly. These adverse effects on health are consistent with higher levels of air pollution resulting from unconventional natural gas development. Our results have important implications for public policy because they provide evidence of an adverse impact of shale gas development on health, which is currently of concern to policy makers.