Association Between Unconventional Natural Gas Development in the Marcellus Shale and Asthma Exacerbations
Asthma is common and can be exacerbated by air pollution and stress. Unconventional natural gas development (UNGD) has community and environmental impacts. In Pennsylvania, UNGD began in 2005, and, by 2012, 6,253 wells had been drilled. There are no prior studies of UNGD and objective respiratory outcomes.
A nested case-control study compared patients with asthma with and without exacerbations from 2005 through 2012 treated at the Geisinger Clinic, which provides primary care services to more than 400,000 patients in Pennsylvania. Patients with asthma aged 5 to 90 years (n = 35,508) were identified in electronic health records; those with exacerbations were frequency matched on age, sex, and year of event to those without.
The study identified 20,749 mild, 1,870 moderate, and 4,782 severe asthma exacerbations and frequency matched these to 18,693, 9,350, and 14 ,104 control index dates, respectively.
Residential UNGD activity metrics were statistically associated with increased risk of mild, moderate, and severe asthma exacerbations. Whether these associations are causal awaits further investigation, including more detailed exposure assessment.