A new study conducted by researchers at the Johns Hopkins Bloomberg School of Public Health has found a statistical link between unconventional oil and gas drilling in Pennsylvania and an increased risk of flare-ups in asthma patients.

The study, published online Monday in The Journal of the American Medical Association Internal Medicine, was based on electronic health records of asthma patients reporting to the Geisinger Clinic in Pennsylvania. Researchers looked at incidences of mild, moderate and severe asthma exacerbations and found that those living closer to oil and gas activity were “statistically associated with an increased risk” of needing medical treatment for asthma symptoms.

The study found that, out of 35,508 patients with asthma, those living in the highest quartile of oil and gas drilling activity “had significantly higher odds” of needing medication, visiting an emergency room or being hospitalized for their asthma.

“Whether these associations are causal awaits further investigation, including more detailed exposure assessment,” the researchers wrote.

Researchers identified and accounted for different phases of oil and gas development and the activity occurring in the areas studied.

They collected data from the Pennsylvania Department of Environmental Protection, the Pennsylvania Department of Conservation and Natural Resources and SkyTruth to determine well pad locations; dates of spudding, stimulation and production; total depth; and production volume and duration.

The study was funded by a grant from the National Institute for Environmental Health Sciences, with additional support from the Degenstein Foundation, the Robert Wood Johnson Foundation Health & Society Scholars program and the National Science Foundation Integrative Graduate Education and Research Traineeship.

Dr. Brian S. Schwartz, one of the lead authors, is a fellow with the Post Carbon Institute, serving as an unpaid informal adviser on issues related to climate, energy and health, according to a disclosure statement published with the study.