A study released July 18 points to asthma as another potential fracking health impact.

Published in the JAMA Internal Medicine journal, the study by seven researchers—most from the John Hopkins Bloomberg School of Public Health—shows that residents who live near drilling sites experienced an increased risk of “mild, moderate and severe asthma exacerbations.” The exacerbation levels were determined by the number of new medication orders, hospital emergency encounters and hospitalizations, respectively. But the study is explicit in nothing that further investigation is needed before drawing a causal link between fracking and asthma.

The study looked at 35,5080 Pennsylvania and New York patients between ages 5 and 90 who already have asthma. Those closest to drilling wells lived a median of about 12 miles away. Patients farthest away lived a median of about 34 mile from a well.

The study found 4,782 severe, 1,870 moderate and 20,749 mild exacerbations among patients. Those with moderate exacerbations were more likely to be Black and on medical assistance than other participants. 

People of color already suffer disproportionately from asthma: Latinxs, for one, are 60 percent more likely to visit the hospital for asthma, compared to White people, according to the U.S. Department of Health and Human Services. 

Read the full study here.