A new study has found that those who live near areas where oil companies are conducting controversial hydraulic fracturing — or “fracking” — are much more likely to get hospitalized for a range of terrible illnesses, including cancer, heart conditions, and neurological illnesses.

The findings, published in the journal PLOS ONE by researchers from the University of Pennsylvania as well as Columbia University, examined the practice of fracking, or an oil and gas extraction technique where water, chemicals, and sand are mixed together and use to break apart underground rock in order to get at the oil and gas trapped beneath, according to a Columbus Dispatch report.

Fracking has been a controversial subject in U.S. energy production lately, and it has stirred up a massive debate about how it affects local communities.

The study examined hospitalization rates in Pennsylvania between 2007 and 2011 and found that they were higher in areas where fracking took place as compared to areas that didn’t have fracking nearby.

The main concern is that fracking may cause water pollution, and the researchers suspects that residents were exposed to lots of toxins. Then there’s the noise and social stressors that fracking allegedly causes near homes. Taken all together, it could explain the higher rates of hospitalization for cancer and heart disease and other causes around hydraulic fracturing operations by oil companies.

About 18 ZIP codes were examined in the study that had well densities greater than 0.79 wells per square kilometers. The researchers found a 27 percent increase in hospitalizations for heart conditions in those ZIP codes compared to other areas.