Alabama and New Hampshire are tied for second in the country for the highest number of water sites contaminated by toxic chemicals known as PFCs, a new joint study from Northeastern University and the Environmental Working Group found. Both states had five contaminated sites, trailing only New Jersy with six. The state of New York rounded out the top four with four sites contaminated by PFCs.

“At many of the sites, contamination levels are extremely high,” the EWG said in a statement.

According to the National Institute of Health, PFC — abbreviation for perfluorochemicals — is a large group of manufactured compounds that are widely used to make everyday products more resistant to stains, grease, and water. Although some studies have stated that exposure can cause serious health issues, the NIH notes that several other studies have failed to provide conclusive links.

In Alabama, the study found contaminated sites in the northern part of the state in Morgan, Limestone, Etowah, and Dekalb Counties. Overall, the U.S. Environmental Protection Agency has found 15 public water systems in Alabama where PFCs have been detected.

To be on the safe side, David Andrews, a senior scientist with the Environmental Working Group, told WBHM that residents should have their water tested through their local utility provider.