Piscataway, NJ — A recent study of volunteer firefighters shows that their bodies have higher levels of “forever chemicals” than those of people in the general public, and the amount of these potentially harmful substances likely rises with time and exposures.

Researchers from Rutgers University measured the levels of nine per- and polyfluoroalkyl substances, or PFAS, in the blood of 135 volunteer firefighters and compared them with the levels found in members of the general public. Findings show that higher amounts of the chemicals are present in the volunteer firefighters. One substance, perfluorododecanoic acid, was discovered in 80% of the firefighters but scarcely seen in the members of the public.

Although more than 4,000 PFAS exist, the researchers tracked the chemicals with greatest prevalence among the general public, per a Centers for Disease Control and Prevention evaluation. Found in everyday items such as carpeting, food packaging and electronics, PFAS have been “associated with multiple adverse human health outcomes” such as cardiovascular disease, kidney disease, immune suppression and cancer, the researchers say.

Additionally, results show that higher chemical levels are linked to a greater number of years spent firefighting. In a press release, lead study author Judith Graber, an associate professor at the Rutgers School of Public Health, suggests volunteer firefighters may accrue more on-the-job exposure to PFAS than career firefighters, as they always are on call. Potential channels to exposure include firefighters’ protective gear and fires that burn items containing PFAS, according to the study.

The release notes that volunteer firefighters account for more than 65% of the U.S. fire service.