Firefighters’ PFAS Side Effects May Include Genetic Changes Linked to Cancer, Other Diseases: Study

Research suggests that exposure to PFAS in firefighting foam and turnout gear can alter human microRNA, which may explain firefighters’ cancer risks.

The findings of a new study may play an important role in hundreds of firefighter cancer lawsuits now being pursued against the manufacturers of toxic PFAS chemicals, indicating that consistent exposure to the “forever chemicals” can affect humans on the genetic level, increasing their risk of developing various forms of cancer and other chronic diseases.

According to a report published in the journal Environmental Research on August 15, side effects of PFAS (per- and polyfluoroalkyl substances) can change human microRNA, or miRNA, in ways that result in cancers, autoimmune diseases and neurological conditions.

MicroRNA are short ribonucleic acid (RNA) molecules that play a crucial role in the cellular protein-making process. When miRNA is disrupted, a variety of cellular malfunctions can occur, including the development of cancer and other diseases.

PFAS include a group of over 9,000 man-made substances that have been widely used for decades to resist grease, oil and water. However, a great deal of attention has focused in recent years on the chemicals’ use in firefighters’ turnout gear and aqueous film-forming foam (AFFF), which is used to fight fuel-based fires, and has also caused widespread PFAS water contamination in communities nationwide.

There is now growing evidence that exposure to these toxic “forever chemicals” may cause various cancers, liver damage, thyroid disease, decreased fertility, high cholesterol, obesity, hormone suppression and other injuries, due to the slow rate at which the chemical compounds break down in the environment and human body.

As a result of these findings, several thousand PFAS exposure injury lawsuits are being pursued against more than a dozen chemical and safety equipment manufacturing companies, both by firefighters directly exposed to the chemicals through their work and individuals who have been drinking contaminated water.

In the new study, researchers from the University of Arizona, Mel and Enid Zuckerman College of Public Health, analyzed how PFAS side effects correlates with miRNA changes in firefighters, using cross-sectional data.

The team, led by Melissa A. Furlong, examined active-duty municipal and airport firefighters from several different departments, who provided blood samples and completed health surveys to help assess the effects of their PFAS exposure. A subset of samples was selected for genetic analysis, with participants chosen from across departments to ensure a balanced representation.

Furlong’s team found that higher levels of certain PFAS, especially perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonic acid (PFHxS), were linked to changes in several cellular miRNAs.

These changes were most commonly connected to diseases like cancer, autoimmune conditions and neurological disorders. One key miRNA, called miR-128, was found at lower levels when PFOS was high in the blood. This same miRNA has been found to be lower in certain cancers, like breast and pancreatic cancer, and is linked to poor treatment responses.

“We were able to study this research question in firefighters, an engaged community with high levels of interest in the health effects of PFAS due to their typically higher exposures relative to the general population. Thus, we were able to report on some PFAS serum concentrations that have been found to be higher on average in some studies of firefighters than the general population, such as PFHxS.”

-Melissa A. Furlong, Per- and polyfluoroalkyl substances (PFAS) and microRNA: An epigenome-wide association study in firefighters

Furlong’s team admitted that their sample may not represent the general population, since many firefighters are male, non-Hispanic white and tend to be extremely active.

PFAS and AFFF Lawsuits

More than 10,000 AFFF and PFAS water contamination lawsuits have been filed by firefighters, residents and municipalities over exposure to firefighting foam and contamination in drinking water. These cases, which raise similar allegations about the health risks of the toxic chemicals, have been consolidated in a federal multidistrict litigation (MDL) overseen by U.S. District Judge Richard M. Gergel in South Carolina.

As part of the coordinated proceedings, a small group of representative “bellwether” cases are being prepared for trial to help gauge how juries might respond to the evidence. The first trial is set for October 2025 and will involve claims from individuals who developed cancer after being exposed to PFAS-contaminated water near military bases and firefighter training sites.

Although the bellwether verdicts will not directly determine the outcome of other cases, they are expected to shape settlement discussions and help establish potential compensation values in the broader AFFF litigation.