Federally-Mandated Chemical Used in Car Interiors May Cause Cancer: Study

Production workers assemble car seats at the Bridgewater Interiors manufacturing plant in Warren, Mich., on March 8, 2004. Bill Pugliano/Getty Images

Interior vehicular air is found to be contaminated with harmful chemicals linked to cancer and IQ decline among children, according to a new U.S.-based study.

The peer-reviewed study, published in ACS Publications on May 7, investigated the use of flame retardants (FR) inside vehicles and their health implications on people. Flame retardants are chemicals applied to materials like vehicle seat foams to prevent burning or slow the spread of fire. The use of flame retardants inside vehicles is mandatory under the U.S. National Highway Traffic Safety Administration’s (NHTSA) guidelines. In the study, researchers analyzed 101 vehicles manufactured between 2015 and 2022.

“TCIPP was detectable in 99 percent of vehicles, and vehicle foam was identified as a source of this compound,” the study said. TCIPP is a flame retardant investigated by the U.S. National Toxicology Program for its potential carcinogenic effects.

TCIPP belongs to a class of flame retardants called Organophosphate esters (OPEs). Other OPE flame retardants, including TCEP and TDCIPP, were also found in vehicles that are identified as carcinogens under California’s Proposition 65 initiative.

In addition to causing cancer, these and other flame retardants have been associated with reproductive and neurological harm. TDCIPP specifically has been associated with “decreased fertility, altered thyroid hormone function, and cancer,” the study noted.

“Our research found that interior materials release harmful chemicals into the cabin air of our cars,” said lead author Rebecca Hoehn, a scientist at Duke University.

“Considering the average driver spends about an hour in the car every day, this is a significant public health issue. It’s particularly concerning for drivers with longer commutes as well as child passengers, who breathe more air pound for pound than adults.”

The researchers tested the cars in both summer and winter. Hotter weather was linked to higher concentrations of flame retardants since off-gassing from components like seat foam rises when temperatures climb. The interior of vehicles can reach up to 150 degrees Fahrenheit.

An analysis of seat foam samples from 51 cars was conducted, and it was discovered that vehicles with seat foams containing TCIPP had higher concentrations of this chemical in the indoor air. This confirmed that the foam was the source of this retardant present in cabin air.

Previous studies have shown that the average American child suffers a three—to five-point decline in IQ after being exposed to just one flame retardant widely used in furniture and cars.

“You may be able to reduce your exposure to flame retardants in your car by opening your windows and parking in the shade,” said co-author Lydia Jahl, a senior scientist at the Green Science Policy Institute.

“But what’s really needed is reducing the amount of flame retardants being added to cars in the first place. Commuting to work shouldn’t come with a cancer risk, and children shouldn’t breathe in chemicals that can harm their brains on their way to school.”

The study was funded by the National Institute of Environmental Health Sciences (NIEHS) of the National Institutes of Health (NIH), the Falk family, the Jonas Family Fund, the Cornell Douglas Foundation, and the Passport Foundation. The authors declared “no competing financial interest” in the study.

1970’s Regulation

Flame retardants are mandated in vehicles per NHTSA’s Federal Motor Vehicle Safety Standard (FMVSS) 302—an unchanged open-flammability standard from the 1970s. Researchers noted that other industries have updated their flame retardant usage guidelines.

For instance, in 2013, California’s flammability standard for upholstered furniture was updated, which allowed for the achievement of fire safety without the use of flame retardants. Multiple studies on this subject indicate that the 2013 update led to reduced retardant levels in home furnishings, researchers wrote.

The May 7 study “indicates that vehicles are likely important sources of human exposure to potentially harmful FRs. Coupled with the uncertain fire safety benefits of adding FRs to personal vehicle interiors, these results suggest that FMVSS 302 should be reevaluated,” the researchers said.

Patrick Morrison, who oversees the health and safety of 350,000 U.S. and Canadian firefighters at the International Association of Fire Fighters, has expressed worries about flame retardants. “Firefighters are concerned that flame retardants contribute to their very high cancer rates,” he said.

“Filling products with these harmful chemicals does little to prevent fires for most uses and instead makes the blazes smokier and more toxic for victims, and especially for first responders. I urge NHTSA to update their flammability standard to be met without flame retardant chemicals inside vehicles.”

Advocacy Consumer Reports (CR) also called on the NHTSA to update fire safety standards for vehicle interiors. CR has launched a petition to this effect, stating that it was time to update the standard that “needlessly leads to daily toxic exposure.”

“It’s long overdue for NHTSA to consider a better flammability standard for the inside of our cars,” said William Wallace, associate director of safety policy for Consumer Reports. “If there’s an alternative that can similarly protect consumers from fires while sparing them the long-term health harms of toxic chemical exposure, then there’s no excuse for delay.”

“While we’re urging NHTSA to update its flammability standards, we recognize that changing federal regulations can take a long time. In the near term, we want to work collaboratively on expedited ways to reduce every child’s exposure to flame-retardant chemicals in their car seats—including with child seat manufacturers, public health and safety experts, policymakers, and consumers nationwide.”