Carcinogenic chemicals constantly emanate from the seats of many vehicles

While much research on car pollution focuses on external air pollutants entering the interior of vehicles and thereby affecting passengers, a new study shows that chemicals emanating directly from the interior could also be of concern. At least, this is the conclusion of a new study by UC Riverside, published this month in the journal Environment International.


The study reveals in particular that the longer the journey, the more you are exposed to a known carcinogenic chemical flame retardant, which has in particular been eliminated from certain furniture. Although there are other chemicals that are commonly used in the manufacture of automobiles, this flame retardant has just been added to the list of products to avoid or prohibited.

Some scientists have assumed that the chemical, called TDCIPP or "tris chlorinated", ceased to be used after it was placed on the Proposition 65 list in California in 2013. However, it is still widely used in the foam of car seats. The study shows that not only is your car a source of exposure to TDCIPP, but that less than a week of journeys leads to high exposure to it.



David Volz, associate professor of environmental toxicology at UCR (California), said the results were unexpected. "I was pretty skeptical at first because I didn't think we were going to find any significant concentration in this short period of time, let alone the importance of travel time," said Volz. "So we were surprised twice, which was really unusual."

Impact on fetal development, infertility and risk of cancer

For the past decade, Volz has studied how various chemicals affect the trajectory of early development. Using zebrafish and human cells as models, the Volz laboratory has been studying the toxicity of a new class of flame retardants called organophosphorus esters since 2011.

Little is known about the toxicity of these organophosphorus esters - of which TDCIPP is a part, but be aware that they replaced the old flame retardant chemicals, which persisted longer in the environment and took longer to metabolize.

Using the zebrafish as a model, Volz discovered that TDCIPP prevents an embryo from developing normally. Other studies have reported a strong association between TDCIPP and infertility in women undergoing fertility treatments.

Knowing that its use is still widespread in vehicles, Volz wondered whether the total exposure of a person was linked to the duration of the journey. Undergraduate students at UC Riverside have made excellent subjects for study, as the majority of them make long daily car trips.

The research team included collaborators from Duke University and was funded by the National Institutes of Health (NIH) as well as the USDA National Institute of Food and Agriculture.

Participants included approximately 90 students, each of whom had journey times varying from less than 15 minutes to more than two hours round trip. All received silicone bracelets to wear continuously for five days. The molecular structure of silicone makes it ideal for capturing airborne contaminants.

A study participant wearing the silicone bracelet used to capture TDCIPP fumes. Credits: David Volz / UCR

Since TDCIPP is not chemically linked to foam, it is expelled over time and ends up in the dust (which is inhaled), according to Aalekyha Reddam, a graduate student from the Volz laboratory.

Strong correlation with travel time

Several organophosphorus esters were tested, but the TDCIPP was the only one to show a strong positive association with travel time. "Your exposure to TDCIPP increases the more time you spend in your vehicle," said Reddam.

Although Volz and his team did not take urine samples to verify that the chemical had migrated into the participants' bodies, the latter was a certainty for them. "We assume this is the case because of the difficulty in avoiding ingestion and inhalation of dust," said Volz. In addition, other studies have looked at the accumulation of TDCIPP in the urine, but not by travel time.

In the future, the research team would like to repeat the study with a larger group of people, whose ages would be more varied. They would also like to explore ways to protect motorists from this exposure, as well as from other toxic compounds.

Until more specific reduction methods can be identified, the team encourages frequent dusting of vehicle interiors and follow guidelines from the United States Environmental Protection Agency to reduce exposure to contaminants.



Until safer alternatives are identified, more research is needed to fully understand the effects of TDCIPP on commuters.

"If we were able to achieve meaningful results in just five days, what does this mean for long-term chronic exposure, for people who travel long distances throughout the year, for decades?" Asks Volz.

Bibliography: Environment International Volume 136, Longer commutes are associated with increased human exposure to tris(1,3-dichloro-2-propyl) phosphate Aalekhya Reddam David C.Vol https://doi.org/10.1016/j.envint.2020.105499