Heat promotes the circulation in cars of a toxic gas from products supposed to slow fires, according to an American study published Tuesday in the journal Environmental Science & Technology.
Several parts of the interior of many cars contain flame retardants (flame retardants), such as organophosphate compounds. These products are also used in foams for furniture, electronic devices, or clothing.
The study carried out by researchers from Duke, Berkeley and Toronto universities shows that one of these products, triphosphate (TCIPP), is present in the air of 99% of the vehicles tested.
The experiment consisted of hanging a sample of silicone on the interior rear-view mirror of recent vehicles for a week, then analyzing the substances found on this sample.
Under normal conditions, the concentration of TCIPP was found to be similar to that found inside a house.
But when the temperature rises, both outside and in the passenger compartment, the concentrations of this substance rise sharply, multiplied by a factor of two to five. The presence of TCIPP in the seat foams reinforces this effect.
The problem is that TCIPP is potentially carcinogenic, according to a 2023 report from the U.S. Department of Health. Tested on rats and mice, it caused liver and uterine tumors.
TCIPP already replaces in passenger compartments another flame retardant product, TDCIPP, which was placed in 2011 on a list of carcinogenic products in California.
The authors of the study are concerned about the long-term effects of these products on motorists who stay in their vehicle for a long time for work, or on children.
They recommend controlling the temperature in the vehicle even on hot days, parking it in the shade if possible and opening windows to circulate air when starting.