by Bill Schlesinger
Ah, the smell of a new car. To get inside a new car for a drive with friends is part of the American experience. The “new car smell” is a sign that you have arrived.
When we close the door to begin the journey, we are encapsulated in a mix of volatile organic compounds (VOCs), carbon dioxide, various body odors, a few local air pollutants that are entrained from outside, and a smidgeon of the refrigerants that can leak from the car’s air conditioning system. There are many sources for inadvertent exposure to all these gases in cars, many of them normally considered air pollutants. Exposure to fine particles, known as PM2.5, inside cars is less problematic. Many new cars have filtration systems that remove particulate matter.
Most of the VOC are emitted from plastics, including the carpet, that are ubiquitous in new cars. Chain hydrocarbons, known as aliphatic compounds dominant the mix, although a few aromatics, such as benzene and toluene, are often measured. More than 150 VOCs have been identified by gas chromatography. Hot weather causes greater volatilization of these gases (aka outgassing), which declines with the age of the car. Park a car in the coolness of shade or in a garage and some of these compounds will condense on the inside of the glass, which typically cools more rapidly than other materials.
Investigations of the health effects of carbon dioxide and body odors as components of new car smell have found no effects on the cognitive ability of the driver, although the experimental levels and specificity of the body odors are often vague. (My own experiences are at variance with this observation).
In new cars, most VOCs are typically found at levels below known human health effects. Aromatic VOCs and other known organic emissions (e.g., formaldehyde) have known carcinogenic effects at high concentrations, which (collectively) can sometimes exceed health guidelines of 300 micrograms per cubic meter in new car smell. Condensation means that all these gases are an annoyance to those who wish to keep the inside of the windshield clean.
A ride in a new car may seem like we have entered a test capsule for air pollutant effects. If you are worried, walking is always an option.
References
Besis, A., T. Katsaros, and C. Samara. 2023. Concentrations of volatile organic compounds in vehicular cabin air—implications to commuter exposure. Environmental Pollution 330: doi: 10.1016/j.envpol. 2023.123753
Brodzik, K., J. Faber, D. Lomankiewiez, and A. Goida-Kopek. 2014. In-vehicle VOCs composition of unconditioned, newly produced cars. Journal of Environmental Sciences 26: 1052-1061
Wang, C., Y. Lin, Y. Ptukhin and S. Liu. 2024. Air quality in the car: How CO2 and body odor affect drivers’ cognition and driving performance? Science of the Total Environment 911: doi. 10.1016/j.scitotenv.2023.168785
Yoshida, T. and I. Matsunaga. 2006. A case study on the identification of organic compounds and time courses of their concentrations in the cabin of a new car for private use. Environment International 32: 58-79.
