Exhaust fumes probably come to mind when considering vehicle emissions, but they aren’t the only source of pollutants released by a daily commute. In a recent ACS’study, researchers report that alcohols in windshield washer fluid account for a larger fraction of real-world vehicle emissions than previous estimates have suggested. Notably, the levels of these non-fuel-derived gases will likely remain unchanged, even as more drivers transition from gas-powered to electric vehicles.
Cars’ average carbon dioxide emissions have dropped by 25% since the early 2000s, according to the U.S. Environmental Protection Agency, but this gas only accounts for part of the total. Another important component of emissions is volatile organic compounds , a broad classification of carbon-based molecules that are easily vaporized and that can contribute to ozone formation.
To measure the VOCs actually emitted by vehicles, the researchers outfitted a van with several instruments, including a mass spectrometer, and parked it near a busy roadway. By comparing the van’s measurements with those from a university site with minimal traffic influence, they calculated the average amount of vapor given off per car for each kilometer traveled for several key VOCs.
The measured values matched inventory estimates for aromatic compounds that are commonly monitored and regulated, but those for alcohols – key ingredients in windshield washer fluid – far exceeded inventory numbers. In fact, the release of two alcohols, ethanol, and methanol, was nearly twice the amount of all VOCs released in exhaust.
Reference: “Unreported VOC Emissions from Road Transport Including from Electric Vehicles” by Samuel J. Cliff, Alastair C. Lewis, Marvin D. Shaw, James D. Lee, Michael Flynn, Stephen J. Andrews, James R. Hopkins, Ruth M. Purvis and Amber M. Yeoman, 16 May 2023,