State’s Cleaner Gasoline is Significantly Reducing Air Pollution, OEHHA Study Shows: Gasoline-related pollutants associated with health concerns steadily declining


Sam Delson
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SACRAMENTO – A new analysis released today by state environmental health researchers shows that California’s cleaner gasoline and vehicle controls have significantly reduced emissions of toxic pollutants and lowered cancer risks. Since 1996, estimated total emissions of volatile air pollutants from gasoline-related sources declined nearly 70% statewide, including significant declines for toxic chemicals such as benzene and toluene. 

“These reductions in toxic gasoline-related chemicals demonstrate the substantial progress California has made in reducing air pollution,” said Dr. Lauren Zeise, Director of the Office of Environmental Health Hazard Assessment (OEHHA). “When we reduce air pollution, important public health benefits follow.”

Using emissions data and ambient air-quality measurements from the California Air Resources Board (CARB) and other sources, OEHHA researchers estimated average gasoline-related exposures and associated health risks statewide and for five major air basins. OEHHA’s analysis covers the years 1996 to 2014. Significant findings include:

  • Estimated emissions of total volatile air pollutants from gasoline-related sources declined nearly 70% statewide between 1996 and 2012. Pollutants with the most substantial declines include harmful carcinogens like benzene and reproductive toxicants like toluene.
  • Emissions of gasoline-related pollutants declined even while gasoline sales remained steady and California’s population grew. By 2012, total emissions from on-road gasoline-powered vehicles had decreased so substantially that they were not much higher than the total emissions from off-road sources like lawn and garden equipment, recreational boats, and off-road vehicles. (See chart)
  • Cancer risks associated with average gasoline-related exposures to the most highly emitted carcinogens declined by more than 80% between 1996 and 2014.

Since 1996, CARB has worked to adjust the state’s gasoline formula in an effort to reduce gasoline-related pollutants. To maximize those benefits, the Board has also promoted cleaner vehicle technologies.

“California’s fuel standards are clearly working, but clean gasoline is only part of the solution,” said CARB Executive Officer Richard W. Corey. “Californians will see progressively cleaner air—and savings in fuel costs—as the number of electric and hydrogen powered vehicles increase.”

Researchers recommend a future study focused specifically on exposures in high traffic areas, especially in disadvantaged communities. Recently enacted legislation, AB 617 (C. Garcia, Chapter 136, Statutes of 2017), aims to reduce air pollution exposure in California’s most burdened communities. CARB will consult with OEHHA on this new effort.

The analysis—Gasoline-Related Air Pollutants in California: Trends in Exposure and Health Risk 1996 to 2014—can be found at

OEHHA is the primary state entity for the assessment of risks posed by chemical contaminants in the environment. Its mission is to protect and enhance public health and the environment by scientific evaluation of risks posed by hazardous substances.