Acetaldehyde at John Swett

This page last reviewed August 24, 2010


One of the important contributors to health risk from air pollution, acetaldehyde is a colorless liquid and at dilute concentrations has a very noticeable fruity odor. Acetaldehyde will quickly evaporate at ambient temperature and pressure. Acetaldehyde can cause eye, skin and respiratory tract irritation. California has determined under Assembly Bill 1807 and Proposition 65 that acetaldehyde is a cancer-causing compound. The ARB has taken regulatory actions to reduce acetaldehyde emissions.

The predominant sources of acetaldehyde emissions in the atmosphere are gasoline motor vehicle exhaust. Mobile sources contribute 85% and industry-related stationary sources contribute 15% of the statewide emissions. Approximately 60% of mobile source acetaldehyde emissions are from on-road motor vehicles, with the remainder from non-road mobile sources. Acetaldehyde emissions also occur naturally during the respiration of higher plants and can be found in ripening fruit such as apples.

The ARB emission standards for new vehicles have resulted in steady decline in vehicular emissions of acetaldehyde. The decline is expected to continue. (Over the years 1996 through 2000, the ambient acetaldehyde levels remained relatively constant.)

Ambient Monitoring Results

Ambient levels of acetaldehyde are routinely monitored at approximately twenty sites in the California air toxics monitoring network. The statewide average concentration of acetaldehyde during 1998-2000 was 1.2 ppb (parts per billion), based on values ranging from 0.05 ppb to 8.1 ppb. The current routine monitor closest to Crockett is in Fremont. Relative to the statewide average, the Fremont region was 38% lower, with an average concentration of 0.74 ppb for the same time period.

The ambient monitoring results at John Swett are provided here:

  • A graph comparing the monthly summaries of acetaldehyde at the community with historical statewide and regional levels
  • A table of summary statistics
  • Raw data in Excel format

Cancer Risk

Cancer risk is the number of excess cancer cases among a million people if the people are exposed to levels of a toxic air pollutant over 70 years. Acetaldehyde represents approximately 2% of the potential cancer risk of the nine measured compounds, excluding diesel particulate matter. Acetaldehyde represents less than 1% of the potential risk of the nine measured compounds and the estimated diesel particulate matter.