Air Toxics

What are air toxics?

Chemicals that can cause cancer and other adverse health effects such as harm to the human respiratory system are known as toxic substances. When these toxic substances are released in the air in the form of fine particles or gasses, they are called air toxics. Air toxics that exist as particles can include heavy metals, such as cadmium, mercury, chromium, and lead compounds, as well as organic compounds, such as diesel particulate matter (DPM) and polycyclic aromatic hydrocarbons (PAHs), which are emitted during the combustion of fossil fuels. Gaseous air toxic pollutants include benzene, toluene, and xylenes, found in gasoline; formaldehyde from the combustion of fossil fuels; and ethyl benzene used as a solvent by various industries. Whether air toxics have a harmful effect on an individual’s health depends upon a number of factors, including the concentration of toxics in the air, the length of exposure, and the age and general health of the persons exposed.

The State of California Air Resources Board (CARB) and the United States Environmental Protection Agency (EPA) have created lists of air toxics for various regulatory purposes.

CARB Listed Substances

The California Health and Safety Code section 44321 requires CARB to "compile and maintain a list of substances" that must be quantified and reported under the AB 2588 Air Toxics "Hot Spots" program. The list of substances can be referenced in Appendix A of theEmissions Inventory Criteria Guidelines Report (EICGR)which can be found onCARB’s "Hot Spots" Inventory Guidelines website↗.


AB 2588 Program

The Air Toxics "Hot Spots" Information and Assessment Act (AB 2588, 1987, Connelly) was enacted in 1987, and requires stationary sources to report the types and quantities of certain substances routinely released into the air. The goals of AB 2588 are to collect emission data, to identify facilities having localized impacts, to ascertain health risks, to notify nearby residents of significant risks, and to reduce those significant risks to acceptable levels. Facilities that are subject to this regulation are required to prepare and submit a toxic emissions inventory plan, toxic emissions inventory report, and if a screening risk assessment indicates that they may pose a significant risk to public health, they will need to prepare a refined health risk assessment.

2023-Annual-AB2588-Report.pdf(PDF, 298KB)


EPA Screening Tool

The US Environmental Protection Agency (EPA) developed AirToxScreen as a screening tool to identify which pollutants, emission sources and places merit study of possible risks to public health from air toxics. AirToxScreen gives a snapshot of outdoor air quality with respect to of air toxics. It suggests the long-term risks to human health if air toxics emissions are steady over time. AirToxScreen has replaced the National Air Toxics Assessment. This data can be accessed on EPA’s website: