The impact of exposure to air toxics on an individual’s health depends on the toxicity of the chemical, its concentration in the air, the length of exposure, and the age and general health of the persons exposed. Exposure to some air toxics may cause adverse effects and health symptoms to occur within a short period of time, whereas exposure to other air toxics may take years for symptoms to arise.
Exposure to some air toxics can cause cancer by disrupting the way cells are produced in the body and mutating their DNA. These cancerous cells can then crowd out healthy cells, causing a cascade of effects. The risk of developing cancer through air toxic exposure can be quantified in a Health Risk Assessment and is typically expressed as the probability of one or more persons developing cancer in a population (in a million) as a result of continuous annual air toxic exposure for a specified duration (e.g., 40 years for a worker or 70 years for a resident). For example, a 10-in-a-million cancer risk estimate indicates that of an exposed population of one million people, 10 additional cases of cancer may occur due to the exposure. Note that risk doesn’t mean that something bad will definitely happen. It’s just a possibility.
The health effects from long-term exposure to some air toxics can cause chronic health problems such as cardiovascular disease, reproductive and developmental health problems; and can adversely affect organ health (for example, lungs, heart, liver, kidneys, brain, and nervous system). The health effects from short-term acute exposure of certain air toxics can cause irritation of the eyes, nose, and lungs or the development of asthma. Unlike cancer, non-cancer health effects are expressed as a hazard index (HI). A HI is a ratio that compares the estimated concentrations at which someone is exposed to a specific pollutant to the concentration at which no adverse non-cancer health effects are anticipated to occur. If the HI is calculated to be less than one, then no adverse health effects are expected as a result of exposure. If the HI is greater than one, then adverse health effects are possible.
California Air Resources Board
Consolidated Table of OEHHA / CARB Approved Risk Assessment Health Values
U.S. Environmental Protection Agency
Health Effects Notebook for Hazardous Air Pollutants
Research on the Health Effects from Air Pollution
