Health Studies of Criteria Air Pollutants

Health studies are used to establish guidelines for air quality standards, including those recommended by OEHHA and established by the California Air Resources Board.  These include epidemiology studies, which examine real-life exposures in human populations, and how they relate to the incidence or prevalence of disease.  Together with controlled human exposure studies and toxicology studies, they form the scientific basis for our air quality standard recommendations. 

OEHHA has conducted a number of epidemiological studies on the health effects of particulate matter in California, and are working on a number of studies looking at other widespread air pollutants identified in the Clean Air Act.  These studies join other studies done in California, nationally, or internationally that examine the health impacts of air pollution exposure.

Our work at OEHHA has focused on a number of areas based on two legislative mandates:  1) the ascertainment of air pollution constituents most strongly linked to disease, and 2) the identification of subpopulations most vulnerable to the impacts of pollutants (e.g. young children, the elderly, low socioeconomic status individuals).

Criteria Pollutants Studied by OEHHA Staff


Fine particulate matter, or PM2.5, encompasses any airborne liquids or solids less than 2.5um in diameter.  Airborne particles of this size are troublesome because they can penetrate deep into the lungs, sometimes entering the bloodstream and causing systemic impacts.  These generally form through combustion processes.  Main sources of emission include gas- and diesel-fueled vehicles, power plants, fireplaces and other biomass burning sources, and combustion and other process emissions from industrial sources.  Health effects of PM2.5 are wide-ranging, with strong links to all-cause mortality, cardiovascular mortality and hospitalizations, and respiratory and asthma hospitalizations.  Impacts on health have been observed within hours or days of exposure, but chronic exposure impacts have also been seen for a number of endpoints.  Similarly, PM2.5 exposures over pregnancy periods have been associated with birth outcomes, like reduced birth weight and preterm birth.

Coarse Particles

Coarse particles, sized between 2.5 and 10um in diameter, are generated through mechanical, erosive processes, and can deposit in the larger airways in the lungs and cause inflammation.  Research points to a relationship between coarse particle exposures and respiratory hospitalizations and ER visits, especially among children, with additional evidence that coarse particles may be related to cardiovascular morbidity and mortality as well.

Nitrogen Dioxide and Ozone

Nitrogen dioxide is produced as a result of emissions from the burning of fuels in vehicles and stationary sources.  Ozone is formed through the combination of nitrogen oxides, including nitrogen dioxide, and volatile organic compounds, with help from sunlight and heat.  Exposure to either can impact respiratory health, causing respiratory inflammation and asthma exacerbations.

Health Studies of Criteria Air Pollutant News