The California Environmental Protection Agency has been charged with reviewing the ambient air quality standards for particulate matter (PM) and sulfates to ensure they are protective of children. Toxicology studies provide a critical component of the overall standards review process. Toxicology studies can provide information essential for identifying which components or characteristics of PM air pollution may be more harmful or more closely associated with the adverse health effects seen in epidemiological studies of human populations exposed to ambient levels of PM. Toxicology studies can also provide valuable information on the biological mechanisms involved in causing adverse health effects in animals and humans exposed to PM. This report provides a critical review of the peer reviewed toxicology literature as it pertains to PM and PM component exposure. It is not an exhaustive summary of all toxicology studies conducted using PM or PM components. This report reflects a focused effort to examine the results of toxicology studies that the authors believe will be most helpful in addressing the ongoing air quality standards review in California. As of the completion of this report, the majority of the toxicology studies reviewed found associations between exposure to PM of many different sizes and compositions resulted in direct effects on the respiratory tract. These effects include general as well as site specific cell and tissue injury, increased production of inflammatory biochemical species leading to increased pulmonary inflammation, increases in airway tissue reactivity leading to exacerbation of existing respiratory conditions, typically in compromised animal models. Changes have also been noted in immune cell populations or function that may lead to increased host susceptibility to respiratory infections. To date, few studies have provided much concrete information regarding the effects of PM exposure on other organs or systems in the body or on systemic effects that may result in biological events which will lead to mortality or morbidity in animals or humans. A very few carefully controlled studies do suggest that PM exposure to concentrated ambient particles, combustion particles or coarse particles containing endotoxin may result in systemic effects which could help explain the cardiorespiratory effects seen in epidemiological studies of human populations exposed to PM.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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