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Research Programs: Particulate Matter (PM) Health Effects
Research Areas: Mechanisms of Injury
PM Health Effects
While five years ago a description of PM health effects would typically have included a caveat that the underlying biological mechanisms were unknown, recent studies have promoted rapid growth in scientists' understanding of how PM can cause adverse effects. Because PM is a complex mixture of many different components, scientists recognize that exposure to PM may affect multiple organ systems through the activation of multiple, complex biochemical pathways.
The primary portal of entry for PM air pollution is the lung. Interactions of PM with the lining of the lung can cause a wide range of effects including lung injury, inflammation, changes in respiratory rate, an increased sensitivity to allergens, and depressed resistance to infection.
Soluble components of PM may diffuse from the lungs into the circulatory system and may be distributed systemically. Research has demonstrated that PM can cause inflammation of cardiac cells and can alter blood viscosity — two changes that are consistent with an increased risk of cardiac events especially for those with already diseased or stressed hearts.
Potential PM Effects on the Cardiovascular System.
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The growing number of reports associating PM with cardiac death, morbidity, and altered cardiac function has spurred new thinking about how these problems could occur. One route under investigation by EPA involves the nervous system: researchers believe that PM may affect cardiac function via neural reflexes activated by pulmonary inflammation. Through its intramural and extramural programs, EPA is testing this and other hypotheses about the ways exposure to PM causes health effects.
