Particulate Matter: Widespread and Deadly Posted by Barbara Gottlieb on August 22, 2012
Particulate matter (PM) is the most widespread air pollutant in the country, and it can be deadly. Airborne particulates, especially the smallest, contribute to the four leading causes of death in the United States: heart disease, cancer, chronic lower respiratory diseases, and stroke. PM also contributes to preterm and low birth weight babies, irregular heartbeat and aggravated asthma, as well as other dangerous health effects. Because of PM’s prevalence and its high levels of toxicity, the Environmental Protection Agency (EPA) is currently updating its standards for limits on PM in the atmosphere.Rather than being a specific substance, PM is a mixture of airborne particles, both solid and liquid, classified by size. “Coarse” particulates are those with a diameter larger than 2.5 micrometers and smaller than or equal to10 micrometers; these particles are known as PM10. “Fine” particulates have a diameter of 2.5 microns or smaller. By comparison, the average human hair is about 70 micrometers in diameter – 30 times larger than the largest fine particle. Coal-fired power plants, industries, diesel vehicles and cars are responsible for most of the fine PM in the country
Whether fine or coarse, PM can be inhaled and can pass through the throat and nose and enter the lungs. The finest particles travel deeply into the lung where they trigger disease-producing processes including inflammation, oxidative stress, and resulting tissue damage. Particulates with the smallest diameter can also cross nasal membranes into the brain, where evidence suggests that they trigger inflammatory responses and the creation of reactive oxygen species that induce oxidative stress that leads to cell death.
What harm is being caused by PM exposure, and what populations are most vulnerable? Are the proposed EPA standards sufficient to protect public health? This month’s Environmental Health Policy Institute proposes to answer those questions. The answers have an important bearing on the health of Americans from coast to coast.