The Science Behind Particulate Matter

image by net_efekt used under Creative Commons license

The two forms of air pollution that prompt Clean Air NY to send out an alert for an Air Quality Action Day are ground-level ozone pollution and particulate matter (PM). Here we explain how particulate matter is formed, the different ways it is classified and how it affects us. If you want to learn more about ground-level ozone pollution, check out the blog we wrote about the science behind ground-level ozone.

PM is created in numerous ways. It can be generated indirectly when emissions from burning fuels — especially emissions from motor vehicles, electric power plants and other industrial processes — react with sunlight and water vapor. It also is produced by grilling food on charcoal or gas, burning leaves and brush and burning wood in a fireplace or wood stove. PM pollution also is released into the atmosphere when gaseous pollutants, such as sulfur dioxide and nitrogen oxide, react to form fine particles.

Particulate matter is measured in microns and traditionally is classified into two size categories — PM2.5 and PM10. Particulates of the smaller size category (PM2.5) can be called fine particulates, fine particles or ambient fine particulate pollution. The larger particulate category (PM10) most commonly is called inhalable coarse particulates. Some of the most severe health effects, depending on exposure levels, are associated with ambient fine particulate pollution.

Fine particulate matter is one of the most serious air pollutants: the particles are so small that they can get right through the nasal passage, past the trachea and into the deepest parts of the lungs. The particles also can enter the bloodstream via the lungs and damage the body in ways similar to cigarette smoking. PM pollution can cause heart attacks, strokes and lung cancer and has been linked to aggravation of respiratory and cardiovascular symptoms.