Particulate Matter

Particulate matter is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets.  Many manmade and natural sources emit particulate matter directly or emit other pollutants that react in the atmosphere to form particulate matter.  Sources of fine particles include all types of combustion activities (motor vehicles, power plants, wood burning, etc.) and certain industrial processes.  Other particles may be indirectly formed when gases from burning fuels react with sunlight and water vapor.

Particles less than 10 micrometers in diameter (PM10) pose a health concern because they can be inhaled into and accumulate in the respiratory system.  Particles less than 2.5 micrometers in diameter, PM2.5 are referred to as “fine” particles and are believed to pose the greatest health risks.  Because of their small size (approximately 1/30th the average width of a human hair), fine particles can lodge deeply into the lungs.  Particles with diameters between 2.5 and 10 micrometers are referred to as “coarse.”

Health studies have shown a significant association between exposure to fine particles and premature death.  Other important effects include aggravation of respiratory and cardiovascular disease (as indicated by increased hospital admissions, emergency room visits, absences from school or work, and restricted activity days), lung disease, decreased lung function, asthma attacks, and certain cardiovascular problems such as heart attacks and irregular heart beat.  Individuals particularly sensitive to fine particle exposure include older adults, people with heart and lung disease, and children.  Roughly one out of every three people in the United States is at a higher risk of experiencing PM2.5 related health effects: active children because they often spend a lot of time playing outdoors and their bodies are still developing and oftentimes the elderly population is at risk.