Particulate Matter is a mixture of extremely small particles and liquid
droplets found in the air. Sources of particulate pollution include woodstoves,
fires, wind-blown dust, automobiles, and industry.
PM10 refers to particulate matter 10 microns in
diameter and smaller, whereas PM2.5 refers to
particulate matter 2.5 microns in diameter and smaller. (The average strand of
human hair is 70 microns in diameter.)
Health studies over the past decade show that there are harmful effects from
breathing PM particles. PM can be inhaled deep into the lungs and can lodge
there for weeks and months, aggravating asthma, heart disease, and other
respiratory and heart conditions.
PM2.5 National Ambient Air Quality Standard
On December 18, 2006, EPA reduced the 24-hour fine particulate matter
(PM2.5) National Ambient Air Quality Standard. By issuing
this rule, EPA intends to further protect vulnerable individuals from air
pollution in communities across the U.S. DEQ plans to work with Oregon
communities interested in developing strategies to reduce particulate pollution.