Criteria Pollutant: Particulate Matter

Particulate matter can consist of solid matter or liquid droplets from smoke, dust, fly ash and condensing vapors. There are two types of Particulate Matter: PM10 and PM 2.5. These numbers relate to the monitoring criteria and size of the particles. The 10 and the 2.5 are 'microns', so PM10 means particulate matter size 10 microns or smaller. PM2.5 means particulate matter size 2.5 microns or smaller. PM 10 has been studied and monitored for a long time, but PM 2.5 is newer. Soon, a new PM2.5 standard will be adopted. It will better protect human health since the smaller the particle, the deeper it can go into your lungs.

Particulate matter can be either man-made or naturally occurring. Natural sources include: soil, bacteria and viruses, fungi, molds, yeasts, pollen, and salt particles from evaporating sea water. Human sources include: soot from smokestacks, dirt kicked up by vehicles on gravel or dirt roads, dust from bulldozing, mining, smoke from burning wood, and gasoline and diesel exhaust.

Health and Other Effects
Over 99 percent of inhaled particulates are exhaled or expelled from the body by coughing. The remaining percent of particle are so small that they can get lodged in the lung capillaries and alveoli causing shortness of breath and strain to the heart which must work harder to compensate for oxygen loss. Elderly, children, and those with lung or heart disease are more susceptible.

Some particulates may be poisonous if inhaled or absorbed, damaging organs like the kidneys and liver. Poison laden mucous can damage the gastrointestinal system if swallowed.

Irritating odors are generally associated with particulates, such as the smell of diesel exhaust or trash burning.

Particulate matter can also:

• Corrode metals and building facades
• Cover leaf surfaces of crops, trees, and shrubs, injuring or inhibiting growth
• Reduce visibility

Go on to the next criteria pollutant--sulfur dioxide>