Fine particles, that is particulate matter in the air measuring less than 2.5 microns in diameter, can cause serious health problems.  According to the American Lung Association, "tens of thousands of premature deaths each year are attributed to fine particle air pollution," microscopic substances such as acid aerosols, organic chemicals, metals, and carbon soot.

Long-term studies have repeatedly shown that people living in areas with high fine particle concentration may have their lives shortened by 1 to 2 years on average (as compared to those living in cleaner locations).
 
To limit your exposure to fine particle air pollution:

• Stay in an indoor environment where the air is filtered or air-conditioned.  You can build an inexpensive air purifier by taping a micropore HEPA air conditioner filter over a large box fan. 

• Do not exercise outdoors when particulate levels are high.  Never exercise near high-traffic areas.

• Drink plenty of fluid: See Tip 36.

• Take a cool shower or bath: Removes superficial particulate matter from your skin.

In the United States, the Air Quality Index (AQI) is the standard system that state and local air pollution control programs use to notify the public about levels of air pollution.  The U.S. Environmental Protection Agency (EPA) posts the daily AQI at http://www.epa.gov/airnow.