Background

FAQs on Particulate Matter (Soot)

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What is Particulate Matter (PM)?

• Particulate matter, or particle pollution, also commonly known as "soot," is particles of dust, smoke, and haze that are released or kicked up into the air by vehicle travel on dirt roads, industrial crushing and grinding, and windblown dust. Burning fossil fuels, garbage, and agricultural products also releases particle pollution into the air.
• Particulate matter can also be formed when chemicals (many of the same that form smog) react and condense in the atmosphere.
• Particulate matter is regulated based on the size of the particles(1). Current standards use ten microns as a standard, which is about one-seventh of the diameter of a human hair(2).
• Levels of particulate matter vary depending on rainfall and wind conditions.
• Small particles are only regulated on a 24-hour and annual average, while large particles are regulated on an hourly basis.
• Particulate matter reduces visibility and clouds the views in the Valley, the Sierra Nevada, and even in our national parks.

Particulate matter in the San Joaquin Valley

• The San Joaquin Valley is classified as a "serious" non-attainment area for particulate matter, the most serious designation available under the Clean Air Act.
• Particulate matter emissions increased between 1985 to 1995 in the San Joaquin Valley(3).
• The region faces a deadline for attaining the particulate matter standards by December 31, 2001. However, the local air district does not have a plan that will ensure healthy air by even 2006.

Sources:

"State of the Air: 2001," published by the American Lung Association

Footnotes:

1. The EPA has also proposed new standards for particles smaller than 2.5 micrograms because recent studies have documented that the smaller particles are even more deadly than larger particles (See fact sheet on 'Effects of Pollution').

2. Source: Bay Area Air Quality Management District 2001

3. Great Valley Center Report