Information and Data

Learn about particulate matter pollution, its negative effects on human health and the environment, and what the Air District is doing to reduce emissions in the Bay Area.

Particulate Matter

Particulate matter, or PM, is a complex pollutant composed of an assortment of tiny airborne particles that vary in size and mass (ultrafine, fine, or coarse), physical state (solid or liquid), chemical composition, toxicity, and atmospheric behavior. These particles originate from a variety of man-made and natural sources, including fossil fuel combustion, residential wood burning and cooking, wildfires, volcanoes, sea salt, and dust.

Residential wood burning is the largest source of particulate matter in the Bay Area during the winter. While the Air District has made significant progress reducing overall PM levels and related human exposure, it is still the most hazardous air pollutant in the Bay Area in terms of health impacts.

Negative Effects of Particulate Matter

Health Impacts

Because they are so small, PM particles can bypass the body’s natural defenses and penetrate deep into the lungs, bloodstream, brain, other vital organs, and individual cells. Health studies have shown that exposure to PM can have a wide range of negative health effects, including:

  • Asthma
  • Chronic bronchitis
  • Coughing and difficult or painful breathing
  • Impaired lung development in children
  • Hardening of the arteries
  • Heart attack
  • Stroke
  • Premature death

Environmental Damage

PM also causes environmental damage, including:

  • Poor visibility (haze) in urban and rural areas
  • Staining and damage to buildings, monuments, and landmarks
  • Acidification of lakes and streams
  • Damage to sensitive crops and forests
  • Depletion of soil nutrients
  • Damage to coastal and river ecosystems

PM Report

Although the Bay Area does not yet attain all national and state PM standards, the Air District has made major progress in reducing PM levels over the past 20 years.

The Air District chronicles this effort in a comprehensive report on PM in the Bay Area entitled Understanding Particulate Matter: Protecting Public Health in the San Francisco Bay Area. A summary of the report is also available. The report will guide the Air District’s ongoing efforts to protect public health by further reducing PM in the Bay Area.

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Last Updated: 3/24/2021