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Particulate Matter Air Pollution

Particulate matter -- particulates or PM for short -- refers to the many types and sizes of particles suspended in the air we breathe each day. Particulates include products of combustion, such as soot or ashes, wind blown dust, and minute droplets of liquids known as aerosols.

Particulate Matter Air Pollution


What is Particulate Matter?


Particulate matter -- particulates or PM for short -- refers to the many types and sizes of particles suspended in the air we breathe each day. Particulates include products of combustion, such as soot or ashes, wind blown dust, and minute droplets of liquids known as aerosols. PM can range in size from visible pieces of sand and dirt to microscopic particles so small that 500,000 of them could fit on the period at the end of this sentence.


Why should you be concerned about PM?


Particulate matter not only impairs visibility, it also poses a serious health threat to citizens. Our respiratory systems are equipped to filter out larger particles. However, the lungs are vulnerable to particles less than 10 microns in diameter (PM10), which can slip


past the respiratory system's natural defenses. Very tiny particles (PM2.5) can penetrate deeply into the lungs and do the most harm.


The particulates we breathe enter the lungs and pass through progressively smaller airways until they reach the alveoli, tiny air sacs where oxygen enters the blood stream. Particulates that get trapped in these most sensitive tissues interfere with oxygen uptake. Toxic and cancer-causing compounds can "hitchhike" into the lung on these particulates and be directly absorbed into the lungs.


What are the health effects of PM air pollution?


PM air pollution can cause coughing, wheezing, and overall decreased lung function in otherwise healthy children and adults. Particulate pollution can trigger asthma attacks and respiratory illness in the more sensitive subgroups of the population, such as the elderly and those with heart and lung disease. Children are more susceptible to particulates because they have smaller lungs and less mature immune systems. In the past 10 years, more than two dozen health studies have linked high concentrations of particulate air pollution with an increase in emergency room visits, hospital admissions, and even premature death.



What causes PM air pollution?


PM is introduced to the air through both natural and human causes. The primary sources of PM in California, excluding agricultural dust, are motor vehicles; diesel trucks and buses; residential wood stoves and fireplaces; industrial emissions; agricultural, slash and yard waste burning; and even exhaust from lawn mowers and boats. PM concentrations tend to be especially high in area with greater population density, nearby industries or agriculture, or where local topography or weather conditions contribute to air stagnation.


Here are a couple of quick facts about sources of particulate matter:


During wintertime air inversions, wood stoves and fireplaces release more hazardous particles.


Diesel trucks and buses are major producers of particulate matter and should be replaced with natural gas-, methanol-, or electric-powered vehicles.


As our population increases, our vehicle miles traveled increases at a much higher rate, which means more cars on the road and more air pollution from motor vehicle exhaust.


Industrial emissions are a major source of air pollution. The best control technologies should be encouraged to protect human health and the environment.

What is being done to control PM air pollution?


Our nation's Clean Air Act of 1970, in combination with important amendments adopted in 1977 and 1990, requires that the United States Environmental Protection Agency (EPA) identify and set standards for air pollutants. These National Ambient Air Quality Standards (NAAQS) must be strict enough to protect the health of even the most sensitive members of the population. PM10 is currently one of six "criteria" pollutants identified by the EPA. Here in California, the Department of Ecology and local air pollution control agencies cooperate with the EPA to implement laws designed to reduce PM levels.



A new PM standard


Though our air quality has improved since adoption of these laws, our visibility has worsened. There is also mounting evidence that the PM10 standards may not be strict enough to protect lung health. A 1996 analysis by the Natural Resources Defense Council (NRDC) estimates that PM levels far below current air pollution limits contribute to over 1,000 premature deaths each year in Washington state. Experts suggest that changing the PM standard to contain limits on fine particles (those 2.5 microns or less in diameter) would better protect lung health. A PM2.5 standard might mean tougher restrictions on diesel trucks and buses, wood stove and fireplace usage, outdoor burning, and industrial sources. It will also mean that citizens will breathe easier and spend less on health care to treat PM-induced illnesses.



SOURCES : Wood burning, motor vehicles, industry, outdoor burning, windblown dust, construction, mining, unpaved roads, diesel

HEALTH EFFECTS : Eye and nose irritation, airway irritation, cough, decreased lung function, increased respiratory illness, premature mortality

STANDARD : 3 PM10 150 g/m (24-hour average) PM 50 g/m3 10 (annual average)

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