Chapter 20
Particulate Matter
Particulate matter is the sum of all solid and liquid particles suspended in air, many of which are hazardous. This complex mixture contains for instance dust, pollen, soot, smoke, and liquid droplets.
These particles come in many different size ranges such as coarse, fine and ultrafine. They also vary in composition and origin.
Particles are either directly emitted into the air by sources such as combustion processes and windblown dust, or formed in the atmosphere by transformation of emitted gases such as SO2.
Extensive research indicates that exposure to outdoor PM 10 and PM 2.5 levels exceeding current air quality standards is associated with increased risk of hospitalization for lung and heart-related respiratory illness, including emergency room visits for asthma. PM exposure is also associated with increased risk of premature deaths, especially in the elderly and people with pre-existing cardiopulmonary disease. In children, studies have shown associations between PM exposure and reduced lung function and increased respiratory symptoms and illnesses. Besides reducing visibility, the acidic portion of PM (nitrates, sulfates) can harm crops, forests, aquatic and other ecosystems.
In Europe, sulphate and organic matter are the main components of particulate air pollution in terms of the mass of the particles. Mineral dust, nitrate, and soot can also be major components under certain conditions.
In Europe, long-term exposure to current ambient particulate matter concentrations may affect the lungs of both children and adults and may reduce life expectancy by a few months, mainly in subjects with pre-existing heart and lung diseases.
Ambient particulate matter is responsible for harmful effects on health, even in the absence of other air pollutants. Both fine and coarse particles have been shown to affect health, in particular the respiratory system.
Fine particles are more dangerous than coarse particles. Apart from the size of the particles, other specific physical, chemical, and biological characteristics that can influence harmful health effects include the presence of metals, PAHs, other organic components, or certain toxins.
When particulate matter is combined with other air pollutants, the individual effects of each pollutant are cumulated. In certain cases, especially for combinations of particulate matter with ozone or allergens, effects were shown to be even greater than the sum of the individual effects. When particulate matter interacts with gases, this interaction changes its composition and, therefore, its effects.
Certain groups of people are more susceptible to suffer health effects due to ambient particulate matter. These include elderly people, children, people with a pre-existing heart and lung disease, asthmatics, and socially disadvantaged and poorly educated populations.
Some persons are vulnerable even at low concentrations of ambient particular matter, no threshold has been identified below which nobody’s health is affected
In June 2002, the ARB adopted new ambient air quality standards for PM 10 and PM 2.5, resulting from an extensive review of the health-based scientific literature.
California Ambient Air Quality Standards for PM
PM may be divided into many size fractions, measured in microns (a micron is one-millionth of a meter). ARB regulates two size classes of particles - particles up to 10 microns (PM10) and particles up to 2.5 microns in size (PM2.5). PM2.5 particles are a subset of PM10.
A picture of a human hair compared to the relative sizes of PM 10 and PM 2.5 particles PM10 and PM2.5 are each measured and expressed as the amount (in micrograms) of particles contained in a cubic meter of air, expressed as micrograms per cubic meter (µg/m3).
REFERENCE
California Environmental Protection Agency Air Resources BoardAmbient Air Quality Standards (AAQS) for Particulate Matter, November 24, 2009
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