PARTICULATE MATTER (PM-10 and PM-2.5)
Nature and Sources of the Pollutants:
Particulate matter is the term for solid or liquid particles found in the air. Some particles are large or dark enough to be seen as soot or smoke. Others are so small they can be detected only with an electron microscope. Because particles originate from a variety of mobile and stationary sources (diesel trucks, wood stoves, power plants, etc.), their chemical and physical compositions vary widely.
Health and Other Effects:
In 1987, EPA replaced the earlier Total Suspended Particulate (TSP) air quality standard with a PM-10 standard. The standard focuses on smaller particles that are likely responsible for adverse health effects because of their ability to reach the lower regions of the respiratory tract. The PM-10 standard includes particles with a diameter of 10 micrometers or less (0.0004 inches or one-seventh the width of a human hair). EPA's health-based national air quality standard for PM-10 is 50 micrograms per cubic meter (measured as an annual average) and 150 micrograms per cubic meter (measured as a daily average). In 1997, EPA promulgated a PM-2.5 standard which includes particles with a diameter of 2.5 microns or less. These smaller particles have the best chance of reaching the lower respiratory tract. The health-based national ambient air quality standard for PM-2.5 is 15 micrograms per cubic meter (measured as an annual average) and 65 micrograms per cubic meter (measured as a daily average).
Major concerns for human health from exposure to particulate matter are: effects on breathing and respiratory systems, damage to lung tissue, cancer, and premature death. The elderly, children, and people with chronic lung disease, influenza, or asthma, tend to be especially sensitive to the effects of particulate matter. Acidic particulate matter can also damage manmade materials and is a major cause of reduced visibility in many parts of the U.S.
SULFUR DIOXIDE (SO2)
Nature and Sources of the Pollutant:
Sulfur dioxide belongs to the family of sulfur oxide gases (SOx). These gases are formed when fuel containing sulfur (mainly coal and oil) is burned, and during metal smelting and other industrial processes.
Health and Other Effects:
The major health concerns associated with exposure to high concentrations of SO2 include effects on breathing, respiratory illness, alterations in pulmonary defenses, and aggravation of existing cardiovascular disease. Major subgroups of the population that are most sensitive to SO2 include asthmatics and individuals with cardiovascular disease or chronic lung disease (such as bronchitis or emphysema) as well as children and the elderly. EPA's health-based national air quality standard for SO2 is 0.03 ppm (measured on an annual average) and 0.14 ppm (measured over 24 hours). Emissions of SO2 also can damage the foliage of trees and agricultural crops. EPA has a secondary SO2 national ambient air quality standard of 0.50 ppm (measured over 3 hours) designed to prevent this type of environmental deterioration. Together, SO2 and NOX are the major precursors to acid rain, which is associated with the acidification of lakes and streams, accelerated corrosion of buildings and monuments, and reduced visibility.
Section I: Introduction
Section II: Present (YOU ARE CURRENTLY IN THIS SECTION)
Section III: Future
Complete Table of Contents
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