If you've already read the section called Air
Pollution - the Basics, you know that in the United States currently
there are air quality standards set on six criteria pollutants, established
in the Clean Air Act Amendments of 1970.
Below are short descriptions of each of these pollutants.
If you click on the pollutant's name (underlined), it will take you
to a full page of information on that pollutant.
Ozone (03)
Ozone is a colorless gas. It is a major constituent of smog at the earth's
surface. It is formed in the lower atmosphere as a result of the chemical
reaction between oxygen, volatile organic compounds, and nitrogen oxides
in the presence of sunlight - especially during hot weather. Ozone can
irritate the respiratory tract, impair lung function, cause throat discomfort,
chest pain, cough, lung inflammation, and susceptibility to lung infection.
Ozone is especially bad for people with asthma. Ozone reduces crop yields
and harms forests. It the most injurious pollutant to plant life. Vehicles,
factories, landfills, farm/lawn equipment, and industrial solvents all
lend to ozone's creation. To find out more about this pollutant in your
state, explore at http://www.epa.gov/epahome/comm.htm.
Carbon Monoxide (CO)
Carbon Monoxide is a colorless, odorless gas that is emitted in engine
exhaust as the result of incomplete fossil fuel combustion. Its elevated
presence in the environment affects the cardiovascular and nervous system
by reducing the ability of blood to deliver oxygen to vital tissues.
It can negatively affect individuals with pre-existing heart conditions.
It decreases exercise performance, can cause dizziness, headaches, fatigue
and even death. The largest sources of CO are automobiles, buses, trucks,
small engines, and some industrial processes. To find out more about
this pollutant in your state, explore at http://www.epa.gov/epahome/comm.htm.
Nitrogen Dioxide (NO2)
Nitrogen Dioxide is a light brown gas at lower concentrations. In high
concentrations, it becomes a major component in brown
urban haze. NO2 causes smog and acid rain. It may increase respiratory
illness in children and can cause great difficulty for asthmatics. NO2
is a by-product of burning fossil fuels in cars, trucks, utility plants,
and industrial boilers. To find out more about this pollutant in your
state, explore at http://www.epa.gov/epahome/comm.htm.
Particulate Matter
(PM)
Particulate matter can consist of solid matter or liquid droplets from
smoke, dust, fly ash and condensing vapors. Its presence in the air
hinders breathing, increases respiratory illness, lung damage, and possibly
premature death - especially in children, the elderly and people with
heart or lung disease. It damages plants, soils, and clothing. It also
reduces visibility. Irritating smells are often associated with particulate
emissions. Particulates are released from gas and diesel exhaust, dust
from paved and unpaved roads, paint spraying, construction, agricultural
ground breaking, and from burning industrial fuels, trash and wood.
To find out more about this pollutant in your state, explore at http://www.epa.gov/epahome/comm.htm.
Sulfur Dioxide (SO2)
Sulfur Dioxide is colorless and odorless at low concentrations. At high
concentrations, it smells like a struck match. It is a major smog-causing
pollutant. At high concentration, the gas can constrict the bronchi
and increase mucous production, making breathing difficult. Prolonged
exposure to lower doses impairs the respiratory system's defenses, leading
to increased respiratory infections. Children, the elderly, and asthmatics
are more susceptible. Sulfur dioxide combines readily with water vapor,
forming aerosols of highly corrosive sulfurous acid - commonly known
as Acid Rain. This acid harms vegetation and metals. SO2 is emitted
from furnaces and boilers. It is also released from petroleum refineries,
smelters, paper mills, and chemical plants. To find out more about this
pollutant in your state, explore at http://www.epa.gov/epahome/comm.htm.
Lead (Pb)
Lead can hinder mental development and performance. It can adversely
affect kidney function and blood chemistry. Young children are the most
susceptible since they are more likely to ingest lead contaminated soils
and dusts. Young tissues are also more sensitive to lead. Lead emissions
come from coal combustion, smelters, car battery plants, and the combustion
of garbage that contains lead. It also comes from transportation sources
within countries that continue to use leaded gasoline. To find out more
about this pollutant in your state, explore at http://www.epa.gov/epahome/comm.htm.
