Massachusetts Vehicle Check - Mass08 Management Module ...

Non-Commercial
Where Does Air Pollution Come From?
Air pollution is defined as “contamination of the atmosphere by gaseous, liquids or
solid wastes or byproducts that can endanger human health and the health and welfare of
plants and animals, or can attack materials, reduce visibility, or produce undesirable odors.”
Air pollutants can be emitted from either natural or human-made sources. The EPA
established National Emissions Standards for Hazardous Pollutants (NESHAPS) for the
sources of seven of the eight substances listed as hazardous air pollutants. Among them are
asbestos, beryllium, mercury, radionuclides, inorganic arsenic and benzene. Radon, the
eighth, is a byproduct of the radioactive decay of uranium minerals. If radon exists in high
enough concentrations, it could increase the risk of lung cancer in humans.
Human-made air pollutants emitted from various sources account for most of the
world’s air pollution problems. Industrialized countries generate billions of tons of air
pollutants annually. Some pollutants come from identifiable sources such as sulfur dioxide
(SO2), which is mainly generated from coal and oil burning power plants. Other pollutants
are formed through reactions of different gases and pollutants in the atmosphere, such as
smog and ground level ozone (O3), formed from a reaction of hydrocarbons (HC) and
nitrogen oxides (NOx) in the presence of sunlight.
Human-made air pollution sources are categorized into three types: stationary sources
such as power plants, factories and refineries; mobile sources such as automobiles, trucks,
trains, ships, etc. and area sources such as homes in communities. The fact that a pollutant
was generated from a stationary source does not mean the pollutant is localized and
stationary. The geography and topography of the area, plus atmospheric conditions – such as
wind and thermal inversions – will have an affect on where the pollutant might stagnate or
have its worst effect.
Massachusetts Vehicle Check
Ch. 1 - 2