Ambient Air Pollution

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Ambient Air Pollution
Thomas Robins, MD, MPH University of
Michigan Environmental Health Sciences
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Air Pollution
Definition The addition of harmful substances to
the atmosphere resulting in damage to the
environment, human health, and quality of life.
Just one of many forms of pollution, air
pollution occurs inside homes, schools, and
offices in cities across continents and
globally. Ambient (outdoor) air pollution is the
focus of this presentation.
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Severe Air Pollution Episodes
In 1948 in the steel-mill town of Donora,
Pennsylvania, intense local smog killed 19
people. In 1952 in London over 3,000 people died
in one of the notorious smog events known as
London Fogs in 1962 another 700 Londoners died
in a similar event.
Donora, PA at noon on Oct. 29, 1948 Deadly smog
envelops the town.
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Major Pollutant Sources
Most air pollution comes from one human activity
burning fossil fuels . . . (natural gas, coal,
oil) . . . to power industrial processes and
motor vehicles. The harmful pollutants that this
fossil fuel burning puts into the atmosphere
include carbon dioxide, carbon monoxide, nitrogen
oxides, sulfur dioxide, and tiny solid particles
(including lead) from additives called
particulates.
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Local and Regional Pollution

• Pollution sources tend to be concentrated in
  cities.
• In the weather phenomenon known as thermal
  inversion, a layer of cooler air is trapped near
  the ground by a layer of warmer air above.
  Normal air mixing is greatly diminished and
  pollutants remain trapped in the lower layer.
• Smog is intense local pollution usually trapped
  by a thermal inversion.

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This cloud of smog was typical of the skyline
hovering over Los Angeles in the 1940s and 1950s.
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Air pollution affects human lungs, like these of
this non-smoker in Los Angeles.
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Citizens demanding a smog control agency.
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Transport of Air Pollutants
Air pollutants reaching higher altitudes may be
transported thousands of kilometers. This may
result in air pollutants generated in one region
or country having profound effects in another
region or country. As an example, emissions from
Midwest power plants contribute substantially to
air pollution on the East Coast of the United
States. Significant pollution may occur in
previously pristine environments (example
Greenland) located far from the original
pollution sources.
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REGULATION IN THE UNITED STATES
The 1970 Clean Air Act established the public
health basis of the nation's effort to control
air pollution. About the same time, the executive
branch established the Environmental Protection
Agency (EPA).
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REGULATION IN THE UNITED STATES
EPA periodically reviews a large body of
scientific research dealing with the adverse
health effects of pollutants. The subsequently
produced documents are used in the development of
a National Ambient Air Quality Standard (NAAQS)
for each of the so-called criteria pollutants.
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REGULATION IN THE UNITED STATES
Based on new data from epidemiologic studies, EPA
promulgated revisions of the standards for
particulate matter and ozone. These changes
continue to be a subject of controversy.
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