Wednesday, April 18, 2012


The EPA uses six "criteria pollutants" as indicators of air quality and has
set standards for each of these under the NAAQS. When an area does not
meet these standards, it is designated as a nonattainment area and must
develop and implement a plan for attainment. The six criteria pollutants
are ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, particulate
matter, and lead.


Ozone, an odorless, colorless gas, made up of three atoms of oxygen, is
the major component in smog. There is "good" ozone and "bad" ozone
depending on its location. The "good" ozone is in the upper atmosphere
and provides a shield from harmful ultraviolet radiation. 
(This ozone shield is being seriously threatened 
by various global warming processes.) 
The "bad" ozone is at ground level where it poses a significant threat to human
health by damaging lung tissue, reducing lung function, and sensitizing
the lung to other irritants, causing a range of symptoms including coughing,
sneezing, pulmonary congestion, and chest pain.
Ozone is created by a complex set of Volitile Organic compounds (VOCs)
and oxides of nitrogen in the presence of sunlight. These chemical reactions
are affected by sunlight and heat, resulting in greater production of
ozone in warmer seasons. Volatile organic compounds are emitted by a
wide range of polluting sources, including dry cleaners, cars, chemical
manufacturers, paint shops, and many others.


Carbon monoxide is a colorless, odorless, and poisonous gas produced
during the burning of fossil fuels (coal and oil). The vast majority of carbon
monoxide is produced by automobiles. However, incinerators, woodburning
stoves, and other industrial sources also contribute. Carbon
monoxide binds with human hemoglobin in a way that precludes the binding
of oxygen. This results in anoxia. The most sensitive populations to
carbon monoxide poisoning are people with cardiovascular diseases and
chronic obstructive pulmonary disease (COPD) and smokers. There is some
evidence that carbon monoxide exposure may actually accelerate atherosclerosis.
Flu-like symptoms such as headache and fatigue are associated
with low-level exposures. Neurologic manifestations include changes in
auditory and visual perception, psychomotor function, and dexterity.


Sulfur dioxide is a gas that is formed during the combustion of fossil fuels,
during an array of industrial processes, and during the production of energy
from coal, oil, and biomass. It is a major contributor to acid rain. Sulfur
dioxide is also associated with a constellation of health effects, including
respiratory illness, alterations in pulmonary function, aggravation of existing
cardiovascular diseases, and exacerbations in asthma.


In agricultural areas, where aerial pesticide applications are made, pesticides
may drift, volatilize, and disperse downwind. Ground water, surface
water, soil, and food may become contaminated. The indoor air is also
likely to become contaminated with the pesticide drift. General population
exposure has been well documented, with residues of pesticides and
metabolites found in blood, urine, breast milk, fat tissue, and other tissues.
Health practitioners should factor such potential exposures into their patient
and community assessments.
Incinerators pose a threat to air quality, releasing a range of pollutants
depending on the waste stream composition. They will typically include
the metals (mercury, lead, arsenic, cadmium, chromium, manganese, nickel,
antimony, selenium, zinc, and vanadium); PCBs, furans, polycyclic aromatic
hydrocarbons, and acid gases and oxides of nitrogen, sulfur, and carbon.
Proximity to incinerators is associated with increased local soil lead levels.
A particular concern arising from our poor air quality is global warming,
a change in our global climate resulting from the changes in industrial
and agricultural processes that, in turn, have changed the gases in our
atmosphere. So-called greenhouse gases are those gases (both naturally
occurring and man-made) that are capable of adsorbing heat in the atmosphere.
The naturally occurring greenhouse gases are water vapor, carbon
dioxide, methane, nitrous oxide, and ozone. Man-made contributions to
these gases include carbon dioxide, methane, nitrous oxide, and several
very powerful greenhouse gases: hydrofluorocarbons (MFCs), perfluorocarbons
(PFCs), and sulfur hexafluoride (SF6), which are generated by
industrial processes.
The resulting climate changes occurring from the extraordinary addition
of man-made, greenhouse gases are rising temperatures (.5-1 degree
since the nineteenth century) and a rise in the sea level (4-8 inches in the
last century). Alterations in forests, crop yield, and water supplies are predicted.
There is nothing that will reverse this trajectory in the near future,
and only a global strategy will succeed in addressing the long-term trends.
Because of the inevitability of the warming processes and the potential
public health ramifications of global warming, health professionals should
be educating themselves and weighing in on this very important issue.

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