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Outdoor Air:
Particulate Matter
Particles suspended in the air
come in different sizes and are composed of different materials. In general, the
smallest of the particles are the most dangerous because they stay suspended
into the air, enter interior spaces easily,
 and
enter into the smallest spaces of our lungs where the oxygenation of blood takes
place. Recent health data suggests that particles 2.5 microns or smaller in
diameter (PM2.5) are the most hazardous. These are largely formed by combustion
or by conversion of certain gases into particles. For example, nitrates and
sulfates in our air are the particulate form of nitrogen oxide and sulfur
dioxide combustion gases. Major sources of PM2.5 include industry,
gas, diesel, meat cooking, as well as other minor but occasionally significant
sources from fires, road dust, and fireworks.
Why is fine particulate matter bad?
The American Lung Association has prepared an annotated bibliography,
2005 Research Highlights: Health Effects of Particulate Matter and Ozone Air Pollution.
Increased levels of fine particulate matter have been linked to
- increased hospital admissions;
- worsening of asthma symptoms;
- increased risk of low birth rate, preterm birth and infant mortality;
- acute respiratory symptoms (e.g., chest pain, coughing);
- chronic bronchitis;
-
cancer;
- decreased lung function; and
- higher death rate resulting from respiratory and cardiovascular disease.
A recent study commissioned by the City of Houston (Sonoma Study, 1999)
estimated that approximately 435 area residents die prematurely each year
due to our current particulate levels, even though our levels rarely exceed the
federal health standards.
Why does Houston have high levels of fine particulate matter in the air?
Sources of particulate matter in Houston include
industrial emissions, diesel emissions,
tire dust, electric utility plants, gasoline-burning vehicles of all kinds, and aerosol
pesticides,
all of which are abundant in Houston.
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