Environmental Engineering Reference
In-Depth Information
Beach, was twice as great as the risk for people in the surrounding area.
Diesel particulates accounted for 70 percent of the risk. 6
The effect PM has on our bodies depends to a large degree on its size
and chemical composition. Those larger than 10 microns are kept out
of our bodies by blockages such as nose hairs and the coughing mecha-
nism in our throats. Particles smaller than 10 micrometers are trapped
in our lungs, and those smaller than one-tenth of a micrometer are so
minute they can pass through the lungs into the bloodstream, just like
the oxygen molecules we need to survive. Soot contains up to forty
cancer-causing chemicals.
Because the particles in PM are formed in so many ways, they can
be formed of many substances. The larger ones are rich in soil dust,
and all animals, including humans, have always lived with them. The
smaller ones may be solids or liquids; some are solids suspended in
liquids. PM smaller than 2.5 microns is so tiny that it stays suspended
in the air for days or months before settling to the ground. This means
that much of it comes from sources outside any particular region.
Several states on the East Coast receive cryptodust from the Sahara
Desert. The western United States receives cryptodust from the Gobi
Desert in China. The relative percentages of homemade cryptodust and
imported cryptodust are not known, but one would suspect that most
is produced locally, meaning that we cannot blame others for the
particulate pollution we inhale.
Short-term exposure to particle pollution can kill. Deaths can occur
the same day that particle levels are high or one to two months later. In
Britain, research has shown that people are twice as likely to die from
respiratory disease when they are heavily exposed to soot emitted from
vehicle exhausts. Particle pollution does not just cause people to die a
few days earlier than they would otherwise. It also diminishes lung func-
tion, and it causes greater use of asthma medications and increased rates
of school absenteeism, emergency room visits, and hospital admissions.
Other adverse effects can be coughing, wheezing, cardiac arrhythmias,
and heart attacks. Particle pollution from power plants in the United
States leads to over 30,000 deaths each year, a number that can be
compared to the 16,272 murders committed in 2008. 7
Between 1980 and 2008, the concentration of particles nationwide
decreased by 25 percent; from 2000 to 2008, the decrease was 8.3
percent. 8 These decreases have added several months to the life expec-
tancy of the average person. Clearly there has been and continues to be
signifi cant progress in reducing the amount of particulates in the air,
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