- ATLANTA, Georgia (ENS) - Healthy adults are facing previously
unsuspected threats from air pollution. Tiny particles can zoom through
human lungs up to two times faster and penetrate more deeply than assumed
before, a University of Delaware scientist says. Children and the elderly
are at even greater risk.
- "Smog kills perhaps partly because pollutant particles
are so deeply deposited in our airways," says Anthony Wexler, a professor
of mechanical engineering at the University of Delaware.
- A Georgia Institute of Technology researcher measures
wind speed and direction at an Atlanta air quality testing facility (Photo
courtesy Georgia Institute of Technology) Scientists from around the world
have gathered in Atlanta this month to determine the best ways to measure
this fine particulate matter that is polluting the nation's air, particularly
in large urban areas. Atlanta,s air pollution problems have halted several
new highway construction projects that officials feared would increase
already dangerous city smog levels.
- Particulate matter, which is federally regulated, is
created by the burning of coal and oil. Numerous studies link it to serious
- Fine particulate matter, called PM 2.5 because it is
less than 2.5 microns in diameter - about 30 times smaller than the diameter
of a human hair, includes soot, dust, aerosols, metals and sulfates. These
particles emitted by vehicles, factories and industrial facilities contribute
to the smog so common in American cities.
- In the first of two studies initiated by the U.S. Environmental
Protection Agency (EPA), about 60 scientists have converged at an Atlanta
air quality research facility owned by Georgia Power. Scientists began
measuring PM 2.5 around the clock at 7:00 am August 3 and will continue
through 7:00 am September 1.
- "We are trying to determine how to measure the concentration
and composition of fine particulate matter in the atmosphere and the types
of instruments best suited to do that," said Dr. William Chameides,
a professor in the Georgia Institute of Technology's School of Earth and
Atmospheric Sciences and head of the study. "We need to do this to
understand the health effects and the sources, and to monitor compliance
with EPA standards."
- Smog causes problems in cities across the U.S., sometimes
in hard to predict locales. In the nation,s smog capital, Los Angeles residents
are now enjoying one of their least polluted summers ever. The Los Angeles
region has made it to mid-August without suffering a single full scale
smog alert - the first time that has happened since officials began tracking
- Texas is promoting car pools to help combat air pollution
(Photo courtesy North Central Texas Council of Governments) But in east
Texas and along the Eastern Seaboard, residents are coping with some of
the worst smog seasons on record. Texas City, near Galveston, Texas, has
recorded the highest one-hour concentration of urban ozone so far this
summer. On August 6, the town had 0.206 parts per million of particulate
matter, the equivalent of a Stage 1 smog alert. Today, the Dallas/Fort
Worth area declared an Ozone Alert Action Day, warning of dangerous levels
of air pollutants.
- Air pollution may be even more dangerous than experts
have suspected. A study by Wexler and Ramesh Sarangapani, expected to appear
in the next "Journal of Aerosol Science," reveals how PM 2.5
particles penetrate buildings and people's airways more quickly and deeply
than previously known.
- "As people breathe," Wexler explains, "a
clump of fine particles called a bolus will rapidly disperse throughout
the lungs. At the terminal alveoli - little sacks at the end of each respiratory
branch, where oxygen and carbon dioxide trade places with blood - these
particles take up water and expand, much like a sponge, because of hydroscopic
- Mathematical models of these physical events - dispersion
and hydroscopic expansion - suggest that "the smallest particles can
sometimes penetrate almost two times farther into airways than we had suspected,"
- That happens because air in the center of a lung tube
flows faster than the surrounding stream, Wexler explains. Particle laden
air mixes with clean air at each intersection of the respiratory branches.
All that secondary mixing "dramatically speeds the movement of these
fine particles through the respiratory system," Wexler reports.
- The next step, Sarangapani says, is to further investigate
why fine particles can be toxic in the lungs. "With the current amount
of knowledge available to us," he says, "I think that the EPA's
current standards are a reasonable response. But, additional research is
needed to identify the precise mechanisms involved in particulate toxicity."
- Professor Anthony Wexler calls air pollution a fast and
invisible threat (Photo courtesy University of Delaware) In 1997, the EPA
set a new, tighter standard for PM 2.5, in response to studies associating
exposure to air pollution with serious health problems. But trucking associations
and other industry groups have challenged the new standards in federal
court, preventing them from being implemented.
- Earlier this year, two judges of a three judge panel
ruled that the new PM 2.5 standard was unconstitutional. The panel did
not challenge the science on which the new standard is based and in fact,
said there was ample scientific support for the new standard. The Department
of Justice is appealing the ruling.
- Health effects of smog include increased hospital admissions
and emergency room visits, increased respiratory disease, decreased lung
function, and changes in respiratory tract defense mechanisms.
- "Tens of thousands of elderly people die prematurely
each year from exposure to ambient levels of fine particles," according
to the EPA. Because children breathe 50 percent more air per pound of body
weight, compared to adults, they are more susceptible, especially if they
suffer from asthma. Even adults can die from air pollution exposure, because
of the way the particles act in the lungs.