|
Last Updated: Dec 30, 2007 |
Earth Talk
From The Editors of E/The Environmental Magazine
GOT AN ENVIRONMENTAL QUESTION? Send it to: EarthTalk, c/o E/The Environmental Magazine, P.O. Box 5098, Westport, CT 06881; submit it at: www.emagazine.com/earthtalk/thisweek/, or e-mail: earthtalk@emagazine.com. Read past columns at: www.emagazine.com/earthtalk/archives.php.
 |
| "Car exhaust, industrial emissions, chemicals and gasoline vapors bond together with the help of the sun's rays to create "bad ozone," a key component of unhealthy smog." (Photo by Getty Images) |
Dear EarthTalk: I
know of issues associated with the Earth’s ozone layer, but what is
“ground level ozone” and why is that a problem?
–D. Goetz, Palm Beach, FL
Ozone (O3) is a colorless gas formed when three atoms of oxygen bond
together. About 90 percent of the Earth’s ozone forms naturally in the
stratosphere, dozens of miles above ground. It forms the protective
layer that shields us from overexposure to the sun’s radiation, and is
therefore considered “good” ozone.
The rest of the ozone found on Earth occurs at ground level, and forms
when nitrous oxides and various “volatile organic compounds’
(VOCs)—originating with car exhaust, industrial emissions, chemicals
and gasoline vapors, as well as some natural sources—bond together in
the presence of sunlight.
Ground level ozone, or “bad” ozone, is a key component of smog, which
wreaks havoc on human health and the environment, especially in urban
areas. The U.S. Environmental Protection Agency (EPA) reports that
exposure to even relatively low concentrations of ground-level ozone
for extended periods (several hours) can significantly reduce lung
function and cause respiratory inflammation in normal, healthy people.
Symptoms can include chest pain, coughing, nausea and congestion. For
people with asthma and other respiratory illnesses, exercising in
ozone-rich air can be deadly. Repeated exposure to high levels of ozone
for several months or more can produce permanent structural damage in
the lungs.
Beyond its effects on our health, the EPA estimates that pollution from
ground-level ozone is responsible for nearly $2 billion in agricultural
crop yield losses in the U.S. alone each year. The pervasive gas has
also been shown to damage forests in California and the eastern U.S.
and to contribute to global warming.
Under the mandate of the Clean Air Act, the EPA is charged with
monitoring and limiting the amount of ground-level ozone in urban
areas, and issuing warnings when smog levels are above its standard of
0.12 parts per million. But new studies indicate that ground-level
ozone causes adverse health effects at even lower concentrations. And,
according to the EPA, even rural areas suffer increased ozone levels,
because wind carries ozone and the pollutants that form it hundreds of
miles away from their original sources. As a result, the EPA is
reviewing whether revisions to ozone standards and policies are
warranted.
High concentrations of ground-level ozone are not as common in Canada,
but three urban regions—British Columbia’s Lower Fraser Valley, the
Windsor-Québec City Corridor and the Southern Atlantic Region that
includes New Brunswick and Nova Scotia—do suffer several “bad air days”
each year. The Canadian government, through its own Clean Air Act, has
even stricter standards for exposure to ground-level ozone than in the
U.S., though enforcement is not as big a priority given the smaller
scope of the problem there.
To help minimize ground-level ozone, avoid car trips and the use of
power lawn equipment during especially hot or windless days. Paints and
solvents, most which off-gas VOCs that create ozone and form smog, are
also best to steer clear of with hot summer temperatures coming on
strong. Those concerned about their respiratory health should follow
local weather sources, most which post smog alerts.
CONTACTS: U.S. EPA Ground-Level Ozone Information,
www.epa.gov/air/ozonepollution; Canada’s Clean Air Act,
www.ec.gc.ca/cleanair-airpur/Home-WS8C3F7D55-1_En.htm.
This Week In Texas
Top of Page
|
