Increasing 'Bad' Ozone Threatens Human and Plant Health
On July 6 this summer, Virginia's Department of Environmental Quality issued
the region's first "unhealthy" air alert since 2008.
The culprit? "Bad" ozone and other air pollution that had combined to
produce an abnormally high reading of 119 parts per billion in Suffolk and
70-80 parts per billion in other parts of southeastern Virginia. That
compares to the natural concentration of ozone of about 10 parts per billion
that was the norm more than a century ago.
Ozone spikes are part of a pattern of increasing O3
levels globally, in even
the most remote areas, says Dr. Jack Fishman, senior research scientist in
the Science Directorate at NASA Langley Research Center in Hampton, Va.
"I think what we have to dispel is that ozone pollution is confined to
places like Los Angeles and Houston," says Fishman. "Despite emission
controls that have resulted in notable reductions in many American cities,
concentrations in non-urban areas in both the U.S. and around the world
are increasing, with negative impacts to all living things -- plants,
animals, and people."
Fishman is an expert in the composition of the troposphere, which is the
part of the atmosphere that extends from the ground up to four to 12 miles (19.3 km),
depending on where it is measured. In general, the troposphere is deeper in
the tropics than at higher latitudes.
The troposphere contains about 75 percent of the atmosphere's mass, 99
percent of its water vapor and is where weather occurs.
Although 'good' ozone high in the stratosphere -- the layer just above the
troposphere -- provides a shield to protect life on Earth, direct contact
with it is harmful to plants and animals, including humans.
According to the Environmental Protection Agency, exposure to ozone levels
of greater than 80 parts per billion for eight hours or longer is unhealthy.
Harmful effects can include throat and lung irritation or aggravation of
asthma or emphysema.
Ground-level 'bad' ozone forms when nitrogen oxide gases from vehicle and
industrial emissions react with volatile organic compounds --
carbon-containing chemicals that evaporate easily into the air, such as
gasoline and paint thinners.
In addition to impacting human health, rising ozone levels are
measurably reducing crops yields, says Fishman.
Among the crops affected are soybeans, rice, alfalfa, barley, cotton, oat,
peanut, potato and wheat. Research by Fishman and others suggests that
globally, the cost of crop damage by surface ozone is as much as $26 billion
And it's likely to get worse.
"Coupling our recently published crop productivity statistical findings with
a global model that simulates the formation and transport of ozone
pollution, our findings suggest that we are now at a crossroads with respect
to agricultural productivity," the St. Louis native says.
Surface ozone, Fishman adds, knows no geographic or political boundaries.
Indeed, he says, "the influx of pollution from east Asia might have been a
factor that led to crossing a threshold concentration in the U.S. so that
the impact of such pollution is now observable. In other words, if we had
done the same analysis using agricultural and ozone data from the 1980s or
even 1990s, the impact of ozone on crops would not have been seen."
"Certainly, in the 19th and early 20th century, background surface ozone
concentrations were so low that an increase of 25 percent would not have
affected living organisms," says Fishman. "But with the IPCC-projected
increase on the order of 10 to 20 percent in the next decade or two, the
currently observable effects on crop productivity will be significantly
How data are gathered
Ozone data have been collected from space by NASA's Total Ozone Mapping
Spectrometer (TOMS) aboard several satellites that flew between 1978 and
2005 and now from the Ozone Monitoring Instrument (OMI) on the Aura
satellite, launched in 2004.
At NASA's Langley Research Center in Hampton, Va., air-quality monitoring is performed onsite daily by
Virginia's Department of Environmental Quality (DEQ) and the U.S.
Environmental Protection Agency. The monitoring station opened this past
spring under an agreement between NASA and the DEQ.
Measured are pollutants -- from factories, power plants and cars -- that can
damage human health, plants, the environment and infrastructure. The
pollutants include ozone, carbon monoxide, nitrogen oxides, sulfur oxides
and airborne particulates.
The site "will bring together the partnership of NASA, DEQ, and the EPA in a
coordinated effort to assess the relationship between space-based
observations and surface observations of air quality," Langley scientist
Margaret Pippin said last April. She is the scientist coordinating the DEQ's
move to Langley.
The Langley site will house a complementary instrument that is essentially a
ground-based version of the Ozone Monitoring Instrument. In parallel, both instruments will provide
unique insight into how satellites can be used to improve our understanding
of the formation of widespread air pollution episodes.
Ground-based air-quality measuring stations are located around the world.
Although these provide valuable data, their coverage is limited. Satellites
can provide a more global picture of air quality, but the quantities they
measure from space are dependent on other factors in addition to the
concentration measured at the surface.
In addition to the DEQ/EPA/NASA venture, a Langley-led campaign will make
trace gas and particulate measurements from instruments aboard NASA
aircraft. The campaign is intended to improve the use of satellites for
monitoring air quality, and to better understand the relationship between
ground and satellite measurements.
The five-year effort will draw on researchers at Langley, Goddard Space
Flight Center in Greenbelt, Md.; Ames Research Center, outside San
Francisco; and multiple universities. The campaign is called DISCOVER-AQ
(Deriving Information on Surface Conditions from Column and Vertically
Resolved Observations Relevant to Air Quality).
NASA Langley Research Center
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