Shop Windows to the Universe

With Explore the Planets, investigate the planets, their moons, and understand the processes that shape them. By G. Jeffrey Taylor, Ph.D. See our DVD collection.
Wildfires across much of California and Nevada increased ground-level ozone to high levels.
Click on image for full size
Image Courtesy of the Wikipedia Commons

Health Standards Exceeded by Ozone Pollution in Wildfires
News story originally written on October 9, 2008

Wildfires can boost ozone pollution to levels that violate U.S. health standards, a new study concludes.

The research, by scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., focused on California wildfires in 2007, finding that they repeatedly caused ground-level ozone to spike to unhealthy levels across a broad area, including much of rural California as well as neighboring Nevada.

Results of the study are published today in the journal Geophysical Research Letters, published by the American Geophysical Union. The research was funded by the National Science Foundation (NSF), which sponsors NCAR, and by NASA.

"It's important to understand the health impacts of wildfires," says NCAR scientist Gabriele Pfister, the paper's lead author. "We found that ozone can hit unhealthy levels even in places where you are not seeing any smoke."

Although scientists have long known that wildfires can affect air quality by emitting particles and gases into the air, there has been little research to quantify the impacts.

Fires worsen ozone levels by releasing nitrogen oxides and hydrocarbons, which can form ozone near the fire or far downwind as a result of chemical reactions in sunlight.

The researchers, using a combination of computer models and ground-level measurements, focused on intense California wildfires that broke out in September and October of 2007. They found that ozone was three times more likely to exceed safe levels when fire plumes blew into a region than when no plumes were present.

"Increasingly in the atmospheric sciences, the blending of model results and observations yield new insights into complex natural processes and societal impacts," said Cliff Jacobs, program director in NSF's Division of Atmospheric Sciences. "This study is an excellent example of this research paradigm."

At the time of the wildfires, the public health standard for ozone set by the Environmental Protection Agency (EPA) was 0.08 parts per million over an eight-hour period.

The EPA has since tightened the standard to 0.075 parts per million. Under the stricter standard, the number of violations would have nearly doubled.

While ozone in the stratosphere benefits life on Earth by blocking ultraviolet radiation from the Sun, ozone in the lower atmosphere can trigger a number of health problems.

These range from coughing and throat irritation to more serious problems, such as aggravation of asthma, bronchitis, and emphysema. Ground-level ozone pollution also damages crops and other plants.

"Wildfires are expected to worsen in the future, especially as our climate grows warmer," Pfister says. "But we are only now beginning to understand their potential impacts on people and ecosystems, not only nearby but also potentially far downwind."

The unhealthy levels of ozone the researchers detected occurred mostly in rural areas. That rural focus may be a result of the computer modeling, which lacked the fine detail to zoom in on relatively compact urban areas.

However, the authors also speculate that wildfire emissions have a greater impact on the countryside than on cities. The reason has to do with chemistry: cities tend to have higher levels of pollutants, and one of those pollutants, nitrogen dioxide, can, at high levels, reduce the efficiency with which ozone is produced and can even act to destroy ozone.

"The impact of wildfires on ozone in suburban and rural areas, far from urban sources of pollution, was quite notable," says NCAR scientist Christine Wiedinmyer, a co-author of the paper.

The paper notes that ozone levels would likely have been even greater except that Santa Ana winds in October blew wildfire plumes over the Pacific Ocean, safely away from populated areas.

To measure the impact of the fires on ozone formation, the researchers turned to computer models developed at NCAR.

Using a specialized fire model, they estimated the amount of vegetation burned and resulting emissions of nitrous oxides, sulfur dioxide, and other pollutants. Those results went into a global air chemistry model, which simulated the evolving chemistry and movement of the emissions and tracked the resulting formation of ozone as the fire plumes spread downwind.

The scientists compared their modeling results with ozone measurements from a network of EPA ground stations at various sites in California.

This enabled them to determine both the number of ozone violations and the extent to which the wildfires contributed to those violations.

Text above is courtesy of the National Science Foundation

Last modified January 27, 2009 by Becca Hatheway.

Shop Windows to the Universe Science Store!

Our online store includes issues of NESTA's quarterly journal, The Earth Scientist, full of classroom activities on different topics in Earth and space science, as well as books on science education!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Ozone - An Overview

The Ozone Hole. The Ozone Hoax. Pollution. Skin Cancer. The topic of ozone makes headlines on a regular basis, but why does a single molecule merit such media coverage? How important is the ozone in our...more

Ozone in the Troposphere

10% of the ozone in the Earth's atmosphere is found in the troposphere, the first layer of the Earth’s atmosphere. In the troposphere, ozone is not wanted. Ozone is even more scarce in the troposphere...more

Aerosols: Tiny Particulates in the Air

Aerosols, also called particulates, are tiny bits of solid or liquid suspended in the air. Some aerosols are so small that they are made only of a few molecules – so small that they are invisible because...more

Global Warming: Scientists Say Earth Is Heating Up

Earth’s climate is warming. During the 20th Century Earth’s average temperature rose 0.6° Celsius (1.1°F). Scientists are finding that the change in temperature has been causing other aspects of our planet...more

Pollution's Effects on Us

The atmosphere is one of the few resources shared among all Earth’s inhabitants. As a consequence, the pollution that spews from a factory in Asia, a fire in Australia, a dust storm in Africa, or car emissions...more

Air Pollution

What do smog, acid rain, carbon monoxide, fossil fuel exhausts, and tropospheric ozone have in common? They are all examples of air pollution. Air pollution is not new. As far back as the 13 th century,...more

Type of Wind: Chinook or Foehn

There are several different types of wind that occur locally at the small scale. One type of small scale wind is the foehn wind. This type of wind is characteristic of mountainous areas such as the Rocky...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF