BACKGROUND: New satellite observations mark the first time space-based instruments have detected the regional impact of pollution controls first put into place in the 1990s. Locally, we can see results from actions taken less than 20 years ago. The new study focuses on the Ohio River Valley, but the results of the research impact the entire planet.
ABOUT THE STUDY: The Ohio River Valley is home to many large power plants, and the region produced a third of all US nitrogen oxide emissions from power plants during the 1990s. Those emissions drift downwind, producing ozone in urban areas hundreds of miles away. Utility companies, especially coal-burning power plants, started controlling their pollution in response to new regulations by the nation's Environmental Protection Agency in 1999. The satellites located above the valley contain remote sensing instruments that detect reflected light, and then analyze the colors of the reflected light to determine which chemical elements are present -- this is a process called spectroscopy.
WHAT THEY FOUND: High-precision instruments aboard European satellites have detected a 38% decline in nitrogen dioxide in the Ohio River Valley and nearby states between 1999 and 2005, even though electricity production increased during this period. Nitrogen dioxide and nitric oxides are two gases that form a group of pollutants known as nitrogen oxides, which are produced by burning fossil fuels. When combined with other gases and sunlight, they form ozone, a major air pollutant in smog. Ground-level ozone is harmful to human health. The new data indicate that there should be lower ozone pollution across much of the eastern United States. The NOAA study is the first to verify from space that these single-point reductions have had a measurable impact on the atmosphere across the entire region. The study found much smaller decreases in satellite measurements of atmospheric nitrogen dioxide in the northeastern states, where the primary source is fossil fuel combustion in cars and other vehicles. The highest nitrogen dioxide levels were found in areas with combined urban, industrial and power plant sources, such as Chicago, Pittsburgh, Detroit, Toronto, Atlanta, Dallas and Houston.
ABOUT OZONE: Ozone is a rare element in our atmosphere; there are about three molecules of ozone per every 10 million air molecules, and yet it plays a vital role in human health. Most ozone (90%) can be found in an upper layer of the earth's atmosphere called the stratosphere. It is beneficial because it absorbs most of the damaging ultraviolet sunlight, which can cause skin cancers, among other conditions. The remaining 10% of ozone can be found in a lower region called the troposphere. Here, it reacts with other molecules to produce smog, which has toxic effects on crops, forest growth, and human health.
The American Geophysical Union contributed to the information contained in the TV portion of this report.