Amendments have been required to make the original U.S. Clean Air Act, passed in 1963, a truly effective tool for bettering the environment. Particularly effective was landmark legislation passed with overwhelming support by the U.S. House of Representatives and Senate in 1990.
That legislation has led to substantial cuts in air pollution over the last decade.

In 1990, the U.S. Congress passed landmark bipartisan legislation that substantially strengthened the Clean Air Act. The 1990 amendments gained overwhelming support from the House and Senate, setting ambitious air pollution reduction goals. The Clean Air Act, originally passed in 1963, had previously been amended only twice -- in 1970, when the Environmental Protection Agency (EPA) was formed, and again in 1977.

Robert Perciasepe, assistant administrator of EPA's Office of Air and Radiation, told a Senate subcommittee recently that the 1990 amendments have led to substantial cuts in air pollution over the last nine years.

"The legislation was designed to achieve real results -- and it has done so," he said. "We have made great strides in combating urban air pollution, toxic air pollution, depletion of the stratospheric ozone layer, and acid rain."

The Clean Air Act requires the EPA to establish National Ambient Air Quality Standards for reducing six of the most prevalent and health-threatening air pollutants, sometimes referred to as "criteria" pollutants: carbon monoxide, lead, nitrogen dioxide, sulfur dioxide, ground-level ozone, and particulate matter or soot.

According to the agency's latest report on air quality -- based on the use of monitors to measure pollutant concentrations in urban and other areas across the country -- emissions of the criteria pollutants fell 31 percent between 1970 and 1997. This included a 32-percent drop in carbon monoxide emissions, a 35-percent decrease in sulfur dioxide, a 75-percent reduction in soot, and a 98-percent decrease in lead emissions.

The near total elimination of lead pollution, a major health concern because of its link to neurological damage, is considered to be one of the biggest successes of the Clean Air Act. The reduction in lead emissions was brought about by phasing out lead in gasoline. Another major factor, according to a new study in the March 2000 issue of Environmental Science and Technology, was limiting the incineration of municipal solid waste, which contains such things a paint and solder. Researchers at Rensselaer and Columbia universities in New York say the study's findings are vitally important to assessing the impact of unregulated incineration of solid waste in many countries of the world.

Perciasepe said that in addition to the significant reductions in the criteria air pollutants like lead and sulfur dioxide, rules issued since 1990 are expected to reduce toxic emissions from industries such as chemical plants and dry cleaners by 1.5 million tons a year -- about 10 times the reductions achieved prior to 1990. Many of these hazardous air pollutants, such as vinyl chloride, arsenic, and benzene, are known to or suspected of causing cancer or other adverse health effects.

"The air in our nation's cities is substantially cleaner than in 1990," Perciasepe said. "Nationally, the 1997 average air quality levels were the best on record for all six common pollutants subject to air quality standards. The 1998 levels were as good or better for all pollutants except ozone.

"Since 1993, an unprecedented number of cities have met the health-based national ambient air quality standards," he added. "For example, of the 42 carbon monoxide areas designated as non-attainment in 1991, only six areas continue to experience unhealthy levels of carbon monoxide." An area is given "non-attainment" status when it does not meet the EPA's clean air standards.

He said a key reason for these air quality improvements is that the Clean Air Act's 1990 amendments call for cleaner motor vehicles and cleaner gasoline. In a typical U.S. city, automobile exhaust accounts for up to 90 percent of carbon monoxide and 60 percent of nitrogen oxide in the air. Largely due to improvements to the catalytic converter, which converts noxious carbon monoxide and nitrogen oxide molecules into innocuous chemicals, cars today are 95 percent cleaner than they were in 1970.

In 1997, EPA mediated an agreement among the states and U.S. auto companies that calls for automakers to produce cars 50-percent cleaner than today's cars by 2001.

EPA officials emphasize that all the improvements in air quality have occurred at a time of growing population and strong economic growth. From 1970 to 1997, U.S. gross domestic product has grown by 114 percent, the U.S. population has grown by 31 percent, and the number of kilometers traveled by motor vehicles has increased by 127 percent.

"Those are all pressures pushing things in the opposite direction -- toward greater pollution," said a spokeswoman with the EPA Office of Air and Radiation. "However, during this period of strong economic growth, we've been able to decrease air pollution. That I think is a significant way of highlighting the success of the Clean Air Act."

According to the Congressional Office of Technology Assessment, the cost of complying with all environmental regulations combined has amounted to 1.5 percent of the U.S. gross domestic product. And yet, according to an EPA report required by Congress, the Clean Air Act has yielded human health and environmental benefits that have exceeded costs by more than 40-to-1.

"We also did a prospective study, looking ahead from 1990 to 2010, and again the benefits exceeded the costs by a ratio of four-to-one," the spokeswoman said. "In any case, the benefits of these programs are far outweighing the costs."

According to Perciasepe, environmental rules have forced the development of new, cleaner technologies -- often at lower costs than originally predicted.

"The Clean Air Act requirements have created market opportunities and pressures for technology breakthroughs and performance improvements," he said. "Over and over again industry has responded ... producing breakthroughs such as alternatives to ozone-depleting chemicals and new super-performing catalysts for automobile emissions."

Perciasepe said there are many examples of technologies that were not commercially available 10 years ago, but that now are important parts of pollution control programs, such as reformulated gasoline, selective catalytic reduction for nitrogen oxide emissions from power plants, and cleaner-burning wood stoves.

"EPA has also identified a number of emerging technologies, ranging from fuel cells to (ground level) ozone-destroying catalysts, that may hold promise for achieving additional cost effective reductions of smog, nitrogen oxide, and particulate matter," he said.

One of the most innovative ideas for controlling pollution has been a market-based program that allows utilities to "trade" emissions allowances to reduce acid rain. When sulfur dioxide and nitrogen oxides from burned fossil fuels mix with water and oxygen in the air they form sulfuric and nitric acids, which fall to the ground as precipitation, damaging trees and acidifying lakes and streams. Higher sulfate levels in the air also increase the frequency and severity of asthma, bronchitis, and other respiratory conditions.

A National Surface Waters Survey found that hundreds of lakes in New York's Adirondack Mountains were too acidic to support a host of fish species, and some of the region's lakes and their estuaries are completely barren to sensitive species like brook trout.

Electric utility plants powered by coal or oil account for about 70 percent of sulfur dioxide and 50 percent of nitrogen oxide emissions in the United States each year. Under the pollution allowance trading system, one allowance equals the right to emit one ton of sulfur dioxide per year. A utility that emits less than that amount accumulates pollution credits, which it can then either sell or save to use later. So far U.S. utilities have exchanged over 23 million trading allowances in more than 660 transactions.

"The results have been dramatic," Perciasepe said. "So far, national sulfur dioxide emissions have been cut by more than five million tons, mostly through this program -- and at lower cost than predicted. As a result, rainfall in the eastern United States is up to 25 percent less acidic, and some ecosystems in New England are showing signs of recovery."

He said separate requirements for nitrogen oxide controls for utilities are expected to achieve a two-million-ton reduction of those emissions beginning next year.

When fully implemented in 2010, the Acid Rain Program, passed as part of the 1990 amendments to the Clean Air Act, calls for sulfur dioxide emissions to be reduced by 10 million tons per year. An industry study in 1989 predicted the cost of fully implementing the program at between $4,100 million and $7,400 million. But most recent estimates by the U.S. General Accounting Office estimate the cost at only $2,000 million, and estimates by independent economists put it as low as $1,000 million.

However, despite continued improvements in air quality, the EPA reports that approximately 107 million people lived in U.S. counties with unhealthy air in 1997. Emissions of nitrogen oxides, which contribute to the formation of ground-level ozone or smog, increased by 11 percent between 1970 and 1997. Smog can reduce lung capacity and decrease the body's ability to fight off infection.

Even some national parks have experienced high levels of air pollutants being transported over great distances from their original source. For example, concentrations of smog in remote locations of the Great Smoky Mountains National Park in the eastern United States have increased nearly 20 percent over the last 10 years.

In 1997, the EPA drafted new national air quality standards for soot and smog, two of the most harmful and persistent criteria pollutants. The new rules sought to control even finer particles of soot -- those as small as 2.5 microns across (a human hair is 40 micros wide). Allowable levels of smog were reduced from 120 parts per thousand million to 80 parts per thousand million.

The new standards were based on the most intense review ever undertaken by the EPA, involving 250 peer-reviewed scientific studies on particulate matter and ozone, plus three Congressional reviews.

But in May 1999, in a suit brought by several industry groups and coal-dependent states, a federal appeals court overturned the agency's new smog and soot rules, saying the EPA had gone beyond its constitutional authority. The court ruled that the EPA had overstepped its legal regulatory bounds by imposing the new standards, and that such rules had to be passed by Congress. The same court upheld its own decision in October 1999, rejecting an EPA appeal. The Department of Justice has filed a petition to have the case heard by the U.S. Supreme Court, but a decision on whether to hear the case will take some time.

In the meantime, Perciasepe has expressed concern that progress on reducing smog appears to have slowed or stopped in a number of areas in the last couple of years, and that in some areas "we are in danger of backsliding." He said the national average ozone level increased by 5 percent in 1998. Also, in recent summers, the agency has seen increases in the number of times air quality exceeded national standards in certain cities and national parks.

Most environmentalists agree that better standards for ozone and particulate matter are needed. Frank O'Donnell of the Washington, D.C.-based Clean Air Trust said the new standards struck down by the court "were an updating of the science and clearly would provide better health protection -- and to more people."

On the other hand, the Justice Department has just announced settlement of a major Clean Air Act action against a Florida utility that the will prevent tens of thousands of tons of air pollution from entering the atmosphere each year. The suit charged that the utility's aging power plants made major upgrades without installing equipment required to control smog, acid rain, and soot.

The settlement -- which could influence the outcome of additional lawsuits against utilities representing 32 aging power plants in 10 states, is unprecedented in scope, and marks a major step in the government efforts to stop pollution illegally released from coal-fired power plants.

Jim Fuller writes on global issues for the Office of International Information Programs, U.S. Department of State