Analyzing National Air Quality Trends

Chart 8 - Growth of Air Pollution Programs

While we await the EPA data for 1998, the 30th anniversary of Earth Day and the first Clean Air Act is a good time to review long-term factors in air quality improvement. In 1999, a major contribution to the scholarship on this subject appeared: Indur M. Goklany's Clearing the Air: The Real Story of the War on Air Pollution.17

 Goklany's review of the subject shows that analyzing air quality improvements is more complicated than it seems. The apparent conclusion to draw from EPA data is that air quality improvements result from regulations such as the 1970 Clean Air Act. Goklany's detailed analysis, however, reveals a more complicated picture. Because comprehensive air quality monitoring did not begin until after the first Clean Air Act, our knowledge of the pre-1970 period is based on the monitoring samples available. However, the samples that do exist provide a consistent picture, and suggest an improving trend before 1970.

Local government efforts to control air quality problems began long before 1970. Chart 8 shows the growth in local air pollution control agencies that occurred with the growth in the public perception of air pollution as a major problem. Very early in the twentieth century, visible air pollution, especially smoke, was identified as a problem to be reduced. More invisible forms of pollution, especially ozone, were more slowly recognized.

The smoke problem was practically solved by the 1960s. In Pittsburgh, between 1946 and 1955, the hours of heavy smoke dropped by 96.6 percent from 298 to 10 hours, drastically improving atmospheric visibility. Nonetheless, state air pollution programs increased after 1960 and smoke restrictions became more stringent.18

Chart 9 shows the trend for settleable dust in the industrial city of Pittsburgh between 1925 and 1965. The rapid decline in the early years between 1925 and 1940 is attributable to the simple efficiency gains from industry upgrading its technology. The industrial drive for cost-saving efficiency also typically leads to cleaner technology. In 1938, dustfall records in Pittsburgh averaged 60.0 tons per month per square mile, but by 1955 the figure had declined to 48.9 tons.19

Although the pre-1970 data for air pollution is not as well quantified as is the post-1970 data, studies indicate that air quality was improving rapidly before the passage of the 1970 Clean Air Act. For example, Paul Portney, an environmental economist with Resources for the Future, writes that it is "extremely difficult to isolate the effects of regulatory policies on air quality, as distinct from the effects of other potentially important factors," because "some measures of air quality were improving at an impressive rate before 1970."20

Historical data show that ambient levels of sulfur dioxide were reduced by almost 50 percent between 1964 and 1970 in New York City (see Chart 10).

Similar improvements occurred nationwide. Based on 21 urban monitors, the mean annual average of SO2 fell approximately 40 percent between 1962 and 1969. This set the stage for progress after the Clean Air Act; the national average dropped more than 60 percent between 1974 and 199721 (see Chart 11).

Although there is little data on ambient carbon monoxide (CO) concentrations until the early 1970s, the available data suggest that CO may have begun improving in the mid-1960s at least in urban areas, as indicated by the data from 1963-1968. These data are from the federally operated six-city CAMP network, which includes Chicago, Cincinnati, Denver, Philadelphia, St. Louis, and Washington. Goklany notes, "The fact that declines apparently began before the Federal Motor Vehicle Control Program went into effect indicates that stationary source reductions played a role in the initial turnaround; those improvements then gathered momentum as an increasing number of vehicles became subject to federal tailpipe controls starting with the 1968 model year."22

The Organization for Economic Cooperation and Development (OECD) notes in a 1991 report on the U.S. environment that "emissions have also fallen in other OECD countries, sometimes by as much or proportionally more than in the United States," but with less stringent regulation.23 Although such findings seem counter-intuitive, they demonstrate the difficulty in calculating the effectiveness of the large investment the United States has made in environmental regulation, with air quality control now costing nearly $40 billion per year.

These analyses are not meant to imply that regulations have played no role in air quality improvements over the past 30 years. Rather, they indicate that the regulatory approach is neither the only nor the most effective way to address air quality problems. Improvements in the United States occurred before the enactment of regulations, and during the same time period other developed nations with less strict regulations saw improvements not only comparable but, in some cases, greater. As these developments suggest, regulations are not the sole cause of U.S. air quality improvements; rather, they are the mechanism that the United States chose to use in response to the public's demand for a cleaner environment.

The rising costs of regulations, coupled with the decreasing health benefits they deliver, indicate that the current regulatory approach may not be the best way to achieve further progress. Continued improvement is likely to come from technological breakthroughs, such as clean-fuel cars and upgrading industrial processes. Regulatory strategies might also be adapted to emphasize emission reductions on certain days of the year when meteorological conditions suggest that a high pollution day can be expected, similar to the manner in which electric utilities practice "load shedding" on days of peak electricity demand.