Despite vast improvements in air quality throughout the 20th Century, most Americans believe we've made no progress on air pollution or even that air pollution has been getting worse. Media reports on the environment are almost uniformly gloomy and go a long way toward explaining why people's perceptions depart so decisively from reality.
A recent New York Times story on air pollution in Los Angeles could serve as a clinic on how news stories often leave readers with false impressions about the environment. The story opens with "Air quality in the Los Angeles basin this year has been the best in 25 years largely because of a fluke in the weather."
Ah, so we haven't really cleaned up the air; we just got a lucky break from nature.
Not quite. Weather is indeed a major determinant of smog levels in any given year. All else equal, cooler, wetter, windier weather generates less ozone. Whatever the long-term trend, weather will cause large year-to-year variations in ozone levels. But weather is only part of the story in 2004's low air pollution. A number of previous years have had weather unfavorable for ozone formation, but 2004 had the lowest smog levels on record in most of the country. Ongoing reductions in emissions of ozone-forming pollutants explain the long-term improvements.
Figure 1 shows the trend in ozone for the Los Angeles metropolitan area, based on days per year exceeding EPA's 1-hour ozone standard and its new, more-stringent 8-hour standard. The graphs show the number of exceedances at the worst location in the area among all monitoring sites that operated in a given year, and at a group of 14 sites that operated continuously from 1980 through 2004. Note the 90 percent reduction in 1-hour ozone exceedances and the 80 percent reduction in 8-hour exceedances at the average location since the early 1980s. By three out of the four measures, 2004 was the best year on record, while only 1999 and 2000 fared better based on the average number of 8-hour ozone exceedances. Needless to say, weather has nothing to do with these long-term improvements. In fact, if anything, weather trends favor increased pollution. Increasing urbanization has raised temperatures in Los Angeles and other cities due to the urban-heat-island effect, and higher temperatures favor greater ozone formation. Nevertheless, ozone has declined.
Figure 1. Trend in Ozone Exceedance Days in the Los Angeles Region
Source: California Air Resources Board monitoring data.
Despite the large long-term declines in air pollution, note that ozone levels rose from 1999 to 2003. Based on this, a spokeswoman for the Natural Resources Defense Council (NRDC) argued that 2004 was a fluke and that ozone levels would rise again in 2005: "The number of bad air days has dropped, but scientists agree that it was the result of the weather and not success in battling air pollution�if we have a typical year next year, we'll see a jump in the number of bad air days."
Here's where the Times missed one of the biggest emerging stories in air pollution policy. NRDC may be right about next year's ozone levels, but for the wrong reasons. Ozone is formed from reactions involving nitrogen oxides (NOx) and volatile organic compounds (VOC), which are therefore called "ozone precursors." We have trend data on both emissions and ambient levels of ozone precursors demonstrating ongoing declines in these pollutants.
In other words, ozone precursors are dropping, yet ozone is going up. Scientists have known for at least two decades that the ratio of VOC to NOx is a key determinant of ozone levels. When the ratio is low, reducing NOx can actually increase ozone. A recent field study by government and university scientists concluded that this is exactly the situation in southern California. Los Angeles has stopped making progress on ozone not because, as NRDC would have it, of a lack of success in battling air pollution, but because of too much success in fighting the wrong battle. This doesn't sit well with the regulate-first-and-ask-questions-later stance of most regulators and environmental activists, and these groups have thus ignored or glibly dismissed the scientific results.
The Times also blew smoke on actual air pollution levels in Los Angeles during the last couple of years, claiming, for example, that the area exceeded the 1-hour ozone standard on 68 days in 2003 and 27 days in 2004. Inspection of the left-hand graph in Figure 1 shows these values are nearly a factor of two greater than ozone levels at even the worst site, and several times greater than at the average site. The Times went astray by choosing to parrot the claims of regulators and activists rather than checking actual pollution data or seeking others who have done so.
Likewise, the Times let stand a claim by a spokesman for the Coalition for Clean Air, a Los Angeles advocacy group, that particulate pollution is growing in southern California, and that the increase is due largely to emissions from the Los Angeles-Long Beach port, which is the busiest in the nation. On the contrary, fine particulate (PM2.5) levels in the Los Angeles area have declined about 40 percent since the late 1980s and have declined during the last couple of years, as shown in Figure 2 for Long Beach. In fact, the Long Beach area has among the lowest ozone and PM2.5 levels in the entire region.
Furthermore, pollution emission inventories indicate that the port accounts for 4.8 percent of NOx, 0.2 percent of VOC, and 2.1 percent of PM2.5 in the Los Angeles metro area -- hardly a major portion of the total. These facts would have been easy to check, had the Times been inclined to do so. Recall also that reducing the port's NOx emissions, a main focus of campaigns to reduce port pollution, will likely make southern California's ozone worse, as discussed earlier.
Although the Los Angeles region's air pollution is much better than it used to be, parts of the area are the worst in the nation. But even for this most polluted of urban areas, the Times manages to muddle and exaggerate the health implications. The Times makes much of the Children's Health Study (CHS), a long-term study of lung function in children living California areas with high, medium, and low levels of air pollution, claiming, for example, that the CHS showed high air pollution is a cause of higher rates of asthma. This is how the study was portrayed by regulators and the researchers who performed it. But in fact, the CHS reported that children living in high-ozone areas had a 30 percent lower risk of developing asthma when compared with children in low-ozone areas, and reported no relationship of other pollutants with asthma incidence. The CHS results are also based on pollution levels during the late 1980s through the mid-1990s, which were much higher than current levels.
The Times story is notable not only for what it gets wrong, but also for what it misses completely. I've already discussed the risks of NOx reductions. Here are two more: First, on-road pollution measurements show that gasoline vehicles contribute about 75 percent of all VOC emissions, and that half the automobile contribution comes from the worst five percent of the fleet. These "gross polluters" are on the road in spite of vehicle inspection programs and regulators and activists have not acknowledged the problem. In fact, the state's official air management plan makes believe these gross polluters don't exist. Yet repairing or scrapping these cars could rapidly reduce total VOC emissions by as much as 30 percent, and at much lower cost than any other policy available.
Second, even though real-world data show that gasoline vehicles contribute three-quarters of VOC, the official emissions inventory regulators use to determine where and how to reduce ozone precursors puts their contribution at about 40 percent of the total. The combined effect of these two absurdities amounts to billions of dollars wasted on high-cost/low-benefit measures, while opportunities for cheap, rapid pollution reductions go untapped.
Perhaps the Paper of Record's greatest failing is assuming that regulators, activists, and health researchers -- the only groups quoted in the story -- are neutral experts who necessarily provide correct and unbiased information on air pollution levels, trends, health risks, and mitigation policies. This is a surprisingly na�ve approach for what is ostensibly one of the most sophisticated news outlets in the world.
Air pollution policy has for too long been based on unwarranted pessimism about air pollution trends, exaggerated fears about air pollution's health effects, and misguided policies for pollution reduction. This serves the interests of those whose jobs and power depend on having a grave and urgent problem to solve, but shortchanges the public, whose interest is in an accurate portrayal of air pollution issues. Unfortunately, the Times continues to be part of the problem.
Joel Schwartz is an adjunct fellow at Reason Foundation and visiting scholar at American Enterprise Institute.
 J. M. Broder, "Cleaner Air in Los Angeles? Don't Hold Your Breath," New York Times, November 14, 2004.
 See, for example, A. J. Kean, R. F. Sawyer et al., Trends in Exhaust Emissions from In-Use California Light-Duty Vehicles, 1994-2001 (Warrendale, PA: Society of Automotive Engineers, 2002), C. L. Blanchard, Trends in Ambient NOx and Particulate Nitrate in Concentrations in California, 1980-2000 (Alpharetta, GA: Coordinating Research Council, June 2003), (download here).
 E. M. Fujita, W. R. Stockwell et al., "Evolution of the Magnitude and Spatial Extent of the Weekend Ozone Effect in California's South Coast Air Basin 1981-2000," Journal of the Air & Waste Management Association, vol. 53, no. 7 (2003), pp. 864-875, D. R. Lawson, "The Weekend Effect--the Weekly Ambient Emissions Control Experiment," Environmental Manager (July 2003).
 Based on an emissions inventory for the port for 2001 and for all of southern California for 2002. See here and here for the relevant data. The PM2.5 figure is for direct PM2.5 emissions. Much PM2.5 is also formed from VOC and NOx after they are emitted to the atmosphere.
 The data in Figure 2 are in two series, because the PM2.5 sampling method changed in 1999. The actual dichotomous sampler values (1988-1999) were multiplied by 1.136 to make this chart, because CARB researchers recently showed that, given the same ambient PM2.5 levels, the new Federal Reference Method (FRM) gives readings that are, on average, 13.6 percent higher than the dichotomous samplers. The reason is that FRM samplers are kept at a relatively low constant temperature and therefore do not lose "semi-volatile" particulates, such as nitrates and some organics, that evaporate from the dichotomous samplers. Note that the 1999 values are the same after making this correction, giving confidence in CARB's analysis of the two different measurement methods. See N. Motallebi, J. Taylor et al., "Particulate Matter in California: Part 1--Intercomparison of Several PM2.5, PM10-2.5, and PM10 Monitoring Networks," Journal of the Air & Waste Management Association, vol. 53, no. 12 (2003), pp. 1509-1516.
 Unlike the ozone data, PM2.5 data are available only through 2003. The reason is that PM2.5 is regulated based on its annual-average level, so a full year of data is necessary. Furthermore, PM2.5 is highest in December and January, so we won't know how 2004 will turn out until the year is over. In contrast, ozone is elevated only during the warm months, allowing an accurate assessment of a given year's ozone levels after the end of September.
 R. McConnell, K. Berhane et al., "Asthma in Exercising Children Exposed to Ozone: A Cohort Study," Lancet, vol. 359, no. 9304 (2002), pp. 386-391.
 E. M. Fujita, D. E. Campbell et al., "Diurnal and Weekday Variations in the Source Contributions of Ozone Precursors in California's South Coast Air Basin," Journal of the Air & Waste Management Association, vol. 53, no. 7 (2003), pp. 844-863, J. Schwartz, No Way Back: Why Air Pollution Will Continue to Decline (Washington, DC: American Enterprise Institute, July 2003), http://www.aei.org/docLib/20030804_4.pdf.
 For more on these issues, see J. Schwartz, Finding Better Ways to Achieve Cleaner Air (Washington, DC: American Enterprise Institute, 2004), http://www.aei.org/docLib/20040917_%2317319graphics.pdf, J. Schwartz, "Clearing the Air," Regulation (Summer 2003), http://www.cato.org/pubs/regulation/v26n2-4.pdf.