There is good news about air quality in North Carolina. Yet, the news has not been reported by either the media or the state’s usually vocal environmental pressure groups. Certainly, anyone truly concerned about improvements in air quality should be celebrating.
In 2003 North Carolina had the fewest number of high-ozone days in more than 10 years. In addition, 2003 continued a five-year downward trend that began in 1998 and was interrupted only in the abnormally warm year of 2002.
From 1998 to 2003 the average number of high-ozone days per ozone monitor in the state fell from 14.5 days to 2.4 days a year. And what is true for the state is true for its major cities. Charlotte, the Triad, and the Triangle all had near-decade low ozone levels in 2003 and like the state, the lows are part of a similar five-year trend. Charlotte has gone from a high of 25.4 days per ozone monitor in 1998 to four days in 2003; the Triad has dropped from 13.4 days to 2.4; and the Triangle has gone from a decade high of 17.9 high-ozone days per monitor to 3.3 in 2003.
Ground-level ozone is a byproduct of certain air pollutants, in particular nitrogen oxide and what are called volatile organic compounds. The pollutants are emitted from a variety of sources, including automobiles and electric power plants. In the presence of heat and sunlight the pollutants form ozone. The concern is that at relatively high levels, ozone can be a lung irritant, particularly for people with asthma. A countervailing health benefit of both ground-level and atmospheric ozone (the ozone layer) is that it is a sunscreen that blocks the ultraviolet rays of the sun.
So why, despite the fact that the state continues to grow and more cars fill the roads, do North Carolina’s ozone concentrations continue to improve? In all likelihood, the most important reason is cleaner cars. As each year passes, newer cars are replacing older cars on our state’s streets and highways. It is estimated that emissions from gasoline vehicles are dropping by about 10 percent per year as the fleet turns over to more recent models that start out and stay much cleaner than vehicles built years ago. Since vehicle miles traveled in the state are increasing by about 4 percent a year, total auto emissions are decreasing by about 6 percent annually.
North Carolina has 47 ozone monitors. The importance of looking at high-ozone days per monitor, rather than looking at the total number registered, is that it allows comparisons of data from year to year. In an attempt to gain more accurate information regarding the state’s ozone problem the North Carolina Division of Air Quality has continued to increase the number of monitors in the state. Because of this, year-to-year comparisons that do not adjust for the changing number of monitors will be useless. The more monitors a state has, the more likely it is that any one monitor will register high ozone. Since the number of monitors is regularly increased, unadjusted data will always be biased against later years and against states that have more monitors.
Widely reported studies of ground-level ozone by environmental pressure groups never adjust for changes in the number of monitors, either from year to year or from state to state. Typically these studies make it sound like North Carolina has an ozone problem that is getting continuously worse and that is bad relative to other states. But North Carolina is among the states with the highest number of monitors in the country. This means that these studies will always be biased against North Carolina, ultimately because it is doing a better-than-average job at monitoring its ozone pollution.
There is plenty of good news to report about air quality in North Carolina. Emissions of major pollutants, including nitrogen oxide, carbon monoxide, and sulfur dioxide have been consistently well below the maximum allowed by the EPA and have been in steady decline for nearly 20 years. But don’t expect to hear about this from environmental-interest groups, who claim to be concerned about clean air and public health. They understand that bad news justifies their existence and good news dries up contributions. Similarly, the news media understands that scary headlines about environmental disaster sells newspapers and stories about how well things are going leave the vending boxes full.