How clean is the air we breathe in Tennessee? Air quality experts believe that, overall, Tennessee's air quality is good and is continuing to improve. Since 1975, the number of times each year that air quality standards have been exceeded has dropped dramatically. Both state and local air pollution agencies are working hard to improve those areas where problems have been identified.
Today, we have achieved national standards in all but two pollutants of concern -- ground-level ozone and lead. Two areas in the state classified as nonattainment for sulfur dioxide have now complied with the standard and are being reclassified as attainment areas.
The most pervasive air pollutant in Tennessee and the nation is ground-level ozone. Ground-level ozone forms when gaseous emissions of volatile organic compounds (VOCs) and nitrogen oxides (NOx) interact in the presence of sunlight. Some ozone forms naturally from vegetation, soil and lightning. However, these compounds also come from automobiles, other types of combustion engines, factories and boilers.
As you might expect, some of the areas that have experienced ground-level ozone problems are those with the greatest concentration of vehicles. The good news is that Hamilton, Knox and Shelby counties have achieved compliance with the ozone standard. However, several Middle Tennessee counties are still working to meet the national standard for ozone.
Even though vehicles have become much cleaner and more efficient in recent years,
this is offset by the growing number of vehicles and the increased number of miles
the average car is driven per day. Other factors also figure into this equation.
For example, Nashville is a major interstate transportation hub in the Southeast, and thousands
of vehicles travel through the county each day. Further, it is estimated that 40
percent of the vehicles driven in Davidson County each workday come from outside
the county.
A plan is being developed to help resolve the Middle Tennessee area ozone situation, including an inspection and maintenance program for automobiles in Sumner, Wilson, Rutherford and Williamson counties. Davidson County has had such a program for several years. However, until other vehicles coming into the area are also regu-lated, it will be difficult, if not impossible, to meet the ozone standard consistently.
The Middle Tennessee area will also benefit from a ground-level ozone study led by the Southern Oxidants Study, a research group based at the University of North Carolina. This alliance of participating agencies will conduct intensive research during 1994 and 1995 to determine causes and effects of ground-level ozone pollution in Middle Tennessee and will recommend actions to correct this problem.
There are three areas classified as nonattainment for lead emissions within Williamson, Shelby and Fayette counties. The Williamson and Fayette county areas have now shown their compliance and are being reclassified as attainment areas. A small area in Shelby County, however, is still working to meet the national standard for lead.
One aspect of air quality that receives a lot of public attention in Tennessee is
the large quantity of materials discharged into the atmosphere that have been classified
as "toxic" by Congress. In spite of what appear to be large releases of these materials, chemical air concentrations in the state are actually very low. Voluntary reductions
of these chemical emissions by Tennessee industry have improved air quality. These
discharges are discussed in greater detail in the Hazardous Chemicals section of
this report.
With stricter air quality standards and continuing efforts to control emissions of harmful pollutants, we have made steady progress in improving the quality of Tennessee's air. Even stricter standards will be imposed by new federal requirements, and many more chemicals will be regulated. These steps are expected to accelerate the reduction of toxic chemical releases significantly, as well as reduce other pollutants being emitted into the air.