Air quality in the United States has been improving in recent years as a result of both regulations and voluntary measures. To help the US meet National Ambient Air Quality Standards (NAAQS), the EPA has established attainment/non-attainment zones for each state throughout the United States. When a zone is designated as non-attainment for any criteria pollutant, the affected state must establish a state implementation plan. The state implementation plan regulates emissions of air pollutants so that the non-attainment zones can achieve the National Ambient Air Quality Standards. Although the majority of the US is classified as "ozone attainment," there are many “ozone non-attainment” areas and several cities have had persistent ozone problems for many years. More information about non-attainment zones can be obtained at the EPA Web site.
The number of ozone non-attainment days (i.e., days when the ozone air quality standard is exceeded) has been decreasing in recent years as shown in the table below for Mid-Atlantic States. A number of industries are actively engaged in helping to meet air quality targets. The solvents industry is playing its part in a number of ways including developing new solvent products that qualify for VOC exemption (based on a determination that they have negligible photochemical reactivity, which is a measure of a compound’s potential to contribute to ozone formation), aiding product formulators in the development of new formulas for coatings and other products with lower overall ozone forming potential, supporting scientific research to aid in the understanding of how ozone is formed in the atmosphere, and working with regulators to support programs that encourage development of products that meet environmental needs without compromising performance.
Obtained from http://aqmd.gov/smog/,10/29/02
Under the Clean Air Act, air pollutants include criteria pollutants, hazardous air pollutants and VOCs. The six criteria air pollutants for which the EPA has established National Ambient Air Quality Standards are carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NO2), ozone (O3), particulates (PM), and lead compounds (Pb). Ozone, while a measure of air quality, is not directly emitted into the air; it is formed when VOCs and NOx react in the presence of sunlight. The extent to which VOCs participate in this reaction varies, and thus so does the extent to which they contribute to ozone formation. Work is underway to enable the scientific community and the regulatory bodies to better understand which VOCs contribute the most to ozone formation. With this better understanding will come a more effective way to target those chemicals that contribute the most to the ozone problem.
In 1990, amendments to the federal Clean Air Act established a new program to reduce emissions of hazardous air pollutants (HAPs). A few common solvents are on the list here.
The EPA also requires annual reporting on environmental releases of more than 600 chemicals and chemical categories in the Toxics Release Inventory (TRI), including a number of oxygenated and hydrocarbon solvents. Details of these reports can be found here. Additional information is also provided here.
The tables below show that during the last twenty years air quality has been improving and all criteria air pollutants emitted, with the exception of carbon monoxide, have been decreasing.
Summary of Air Quality and Emissions Trends (USEPA Web site 9/23/02)
*Includes only directly emitted particles
Negative numbers indicate improvements in air quality or reductions in emissions. Positive numbers show where emissions have increased. Obtained from http://aqmd.gov/smog/ 10/29/02
This improvement in air quality has been achieved during a time when the U.S. population, vehicle miles traveled, gross domestic product, and energy consumption have all risen dramatically as shown in the figure below.
http://www.epa.gov/airtrends/sixpoll.html
Additional information about VOC and HAPs can be found in the Regulatory Section of this site and under Publications.
