EPA'S Updated Clean Air Standards

EPA is making available this primer to provide information to frequently asked questions concerning its updated public health air quality standards. It is critical that public debate on these standards be based upon accurate and complete information.

OVERVIEW OF EPA'S UPDATED CLEAN AIR STANDARDS

EPA recently finalized new public health standards for two common air pollutants -- ozone and particulate matter. It is the first update in 20 years for the smog standard, and the first in 10 years for soot. The new standards will protect 125 million Americans, including 35 million children, and will prevent approximately 15,000 premature deaths every year, as well as avoid one million cases of significant lung function decrease in children and 350,000 cases of aggravated asthma. Combined with the Implementation Package announced by the President, these public health protections will be achievable in common-sense and cost-effective ways that are fully compatible with the nation's continued economic progress.

Basic Facts about the New Air Standards

What are the National Ambient Air Quality Standards (NAAQS)?

Since the Clean Air Act's inception in 1970, Congress has directed EPA to set National Ambient Air Quality Standards (NAAQS) for the six most common air pollutants. The Clean Air Act requires these standards to be set at levels that protect public health with an adequate margin of safety and without consideration of cost. These standards serve two important purposes: first, they provide information to the American people about whether the air in their community is healthful; and second, they present state and local governments with the targets they must meet to achieve clean air.

What are ozone and particulate matter?

Ground level ozone is the prime ingredient of smog, the pollution that blankets many urban areas during the summer. When inhaled, even at low levels, ozone can cause respiratory problems and aggravated asthma in children, the elderly, those with respiratory disease, and even otherwise healthy adults who are working or exercising outside on a smoggy day. Children are most at risk from exposure to ozone because they are often active outside in summertime smog. Long-term exposures to ozone may lead to premature aging of the lungs and chronic respiratory illnesses. Ozone also harms the environment by damaging crops, harming sensitive waterways and reducing visibility. Ozone results from the combination in the atmosphere of other pollutants -- primarily volatile organic compounds and nitrogen oxides -- during warmer weather.

Particulate matter is a mixture of solid particles and liquid droplets found in the air otherwise know as soot. EPA has previously regulated inhalable particles. Now, for the first time, EPA has set a new standard for smaller, fine particles -- which travel deeper into the lungs and have been linked to premature deaths, chronic bronchitis and aggravated asthma. A significant measure of fine particles result from the combustion of fuel by power plants and diesel trucks and buses, among others. Early episodes of extreme pollution by fine particles -- the most famous of which occurred in Donora, Pennsylvania and London in the 1930's, 40's, and 50's and killed thousands of people -- highlighted the importance of addressing this form of air pollution. We now understand that even at low concentrations fine particles which are inhaled and become imbedded deeply into the lungs are linked to premature death, chronic bronchitis and aggravated asthma. Children with asthma, the elderly and people with cardiovascular or respiratory disease are especially at risk from fine particle pollution. Particulate matter also reduces visibility in our national parks and wilderness areas.

What is the new ozone standard?

EPA is replacing the previous 1-hour ozone standard with a new 8-hour standard. A National Ambient Air Quality Standard (NAAQS) has three parts: the concentration or level, the measurement period and the "form" of the standard. The new standard is set at a concentration of 0.08 parts per million (ppm). The measurement period is 8 hours. Under the form adopted by EPA, areas are allowed to disregard their three worst measurements every year and average performance over three years to determine if they meet the standard.

What are the new particulate matter standards?

EPA is adding new fine particle standards (PM2.5) to the existing PM10 standards. The numbers, 2.5 and 10 refer to the particle size measured in microns. EPA is adding an annual PM2.5 standard set at a concentration of 15 micrograms per cubic meter (µg/m³) and a new 24-hour PM2.5 standard set at 65 µg/m³. The annual component of the standard was set to provide protection against typical day-to-day exposures as well as longer-term exposures, while the daily component protects against more extreme short-term events. EPA is retaining the current annual PM10 standard of 50 µg/m³ and revising the form of the PM10 24-hour standard set at 150 µg/m³.

What refinements were made from EPA's November 1996 proposal?

In addition to the important implementation principles discussed above, EPA altered its approach from its November 1996 proposal in two significant ways. For ozone, the final standard is set at the 4th highest maximum 8-hour concentration exceedance instead of the 3rd, a point toward the upper-end of the range on which EPA took public comment. This should provide greater stability in the standard by requiring more "bad air" days before an area is found to be out of attainment. For particulate matter, the final standard sets the 24-hour limit at 65 micrograms per cubic meter, instead of at 50, to provide maximum flexibility for local areas and sources while still retaining the public health protections of the proposal that are incorporated into the annual standard. These changes were based upon EPA's consideration of public and agency comments.