The National Ambient Air Quality Standards PROPOSED UPDATES TO THE AIR QUALITY STANDARDS FOR GROUND-LEVEL OZONE: INFORMATION ABOUT PROPOSED PRIMARY AND SECONDARY STANDARDS, AND UPDATES TO THE AIR QUALITY INDEX (AQI) On Nov. 25, 2014, the U.S. Environmental Protection Agency (EPA) proposed to update the nation's air quality standards for ground-level ozone to improve public health and environmental protection. The proposed updates would particularly help children, older adults, and people of all ages with lung diseases, such as asthma. The proposal will expand the ozone monitoring season in many states, and it will update the Air Quality Index to ensure people are notified when air quality is unhealthy. And it will improve the health of trees, plants and ecosystems. EPA will take comment on the proposal for 90 days after it is published in the Federal Register and will hold three public hearings. The Agency will issue a final rule by Oct. 1, 2015. States would have time to develop and implement plans to meet revised standards, and existing and proposed federal rules will help by making significant strides toward reducing ozone-forming pollution. EPA projections show the vast majority of U.S. counties would meet the proposed standards by 2025 just with the rules and programs now in place or under way. AIR QUALITY STANDARDS • The Clean Air Act requires EPA to set two types of outdoor air quality standards for ozone: a primary standard, to protect public health, and a secondary standard, to protect the public welfare. The law requires EPA to review the standards every five years. Proposed Primary Standard to Protect Public Health: • EPA's current primary (health) standard is an 8- hour standard of 75 parts per billion (ppb), set in 2008. An area meets the primary standard if the fourth-highest maximum daily 8-hour ozone concentration per year, averaged over three years, is equal to or less than 75 ppb. • The Clean Air Act requires that primary standards be "requisite to protect public health with an adequate margin of safety," including the health of groups of people considered more at risk. EPA is proposing that the current ozone standard is not adequate to protect public health as the law requires and that the standard should be revised to improve public health protection for millions of Americans. Protecting Public Health with an Adequate Margin of Safety The Clean Air Act requires EPA to set primary air quality standards to reduce risk sufficiently to protect public health with an "adequate margin of safety," including the health of at-risk groups. In making this judgment, EPA considers factors such as the nature and severity of health effects, the size of the at-risk groups affected, and the degree of certainty and uncertainty in the science. EPA's task is to set standards that are "requisite" - neither more nor less stringent than necessary - to accomplish this. The law does not require EPA to set primary standards at a zero-risk level. 1 ------- • EPA is proposing to strengthen the health standard from a level of 75 ppb to a level within a range from 65 to 70 ppb. The agency is proposing to retain the form and averaging time for the standard. An area would meet the primary standard if the fourth-highest maximum daily 8-hour ozone concentration per year, averaged over three years, is equal to or less than the level of the standard. • EPA also is seeking comment on levels for the health standard as low as 60 ppb. The agency will accept comments on all aspects of the proposal, including on retaining the existing standard. • A significantly expanded body of scientific evidence shows that ozone can cause a number of harmful effects on the respiratory system, including difficulty breathing and inflammation of the airways. For people with lung diseases such as asthma and COPD (chronic obstructive pulmonary disease), these effects can lead to emergency room visits and hospital admissions. Ozone exposure also is likely to cause premature death from lung or heart diseases. In addition, evidence indicates that long-term ozone exposure is likely to result in harmful respiratory effects, including the development of asthma. • People most at risk from ozone exposure include: children; people with asthma and other respiratory diseases; older adults; people who are active outdoors, especially outdoor workers; people with certain genetic characteristics; and people with reduced intake of certain nutrients, such as vitamins C and E. • An estimated 25.9 million people have asthma in the U.S., including almost 7.1 million children. Asthma disproportionately affects children, families with lower incomes, and minorities, including Puerto Ricans, Native Americans/Alaska Natives and African-Americans. Proposed Secondary Standard to Protect the Public Welfare • The Clean Air Act also requires EPA to set secondary standards that specify the level of air quality that is "requisite to protect the public welfare from any known or anticipated adverse effects." These effects include effects on soils, water, crops, vegetation, man-made materials, weather, visibility and climate, among others. • The current secondary standard for ozone is identical to the primary standard, an 8-hour standard of 75 ppb. • New studies since the last review of the standards add to evidence showing that repeated exposure to ozone reduces growth and has other harmful effects on plants and trees. These types of effects have the potential to impact ecosystems and the benefits they provide. • EPA is proposing that the existing secondary standard is not adequate to protect the public welfare, particularly against harm to trees, plants and ecosystems. The agency is proposing a two-step approach to provide appropriate protection: defining a target level of protection and revising the standard to achieve that level of protection. • The impact of ozone exposure on trees, plants and ecosystems often is assessed using a seasonal index known as a "W126 index." A W126 index, named after portions of the equation used to 2 ------- calculate it, is a weighted index designed to reflect the cumulative exposures that can damage plants and trees during the consecutive three months in the growing season when daytime ozone concentrations are the highest and plant growth is most affected. • The agency is proposing that air quality meeting a W126 index value between 13 and 17 parts per million-hours (ppm-hours), averaged over three years, would provide the "requisite protection" that the law requires. • To achieve that level of protection, EPA is proposing to revise the level of the secondary standard to a level within the same range proposed for the primary standard (an 8-hour standard in the range of 65 to 70 ppm). Analyses show that a standard in this range would provide protection equivalent to a W126 index of 13 to 17 ppm-hours. EPA analyzed data from air quality monitors and found that setting a standard in a W126form would not provide additional protection beyond an 8-hour standard. • The agency is proposing to retain the form and averaging time of the current secondary standard. An area would meet the secondary standard if the annual fourth highest maximum daily 8-hour average, averaged over three years, is equal to or less than the level of the standard. • EPA is seeking comment on setting the standard based on the W126 metric within a range of 13 to 17 ppm-hours, averaged over three years. The Agency also is seeking comment on defining a target protection level in terms of a W126 index value as low as 7 to 13 ppm-hours. The agency will accept comments on all aspects of the proposal, including on retaining the existing standard. PROPOSED REVISIONS TO THE AIR QUALITY INDEX • EPA is proposing updates to the Air Quality Index (AQI) for ozone. The AQI is EPA's color-coded tool for telling the public how clean or polluted the air is, and recommending steps people can take to reduce their daily exposure to pollution. • The AQI converts ozone concentrations to a number on a scale from 0 to 500. This scale is used by cities and states across the country to report current and daily ozone concentrations and for daily ozone air quality forecasting. Calculating the W126 Index: A W126 index is a seasonal index that scientists often use designed to assess the impact of ozone on plants and trees. Here's how it's calculated for EPA's proposal: • Measure hourly ozone concentrations for each hour from 8 a.m. to 8 p.m. - the time when ozone has the greatest potential to cause harm; • Weight each hourly measurement, with more weight given to higher ozone concentrations (higher concentrations are more damaging to plants); • Add the 12 weighted hourly values to get a daily value; • Add the daily values for each month to get a monthly value; • Add the monthly values in each consecutive three-month period during the ozone season. The highest of these three-month sums is the seasonal index value. • Average the seasonal index values over the most recent three years. 3 ------- • EPA is proposing to change the breakpoints for each AQI category, based on the level of the proposed primary standard and information from the health studies examined as part of the review of the standards. • EPA is proposing to set the 100 value of the index at the level of the primary 8-hour ozone standard (in a range from 65 to 70 ppb). An AQI of 100 is the upper end of the "Moderate" or "Code Yellow" range, and marks the level above which EPA begins cautioning at-risk groups. The "Unhealthy for Sensitive Groups" or "Code Orange" range (AQI of 101-150) would begin 1 ppb above the level of the proposed standard (66 to 71 ppb) and would extend to 85 ppb. • EPA is not proposing to change the level at the top of the index (an AQI value of 500). This level is typically set equal to the Significant Harm Level, a level that represents imminent danger. The Significant Harm Level for ozone is 600 ppb, averaged over two hours. Some states are required to have contingency plans in place to avoid reaching this level. • The proposed AQI breakpoints are outlined in the table below. AQI Category Index Values Current Breakpoints (2008 AQI) (ppb, 8-hour average) Proposed Breakpoints (ppb, 8-hour average) Note: parentheses indicate a range Good 0-50 0-59 0 to (49-54) Moderate 51 -100 60-75 (50-55) to (65-70) Unhealthy for Sensitive Groups 101-150 76-95 (66-71) to 85 Unhealthy 151-200 96-115 86-105 Very Unhealthy 201-300 116-374 106-200 Hazardous 301-500 375 to the Significant Harm Level* 201 to the Significant Harm Level* *The Significant Harm Level for ozone is 600 ppb, two-hour average 4 ------- BACKGROUND: • The Clean Air Act requires EPA to review the ozone standards every five years to determine whether they should be revised in light of the latest science. Reviewing the NAAQS is a lengthy undertaking and includes the following major steps before EPA issues a proposed rule: planning; a comprehensive review, synthesis and evaluation of the science on ozone (referred to as the Integrated Science Assessment); risk and exposure assessments for public health and the public welfare; and a staff policy assessment. • Scientific review during the development of each of these documents is thorough and extensive. Drafts of all documents are reviewed by EPA's independent science advisers (the Clean Air Scientific Advisory Committee, or CASAC), and the public has an opportunity to comment on them. • The EPA Administrator evaluates all of this information, along with advice from the CASAC, in determining whether to propose revisions to a standard. Proposed rules are made available for public comment, and the agency generally holds public hearings. EPA carefully considers comments received on the proposal before issuing a final rule. • EPA issued the first national air quality standards for ozone in 1971. The agency has revised the standards three times - in 1979,1997 and 2008 - to ensure they continue to protect public health and welfare. (In 1993, the agency reviewed the standards but determined that revisions were not warranted; in 2010, the agency proposed, but did not finalize, revisions as part of a reconsideration of the 2008 standards.) A table of historical ozone standards is available at: http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_history.html • EPA last updated the ozone standards in March 2008 and began the regularly scheduled review of that standard six months later. The proposed revisions are a result of that regularly scheduled review. • EPA proposed to revise the standards Nov. 26, 2014. o On January 21, 2014, the Sierra Club, American Lung Association, Environmental Defense Fund and Natural Resources Defense Council sued EPA for not completing the review of the standards within five years - by March 2013. The groups asked the U.S. District Court for the Northern District of California to order EPA to complete the five-year review of the 2008 standards. The court ordered the agency to sign a proposed rule by Dec. 1, 2014 and a final rule by Oct. 1, 2015. • In July 2013, the U.S. Court of Appeals for the D.C. Circuit upheld the 2008 primary ozone standard but remanded the secondary standard to EPA, on the grounds that the agency had not specified the level of air quality that was requisite to protect public welfare as required by the Clean Air Act, and had not clearly shown how the secondary standard provided this protection. 5 ------- The proposed revisions to the ozone standards respond to this remand. • On Oct. 6, 2014, the U.S. Supreme Court declined to hear an appeal of the D.C. Circuit Court's July 2013 decision. FOR MORE INFORMATION: • To read the proposal and additional fact sheets, visit http://www.epa.gov/glo/actions.html • To comment on the proposal • For technical documents related to this review of the standards, see: http://www.epa.gOv/ttn/naaqs/standards/ozone/s o3 index.html • For your local air quality forecasts and information on current air quality, visit www.airnow.gov 6 ------- |