EPA’s Reviews of the National Ambient Air Quality Standards (NAAQS): Process and Current Status

1. EPA’s Reviews of the National Ambient Air Quality Standards (NAAQS):Process and Current Status Lydia WegmanDirector, Health and Environmental Impacts Division, OAQPS November 11, 2009

2. Clean Air Act Requirements for NAAQS • The Clean Air Act requires EPA to set two types of NAAQS for common air pollutants (“criteria pollutants”): • primary standards to protect public health, including the health of at-risk populations such as asthmatics, children, and the elderly, with an adequate margin of safety • secondary standards to protect public welfare, including protection against visibility impairment and damage to animals, crops, vegetation, and buildings • 6 criteria pollutants: • Ground-level ozone (smog) (O3) – Particulate matter (PM2.5 and PM10) • Carbon monoxide (CO) – Lead (Pb) • Nitrogen dioxide (NO2) – Sulfur dioxide (SO2) • EPA required to review (and revise if appropriate) each NAAQS on a 5-year cycle, with input from the Clean Air Act Scientific Advisory Committee (CASAC) • Different considerations apply to setting NAAQS than to achieving them • Setting NAAQS: health and environmental effects • Achieving NAAQS: account for cost, technical feasibility, time needed to attain

3. Peer-reviewed scientific studies Integrated Science Assessment: concise evaluation and synthesis of most policy-relevant studies Policy Assessment: staff analysis of policy options based on integration and interpretation of information in the ISA and REA Integrated Review Plan: timeline and key policy-relevant issues and scientific questions Workshop on science-policy issues CASAC review and public comment Risk/Exposure Assessment: concise quantitative assessment focused on key results, observations, and uncertainties CASAC review and public comment EPA proposed decision on standards Agency decision making and draft proposal notice Interagency review EPA proposed decision on standards EPA final decision on standards Public hearings and comments on proposal Agency decision making and draft final notice Interagency review NAAQS Review Process

4. Key Components of NAAQS Review • Key components of the standards review process: • Integrated Science Assessment (ISA) • Risk and Exposure Assessment (REA) • Policy Assessment • Multiple drafts of each of document reviewed by the Clean Air Scientific Advisory Committee (CASAC) and the public, and revised by EPA as appropriate • Related analyses (due to the requirements of the Clean Air Act, these analyses are not considered in selecting the standards) • Regulatory Impact Analysis (RIA) – to evaluate the costs and benefits of possible approaches to meeting revised standards • Analysis to assess how many monitored counties have air quality that exceeds various alternative standards under consideration

5. Elements of a NAAQS • Each standard specifies four elements that define whether ambient air measured at a monitor meets or exceeds the standard: • Indicator • Level • Averaging time • Form: the air quality statistic used to determine whether an area is meeting the standards • For example, for an area to attain the ozone standard, the 3-year average of the fourth-highest daily maximum 8-hour average ozone concentrations measured at each monitor over each year must not exceed 0.075 ppm

6. Ongoing NAAQS Reviews: Current Schedules NOTE: Underlined dates indicate court-ordered or settlement agreement deadlines

7. Ozone NAAQS • March 2008: Primary and secondary standards revised by lowering level of 8-hour standard to 0.075 ppm • Standards were not as protective as recommended CASAC: • Primary standard: unanimously recommended revising the standard to within the range of 0.060 to 0.070 ppm • Secondary standard: • “There is a clear need for a secondary standard which is distinctly different from the primary standard in averaging time, level and form.” • “A secondary standard of cumulative form and extending over an entire growing season will be far more effective than a secondary standard that is not cumulative in form and does not include the whole growing season.” • CASAC preferred a form called W126 and suggested a range of levels from 7-15 ppm-hrs • September 2009: EPA announced reconsideration based on scientific and technical record from 2008 review • Proposal by Dec. 21, 2009

8. Estimated Ponderosa Pine Seedling Biomass Loss For 2001 • 2008 Ozone Vegetation Risk Assessment included estimates of potential biomass loss in trees and yield loss in crops, taking into account species-specific growing ranges and responses to seasonal O3 exposures • Important known ozone-sensitive trees in the West include: quaking aspen, ponderosa pine, black cherry & cottonwood • These trees were shown to have estimated annual biomass losses of up to 19% in some areas of California • Growths losses greater than 2% annually can be significant due to compounding effects over life-time of a tree (Heck & Cowling 1997)

9. EPA - all Ozone Monitoring Sites during 2004-06 • 1055 ozone monitoring sites with complete data, 2004-06 • 240 ozone monitoring sites with incomplete data, 2004-06 • 643 counties with complete data, 2004-06

10. 2006 Ozone Monitoring Network: Many Western Counties Excluded Based on EPA-reported monitoring data in the West

11. NO2 NAAQS: Proposal Overview • June 2009 -- Proposed to set a new 1-hour NO2 standard and retain current annual average NO2 standard • Two approaches: • Proposed: standard would reflect maximum allowable peak NO2 concentration anywhere in an area (peaks likely near major roads) • New monitors would be required near major roads in addition to maintaining current community-wide monitors • Level: 80-100 ppb • Alternative: standard would reflect maximum allowable area-wide NO2 concentration • Would generally rely on existing monitoring network; in conjunction with commitment to conduct research monitoring near major roads • Level: 50-75 ppb • Final rule: January 2010

12. Secondary Standards for NOx and SOx • First separate review for secondary standards; first consideration of multi-pollutant standards – focus on deposition-related effects • Challenging policy and technical issues • Reconciling diverse deposition-related effects with a national standard • Translating deposition effects into ambient concentration-based standard • Assessing the role of reduced nitrogen (ammonia) • Developing a monitoring system for remote ecosystems • CASAC’s view: sufficient information to set separate secondary standards; necessary to protect against acidification and nutrient enrichment effects • Just agreed to extend schedule by ~ 2 years • Policy assessment will be released February 2010

13. Impacts of NOx/SOx in the West • Western locations are dominated by NOx and NH3 deposition, reflecting greater NOx and NH3 emissions in the West compared with SO2 • Some western locations, e.g. high-elevation lakes, are highly sensitive to atmospheric nitrogen deposition • Terrestrial systems in the west are also sensitive to nitrogen deposition. Lichens are especially sensitive indicator species

14. EPA included three western areas in the NOx/SOx secondary standards risk and exposure assessment • Western case study areas were selected to address observed effects of nitrogen deposition on Alpine lakes and meadows, and effects of nitrogen saturation in California forests • These effects can include impacts on both aquatic and terrestrial ecosystems, including community level changes in plants and lichens, such as coastal sage scrub, mixed conifer forest in California, and alpine ecosystems in the Rocky Mountains