Lead NAAQS Review: 2 nd Draft Risk Assessment

1. Lead NAAQS Review:2nd Draft Risk Assessment NTAA/EPA Tribal Air Call August 8, 2007 Deirdre Murphy and Zachary Pekar OAQPS

2. Overview • Background • History of Lead NAAQS • Key Policy Aspects • Basis for Current Standard • Current NAAQS Review • What’s changed since 1978? • Human Exposure & Risk Assessment • Next Steps

3. Background: Lead NAAQS History • 1976 – Lead added to list of criteria pollutants • Court Order • 1978 – Primary and Secondary NAAQS set • 1.5 µg/m3, quarterly average • 1980s-90 – First lead NAAQS review • Criteria Document – 1986, with 1990 supplement • Staff Paper – Dec 1990 • 1991- Agency-wide Integrated Lead Strategy • Increased NAAQS enforcement, soil abatement, waste policy, drinking water, products, recycling, research • 2005 (Sept 14) -Court order • New lead NAAQS review

4. Background:Key Policy Aspects • Lead is a multimedia pollutant • Lead emitted into the air is distributed to other media • Human exposures are dominated by ingestion route (e.g., indoor dust) • Lead emitted yesterday (or years ago) can remain available for human exposure • Resuspension of deposited lead contributes to this • In addition to emissions to the air, there are various policy-relevant background exposures • Lead-based paint • Drinking water • Diet • Lead introduced during food processing is background • Lead introduced to food chain via atmospheric deposition, however, is policy-relevant exposure

5. Background:Basis for Current Standard • Level • Sensitive population • Young children, aged 1 to 5 • “maximum safe blood lead level” for individual children • 30 μg/dL blood (anemia symptoms at 40 ug/dL,1977 CD) • Policy goal: keep 99.5% young children < maximum safe level • Translates to population mean of 15 ug/dL blood • Non-air source contributions • 12 μg/dL blood • Limit on air contribution • 3 μg/dL blood • Estimated relationship of air lead to blood lead • 1 ug/m3 to 2 ug/dL blood • Primary NAAQS - 1.5 μg/m3 air • Averaging Time - calendar quarter • Form - not to be exceeded (maximum) value • Indicator - total suspended particulate (TSP) lead Secondary Standard – set equal to primary

6. Current NAAQS Review:What’s Changed Since 1978? (1) • Emissions reduced dramatically, but still arise from many sources • Ambient air concentrations • National mean reduced, but top 10% of sites still average almost 1 ug/m3 • Monitoring network provides incomplete coverage of today’s large emitters • Ambient non-air concentrations • Surface concentrations reduced in quiet forest soils & lake sediments • Trends less clear in systems near sources and with more activity • E.g., resuspension near roadways, primary smelter • Human Exposure – Children’s Blood Lead • U.S. population levels substantially reduced (median: 15 ug/dL to <5 ug/dL) • Health Effects - Adverse effects observed at dramatically lower exposures • More robust evidence for broad array of effects • Focus on children’s IQ (vs. blood effects) • No evidence of threshold • Ecological Effects • Better understanding of Pb ecosystem mobility and transport • Screening levels developed to associate Pb levels with potential for effect

7. Current NAAQS Review:What’s Changed Since 1978? (2) • CDC advisory blood lead level for children • Initially set in 1960 (60 μg/dL) • Revised in 1970 (30 μg/dL), and 1985 (25 μg/dL) • Current level set 1991 (10 μg/dL) • Children with blood lead >advisory level should receive follow-up attention • Reviewed by CDC in 2005 • Recognized no “safe” threshold for blood lead levels in young children • Did not change level as … • Critical to focus resources on children where potential for effects remain greatest • Setting a new level below 10 μg/dL would be an arbitrary decision • Feasibility & effectiveness of intervention activities below 10 μg/dL not yet demonstrated • Emphasized importance of preventing childhood exposures

8. Human Exposure and Risk:Assessment • Case study approach • General urban case study • Hypothetical (non-location specific) with simplifying assumptions, e.g., … • Uniform media concentrations and demographics across study area • Point source-oriented case studies (large & medium) • Primary lead smelter • Secondary lead smelter • Estimated blood lead levels for children • 7 years exposure (from birth) • Predicted associated IQ points lost • Population distribution • Assessed multiple air quality scenarios • current conditions, current NAAQS, alternate NAAQS • Multiple sets of risk results for each combination of case study and air quality scenarios • Recognizes uncertainty in key modeling elements

9. Human Exposure and Risk:Results • Blood lead estimates – all case studies • Lower for all alternate standards compared to current NAAQS • Risk - General urban case study • Average current conditions, <1 to 5 IQ point loss for average child • < 1 IQ point from lead most recently in the air • <1 to 4 IQ point from recent plus past air Pb • Current NAAQS • Average child, 1 to 4-5 IQ point loss from air-related lead exposures • alternative NAAQS (0.5 – 0.05 ug/m3) • Average child, <1 to 2 IQ point loss from air-related lead exposures • Most highly exposed sub-populations • Higher risks and greater risk reductions • Greater uncertainty associated with these estimates • Risk - Primary lead smelter case study • Risk somewhat similar to general urban case study • Risk - Secondary lead smelter case study • Lowest risk estimates

10. Next Steps • October, 2007 - Final Risk Assessment Report • November, 2007 - Policy Assessment • Staff Paper/ANPR • March, 2008 - Proposed Rule • Sept 1, 2008 - Final Rule