Lead NAAQS Review: 2 nd 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/m 3, quarterly average 1980s-90 – First lead NAAQS review –Criteria Document – 1986, with 1990 supplement –Staff Paper – Dec 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/m 3 to 2 ug/dL blood –Primary NAAQS μg/m 3 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/m 3 –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/m 3 ) 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, Final Risk Assessment Report November, Policy Assessment –Staff Paper/ANPR March, Proposed Rule Sept 1, Final Rule