# Presentation: 645132

## Lead NAAQS Review:2nd Draft Risk Assessment

- NTAA/EPA Tribal Air Call
- August 8, 2007
- Deirdre Murphy and Zachary Pekar
- OAQPS

## 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

## 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

## 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

## 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

## 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

**Notes:**
Non-air less clear near current or historic “sources”

## 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

## 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

## 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

## Next Steps

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