Update on US EPA Activities Blood Lead Level
Update on US EPA Activities: Blood Lead Level and IEUBK Model TRW Lead Committee State Risk Assessors Teleconference July 21, 2015
Background • There is no safe level of lead in a child’s body • Prior to 2012, CDC identified 10 µg/d. L or more of lead in a child’s blood as a “level of concern” – 10 µg/d. L was the basis for Superfund’s soil lead risk reduction goal • CDC’s 2012 recommendation for blood lead levels in children cut in half the blood lead reference value to 5 µg/d. L – OSWER and the TRW Lead Committee are evaluating the impacts to the Superfund program and the need for updates to EPA’s Integrated Exposure Uptake Biokinetic (IEUBK) model – Other EPA offices are also evaluating CDC’s recommendation for impacts to their programs
Current Policy • PRG of ~400 ppm at lead sites, determined based on the IEUBK using default exposure parameters and no more than 5% probability of exceeding 10 µg/d. L for 0 -84 month child • Existing directives (1994 and 1998) established 400 ppm as soil screening level for lead – Recommend site-specific study of risks – Levels of contamination above the screening level do NOT automatically require action – In practice, 400 ppm has been used as a cleanup level at many sites • A change in the health goal would likely reduce the PRG or screening level
Where are we? • No more than 5% probability of exceeding 10 µg/d. L remains the soil lead policy • Continue to evaluate the IEUBK Model • Need to coordinate across the Agency • Some success in reducing average blood lead levels below 5 µg/d. L • Use of site-specific information should become routine – Including site-specific IVBA • • Need to prioritize sites with greatest risk Importance of background, especially urban background May need greater flexibility in risk management to achieve health goals Five years reviews conducted according to existing guidance
Proposed Updates to IEUBK Model Variables Variable and Current Default Value(s) Proposed Default Values Basis for Proposed Values Ventilation rate 2– 7 m³/day (age-specific) 3. 22– 8. 89 m³/day (age-specific) Energy expenditure from Institute of Medicine’s doubly-labeled water dataset and equations developed (Brochu et al. 2006 and Layton, 1993) to convert metabolic energy to inhalation rates Maternal Blood Lead Concentration 1 µg/d. L 0. 8 µg/d. L Bioavailability 60% RBA Water Consumption 0. 2– 0. 59 L/day (age-specific) 0. 4– 0. 63 L/day (age-specific) Kahn and Stralka, 2009 (All Water Sources, Consumers Only) ~2. 7– 6. 0 µg/day (age-specific) New FDA food residue information and NCI food consumption analysis Dietary lead exposure ~2– 2. 3 µg/day (age-specific) NHANES Analysis of the full data set and a conservative policy decision Water Lead Concentration 4 ppb 0. 9 ppb Population-weighted estimate from Office of Water 6 -year lead and copper rule data set Transfer of outdoor soil to indoor dust (MSD) 0. 7 Analysis is progress; Likely a range of 0. 3 -0. 7 Information from Bunker Hill Superfund Site in Idaho Soil & Dust Ingestion Rate IRSD) IRSD is Age-specific; 85 -135 mg/day Analysis in progress: (Preliminary information suggests ~62 mg/day) Information from Bunker Hill Superfund Site in Idaho Health Goal Level of Concern 10 ug/dl To be determined ACCLP “Low Level Lead Exposure Harms Children: A Renewed Call of Primary Prevention”
Bioavailability 14% Lead PRG (P 10 of 5%) 61% 88% Observed Soil Lead RBA Average and 5 -95% CI Expressed as Percent (Excluding Firing Ranges)
Soil Ingestion Rate • The ingestion rate for soil and dust (IRSD) is being studied by US EPA Region 10 (RARE grant) – Analysis of Bunker Hill data specifying all IEUBK model variables except for IRSD and solving for IRSD using a measured blood lead concentration – Ongoing research • The mean default soil ingestion rate in the IEUBK model is currently 109 mg/day (average across age ranges) – Preliminary information from the Bunker Hill study suggests a lower value may be appropriate – Manuscript has been submitted for publication to peer-reviewed journal • After publication, additional discussion is needed to determine how the results will be used in determining a estimate of soil-dust ingestion rates that are appropriate for children across the US
Ongoing Activities to Promote Best Science and National Consistency • “Guidance for Sample Collection for In Vitro Bioaccessibility for Lead (Pb) in Soil” • Update the Residential Sites Handbook • Emphasize Site-Specific Data Collection for use in the IEUBK Model • Draft Supplemental Guidance – – In vitro Assay SOP for Lead Bioaccessibility Blood Lead Survey Guidance Assessing Risks for Acute Exposure Scenarios IEUBK Model Training Video • US EPA and ATSDR are collaborating to develop the All Ages Lead Model – Currently in beta testing – Likely many years from becoming an EPA risk assessment tool
Discussion • To what extent are you hearing questions from communities and/or PRPs? • What downsides do you see in using site-specific data to determine cleanup levels more commonly at SF sites? • What supplemental guidance or other information would you like to see from the TRW Lead Committee?
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