A HAPEM Update and Exposure Efforts in our Current Air Toxic Program Air Toxics Workshop II Air Toxics Research: Implications of Research on Policies to Protect Public Health Houston, TX June 12, 2007 Ted Palma,, USEPA, Office of Air Quality Planning and Standards, RTP, NC Chad Bailey USEPA, 2Office of Transportation and Air Quality, U.S. EPA, Ann Arbor, MI

Exposure Efforts in our Current Air Toxic Program Air Toxic Program transition from emission based towards risk based Initial program assessments are focusing on chronic cancer and non-cancer inhalation exposure We are also now beginning to look at acute & multimedia exposures Residual Risk Assessment Exposure and risk assessments at facility level to evaluate remaining risk after technology MACT standards implemented Need to determine both Maximum Individual Risk (MIR) and population exposure (human and ecological) Other National Rules MSAT - February 2007 National/Urban/Local Assessments National Air Toxic Assessment (NATA) City/Neighborhood scale exposure and risk assessments Personal monitoring studies

Overview of Exposure Models Simple HEM3 (Inhalation with no activity patterns) HAPEM6 (Inhalation with activity patterns) HHRAP (Multipathway tool) Complex APEX (Inhalation with activity patterns) SHEDS (Inhalation – ORD tool) TRIM.Fate TRIM.Expo Inhalation Ingestion

Human Exposure Model (HEM3) a tool that combines a dispersion model (ISCST or AERMOD) with 2000 census data to predict population exposure Model does NOT account for human activity pattern Assumes everyone lives at census block centroid for entire exposure period Exploring residency times (less than 70 year) Being utilized in current Residual Risk Assessments Latest version released May 2007 on FERA

What is The Hazardous Air Pollutant Exposure Model (HAPEM)? Screening-level exposure model Long-term inhalation exposures General population, or a specific sub-population Urban to national scale Version 5 HAPEM5 - Exposure model component of the 1999 National Air Toxics Assessment (NATA) Version 6 (release January 2007) HAPEM6 - Mobile Source Air Toxic Rule includes near roadway effects

Overview of HAPEM Six primary sources of information Population data (model supplied) 2000 census for 6 demographic groups at the tract level (66,301 tracts) nationwide (also PR and VI) Activity Data (model supplied) CHAD Microenvironmental (ME) Data (model supplied) Tract-to-tract commuting probability data derived from 2000 census commute file (model supplied) Residence and Workplace relationship to roadway data (model supplied) Near major roadway residential/business file developed nationally for each census tract – 75m and 200m from 4 lane roadway Air Quality Data (user supplied)

Plans for HAPEM Updates Census block and block group resolution Seasonal and monthly air quality Fix random seeds (for sensitivity and reproduction) Regulatory Uses NATA Community Scale projects Criteria Reviews?

Air Pollutant Exposure Model (APEX) Refined inhalation exposure modeling Used to model both criteria and air toxics at urban scale Acute to chronic exposures User selects number and types of microenvironments to be included, selection of time period of interest, use of either monitored ambient data or values provided from dispersion model Models individuals (instead of cohorts) that meet population profile Sub-Census tract resolution; accepts point estimates or distributions for most inputs; includes temperature variation across study area; can build lifetime exposure profile Can use either a mass balance approach or ME factor based approach to estimate indoor or in-vehicle concentrations Programmers and Users Guide Case Study available Runs on PC Available on FERA

TRIM.FaTE (Fate, Transport & Ecological Exposure) TRIM.Risk (Risk Characterization) Farm Food Chain Quantitative risk & exposure characterization, U/V, assumptions, limitations, … FaTE Library Physical/chemical properties,algorith ms, site-specific data, etc. Exposure Input Files (e.g., Activity data, population data, microenvironments, etc) HH Tox Database human health dose- response assessment values (e.g., RfC, URE) Eco Tox Database Ecological effects assessment values EcoHH MULTI-MEDIA IMPACTS Ingestion Inhalation TRIM.Expo (Human Exposure Event) AIR-only IMPACTS AQ Model (CMAQ, ISC, etc) or AQ Data HAPEM [Inhalation Risk][Ingestion Risk][Eco Risk] HH Criteria Pollutant Database Human health dose-, concentration-, and exposure- response functions Total Risk Integrated Methodology (TRIM) {for epi-based assessment}

Comparison Of Inhalation Exposure To Ambient Air Quality Levels

th 95th 25th 75th Median Metals Gases Mixtures 1999 NATA National HAPEM5 to ASPEN Ratios

Summary – HAPEM5 to ASPEN Ratios HAPEM5 exposure concentrations generally lower then ASPEN ambient concentrations Typically ratio (HAPEM5/ASPEN) : for gaseous pollutants for particulate pollutants for gas/particles (mixed) pollutants Can vary across source category because of proximity factor Some ratios greater than 1.0 for on-road sources

Examples of the Effects of Commuting On Exposure Levels

Estimated Reductions in Ambient Benzene Levels (Year 2020, Without-CAAA Minus With-CAAA Scenario)

Estimated Reductions in Benzene Exposure (HAPEM ) (Year 2020, Without-CAAA Minus With-CAAA Scenario)

Summary - Effects of Commuting on Exposure Concentrations Overall exposure pattern: Commuting increases exposure levels in suburbia tracts Exposures accounted for in “home” tract Overall exposure magnitude: Greatest HAPEM to ASPEN ratios in “clean” tracts

Capturing Near-Roadway Exposure Concentration Enhancement with HAPEM6

(after Zhu et al. 2002) Near-Roadway Concentration Enhancement

Ratio of Near-Roadway-to- Remote Concentration

Near-Roadway Effects on Population Risks