A HAPEM Update andExposure Efforts in our Current Air Toxic Program

Air Toxics Workshop IIAir Toxics Research: Implications of Research on Policiesto Protect Public Health

Houston, TX

June 12, 2007

Ted Palma,, USEPA, Office of Air Quality Planning and Standards, RTP, NCChad 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 LibraryPhysical/chemical properties,algorithms, 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 effectsassessment values

EcoHH

----- MULTI-MEDIA IMPACTS -----

IngestionInhalation

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

1.0

0.8

0.6

2.0

5th

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) :

1.0-0.8 for gaseous pollutants0.6-0.4 for particulate pollutants0.7-0.6 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

0.0

0.2

0.4

0.6

0.8

1.0

0 1 2 3 4 5 6 7 8

Ratio

Cu

mu

lativ

e P

rob

ab

ility

0 to 75 meters:median = 2.5

75 to 200 meters:median = 1.6

Near-Roadway Effects on Population Risks

Benzene Risks - Nationwide

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

100,000,0004.

0E-0

4

3.0E

-04

2.0E

-04

1.0E

-04

9.0E

-05

8.0E

-05

7.0E

-05

6.0E

-05

5.0E

-05

4.0E

-05

3.0E

-05

2.0E

-05

1.0E

-05

9.0E

-06

8.0E

-06

7.0E

-06

6.0E

-06

5.0E

-06

4.0E

-06

3.0E

-06

2.0E

-06

1.0E

-06

9.0E

-07

8.0E

-07

Population > than risk bin

Po

pu

lati

on

HAPEM6

HAPEM5