Austin – Round Rock Toxics Study (ARTS)

Albert Hendler URS Corporation

June 13, 2007

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Contents

• Part 1 – ARTS Overview

• Part 2 – Comparison with 1999 NATA

• Part 3 – Source Apportionment

• Part 4 – Acrolein Measurements

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Part 1 – ARTS Overview

• Exploratory study of air toxics levels

• 83 common VOCs, carbonyls, and metals

• 5 sampling sites

• Every 12th day sampling

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Austin-Round Rock Quick Facts

• 2000 population estimate – 1.25 million

38th largest U.S. MSA

• Two largest counties, Travis and Williamson, ranked 85th and 376th in 1999 total NEI HAPS Emissions (among 1207 U.S. urban counties)

• Major source HAP emissions = 1% of total

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Data Uses

• Health risk assessment

• Source apportionment

• Evaluation of NATA results

• Baseline for trend analysis

• Benchmark for other cities

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Part 2 – Comparison with 1999 NATA

Compound

Travis Co. Average (ug/m3)

RatioARTS NATA

Acetaldehyde 1.42 1.48 1.04

Formaldehyde 2.83 1.67 0.59

1,3-butadiene 0.15 0.17 1.12

Benzene 1.18 1.61 1.36

Carbon Tetrachloride 0.66 0.27 0.41

Chloromethane 1.34 1.21 0.91

Dichloromethane 0.59 0.52 0.89

Tetrachloroethylene 0.19 0.25 1.31

Toluene 3.01 3.43 1.14

Total Xylene 1.77 2.17 1.23

• Better than a factor of 2 agreement at county level for most frequently detected VOCs and carbonyls

• Carbon tetrachloride and formaldehyde NATA estimates appear low

• Poor modeled-monitored agreement for acrolein

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• ARTS data estimated assuming ND = ½ DL

• NATA estimates driven mostly by background

• Strong agreement not expected

Monitored-Modeled (1999 NATA) Comparison – Travis County Averages for infrequently detected VOCs and Carbonyls

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Monitored-Modeled (1999 NATA) Comparison – Travis County Averages for frequently detected Metals

• Better than a factor of 2 agreement for lead, nickel and Cr6+

• Worse than a factor of 10 agreement for arsenic, cadmium, and cobalt

• Arsenic one of top 10 risk drivers based on monitoring data – comparatively unimportant based on NATA

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Top 10 Cancer Risk Drivers for Travis County from 1999 NATA and 2005-2006 ARTS

1999 NATA

2005-2006 ARTS

ND = 1/2 DL ND=0

Benzene 1,2-Dibromoethane Carbon tetrachloride

1,2-Dibromoethane Hexachloro-1,3-butadiene Benzene

1,3-Butadiene Carbon tetrachloride 1,3-Butadiene

Carbon tetrachloride Benzene Acetaldehyde

1,1,2,2-Tetrachloroethane 1,1,2,2-Tetrachloroethane Arsenic

Acetaldehyde Acrylonitrile p-Dichlorobenzene

Bis_2_ethylhexyl_phthalate 1,3-Butadiene Chloroform

Naphthalene Acetaldehyde Tetrachloroethylene

Tetrachloroethylene Arsenic 1,2-Dibromoethane

1,2-Dichloroethane p-Dichlorobenzene Hexachloro-1,3-butadiene

Bold type highlights 5 chemicals on all three lists

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Summary of Comparison with 1999 NATA

• Strong agreement between ARTS 2005-2006 monitoring results and 1999 NATA in terms of:

Estimated Concentrations for most frequently detected VOCs and carbonyls

Identification of key species

Estimated risks

• Formaldehyde and carbon tetrachloride NATA estimates appear low

• Wide range of variability in ARTS-NATA agreement for metals

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Part 3 – Source Apportionment

• One site – WETX – had a different VOC fingerprint than the other 4 ARTS sites

• Higher levels of VOC that are constituents of motor vehicle emissions were observed

• Source apportionment objective was to see if a MV source profile could be confirmed and its contribution to the measured benzene and other measured species quantified

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U.S. 2006 Average Benzene Levels from http://www.epa.gov/air/data/index.html

Webberville Rd. benzene average was greater than

80% of 335 averages for 2006 reported in AQS

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EPA Positive Matrix Factorization (PMF)

• Menu-driven source apportionment tool available for download at http://www.epa.gov/heasd/products/pmf/pmf.htm

• Uses temporal variability in measured concentrations and multi-pollutant relationships to infer source types and their contributions to the observed pollutant levels

Inputs are measured levels of multiple VOC, carbonyl, and/or PM chemical species over a long time series of sampling periods

Outputs are chemical source profiles and their estimated contributions to the observed levels

Model user or data analyst identifies source profiles based on key species

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Example of Source Profile Produced by PMF and Identified as Motor Vehicle Emissions

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Other Source Profile Produced by PMF

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Set of 6 Source Profiles Produced by PMF from ARTS VOC and Carbonyl Measurements

Source Profile No.

Description Key Species Key Months/Sites

1 Acrolein/MEK Acrolein, MEK Jun.-Sep./All sites

2 Toluene Toluene Mar.-Nov./RRTX

3 Motor Vehicle Emissions

Benzene, toluene, ethyl benzene, xylene, trimethylbenzene,

acetylene, propylene, butadiene

All months/WETX

4 Background Carbon tetrachloride, chloromethane,

dichlorofluoromethane, trichlorofluoromethane

All months/All sites

5 Secondary Aldehydes

Formaldehyde, acetaldehyde, Jun.-Sep./All sites

6 Undefined (possible

contaminant)

Ethyl benzene, MEK, styrene, xylene, MIBK

Jun.-Sep. 2005/All sites

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Relative Source Strengths by Site

Less than a factor of two variability in average source strengths between sites, except for an apparent toluene source impacting RRTX and motor vehicle emissions impacting WETX

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Reconstructed vs. Measured Benzene (R-Square = 0.87)

• Reconstructed Benzene (y-axis) is the sum of all the source contributions to a particular benzene measurement (x-axis)

• For the ARTS source apportionment, reconstructed benzene agreed reasonably well with the measurements

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Benzene Source Apportionment for Webberville Road (WETX)

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ARTS Sampling Sites and Major Roadways

WETX was the farthest of all ARTS sites from a major freeway

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Webberville Road Sampling Site

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Summary of Source Apportionment

• PMF produced 6 source profiles from the ARTS data set

• The greatest motor vehicle impact was detected for Webberville Road (WETX), where benzene levels averaged about 2x the other ARTS sites

• 79% of the benzene mass measured at WETX was attributed to motor vehicle emissions

• WETX was the farthest of all ARTS sites from a major freeway

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Part 4 – Acrolein Measurements

Analyte

2005-2006 Average Concentrations (μg/m3)

RfC (μg/m3)

Average Hazard

QuotientMUTX PITX RRTX TRTX WETX

Acrolein 3.73 2.51 4.60 2.58 3.77 0.02 172

Formaldehyde 2.78 2.85 3.26 2.98 2.72 9.8 0.30

Acetaldehyde 1.34 1.33 1.38 1.40 1.62 9 0.16

1,3-Butadiene 0.07 0.07 0.07 0.14 0.33 2 0.07

Manganese 0.00 0.01 0.01 0.01 0.01 0.05 0.12

1,2-Dibromoethane 0.10 0.10 0.10 0.11 0.10 0.8 0.13

Acrylonitrile 0.07 0.06 0.06 0.06 0.18 2 0.04

Benzene 0.94 0.80 0.98 1.11 1.88 30 0.04

1,2-Dichloropropane 0.08 0.08 0.09 0.08 0.08 4 0.02

Arsenic 0.00 0.00 0.00 0.00 0.00 0.03 0.02

Top 10 Non-Cancer Hazard Quotients

ARTS acrolein measurements exceeded the EPA RfC by more than 100 times

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U.S. 2005 Average Acrolein Levels from http://www.epa.gov/air/data/index.html

ARTS acrolein averages were the highest reported to EPA AQS in 2005

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Comparison of Monitored and Modeled (1999 NATA) Acrolein Estimates

ARTS acrolein averages exceeded 1999 NATA estimates by factors of about 20 to 60

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Acrolein Monitoring Method and Data Quality Indicators

• Measurements made using TO-15 (canister – GC/MS)

• Acceptable stability in canisters and recovery demonstrated by ERG

• Same method and lab used in 2005 and 2006 for the EPA Urban Air Toxics Monitoring Program

• Good measurement precision in ARTS for 13 of 16 collocated sample pairs

Acrolein Canister Duplicates Average RPD = 49% (N=16)

The data quality appears to be OK but…

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Acrolein Emissions Densities from the 1999 NEI

No known emission sources explain why the ARTS acrolein levels were the highest in the U.S.

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U.S. 2006 Average Acrolein Levels from http://www.epa.gov/air/data/index.html

In 2006, seven Indiana sites joined four ARTS sites to round out the top 10% of reported acrolein

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2006 Acrolein Averages from AQS

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1999 NATA County-Averaged Acrolein Estimates

NATA modeling of known emissions does not explain the Indiana measurements

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Acrolein/MEK Source Profile

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Acrolein Time Series

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Acrolein Follow Up Study – Summer 2007

• Collaborative effort between EPA, TCEQ, and CAPCOG

• Conducted by URS, ERG, UTSPH, and Czartech Analytical

• 3 measurement techniques TO-15

Modified TO-11A (DNPH) – Includes analysis of acrolein decay products

Dansylhydrazine (DNSH) passive sampler (Herrington et al, 2006)

• Field Duplicates

• Replicate analyses

• Through the probe field blanks and challenges

• Blind spiked QC samples

• Data quality assessments for accuracy and precision

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Acrolein Summary

• ARTS acrolein levels were among the highest reported to EPA AQS

• Very poor agreement with NATA estimates

• No known sources account for the measured levels or differences between Austin-Round Rock compared and most other urban sites

Similarly high levels measured in Indiana and Tulsa show the anomaly is not limited to central Texas

• Repeatability of measurements and reliability of measurement method to be tested in summer 2007

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Acknowledgements

• ARTS was sponsored by a grant from the U.S. EPA to the Capitol Area Council of Governments (CAPCOG) Kuenja Chung was the EPA Project Officer Mike Fishburn was the CAPCOG Project Manager Samples were analyzed by Eastern Research

Group (Julie Swift)

• The acrolein follow up study was designed by David Brymer, David Carmichael, and David Manis, TCEQ