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PETITIONED PUBLIC HEALTH ASSESSMENT

NEWTOWN COMMUNITY
GAINESVILLE, HALL COUNTY, GEORGIA


APPENDIX E: ENVIRONMENTAL PROTECTION AGENCY'S CUMULATIVE EXPOSURE PROJECT (NATIONWIDE MODELING)

The Cumulative Exposure Project (CEP) air modeling is very different from the Agency for Toxic Substance and Disease Registry (ATSDR) model discussed above for a number of reasons. First of all, the CEP estimates were developed through a national modeling study of the 1990 emissions of 148 air pollutants in each census tract in the continental United States. ATSDR's modeling only examined the chemicals emitted from the TRI, AIRS/AFS, or state air compliance files, which totaled 25 air pollutants within 4 miles of the community. Also, the CEP estimates used a long-range air transport model to model concentrations from 100 meters (328 feet) to 50 kilometers (31 miles) from a emissions source. ATSDR's modeling used a short-range air transport model with receptors adjacent to the sources and up to 4 miles away. Additionally, the CEP results are reported for each census tract, which means that the concentrations throughout the census tract have been summarized over the census tract. The ATSDR modeling results are at a larger scale allowing details within a census tract to be available. Also important is that the CEP model included the breakdown, deposition, and creation of the pollutants in the atmosphere.

Finally, the CEP model includes the following six sources: (1) manufacturing point sources (e.g., chemical manufacturing, refineries, primary metals); (2) nonmanufacturing point sources (e.g., electric utility generators, municipal waste combustors); (3) manufacturing area sources (e.g., wood products manufacturing, degreasing); (4) nonmanufacturing area sources (e.g., dry cleaning, consumer products, small medical waste incinerators); (5) onroad mobile sources (e.g., cars, buses, trucks); and (6) non-road mobile sources (e.g., farm equipment, airplanes, boats, lawn equipment). ATSDR's modeling included only those facilities required to report to the TRI database or regulated under the Clean Air Act. These facilities include facilities from the first three categories and some facilities from the a part of the fourth category. A significant difference is that CEP included mobile sources and ATSDR did not. Detailed information about CEP is available from EPA at http://www.epa.gov/cumulativeexposure/index.htm .

The Cumulative Exposure Project data for the census tract containing the Newtown Community is presented in Table 2 along with the results from the air monitor. Any comparison between the 1990 CEP model results and the 1997 air monitoring data should be viewed cautiously because the data are from two different years.

The air concentrations for each census tract in Hall County were converted to a cancer and noncancer risk. This conversion is explained in Appendix G. Figures 4 and 5 show the areal distribution of the cancer risks and the noncancer hazard index, respectively in each census tract. These figures also show the components of the cancer risk and noncancer hazard index. The predominant chemicals contributing to cancer risk are 1,3-butadiene, benzene, carbon tetrachloride, chloroform, and formaldehyde. For the noncancer hazard index, acrolein is the predominant chemical. The predominant source of acrolein is from the breakdown from 1,3-butadiene.

ATSDR evaluated the CEP air concentrations and cancer and noncancer risks by evaluating the contributing sources of hazardous air pollutants in Hall County. The CEP study divided the contaminant sources into the following 6 general groups:

  • Metal and non-metal manufacturing point sources (excluding combustion sources). These data were obtained through the TRI and AIRs/AFS database.

  • Municipal waste combustors (MWC). These are facilities that incinerate municipal waste. There were no municipal waste combustors in Hall County in 1990.

  • Treatment, Storage and Disposal Facilities (TSDFs). These are facilities that treat, long-term store, or dispose of hazardous waste. There were no hazardous waste treatment, storage, or disposal facilities (TSDFs) in Hall County in 1990.

  • Refineries of oil. There were no refineries in Hall County in 1990.

  • Other point sources. These sources include large (greater than 100 tons/year of total emissions) manufacturing combustion sources such as coal, oil, and natural gas-fired utility boilers used to generate steam or heat, coke ovens, and all other point source combustion sources not included it the MWC and TSDF groups.

  • Area manufacturing and area non-manufacturing sources (excludes TSDFs). In general, areas sources are facilities with emissions of all criteria pollutants (nitrogen oxides, sulfur dioxide, volatile organic compounds, total suspended particulates, and carbon monoxide) less than 100 tons per year. Facilities emitting 100 tons per year or greater are considered point sources. There are several different categories for these sources (see the table below).

Types of manufacturing and non-manufacturing sources and examples

Type of source Example of source
Stationary source fuel combustion small boilers and heaters burning fossil fuels to generate heat or steam
Aircraft unpaved airstrips airplane emissions not located at a typical airport
Industrial processes chemical manufacturing, food and kindred products, secondary metal production, petroleum refining, wood products, rubber and plastics
Solvent utilization surface coating such as painting, degreasing, dry cleaning, graphic arts, consumer products, and other solvent usage categories too small and/or numerous to be treated as point sources
Storage and transport of petroleum and petroleum products gasoline
Waste disposal, treatment and recovery such as waste incineration (municipal residential, or commercial/institutional), open burning on-site or at dumps, wastewater treatment, and landfills
Miscellaneous area sources such as agricultural field burning, managed/ prescribed burning, forest wildfires, structure fires, oil and gas production, construction, gasoline service stations, on-site incineration, open burning, and wastewater treatment
On-road mobile sources cars, buses, and trucks
Off-road mobile sources gasoline-powered equipment, such as lawn and garden equipment, generators, gasoline-powered offroad motorcycles and recreational boats, diesel-powered construction and farm equipment, aircraft, railroads, commercial boats, and coal and oil-powered commercial boats


Table 1. EPA's cumulative exposure project (CEP) modeling results for the census tract containing the Newtown Community, as compared to measured values

Chemical CEP Model-1990
(µg/m3)
Measured-1997 (µg/m3) Comments
Upper Value Lower Value Mean
Toluene

6.70024

7.2 1.2 2.46 Modeled concentration within range of measured
Benzene

2.81887

2.6 0.1 1.1 Modeled concentration close to range of measured concentration. The range of CEP modeled results overlaps the measured range.
Methylene Chloride

2.78056

46.9 1.2 3.5 Modeled concentration within range of measured
Hexane

1.43689

4.3 0.0707 2.06 Modeled concentration within range of measured
Chloromethane

1.24877

1.4 0.707 0.824 Modeled concentration within range of measured
Tetrachloroethylene

1.13149

<2.4 <2.4 <2.4 Compound was not detected in air samples. Modeled value is below detection limit.
Carbon Tetrachloride

1.01525

<2.19 <2.19 <2.19 Compound was not detected in air samples. Modeled value is below detection limit.
Isooctane

1.00253

1.8 0.0707 0.957 Modeled concentration within range of measured
Methyl Isobutyl Ketone

0.95087

<12.2 <12.2 <12.2 Compound was not detected in air samples. Modeled value is below detection limit.
Trichloroethylene

0.93847

<1.91 <1.91 <1.91 Compound was not detected in air samples. Modeled value is below detection limit.
Chloroform

0.53558

<1.7 <1.7 <1.7 Compound was not detected in air samples. Modeled value is below detection limit.
Ethyl Benzene

0.43483

1.56 0.1 1.42 Modeled concentration within range of measured
1,2-dichloroethane

0.23384

<1.41 <1.41 <1.41 Compound was not detected in air samples. Modeled value is below detection limit.
Naphthalene

0.13965

0.07 0.000212 0.0235  
1,4-dichlorobenzene

0.04381

<2.12 <2.12 <2.12 Compound was not detected in air samples. Modeled value is below detection limit.
Styrene

0.04174

0.9 0.0707 0.39 Modeled concentration within range of measured
Bromomethane

0.03900

<1.34 <1.34 <1.34 Compound was not detected in air samples. Modeled value is below detection limit.
Cumene (Isopropylbenzene)

0.02784

<0.0707 <0.0707 <0.0707 Compound was not detected in air samples. Modeled value is below detection limit.
Chlorobenzene

0.01947

<1.63 <1.63 <1.63 Compound was not detected in air samples. Modeled value is below detection limit.
1,2-dibromoethane

0.00769

<2.69 <2.69 <2.69 Compound was not detected in air samples. Modeled value is below detection limit.
1,1,2-trichloroethane

0.00308

<1.91 <1.91 <1.91 Compound was not detected in air samples. Modeled value is below detection limit.
Lead

0.00270

0.017 0.00219 0.00579 Modeled concentration within range of measured
Manganese

0.00235

0.022 0.00041 0.00914 Modeled concentration within range of measured
Hexachlorobutadiene

0.00181

7.5 1.06 3.8 CEP underestimated hexachlorobutadiene.
Nickel

0.00113

0.0028 0.000919 0.00135 Modeled concentration within range of measured
Selenium

0.00064

0.22 0.019 0.0808 CEP underestimated selenium
Chromium

0.00026

0.0062 0.00032 0.00265  
Hexachlorocyclohexane, Gamma-

0.00025

0.0000283 0.0000212 0.0000222  
Arsenic

0.00017

0.018 0.002 0.00529  
Hexachlorobenzene

0.00009

0.0000566 0.0000354 0.0000441  
Cadmium

0.00008

0.0042 0.00017 0.000647  
Cobalt

0.00003

0.0023 0.0008 0.00135  
Vinyl Chloride

0.00002

<0.919 <0.919 <0.919 Compound was not detected in air samples. Modeled value is below detection limit.
Chloroethane

0.00002

<0.919 <0.919 <0.919 Compound was not detected in air samples. Modeled value is below detection limit.
Beryllium

1.12E-06

0.0017 0.0001 0.000581  
1,2-dichloropropane

1.05E-06

<1.63 <1.63 <1.63 Compound was not detected in air samples. Modeled value is below detection limit.
1,1,2-trichloroethane

5.4587

      Not sampled for.
Mek Total

4.2403

     
Glycol Ethers

1.8511

     
Carbonyl Sulfide

1.2300

     
Formaldehyde

1.0129

     
Methyl Tert-butyl Ether

0.9392

     
Acetaldehyde Total

0.7832

     
Methanol

0.6692

     
Ethylene Glycol

0.3180

     
Dimethyl Formamide

0.2624

     
Propionaldehyde Total

0.1977

     
Polycyclic Organic Matter

0.1744

     
1,3-butadiene

0.1392

     
Acrolein

0.1346

     
Phenol

0.1001

     
Cyanide Compounds

0.0793

     
Phosgene Total

0.0647

     
Cresol Total

0.0640

     
Carbon Disulfide

0.0477

     
1,3-dichloropropene

0.0387

     
Bromoform

0.0212

     
Hydrochloric Acid

0.0138

     
Methyl Iodide

0.0116

     
Hexachloroethane

0.0048

     
Mercury Compounds

0.0016

     
Ethylene Oxide

0.0015

     
Dibutylphthalate

0.0014

     
Bis(2-ethylhexyl)phthalate

0.0014

     
Hydrofluoric Acid

0.0013

     
Methylene Diphenyl Diisocyanate

0.000562

     
Polychlorinated Biphenyls

0.000377

     
Propylene Oxide

0.000367

     
Phthalic Anhydride

0.000106

     
Antimony Total

0.000038

     
Vinyl Acetate

0.000028

     
Chloroprene

0.000016

     
Acrylonitrile

0.000012

     
Chlordane

0.000010

     
Ethyl Acrylate

0.000006

     
Maleic Anhydride

0.000003

     
Epichlorohydrin

0.000001

     
Methyl Methacrylate

0.000001

     
Pcdd/pcdfs

1.55e-08

     
Biphenyl

2.71e-11

     
Other compounds at zero        

Theoretical Non-Cancer Hazard Index From Exposure to 1990 Modeled Ambient Annual Average Air Concentrations in Hall County, Georgia by Census Tract
Figure 1. Theoretical Non-Cancer Hazard Index From Exposure to 1990 Modeled Ambient Annual Average Air Concentrations in Hall County, Georgia by Census Tract

Theoretical Cancer Risk From Exposure to 1990 Modeled Ambient Annual Average Air Concentrations in Hall County, Georgia by Census Tract
Figure 2. Theoretical Cancer Risk From Exposure to 1990 Modeled Ambient Annual Average Air Concentrations in Hall County, Georgia by Census Tract

Cumulative Exposure Project - 1990 -- Emissions of Key Air Contaminants by Emissions Category
Figure 3. Cumulative Exposure Project - 1990 -- Emissions of Key Air Contaminants by Emissions Category

Theoretical Cancer Risk From Exposure to 1990 Modeled Ambient Annual Average Air Concentrations in the State of Georgia
Figure 4. Theoretical Cancer Risk From Exposure to 1990 Modeled Ambient Annual Average Air Concentrations in the State of Georgia

Theoretical Non-Cancer Hazard Index From Exposure to 1990 Modeled Ambient Annual Average Air Concentrations in the State of Georgia
Figure 5. Theoretical Non-Cancer Hazard Index From Exposure to 1990 Modeled Ambient Annual Average Air Concentrations in the State of Georgia

Theoretical Cancer Risk of Select Cities
Figure 6. Theoretical Cancer Risk of Select Cities

Theoretical Non-Cancer Hazard Index of Selecte Cities
Figure 7. Theoretical Non-Cancer Hazard Index of Selecte Cities


APPENDIX F: ENVIRONMENTAL PROTECTION AGENCY NATIONAL AIR TOXIC ASSESSMENT (NATIONWISE MODELING)

NATA

The National Air Toxics Assessment (NATA) model is similar to the CEP model but differs in three ways:

  • Only 33 air toxics were modeled. These 33 toxic air pollutants are a subset of the 188 toxic air pollutants for which EPA must develop emissions standards and a subset of the 148 pollutants modeled in CEP. The 33 were selected based on a number of factors, including toxicity-weighted emissions, monitoring data, past air quality modeling analysis, and a review of existing risk assessment literature.

  • The emissions inventory used to estimate concentrations for 1996 is much improved over the 1990 data used in the CEP. It is based on extensive state and local input and includes specific information (exact locations and emission characteristics) about many more sources than did the inventory used in the CEP.

  • Air concentrations were estimated at the county level instead of the census tract level in the CEP.

*See Appendix E for specific information about the CEP model, which is similar methodology to the NATA model.

Table 1. Comparison of EPA's National Air Toxic Assessment (NATA) to modeled and measured values

Chemical NATA Model-1996 (µg/m3) Measured-1997 (µg/m3) Comments
Upper Value Lower Value Mean
Methylene chloride

0.299596

46.9 1.2 3.5  
1,2-Dibromoethane

0.007701

<2.69 <2.69 <2.69 Compound was not detected in air samples. Modeled value is below detection limit.
Tetrachloroethylene

0.186958

<2.4 <2.4 <2.4 Compound was not detected in air samples. Modeled value is below detection limit.
1,1,2,2-Tetrachloroethane

5.55E-05

<2.4 <2.4 <2.4 Compound was not detected in air samples. Modeled value is below detection limit.
Carbon tetrachloride

0.880182

<2.19 <2.19 <2.19 Compound was not detected in air samples. Modeled value is below detection limit.
Trichloroethylene

0.100483

<1.91 <1.91 <1.91 Compound was not detected in air samples. Modeled value is below detection limit.
Chloroform

0.084145

<1.7 <1.7 <1.7 Compound was not detected in air samples. Modeled value is below detection limit.
1,2-Dichloropropane

1.33E-05

<1.63 <1.63 <1.63 Compound was not detected in air samples. Modeled value is below detection limit.
1,2-Dichloroethane

0.061058

<1.41 <1.41 <1.41 Compound was not detected in air samples. Modeled value is below detection limit.
Benzene

1.137856

2.6 0.1 1.1 Modeled concentration within range of measured
Vinyl chloride

0.000157

<0.919 <0.919 <0.919 Compound was not detected in air samples. Modeled value is below detection limit.
Manganese

0.000822

0.022 0.00041 0.00914 Modeled concentration within range of measured
Lead

0.000207

0.017 0.00219 0.00579  
Arsenic

3.01E-05

0.018 0.002 0.00529  
Chromium

0.000186

0.0062 0.00032 0.00265  
Nickel

0.000721

0.0028 0.000919 0.00135 Modeled concentration within range of measured
Cadmium

1.19E-05

0.0042 0.00017 0.000647 Not sampled for.
Be

6.85E-06

0.0017 0.0001 0.000581
Hexachlorobenzene

9.3E-05

5.66E-05 3.54E-05 4.41E-05
Formaldehyde

0.85395

     
Acrolein

0.086668

     
1,3-Butadiene

0.049752

     
1,3-Dichloropropene

0.03898

     
Polycyclic Organic Matter

0.021966

     
Ethylene Oxide

0.002564

     
Mercury Compounds

0.001571

     
7-PAH

0.000829

     
Polychlorinated Biphenyls

0.00038

     
Acrylonitrile

0.000176

     
Quinoline

6.3E-07

     
Hydrazine

1.85E-07

     
Coke Oven Emissions

0

     

National Air Toxics Assessment - 1996 -- Theoretical Cancer Risk
Figure 1. National Air Toxics Assessment - 1996 -- Theoretical Cancer Risk

National Air Toxics Assessment - 1996 -- Theoretical Non-Cancer Hazard Index
Figure 2. National Air Toxics Assessment - 1996 -- Theoretical Non-Cancer Hazard Index


APPENDIX G: EXPLANATION OF THE DIFFERENCES BETWEEN AND LIMITATIONS OF MODELING DATA AND AIR MONITORING DATA

Advantages of Air Sampling

Air sampling using conventional equipment has the advantages of producing data that produces "real" results, i.e., "real" in the sense that the mix of chemicals identified actually existed in the air at the location and time the sample was taken. Moreover, this mix of chemicals was the result of many different sources. Conventional equipment is defined here as fixed stationary samplers with samples collected by drawing air through a filter or tube and the filter and tube analyzed at a later time for the chemicals collected. Although the sample is considered "real", there are several disadvantages in the sampling procedure:

  • The advantage of sampling substances arising from many and varied sources prevents the correlation of a air sample to a single facility. Sources not pertinent to the investigation could cause interference with the interpretation of the results. For instance, air samples collected near idling buses may have higher concentrations of chemicals in diesel exhaust.

  • Sampling results are based on conditions at the time of the sampling event. These conditions include the meteorological conditions and the amount and rates the chemicals were released. These conditions could be an extreme low or high condition and not representative of average conditions. Conversely, samples are collected over a period of time, several hours to 12 hours, consequently, the result would average out short term small and large transient chemical concentrations.

  • Air sampling is expensive and takes a long time to obtain representative results.

Air dispersion modeling are mathematical equations that predict (simulate or model) the movement of chemicals in the air. This movement is also called dispersion since the chemicals disperse after they are released into the air. The mathematical equations are put into a computer program for ease of use. Data needed for these air dispersion models include weather data and the amount of pollutants released to the air over time. So, where air monitoring shows a "real" result, the mathematical equations of the model produces one result at each specified location that must be adjusted for this error range. Limitations of the models also include the availability of representative meteorological data and amount and release data of pollutants.

On the other hand, we identify four advantages:

  • Models can be used to estimate a substance's concentration 24 hours a day for any time period for which both emissions and meteorological data exits.

  • Models can be used to estimate the level of various substances existing in the ambient air as a result of emissions from a single source or multiple sources.

  • Models can average short-term fluctuations in emissions and meteorological conditions, resulting in a long-term average.

  • Models can estimate a substances' concentration at an unlimited number of locations


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