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Region 2

Serving New Jersey, New York, Puerto Rico, US Virgin Islands and Eight Tribal Nations.

2005 National-Scale Air Toxics Assessment Results for the Region

Announcement

    *Note about effect of inaccuracies in facility emissions

    Where a facility is under investigation for under-reporting emissions, the NATA results should be viewed as possibly underestimating the risk resulting from emissions from that facility. In the vicinity of such a facility, the contribution of point sources to risk may be underestimated. The Tonawanda area is one such area in the Region. Monitoring data and recent EPA investigations have confirmed that emissions of certain toxic compounds are significantly higher than those reported in the 2005 emissions data base. Readers are advised to view the Tonawanda Community Air Quality Study for a more accurate assessment of risk in this area.

Contacts

EPA Region 2 Contact: Carol Bellizzi bellizzi.carol@epa.gov - (212) 637-3712

EPA Headquarters Contacts: For questions about the Assessment, Ted Palma palma.ted@epa.gov.  For questions about the emission inventory, Anne Pope pope.anne@epa.gov.

What is the National-Scale Air Toxics Assessment, NATA?

NATA is EPA’s estimate of cancer and noncancer risk nationwide resulting from inhalation of air pollutants identified in the Clean Air Act as "hazardous air pollutants" (HAPs) and often referred to as "air toxics."  These are screening-level risk estimates* that are available for all populations in Region 2. View a list of the pollutants addressed in 2005 NATA.

*Why is NATA considered a screening-level estimate?
NATA is a state-of-the-science screening tool that uses general information about sources to develop estimates of risks using analytical methods that are more likely to overestimate impacts than underestimate them.  It does not incorporate refined information about emission sources. Therefore, the NATA results are referred to as screening-level estimates.  NATA is not a refined assessment and is not used as the sole source of information leading to regulations or guiding the enforcement of existing rules.

How is the Assessment done?

Models are used to assess the impacts of emissions to outdoor air from sources of all types. To do this, EPA first prepares an inventory of emissions of HAPs nationwide and then models the impacts of the emissions. The resulting impacts are presented in terms of ambient (outdoor) air concentrations, inhalation exposure concentrations, and calculated cancer and noncancer risks resulting from that inhalation exposure. Summaries of the results are presented in tables and map overlays that may be downloaded as files from the Results page of the 2005 NATA web site. Some of the summaries are at the county level and others are at the census tract level. Many include statewide averages and nationwide averages as references.

The details of the inventory and modeling are provided throughout the 2005 NATA web site and in the Technical Methods Documents, both of which link to other EPA resource materials and data sets. This is a complex assessment involving numerous models and judgment in how to use them with available data. For this reason, we encourage exploration of the 2005 NATA web site even as we provide quick links to the Results page.

Four Steps: From Emissions to Risk

Risk is calculated in four steps (see: http://www.epa.gov/ttn/atw/nata2005/natafaq.html#A6). Briefly, they are as follows:

  1. EPA assembles an inventory of emissions of HAPs from stationary sources (point and nonpoint) and mobile sources (onroad and nonroad).
  2. Mathematical models estimate concentrations in ambient (outdoor) air and provide an impact concentration for each census tract nationwide.
  3. Based on these estimated ambient air concentrations and population information, another model calculates how much of the pollutants people are exposed to by inhalation. These are the exposure concentrations.
  4. Finally, the exposure concentrations are processed to provide risks from inhalation exposure to each pollutant individually, and risks from inhalation exposure to all pollutants simultaneously.

Additional contributions to outdoor air concentrations - Background concentrations and Secondary formation

In addition to impacts from direct emissions from U.S. sources to ambient air in the year 2005, there are also impacts from air toxics that are persistent in the environment (i.e., they remain in the air for a long time after they are emitted or formed), are transported to the impact location from areas more than 50 km (31 miles) away, or are emitted by natural (not man-made) sources. The concentrations from these air toxics are referred to as "background concentrations." Another contribution to impacts from the emissions sources comes from HAPs formed when other HAPs or non-HAP pollutants are emitted to the air and then transformed in the environment, e.g., they react with other chemicals or degrade when exposed to sunlight .  The amounts of the NATA HAPs that are expected in ambient air from such processes are referred to as "secondary formation" (also referred to as "atmospheric transformation"). For a more detailed explanation and examples of the different types of sources, please refer to the Technical Methods Document [PDF], Exhibit 2-1.

Limitations of the Assessment

2005 NATA estimates the impacts of 177 HAPs on the current list of 187 Clean Air Act HAPs, and diesel particulate matter (diesel PM). It includes the noncancer risk from diesel emissions, but not the cancer risk. While 2005 NATA addresses the impacts of almost all of the listed HAPs, it does not address risk from every air pollutant to which the general public may be exposed. For the 139 HAPs plus diesel PM for which risk estimates are provided, NATA addresses exposure via direct inhalation, not ingestion or dermal exposures from contact via water, food, and soil.  Also, it does not address emissions from every outdoor source, e.g., emissions from wildfires and Superfund site clean-ups. View a more complete list of limitations of the Assessment. Also see the FAQs at General Background Question 9 for a more complete list of what NATA does not address.

Where can I find the results of the Assessment?

The 2005 NATA Results page may be accessed from a link in the left margin of every 2005 NATA page. The files must be downloaded to be opened. The Readme file at the top of the Results page provides information about the content of each of the files in all but the last section. There is a separate file in the last section--the 2005 Google Earth Risk Maps--with instructions about use of those files.

With the exception of the map overlay files in the last section of the Results page, the Results files are summaries of the results in table form. The last section on that page--the Google Earth section--provides files that are map views of a synopsis of the results. These are files that, once downloaded and unzipped by responding to the prompts that pop up, can be opened in Google Earth to explore the 2005 NATA results at the census tract level. For each state, there is a zipped file that contains 4 files: 3 files for risk and 1 for point sources. With the file displayed in Google Earth, clicking on a location delivers a pop-up with information about the tract. See Results for where you live: Interactive maps in Google Earth for an example of what is displayed in the map views.

What do the 2005 NATA results show overall for Region 2?

Overview

For context, 2005 NATA is based on the year 2000 census, with a total U.S. population of 285,339,128 people in 66,089 census tracts. Of this total, 31,308,029 people, or 11.0% of the nationwide population, reside in Region 2. The distribution of this population is as follows: 60.6% in New York, 26.9% in New Jersey, 12.1% in Puerto Rico, and 0.3% in the U.S. Virgin Islands.

A census tract typically ranges in size from 1500 to 8000 people. Where population is very dense, the area covered by a tract is small. Tracts are larger in rural areas.  In Region 2, there is a census tract with a population of 24,523 and a tract that covers 3 blocks.  There are also three tracts with a population of zero; by definition, risk in these tracts is zero since no one lives there.  (This does not negate the impact of air in these tracts on people who live elsewhere but pass through the tracts.  This sort of scenario is captured in the exposure assessment modeling of Step 4 in the NATA process.)

About 13% of the Region’s population lives in census tracts where the cancer risk is predicted to be greater than 100 in a million. Of this 13%, 97% is in New York and 94% is in New York City. The cancer risk is for all types of cancer combined. Maps showing cancer risk results for Region 2. *Note that the dark brown color in these maps denotes tract-level cancer risk that is greater than 100 in a million. Color key for the map views.

Note: You may want to set the view option in your Acrobat Reader to zoom to a higher magnification to see greater detail in the pdf files.

Noncancer risk—that is, risk from effects other than cancer-- is provided in terms of a hazard index (HI). About 25% of the Region's population lives in census tracts where the noncancer risk is predicted to be at a HI greater than 5. Of this 25%, 90% is in New York, predominantly in New York City, and 10% is in New Jersey. All of the noncancer risk that is greater than a HI of 1 is from adverse health effects on the respiratory system. (The results show that the HI for adverse effects on the nervous system was less than 1 for every census tract in Region 2.) Maps showing respiratory risk results for Region 2. *Note that the dark brown color in these maps denotes tract-level respiratory risk that is greater than a HI of 5. Color key for the map views.

Note: You may want to set the view option in your Acrobat Reader to zoom to a higher magnification to see greater detail in the pdf files.

The HAPs contributing most to risk in Region 2 are as follows: benzene, formaldehyde, carbon tetrachloride, naphthalene, and acrolein.  Recall that the risk represented in the tables and maps of the 2005 NATA results does not include all pollutants to which the public is exposed from breathing air.  Notably, it does not include an estimate of cancer risk from diesel PM.  For further information about risks addressed and not addressed in the 2005 NATA, please see the Frequently Asked Questions section of the NATA website, especially General Background Questions 5 and 9, and Results Question 15.

In general, urban neighborhoods tend to have the highest cancer and noncancer risk due to the density of air toxic emissions from transportation and other population-driven activities. In Region 2, at the county level, point sources contribute little to the risk in the counties with the highest countywide average risks. In some locations, background concentrations contribute more than the modeled emissions to the risk results.

Charts

Here are some charts showing results for Region 2. They are based on results files downloaded from the 2005 NATA Results page.

Emissions source types

Point sources and nonpoint sources are stationary sources.
Point sources- tend to be larger facilities that emit higher amounts of air toxics. Emissions are associated with a particular location. 
Nonpoint sources- tend to be smaller and numerous like gasoline stations and dry cleaners. Emissions are not associated with a particular location.
Onroad mobile sources- cars, trucks, and other vehicles that are operated on roads and highways. 
Nonroad mobile sources- construction equipment, railroads, lawnmowers, and other equipment that is not operated on roads and highways.

About the countywide average risks charts showing contributions by source type
(Created from information provided in files available from the "2005 County-Level Modeled Ambient Concentrations, Exposures, and Risks" section of the 2005 Results page.)

Each set of results shows a total impact and the contributions to that total.  Where the contributions are by source type (also referred to as "source sector"), the contributions are provided in columns labeled Point, Nonpoint,, Onroad Mobile, Nonroad Mobile, Secondary, and Background.  Some, but not all, HAPs have background and/or secondary contributions. Further information about this is available in the Technical Methods Document.

How do I read numbers like 1E-06?
Throughout the files for the NATA results, you will see numbers expressed in scientific notation. The use of scientific notation facilitates presentation of very small and very large numbers. For example, a cancer risk of 1 in a million may be written as 1E-06; and 100 in a million may be expressed as 100E-06 or 10E-05 or, more correctly, 1E-04. If 1E-06 were written using only decimal numbers, it would be 0.000001.  For noncancer risk such as the respiratory hazard index, there are values greater than 1 as well as less than 1.  The same principles apply to reading those numbers.  E.g., 1.5E+00 is 1.5; 1.5E+01 is 15; and 1.5E-01 is 0.15.
Note: You may want to set the view option in your Acrobat Reader to zoom to a higher magnification to more easily read some of the pdf files.

About the pollutant contributions to statewide average risk charts
(Created from information provided in files available from the "2005 County-Level Modeled Ambient Concentrations, Exposures, and Risks" section of the 2005 Results page.)

 A small number of the 124 pollutants that reached the risk calculation step of NATA dominate the overall picture of risk in Region 2, and in the nation generally, at the level of statewide averages. These are referred to as "risk-drivers."  In preparing the charts below, only HAPs that contributed at least 1 in a million (1E-01) to statewide average cancer risk or at least 0.1 (1E-01) to statewide average noncancer risk in at least one of the Region 2 States were identified individually.  The "Other HAPs" class in the legends for the charts represents all the HAPs that were not statewide risk-drivers.

Analysis of NATA results conducted by the New Jersey Department of Environmental Protection
The New Jersey Department of Environmental Protection (NJDEP) conducts its own assessment of risk in New Jersey beginning with the modeled ambient concentration results from NATA. Note: NJDEP bases its risk assessment on ambient air concentrations while EPA employs the modeled exposure concentrations, the results of Step 3 of the 4-step NATA process. For more about this, visit NJDEP's Risk Results page. Also, NJDEP calculates cancer risk from diesel PM, while EPA does not. Learn more about NJDEP's calculation of cancer risks for diesel PM. Learn more about EPA's treatment of diesel PM carcinogenicity. Also see How are diesel PM health effects considered? on the Background on Risk Characterization page.

What else can I see using the files available from the 2005 NATA Results web page?

Results for where you live: Using the interactive maps in Google Earth
Pie chart of contributions to risk in a specific census tract by source type
Pie chart of contributions to risk in a specific census tract by groups within a source type

Note: The results are provided in various file formats, with the file type indicated in each download subsection of the Results page. To use the files, the following software is needed: Microsoft Access, Excel, Google Earth, and/or Adobe Reader, depending on which files you are using. To use the kmz files in Google Earth, you will also need to be connected to the Internet. For other files, once the files are downloaded to your computer, you will not need an Internet connection to work with them.

Complete information about the methods used in developing the 2005 NATA results and instructions on using the results are accessible by clicking through the pages and links beginning at the 2005 NATA top page.

Results for where you live: Using the interactive maps in Google Earth

Below are examples of the risk and point source summary information available in files that open and display in Google Earth. The key to the colors used in the NATA map files is available from the 2005 Results page, in the "2005 Google Earth Risk Maps" section, via the link to "instructions." The instructions also include what you will see as you download the map files. The instructions document may be accessed directly at http://www.epa.gov/ttn/atw/nata2005/05pdf/instructions_google_earth.pdf. The dark brown in the maps below signifies a modeled cancer risk of 100 in a million or higher.

Are there maps showing the locations of emissions from individual nonpoint sources and mobile sources?
No, only the point sources are associated with the specific locational information--latitude and longitude--needed to do such mapping.
Note: You may want to set the view option in your Acrobat Reader to zoom to a higher magnification to more easily read some of the pdf files.

To explore the 2005 NATA results further for where you live or any other location in the Assessment, first identify the census tract or group of tracts of interest.  The tract number is the key to locating summary results for the tract(s) of interest in the downloadable Microsoft Access files of tract-level results.  Refer to the Readme file near the top of the Results page for a list of the data fields in the Microsoft Access files. Note: NATA results should not be used independently to characterize or compare risk at local levels (e.g., between neighborhoods), nor should they be used to estimate risk for individuals or groups within a census block or to design control measures for specific emissions sources or pollutants.  More information about this is available in the Technical Methods Document (TMD), Section 1.5.

  1. With a risk results file open and active in Google Earth, you can type a location into the search window in Google Earth and then click on the location to see the census tract number for the location.
  2. Continuing to explore in Google Earth, the information you see in a pop-up when you click on a location will depend upon what layer you have active.  (Unclicking layers not in use will result in quicker redrawing of maps as you move the cursor for information about different locations.)  The NATA map overlay (kmz) files provide a numerical value for the risk (cancer, respiratory hazard index, or neurotoxicity hazard index, depending upon which layer is active in Google Earth) in the selected tract, along with a breakdown of contributions to risk by source type and then by pollutant.
  3. Once a tract of interest is identified, the tract can be found in a column of the database or spreadsheet files that provide more detail about the results.  These files are summaries that present the results with different levels and types of aggregation.  Most of the results are in Microsoft Access database files.  Some are in Microsoft Excel spreadsheet files.  Refer to the Readme file near the top of the Results page, Explanation of Data elements in NATA Results Tables, for a description and decode of the content of each datafield in these files.  See the next section for examples of data exploration using the Access and Excel files.
Pie chart of contributions to risk in a specific census tract by source type

An alternate graphical presentation of the contributions to risk in a specific census tract can be prepared using a table of nationwide risk results at the census tract level, available from the 2005 Results page in the section titled " 2005 Tract-Level Modeled Ambient Concentrations, Exposures, and Risks."  Here is an example [PDF 7 KB, 1 pp] of a pie chart for contributions to risk in a census tract in New York County, New York.

Pie chart of contributions to risk within a specific census tract by groups within a source type

To explore the nonpoint source contribution to risk, use the set of files on the 2005 Results page in the section titled "2005 Tract-Level Modeled Ambient Concentrations, Exposures, and Risks," in the subsection titled, "Nationwide, Tract-level Results."  The Nonpoint Risks file presents the contributions to risk from 27 groups of nonpoint sources. This section of the Results page also provides files for group contributions to Onroad Mobile Risks (2 groups) and Nonroad Mobile risks (7 groups). Here is an example [PDF 9 KB, 1 pp] of a pie chart showing contributions of nonpoint sources to cancer risk in the census tract. This tract was also used for the previous example.

Can I see the impacts of a particular nonpoint source, e.g., a gas station?

When exploring the impacts of certain types of emissions, it may not be possible to associate the impacts with a particular facility or operation, e.g., with a particular dry cleaner or gas station or port or construction project. This is the case for emissions modeled as nonpoint sources, as well as for emissions from onroad mobile sources and nonroad mobile sources. For these types of sources, emissions information is developed at the county level and is not available at a point-specific level. Because the model that provides ambient air concentrations begins with a point location, the emissions that are developed at the county level are distributed among the census tracts in the county, and then, at the tract level, are treated as if they are from a point at the geographic center of the tract--the census tract centroid. This intermediate step, occurring between steps 1 and 2 of the Assessment, is referred to as "spatial allocation." For these reasons, the impacts for nonpoint sources are best represented by the county-level of the 2005 NATA results, and considered less reliable at the census tract level. For further information, please refer to the Technical Methods Document.

The files that show contributions by groups of source categories within a source type allow a more detailed examination of the risk results. The group level is the most detailed level available for nonpoint results, as well as for mobile source results. More information about nonpoint source modeling is available in the Technical Methods Document (TMD).

 

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