1996 National Air Toxics Assessment Exposure and Risk Data
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
IMPORTANT: These data are provided for those who wish to do their own technical analyses and comparisons using the most refined output available from this national-scale assessment. In performing such analyses, it is extremely important that users be mindful of the purposes for which the national-scale assessment was developed. In our judgment, it would be inappropriate to use these results alone to draw conclusions about local concentrations and risk. The results are most meaningful when viewed at the State or national level. There are important limitations that affect how the data should be used and interpreted. These limitations are related to gaps in emissions data, limitations in the computer models used, default assumptions in the risk assessment and limitations in the overall design of the assessment (intended to address some questions but not others). Please see the limitations section of this website for more details. All data are in Microsoft Excel spreadsheets that have been zipped. Even zipped, the files are very large and may have extended download times.
Individual Pollutant Results of the Exposure Characterization at the Census Tract Level
| Pollutant |
CAS # |
SOROAD # |
File Download |
| 1,3-Butadiene |
106990 |
43218 |
 |
| Formaldehyde |
50000 |
43502 |
|
| Acetaldehyde |
75070 |
43503 |
|
| Acrolein |
107028 |
43505 |
|
| Ethylene Oxide |
75218 |
43601 |
|
| Acrylonitrile |
107131 |
43704 |
|
| Methylene Chloride |
75092 |
43802 |
|
| Chloroform |
67663 |
43803 |
|
| Carbon Tetrachloride |
56235 |
43804 |
|
| Ethylene Dichloride |
707062 |
43815 |
|
| Perchloroethylene |
127184 |
43817 |
|
| Tricholorethylene |
79016 |
43824 |
|
| Ethylene Dibromide |
106934 |
43837 |
|
| Propylene Dichloride |
78875 |
43838 |
|
| Vinyl Chloride |
75014 |
43860 |
|
| Benzene |
71432 |
45201 |
|
| 1,3-Dichloropropene |
542756 |
80152 |
|
| Hexachlorobenzene |
118741 |
80183 |
|
| Hydrazine |
302012 |
80188 |
|
| POM(total) |
N/A |
80230 |
|
| PCBS |
1336363 |
80231 |
|
| Quinoline |
91225 |
80239 |
|
| 1,1,2,2,-TCA |
79345 |
80246 |
|
| Arsenic Compounds |
N/A |
82103 |
|
| Beryllium Compounds |
N/A |
82105 |
|
| Cadmium Compounds |
N/A |
82110 |
|
| Chromium Compounds |
N/A |
82112 |
|
| Lead Compounds |
N/A |
82128 |
|
| Manganese Compounds |
N/A |
82132 |
|
| Nickel Compounds |
N/A |
82136 |
|
| Mercury Compounds |
N/A |
82142 |
|
| Coke Oven Emissions |
N/A |
80411 |
|
| Diesel PM |
N/A |
80400 |
|
Aggregate Results of the Risk Characterization at the Census Tract Level
| Cancer Risk |
|
| Non-Cancer Respiratory Irritation Risk |
|
Individual Pollutant Results of the Exposure Characterization at the County/State Level
| Pollutant |
CAS # |
SOROAD # |
File Download |
| 1,3-Butadiene |
106990 |
43218 |
|
| Formaldehyde |
50000 |
43502 |
|
| Acetaldehyde |
75070 |
43503 |
|
| Acrolein |
107028 |
43505 |
|
| Ethylene Oxide |
75218 |
43601 |
|
| Acrylonitrile |
107131 |
43704 |
|
| Methylene Chloride |
75092 |
43802 |
|
| Chloroform |
67663 |
43803 |
|
| Carbon Tetrachloride |
56235 |
43804 |
|
| Ethylene Dichloride |
707062 |
43815 |
|
| Perchloroethylene |
127184 |
43817 |
|
| Tricholorethylene |
79016 |
43824 |
|
| Ethylene Dibromide |
106934 |
43837 |
|
| Propylene Dichloride |
78875 |
43838 |
|
| Vinyl Chloride |
75014 |
43860 |
|
| Benzene |
71432 |
45201 |
|
| 1,3-Dichloropropene |
542756 |
80152 |
|
| Hexachlorobenzene |
118741 |
80183 |
|
| Hydrazine |
302012 |
80188 |
|
| POM(total) |
N/A |
80230 |
|
| PCBS |
1336363 |
80231 |
|
| Quinoline |
91225 |
80239 |
|
| 1,1,2,2,-TCA |
79345 |
80246 |
|
| Arsenic Compounds |
N/A |
82103 |
|
| Beryllium Compounds |
N/A |
82105 |
|
| Cadmium Compounds |
N/A |
82110 |
|
| Chromium Compounds |
N/A |
82112 |
|
| Lead Compounds |
N/A |
82128 |
|
| Manganese Compounds |
N/A |
82132 |
|
| Nickel Compounds |
N/A |
82136 |
|
| Mercury Compounds |
N/A |
82142 |
|
| Coke Oven Emissions |
N/A |
80411 |
|
| Diesel PM |
N/A |
80400 |
|
Aggregate Results of the Risk Characterization at the County/State Level
| Cancer Risk |
|
| Non-Cancer Risk |
|
Q: Why don't the nationwide cumulative cancer risk estimates in the table of county risk levels match the maps on this website? The table on this page shows a median nationwide upper bound cancer risk levels of about 50 in a million, but the map indicates the 50th percentile cumulative risk level is only about 30 in a million.
A: In the table, the percentiles shown for each county reflect the risks of all the census tracts in the county, and the nationwide percentiles at the top of the table reflect all the census tracts in the US -- not the county medians. In contrast, the map legend reflects the percentiles for the county medians, not the individual tracts. The reason the nationwide median of county risks is different from the nationwide median for tract risks is that different counties contain vastly different numbers of census tracts. Furthermore, counties with larger numbers of tracts tend to be urban (and therefore higher-risk). All these high-risk tracts get represented on the map only by a single county median. In the other extreme, some rural counties have only a one census tract, and that single tract's risk therefore represents an entire county. For this reason, the median of county risks is much more influenced by rural census tracts -- and is correspondingly lower -- than the median of census tract risks.
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