Every American breathes a mix of dozens of cancer-causing chemicals every day — and the dose differs by neighborhood. This interactive map shows the EPA-modeled lifetime cancer risk from breathing hazardous air pollutants for every populated census tract in the United States, based on the 2020 AirToxScreen assessment. Click any tract to see which pollutants and which source categories are driving the risk in that specific community.
Nationally, the population-weighted average is roughly 30.2 excess cancer cases per million people exposed over a 70-year lifetime. But the range across census blocks is enormous — from under 5 in a million in the most isolated rural areas to more than 2000 in a million in the highest-exposed blocks. 4,658 census blocks across 51 states (covering 44,240 residents) have estimated cancer risk above EPA’s “presumptively acceptable” benchmark of 100 in a million.
What the colors mean
The map’s choropleth shows excess lifetime cancer cases per one million people from inhaling hazardous air pollutants over 70 years of continuous exposure. The brighter the red, the higher the modeled risk. EPA uses 100 in a million as a “presumptively acceptable” upper bound when looking at combined hazardous air pollutant exposure, and 1 in a million as a benchmark for “negligible” risk from any single pollutant.
The dropdown above the map lets you switch between total cancer risk and individual source categories — on-road vehicles, off-road equipment (construction, rail, marine), stationary industrial facilities, wildfire smoke, distributed nonpoint sources, biogenic emissions, secondary atmospheric formation, and long-range regional background. This is where the map gets useful as a diagnostic: the same cancer-risk number can have very different causes in different parts of the country.
The 10 states with the highest average air-toxics cancer risk
Average lifetime cancer risk from inhaled hazardous air pollutants, population-weighted across every census block in the state. Click a state’s name to see its tract-level map and per-county breakdown.
| Rank | State | Population | Avg cancer risk (per million) | Blocks above 100 per million | Largest source |
|---|---|---|---|---|---|
| 1 | Oregon | 4,237,256 | 43.2 | 1,569 | Secondary atmospheric formation |
| 2 | District of Columbia | 689,545 | 40.1 | 0 | Secondary atmospheric formation |
| 3 | California | 39,538,223 | 36.1 | 936 | Secondary atmospheric formation |
| 4 | Georgia | 10,711,908 | 35.5 | 0 | Secondary atmospheric formation |
| 5 | Louisiana | 4,657,757 | 34.9 | 227 | Secondary atmospheric formation |
| 6 | Alabama | 5,024,279 | 34.0 | 3 | Secondary atmospheric formation |
| 7 | Missouri | 6,154,913 | 33.6 | 113 | Secondary atmospheric formation |
| 8 | Tennessee | 6,910,840 | 33.2 | 111 | Secondary atmospheric formation |
| 9 | Maryland | 6,177,224 | 32.9 | 4 | Secondary atmospheric formation |
| 10 | Texas | 29,145,505 | 32.4 | 583 | Secondary atmospheric formation |
The 10 states with the lowest air-toxics cancer risk
| Rank | State | Population | Avg cancer risk (per million) | Blocks above 100 per million |
|---|---|---|---|---|
| 1 | Hawaii | 1,455,271 | 16.2 | 0 |
| 2 | Wyoming | 576,851 | 16.4 | 0 |
| 3 | South Dakota | 886,667 | 19.4 | 0 |
| 4 | Montana | 1,084,225 | 19.5 | 0 |
| 5 | North Dakota | 779,094 | 20.5 | 0 |
| 6 | Maine | 1,362,359 | 20.9 | 0 |
| 7 | Vermont | 643,077 | 21.5 | 0 |
| 8 | Utah | 3,271,616 | 21.9 | 14 |
| 9 | New Mexico | 2,117,522 | 22.7 | 50 |
| 10 | Wisconsin | 5,893,718 | 22.9 | 2 |
The pollutants driving US air-toxics cancer risk
AirToxScreen tracks more than 60 individual hazardous air pollutants. A small handful account for the great majority of population-weighted cancer risk nationally — though local rankings can look very different in industrial corridors or near specific point sources.
| Rank | Pollutant | National avg risk (per million) | Share of US average |
|---|---|---|---|
| 1 | Formaldehyde | 19.1 | 63.5% |
| 2 | Carbon tetrachloride | 2.9 | 9.6% |
| 3 | Acetaldehyde | 1.8 | 6.0% |
| 4 | Benzene | 1.5 | 5.0% |
| 5 | Naphthalene | 1.4 | 4.6% |
| 6 | PAHs and POMs | 1.1 | 3.7% |
| 7 | Ethylene oxide | 0.8 | 2.5% |
| 8 | 1,3-butadiene | 0.6 | 2.0% |
| 9 | Inorganic arsenic | 0.1 | 0.4% |
| 10 | Hexavalent chromium | 0.1 | 0.4% |
Where US air-toxics cancer risk comes from
Population-weighted national breakdown of cancer risk by source category. The dominant contributor isn’t industrial smokestacks — it’s a mix of vehicle exhaust, off-road equipment, and atmospheric secondary formation of formaldehyde from other pollutants.
| Source category | National avg risk (per million) | Share of US average |
|---|---|---|
| Secondary atmospheric formation | 16.8 | 55.9% |
| Distributed area sources (cooking, oil and gas, wood smoke) | 3.7 | 12.2% |
| Long-range regional background | 2.9 | 9.6% |
| Biogenic / vegetation | 1.8 | 6.1% |
| On-road vehicles | 1.4 | 4.6% |
| Off-road engines and equipment | 1.3 | 4.3% |
| Stationary industrial facilities | 1.1 | 3.6% |
| Wildfire smoke | 1.0 | 3.3% |
Browse air-toxics cancer risk by state
Each state has its own page with tract-level mapping, county rankings, the pollutants and source categories driving risk in that state, and the highest-exposed individual census blocks.
- Alabama
- Alaska
- Arizona
- Arkansas
- California
- Colorado
- Connecticut
- Delaware
- District of Columbia
- Florida
- Georgia
- Hawaii
- Idaho
- Illinois
- Indiana
- Iowa
- Kansas
- Kentucky
- Louisiana
- Maine
- Maryland
- Massachusetts
- Michigan
- Minnesota
- Mississippi
- Missouri
- Montana
- Nebraska
- Nevada
- New Hampshire
- New Jersey
- New Mexico
- New York
- North Carolina
- North Dakota
- Ohio
- Oklahoma
- Oregon
- Pennsylvania
- Rhode Island
- South Carolina
- South Dakota
- Tennessee
- Texas
- Utah
- Vermont
- Virginia
- Washington
- West Virginia
- Wisconsin
- Wyoming
About the data
Source data: EPA’s AirToxScreen 2020 assessment, the agency’s nationwide screening-level model of cancer and respiratory risk from inhalation exposure to hazardous air pollutants. AirToxScreen replaced the older National Air Toxics Assessment (NATA), which was last updated with 2014 emissions data. The 2020 version uses block-level resolution and includes source-category attribution for every modeled chemical.
The map you’re looking at aggregates the underlying census-block data to the census tract using population-weighted averaging — so the color of each tract reflects the average exposure for the people who actually live there, not a simple average of block values. Tracts with no population are not shown. National figures cover 51 states and the District of Columbia, 331,439,330 residents, 83,845 census tracts, and 5,769,602 populated census blocks.
Important context for interpreting the map
- This is modeled risk based on emissions inventories and atmospheric dispersion modeling, not direct measurement of pollutants. EPA runs continuous air monitoring at a small number of sites for calibration; for most blocks the values are modeled.
- It is inhalation cancer risk only. It does not include cancer risk from drinking water contaminants, occupational exposures, food residues, or non-cancer respiratory and neurological effects of the same chemicals.
- It reflects outdoor ambient air. People spend the majority of their time indoors, where concentrations of many of these chemicals are typically higher due to indoor sources (cooking, off-gassing from furniture and building materials, attached garages, etc.).
- It uses 2020 emissions data. Facility closures, fleet electrification, regulatory changes, and major industrial incidents since then are not captured.
- The “presumptively acceptable” 100-in-a-million benchmark is a regulatory screening threshold, not a safety threshold. Risks below 100 are still real risks worth knowing about.
