State · TRI 2024
Montana Pollution
51 TRI facilities, 813 public water systems, and 19 Superfund / NPL sites across 22 counties. Statewide TRI releases fell meaningfully year over year (-21%). Toxic releases concentrations are roughly unchanged from 2010.
FIPS 30 · population 1,084,225 · 56 counties total
Where the burden sits
County-Level TRI Choropleth
A color-shaded map of pollution data. Darker counties report more pounds of toxic chemicals released to the EPA's Toxics Release Inventory (TRI).
Shaded by total reported releases for 2024. Counties without a published page render as “no TRI data”. Red dots mark this state's top emitters.
Statewide pollutant pathways
Montana Pollutant Multi-Year Trends
PM2.5 annual mean (NAAQS 9 µg/m³ (annual))Health riskFine inhalable particles 2.5 micrometers or smaller. They travel deep into the lungs and into the bloodstream — linked to asthma, heart disease, stroke, and premature death.
PM2.5 annual mean (NAAQS 9 µg/m³ (annual)) concentrations have fallen 43% since 2010.
PM2.5 24-hour 98th percentile (NAAQS 35 µg/m³ (24-hour))Health riskFine inhalable particles 2.5 micrometers or smaller. They travel deep into the lungs and into the bloodstream — linked to asthma, heart disease, stroke, and premature death.
PM2.5 24-hour 98th percentile (NAAQS 35 µg/m³ (24-hour)) concentrations have fallen 23% since 2010.
Ozone 8-hour 4th-highest daily max (NAAQS 0.070 ppm (8-hour))Health riskGround-level ozone (smog) forms when vehicle and industrial emissions react in sunlight. Inflames the airways, triggers asthma attacks, and worsens heart and lung disease.
Ozone 8-hour 4th-highest daily max (NAAQS 0.070 ppm (8-hour)) concentrations are roughly unchanged from 2010.
NO₂ annual mean (NAAQS 53 ppb (annual))Health riskA tailpipe and combustion gas. Concentrates near busy roads and industrial sites; raises risk of airway inflammation, asthma, and lower respiratory infections in children.
NO₂ annual mean (NAAQS 53 ppb (annual)) concentrations are roughly unchanged from 2010.
Lifetime cancer risk all pollutants (100 in a million (EPA elevated threshold))Health riskEPA-modeled added cancer cases per million residents from a lifetime of breathing local air toxics. EPA flags 100-in-a-million as elevated.
Single-vintage exposure modeling — EPA cadence is multi-year, so no trend line yet.
Formaldehyde ambient mean (0.077 µg/m³ (1-in-a-million URE))Health riskAn air toxic emitted by refineries, wood products, and combustion. EPA classifies it as a known human carcinogen — long-term inhalation raises cancer risk.
Single-vintage exposure modeling — EPA cadence is multi-year, so no trend line yet.
Benzene ambient mean (0.13 µg/m³ (1-in-a-million URE))Health riskAn air toxic from gasoline, refineries, and tobacco smoke. A known human carcinogen — chronic exposure is linked to leukemia and other blood cancers.
Single-vintage exposure modeling — EPA cadence is multi-year, so no trend line yet.
TRI air releases (5.1 fugitive + 5.2 stack)Health riskToxic chemicals reported by industrial facilities as released into the air — fugitive leaks plus smokestack emissions. Higher pounds means more inhaled exposure for nearby residents.
TRI air releases (5.1 fugitive + 5.2 stack) concentrations are roughly unchanged from 2010.
TRI water releases (5.3)Health riskToxic chemicals reported by industrial facilities as discharged to surface waters (rivers, lakes, the ocean). Affects fishing, recreation, and downstream drinking-water intakes.
TRI water releases (5.3) concentrations have fallen 47% since 2010.
TRI land + off-site releasesHealth riskToxic chemicals released to land on-site or transferred off-site for disposal — landfills, deep-well injection, and similar. Risks groundwater contamination over time.
TRI land + off-site releases concentrations are roughly unchanged from 2010.
Greenhouse gases (GHGRP large emitters, through 2023)Health riskGreenhouse gases reported by large industrial emitters under EPA's GHGRP, in metric tons of CO₂ equivalent. Drives climate warming and the heat-related health effects that follow.
Greenhouse gases (GHGRP large emitters, through 2023) concentrations are roughly unchanged from 2010.
| County | Population | Facilities | Total releases | YoY | Top chemical |
|---|---|---|---|---|---|
| Silver Bow CountyFIPS 30093 | 35,306 | 3 | 31.7M lb | -21% | Manganese And Manganese CompoundsHealth riskExcess inhalation can cause manganism, a Parkinson-like neurological disorder. (ATSDR) |
| Rosebud CountyFIPS 30087 | 8,310 | 1 | 6.7M lb | -29% | Barium And Barium CompoundsHealth riskSoluble barium compounds are toxic if ingested, affecting the heart, kidneys, and nervous system. Insoluble forms (e.g. barium sulfate) are far less toxic. (EPA) |
| Stillwater CountyFIPS 30095 | 8,978 | 3 | 842k lb | +15% | Nickel And Nickel CompoundsHealth riskNickel compounds are IARC Group 1 carcinogens; inhalation exposure raises lung and nasal cancer risk. (IARC) |
| Yellowstone CountyFIPS 30111 | 165,524 | 12 | 808k lb | +17% | AmmoniaHealth riskSevere respiratory and eye irritant; high concentrations cause chemical burns to lung tissue. (EPA) |
| Cascade CountyFIPS 30013 | 84,423 | 2 | 644k lb | +58% | MethanolHealth riskAcutely toxic if ingested or inhaled. Metabolizes to formaldehyde and formic acid, causing blindness and metabolic acidosis. (EPA) |
| Sweet Grass CountyFIPS 30097 | 3,697 | 1 | 374k lb | -9% | Nickel compoundsHealth riskNickel compounds are IARC Group 1 carcinogens; inhalation exposure raises lung and nasal cancer risk. (IARC) |
| Flathead CountyFIPS 30029 | 105,950 | 3 | 149k lb | +7% | MethanolHealth riskAcutely toxic if ingested or inhaled. Metabolizes to formaldehyde and formic acid, causing blindness and metabolic acidosis. (EPA) |
| Big Horn CountyFIPS 30003 | 13,090 | 2 | 114k lb | -0% | Barium And Barium CompoundsHealth riskSoluble barium compounds are toxic if ingested, affecting the heart, kidneys, and nervous system. Insoluble forms (e.g. barium sulfate) are far less toxic. (EPA) |
| Broadwater CountyFIPS 30007 | 6,977 | 2 | 91k lb | +53% | Lead And Lead CompoundsHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR) |
| Jefferson CountyFIPS 30043 | 12,273 | 2 | 57k lb | -23% | Lead compoundsHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR) |
| Facility | City | Top chemical | Total releases | YoY |
|---|---|---|---|---|
| Montana Resources LLC | Butte | Manganese And Manganese CompoundsHealth riskExcess inhalation can cause manganism, a Parkinson-like neurological disorder. (ATSDR) | 31.7M lb | -21% |
| Colstrip Steam Electric StationTalen Energy CORP | Colstrip | Barium And Barium CompoundsHealth riskSoluble barium compounds are toxic if ingested, affecting the heart, kidneys, and nervous system. Insoluble forms (e.g. barium sulfate) are far less toxic. (EPA) | 6.7M lb | -27% |
| Smc Nye Mine SiteStillwater Mining Co | Nye | Nickel And Nickel CompoundsHealth riskNickel compounds are IARC Group 1 carcinogens; inhalation exposure raises lung and nasal cancer risk. (IARC) | 835k lb | +15% |
| Big Sky Scientific L.L.C. | Sun River | MethanolHealth riskAcutely toxic if ingested or inhaled. Metabolizes to formaldehyde and formic acid, causing blindness and metabolic acidosis. (EPA) | 558k lb | +98% |
| Stillwater Mining CO East Boulder MineStillwater Mining Co | Big Timber | Nickel compoundsHealth riskNickel compounds are IARC Group 1 carcinogens; inhalation exposure raises lung and nasal cancer risk. (IARC) | 374k lb | -9% |
| Chs INC. Laurel RefineryChs INC | Laurel | Nitrate compounds (water dissociable; reportable only when in aqueous solution)Health riskDrinking-water nitrate causes methemoglobinemia ('blue-baby syndrome') in infants; EPA MCL is 10 mg/L as N. (EPA) | 298k lb | +63% |
| Par Montana Billings RefineryPar Pacific Holdings INC | Billings | Sulfuric acid (acid aerosols including mists, vapors, gas, fog, and other airborne forms of any particle size)Health riskAcid mists are an IARC Group 1 carcinogen via inhalation (laryngeal cancer) and corrosive on contact. (IARC) | 184k lb | +16% |
| Weyerhaeuser NrWeyerhaeuser Co | Columbia Falls | MethanolHealth riskAcutely toxic if ingested or inhaled. Metabolizes to formaldehyde and formic acid, causing blindness and metabolic acidosis. (EPA) | 149k lb | +7% |
| Jupiter Sulphur LLCTessenderlo Kerley INC | Billings | AmmoniaHealth riskSevere respiratory and eye irritant; high concentrations cause chemical burns to lung tissue. (EPA) | 146k lb | +24% |
| Hardin Generating StationRocky Mountain Power LLC | Hardin | Barium And Barium CompoundsHealth riskSoluble barium compounds are toxic if ingested, affecting the heart, kidneys, and nervous system. Insoluble forms (e.g. barium sulfate) are far less toxic. (EPA) | 114k lb | -0% |
Water utilities to watch
Largest Water Systems With Unresolved Health-Based Violations
Sorted to surface utilities serving the most people that still have an active health-based SDWIS violation on the record. Systems in compliance with no unresolved issues fall to the bottom of the ranking.
| Water system | PWSID | Population served | Health-based · 5yr | Status |
|---|---|---|---|---|
| Havre City Of Municipal | MT0000524 | 9,921 | 10 | UNRESOLVED |
| Miles City City Of Municipal | MT0000291 | 9,565 | 10 | UNRESOLVED |
| Libby City Of Municipal | MT0000274 | 4,892 | 10 | UNRESOLVED |
| Colstrip City Of Municipal | MT0000180 | 2,350 | 6 | UNRESOLVED |
| East Helena City Of Municipal | MT0000196 | 2,114 | 1 | UNRESOLVED |
| Virginia City Water Dept Municipal | MT0000353 | 1,500 | 9 | UNRESOLVED |
| Whitehall Town Of Municipal | MT0000359 | 1,500 | 65 | UNRESOLVED |
| Boulder City Of Municipal | MT0000158 | 1,400 | 2 | UNRESOLVED |
| Philipsburg Town Of Municipal | MT0000304 | 1,360 | 30 | UNRESOLVED |
| Chinook City Of Municipal | MT0000174 | 1,300 | 11 | UNRESOLVED |
Superfund / NPL sites
Federal Cleanup Sites In Montana
Sites on EPA's Superfund National Priorities List, plus deleted sites whose cleanup objectives EPA has finalized. Federal-facility sites (defense, DOE, etc.) are flagged separately. Each link routes to a per-site page.
| Site | City | Status | Federal facility | Primary contaminant |
|---|---|---|---|---|
| Acm Smelter And Refinery | Black Eagle | NPL FINAL | No | — |
| Anaconda Aluminum Co Columbia Falls Reduction Plant | Columbia Falls | NPL FINAL | No | AluminumHealth riskInhaled aluminum fumes can cause lung scarring (aluminosis); high cumulative exposure has been linked to neurological effects. (NIOSH) |
| Anaconda Co. Smelter | Anaconda-Deer Lodge County | NPL FINAL | No | LeadHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR) |
| Barker Hughesville Mining District | Monarch | NPL FINAL | No | — |
| Basin Mining Area | Basin | NPL FINAL | No | AluminumHealth riskInhaled aluminum fumes can cause lung scarring (aluminosis); high cumulative exposure has been linked to neurological effects. (NIOSH) |
| Billings Pce | Billings | NPL FINAL | No | — |
| Carpenter Snow Creek Mining District | Neihart | NPL FINAL | No | ArsenicHealth riskIARC Group 1 carcinogen via inhalation and ingestion. EPA MCL 10 µg/L; chronic exposure causes skin, lung, bladder cancer and cardiovascular disease. (IARC, EPA, ATSDR) |
| East Helena Site | East Helena | NPL FINAL | No | LeadHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR) |
| Flat Creek Imm | Superior | NPL FINAL | No | AntimonyHealth riskInhaled antimony trioxide is an IARC Group 2B possible carcinogen; respiratory and cardiovascular effects from long-term exposure. EPA MCL 6 µg/L. (IARC, EPA) |
| Idaho Pole Co. | Bozeman | NPL FINAL | No | 2,3,7,8-Tetrachlorodibenzo-P-Dioxin (Tcdd) |
Showing the top 10 sites by status priority. 9 additional NPL-relevant sites in Montana have entity pages — browse them via the host-county or host-city page rollups.
Equity context · ACS 2018-2022 · USEPA-clone EJ disparity
Statewide Population Characteristics
All Montana block groups: 1,084,225 residents. Statewide disparity score for pm2.5 (fine particulate) sits well below the reference (14). Why we surface this →
State-level percentiles are aggregated from block-group EJScreen data. The EJ pattern within the state will be sharper at the county level — drill down for the meaningful spatial detail.
12.4%
Low-income
15.4%
People of color
5.8%
Under age 5
19.4%
Over age 64
- PM2.5 (fine particulate)Health riskFine inhalable particles 2.5 micrometers or smaller. They travel deep into the lungs and into the bloodstream — linked to asthma, heart disease, stroke, and premature death.7below the national median
- OzoneHealth riskGround-level ozone (smog) inflames the airways. Even short exposures trigger asthma attacks and worsen chronic lung and heart disease.13below the national median
- Nitrogen dioxide (NO₂)Health riskA tailpipe and combustion gas. Concentrates near busy roads and industrial sites; raises risk of airway inflammation, asthma, and lower respiratory infections in children.39below the national median
- Diesel particulateHealth riskSoot from diesel engines (trucks, trains, ports, construction). EPA classifies it as a likely human carcinogen and a major driver of childhood asthma near freight corridors.15below the national median
- Toxic releases (RSEI)Health riskEPA's Risk-Screening Environmental Indicators score — weights TRI chemical releases by toxicity, where they go, and how many people are nearby. Higher means greater modeled cancer and chronic-health risk.50near the national median
- Traffic proximityHealth riskPopulation-weighted distance to high-volume roads. Living close to heavy traffic raises exposure to PM2.5, NO₂, and diesel exhaust — and the cardiovascular and asthma risks that follow.29below the national median
- Lead-paint risk (pre-1960 housing)Health riskShare of housing built before 1960, when lead-based paint was common. Dust from deteriorating paint is the leading cause of childhood lead poisoning, which permanently impairs cognitive development.61above the national median
- Superfund site proximityHealth riskPopulation-weighted distance to NPL Superfund sites — the most contaminated waste sites in the country. Nearby groundwater, soil, and air can carry industrial solvents, metals, and other long-lived contaminants.90in the highest 20% nationally
- RMP-facility proximityHealth riskDistance to facilities holding chemicals at quantities large enough to require an EPA Risk Management Plan (refineries, fertilizer plants, etc.). These pose acute exposure risk during accidental releases.42near the national median
- Hazardous-waste site proximityHealth riskDistance to RCRA hazardous-waste handlers (treatment, storage, disposal facilities). Indicates potential exposure to industrial chemicals in air, soil, and groundwater.43near the national median
- Underground storage tanksHealth riskDensity of underground tanks (gasoline, heating oil, industrial fluids). Leaking tanks are a leading source of benzene and other volatile organic compounds in groundwater drinking-water supplies.79above the national median
- NPDES wastewater proximityHealth riskDistance to permitted industrial wastewater dischargers. Closer proximity raises exposure to pollutants released into surface waters used for fishing, recreation, and downstream drinking-water intakes.85in the highest 20% nationally
- Drinking-water non-complianceHealth riskEPA score for public water systems with health-based Safe Drinking Water Act violations. Higher means more residents on systems that recently exceeded safe limits for contaminants like lead, arsenic, or nitrate.86in the highest 20% nationally
| Indicator | Disparity score | Reading |
|---|---|---|
| PM2.5 (fine particulate) | 14 | well below the reference |
| Ozone | 48 | well below the reference |
| Nitrogen dioxide (NO₂) | 41 | well below the reference |
| Diesel particulate | 19 | well below the reference |
| Toxic releases (RSEI) | 24 | well below the reference |
| Traffic proximity | 23 | well below the reference |
| Lead-paint risk (pre-1960 housing) | 47 | well below the reference |
| Superfund site proximity | 37 | well below the reference |
| RMP-facility proximity | 18 | well below the reference |
| Hazardous-waste site proximity | 27 | well below the reference |
| Underground storage tanks | 50 | well below the reference |
| NPDES wastewater proximity | 41 | well below the reference |
| Drinking-water non-compliance | 13 | well below the reference |
Source: Census ACS 2018-2022 (5-year) + USEPA-clone EJ blockgroup stats (raw indicators + EJ disparity mirror). EJ disparity scores via the USEPA-clone GitHub mirror after EPA deprecated the public EJScreen tool in 2025; demographics from Census ACS.
Browse
All 22 Montana Counties With TRI Data
Pollution trends and TRI 2024 pages for every tracked county. Alphabetical.
- Big Horn County pollution· 2 facilities
- Broadwater County pollution· 2 facilities
- Cascade County pollution· 2 facilities
- Dawson County pollution· 1 facility
- Deer Lodge County pollution· 1 facility
- Flathead County pollution· 3 facilities
- Gallatin County pollution· 3 facilities
- Glacier County pollution· 1 facility
- Jefferson County pollution· 2 facilities
- Lewis and Clark County pollution· 2 facilities
- Lincoln County pollution· 1 facility
- Missoula County pollution· 4 facilities
- Ravalli County pollution· 2 facilities
- Richland County pollution· 1 facility
- Rosebud County pollution· 1 facility
- Sanders County pollution· 1 facility
- Sheridan County pollution· 1 facility
- Silver Bow County pollution· 3 facilities
- Stillwater County pollution· 3 facilities
- Sweet Grass County pollution· 1 facility
- Toole County pollution· 2 facilities
- Yellowstone County pollution· 12 facilities
Sources.
- EPA Toxics Release Inventory · retrieved 2026-05-07.