Total TRI releases
Total TRI releases at San Mateo County have more than three-quarters since 2010 (through 2024).
County · TRI 2024
San Mateo County, California Pollution
5 top TRI facilities tracked here. PM2.5 annual mean (NAAQS 9 µg/m³ (annual)) rose meaningfully year over year (+17%). PM2.5 annual mean (NAAQS 9 µg/m³ (annual)) concentrations have more than halved since 2010.
FIPS 06081 · population 754,250
Anomaly engine
Notable Signals
Top facilities mapped
Where Chemicals Are Released In San Mateo County
Each red dot is one of the top TRI facilities. Size reflects 2024 total releases. County boundary outlined in blue.
Pollutant pathways
San Mateo County 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 more than halved 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 more than halved 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 have fallen 21% since 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 have fallen 48% since 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) volumes here are too small to anchor a multi-year trend; YoY movement is still shown above.
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) volumes here are too small to anchor a multi-year trend; YoY movement is still shown above.
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 volumes here are too small to anchor a multi-year trend; YoY movement is still shown above.
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 have fallen 18% since 2010.
Top facilities · 2024
Where The Chemical Releases Are Concentrated
| Facility | City | Top chemical | Total releases | YoY |
|---|---|---|---|---|
| Chemelex LLCChemelex LLC | Redwood City | Zinc compoundsHealth riskGenerally low acute toxicity. Chronic high-dose exposure disrupts copper absorption and immune function. (ATSDR) | 420 lb | -33% |
| US Doe Slac National Accelerator LaboratoryUS Department Of Energy | Menlo Park | LeadHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR) | 9 lb | -54% |
| Granite Rock CO Redwood CityGranite Rock Co | Redwood City | BariumHealth 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) | 5 lb | -38% |
| Univar Solutions USAUnivar Solutions USA INC | Redwood City | Nitric acidHealth riskStrong corrosive irritant to skin, eyes, and the respiratory tract. (NIOSH) | 2 lb | -20% |
| CsbioCsbio | Menlo Park | AcetonitrileHealth riskMetabolizes to cyanide in the body; high exposure causes nausea, weakness, and respiratory effects. (ATSDR) | 1 lb | -78% |
Equity context · ACS 2018-2022 · USEPA-clone EJ disparity
Who Lives In San Mateo County
All block groups in San Mateo County County, CA: 754,250 residents. County disparity score for pm2.5 (fine particulate) sits moderately above the reference (114). Why we surface this →
6.4%
Low-income
63.0%
People of color
5.5%
Under age 5
16.9%
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.85in the highest 20% nationally
- OzoneHealth riskGround-level ozone (smog) inflames the airways. Even short exposures trigger asthma attacks and worsen chronic lung and heart disease.1below 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.51near 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.38below 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.27below 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.87in the highest 20% nationally
- 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.74above 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.64above the national median
- 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.28below 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.90in the highest 10% nationally
- 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.28below 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.76above the national median
| Indicator | Disparity score | Reading |
|---|---|---|
| PM2.5 (fine particulate) | 114 | moderately above the reference |
| Ozone | 4 | well below the reference |
| Nitrogen dioxide (NO₂) | 72 | below the reference |
| Diesel particulate | 55 | below the reference |
| Toxic releases (RSEI) | 36 | well below the reference |
| Traffic proximity | 113 | moderately above the reference |
| Lead-paint risk (pre-1960 housing) | 83 | below the reference |
| Superfund site proximity | 46 | well below the reference |
| RMP-facility proximity | 9 | well below the reference |
| Hazardous-waste site proximity | 117 | moderately above the reference |
| Underground storage tanks | 0 | well below the reference |
| NPDES wastewater proximity | 89 | below the reference |
| Drinking-water non-compliance | 0 | well below the reference |
Source: Census ACS 2018-2022 (5-year) + USEPA-clone EJ blockgroup stats (raw indicators + EJ disparity mirror).
Health context
Co-Located Health Indicators
Modeled adult-prevalence estimates published by CDC PLACES, paired with this county's pollution and demographic context. Comparisons are ecological, not causal — pollution and disease prevalence covary at the area level, but the data does not attribute any individual's diagnosis to local exposure. How this section works →
Adult asthma (current)
8.5%
CDC PLACES · 2025 release · BRFSS 2022-2023
COPD prevalence
4.0%
CDC PLACES · 2025 release · BRFSS 2022-2023
Coronary heart disease
5.2%
CDC PLACES · 2025 release · BRFSS 2022-2023
Diabetes (diagnosed)
10.6%
CDC PLACES · 2025 release · BRFSS 2022-2023
Frequent mental distress
13.1%
CDC PLACES · 2025 release · BRFSS 2022-2023
PLACES uses BRFSS-modeled small-area estimates, not individual records. Crude prevalence shown above is the local rate as published; comparators are age-adjusted vs the California mean and the US mean — both population-weighted across counties — so geographies with different age structures stay apples-to-apples. Sources: CDC PLACES · 2025 release · BRFSS 2022-2023.
Browse
All 18 San Mateo County Cities With TRI Data
Pollution trends and TRI 2024 pages for every tracked city in this county. Alphabetical.
- Belmont pollution· 0 facilities
- Brisbane pollution· 0 facilities
- Burlingame pollution· 0 facilities
- Daly City pollution· 0 facilities
- East Palo Alto pollution· 0 facilities
- Foster City pollution· 0 facilities
- Half Moon Bay pollution· 0 facilities
- Hillsborough pollution· 0 facilities
- La Honda pollution· 0 facilities
- Loma Mar pollution· 0 facilities
- Menlo Park pollution· 1 facility
- Millbrae pollution· 0 facilities
- Montara pollution· 0 facilities
- Pacifica pollution· 0 facilities
- Pescadero pollution· 0 facilities
- Redwood City pollution· 3 facilities
- San Bruno pollution· 0 facilities
- South San Francisco pollution· 0 facilities
Sources.
- EPA Toxics Release Inventory · retrieved 2026-05-07.
All sources are federal public-domain datasets under 17 USC §105. We aggregate but do not relabel; the underlying observations remain attributable to EPA.