Nitrogen dioxide (NO₂) in your home: a safety profile
High risk for your homeInhalation is the only relevant exposure route. NO₂ is a strong oxidant; upper airway scrubbing removes a substantial fraction, but ~25–30% penetrates to the bronchioles and alveoli. Acute high-dose exposure (>2 ppm): tracheobronchitis and pulmonary edema; occupational silo gas exposure (NO₂ from fermenting crop material, 200–500 ppm) has caused rapid fatalities. EPA's NAAQS (100 ppb 1-hour) is designed to protect against acute bronchoconstriction in asthmatics during peak traffic periods. Secondary formation of particulate nitrates and peroxyacetyl nitrate (PAN) amplifies the aerosol health burden of NO₂ emissions.
What is nitrogen dioxide (no₂)?
Also known as: Nitrogen peroxide, Dioxide, Nitrogen, Peroxide, Nitrogen, Nitrogen oxide (NO2).
- CAS number
- 10102-44-0
- Molecular formula
- NO2
- Molecular weight
- 46.006 g/mol
- SMILES
- N(=O)[O]
- PubChem CID
- 3032552
Risk for your household
High riskInhalation is the only relevant exposure route. NO₂ is a strong oxidant; upper airway scrubbing removes a substantial fraction, but ~25–30% penetrates to the bronchioles and alveoli. Acute high-dose exposure (>2 ppm): tracheobronchitis and pulmonary edema; occupational silo gas exposure (NO₂ from fermenting crop material, 200–500 ppm) has caused rapid fatalities. EPA's NAAQS (100 ppb 1-hour) is designed to protect against acute bronchoconstriction in asthmatics during peak traffic periods. Secondary formation of particulate nitrates and peroxyacetyl nitrate (PAN) amplifies the aerosol health burden of NO₂ emissions.
Regulatory consensus
12 regulatory and scientific bodies have classified Nitrogen dioxide (NO₂). The classifications differ — that's the data.
| Agency | Year | Classification | Notes |
|---|---|---|---|
| WHO | — | criteria air pollutant | key indicator of combustion-related outdoor air pollution |
| IARC | — | not classified as a carcinogen (NO₂ alone) | cancer risk from traffic-related air pollution attributed to mixture including PM2.5 and benzene rather than NO₂ specifically |
| EPA CTX / Genetox | — | Genotoxicity: positive (Ames: positive, 4 positive / 0 negative reports) | |
| EPA CTX / Genetox | — | Genotoxicity: positive (Ames: positive, 4 positive / 0 negative reports) | |
| EPA CTX / Skin-Eye | — | Skin Irritation: Skin Corr. 1B (score: very high) | |
| EPA CTX / Skin-Eye | — | Eye Irritation: Serious eye damage/eye irritation - Category 1 (score: very high) | |
| EPA CTX / Skin-Eye | — | Skin Irritation: Skin corrosion/irritation - Category 2 (score: high) | |
| EPA CTX / Skin-Eye | — | Eye Irritation: Category 2 (score: high) | |
| EPA CTX / Skin-Eye | — | Eye Irritation: Eye Dam. 1 (score: very high) | |
| EPA CTX / Skin-Eye | — | Skin Irritation: Skin Corr. 1B (score: very high) | |
| EPA CTX / Skin-Eye | — | Eye Irritation: Category 8.3A (Category 1) (score: very high) | |
| EPA CTX / Skin-Eye | — | Skin Irritation: Category 8.2A (Category 1A) (score: very high) |
Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.
Where your home encounter nitrogen dioxide (no₂)
- Outdoor Air — Vehicle exhaust, Industrial emissions, Power plant discharge
- Indoor Air — Combustion byproducts, Office buildings, Parking garages
Safer alternatives
Lower-risk approaches that achieve a similar outcome to Nitrogen dioxide (NO₂):
-
Safer process chemistry; Green chemistry alternatives; Exposure controls
Trade-offs: Requires R&D investment to redesign synthesis routes; may reduce yield or throughput initially; long-term benefits include reduced waste treatment costs, regulatory compliance, and worker safety; 12 Principles of Green Chemistry framework available.Relative cost: 1.2-2×
Frequently asked questions
Is nitrogen dioxide (no₂) safe for your home?
Inhalation is the only relevant exposure route. NO₂ is a strong oxidant; upper airway scrubbing removes a substantial fraction, but ~25–30% penetrates to the bronchioles and alveoli. Acute high-dose exposure (>2 ppm): tracheobronchitis and pulmonary edema; occupational silo gas exposure (NO₂ from fermenting crop material, 200–500 ppm) has caused rapid fatalities. EPA's NAAQS (100 ppb 1-hour) is designed to protect against acute bronchoconstriction in asthmatics during peak traffic periods. Secondary formation of particulate nitrates and peroxyacetyl nitrate (PAN) amplifies the aerosol health burden of NO₂ emissions.
What products contain nitrogen dioxide (no₂)?
Nitrogen dioxide (NO₂) appears in: Vehicle exhaust (Outdoor air); Industrial emissions (Outdoor air); Combustion byproducts (Indoor air); Office buildings (Indoor air).
Why do regulators disagree about nitrogen dioxide (no₂)?
Nitrogen dioxide (NO₂) has been classified by 12 agencies including WHO, IARC, EPA CTX / Genetox, EPA CTX / Genetox, EPA CTX / Skin-Eye, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.
See Nitrogen dioxide (NO₂) in the home app
Look up products containing nitrogen dioxide (no₂), compare to alternatives, and explore the full data record.
Open in home View raw API dataSources (3)
- US EPA National Ambient Air Quality Standards for Nitrogen Dioxide (2010) — regulatory
- WHO Air Quality Guidelines for Nitrogen Dioxide (Global Update 2021) (2021) — regulatory
- ATSDR Toxicological Profile for Nitrogen Oxides (2002) — report
Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →