Sulfur dioxide (SO₂) in your home: a safety profile
High risk for your homeInhalation is the primary route for environmental and occupational exposure. SO₂ is highly water-soluble; most is absorbed in the upper airways, but sufficient concentrations reach the lower respiratory tract to cause bronchospasm and mucous secretion. Occupational IDLH 100 ppm; OSHA PEL 5 ppm. Acute high-dose exposure in industrial accidents (e.g., cooling system failures using SO₂ refrigerant) causes severe pulmonary edema, potentially fatal. Asthmatics respond at far lower concentrations than healthy adults — NAAQS designed to protect this sensitive subpopulation. Historical 'killer smogs' (London 1952: ~4,000 excess deaths) involved extreme SO₂ + fog + PM synergy.
What is sulfur dioxide (so₂)?
The IUPAC name is sulfur dioxide.
Also known as: sulfur dioxide, sulphur dioxide, Sulfurous anhydride, Sulfurous oxide.
- IUPAC name
- sulfur dioxide
- CAS number
- 7446-09-5
- Molecular formula
- O2S
- Molecular weight
- 64.07 g/mol
- SMILES
- O=S=O
- PubChem CID
- 1119
Risk for your household
High riskInhalation is the primary route for environmental and occupational exposure. SO₂ is highly water-soluble; most is absorbed in the upper airways, but sufficient concentrations reach the lower respiratory tract to cause bronchospasm and mucous secretion. Occupational IDLH 100 ppm; OSHA PEL 5 ppm. Acute high-dose exposure in industrial accidents (e.g., cooling system failures using SO₂ refrigerant) causes severe pulmonary edema, potentially fatal. Asthmatics respond at far lower concentrations than healthy adults — NAAQS designed to protect this sensitive subpopulation. Historical 'killer smogs' (London 1952: ~4,000 excess deaths) involved extreme SO₂ + fog + PM synergy.
Regulatory consensus
13 regulatory and scientific bodies have classified Sulfur dioxide (SO₂). The classifications differ — that's the data.
| Agency | Year | Classification | Notes |
|---|---|---|---|
| WHO | — | criteria air pollutant | |
| US EPA | — | criteria air pollutant | |
| IARC | — | not classified as a carcinogen | |
| EPA CTX / IARC | — | Group 3 - Not classifiable as to its carcinogenicity to humans | |
| EPA CTX / Genetox | — | Genotoxicity: positive (Ames: None, 3 positive / 1 negative reports) | |
| EPA CTX / Genetox | — | Genotoxicity: positive (Ames: None, 3 positive / 1 negative reports) | |
| EPA CTX / Skin-Eye | — | Skin Irritation: Skin Corr. 1B (score: very high) | |
| EPA CTX / Skin-Eye | — | Skin Irritation: Skin corrosion/irritation - Category 1 (score: very high) | |
| EPA CTX / Skin-Eye | — | Eye Irritation: Category 2A (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 8.2B (Category 1B) (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 sulfur dioxide (so₂)
- 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 Sulfur dioxide (SO₂):
-
Physical/mechanical pest control (IPM)
Trade-offs: More labor-intensive. May not be sufficient for severe infestations.Relative cost: 1.2-2×
Frequently asked questions
Is sulfur dioxide (so₂) safe for your home?
Inhalation is the primary route for environmental and occupational exposure. SO₂ is highly water-soluble; most is absorbed in the upper airways, but sufficient concentrations reach the lower respiratory tract to cause bronchospasm and mucous secretion. Occupational IDLH 100 ppm; OSHA PEL 5 ppm. Acute high-dose exposure in industrial accidents (e.g., cooling system failures using SO₂ refrigerant) causes severe pulmonary edema, potentially fatal. Asthmatics respond at far lower concentrations than healthy adults — NAAQS designed to protect this sensitive subpopulation. Historical 'killer smogs' (London 1952: ~4,000 excess deaths) involved extreme SO₂ + fog + PM synergy.
What products contain sulfur dioxide (so₂)?
Sulfur dioxide (SO₂) appears in: Vehicle exhaust (Outdoor air); Industrial emissions (Outdoor air); Combustion byproducts (Indoor air); Office buildings (Indoor air).
Why do regulators disagree about sulfur dioxide (so₂)?
Sulfur dioxide (SO₂) has been classified by 13 agencies including WHO, US EPA, IARC, EPA CTX / IARC, EPA CTX / Genetox, 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 Sulfur dioxide (SO₂) in the home app
Look up products containing sulfur dioxide (so₂), 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 Sulfur Dioxide (2010) — regulatory
- WHO Air Quality Guidelines for Sulfur Dioxide (Global Update 2021) (2021) — regulatory
- ATSDR Toxicological Profile for Sulfur Dioxide (1998) — 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 →