Indoor environment factor · measured in µg/m³
Sulfur dioxide (SO₂)
Also: SO2, sulphur dioxide, sulfurous anhydride
A sharp-smelling, water-soluble gas formed when fuel containing sulfur is burned. Indoors it comes from coal and from some heating oils and kerosene; where those are not used, indoor concentrations simply follow whatever comes in from outside.
Where it comes from indoors
Sulfur dioxide is a fuel-borne pollutant rather than a flame-borne one: it is made from the sulfur in the fuel, so a fuel without sulfur produces none of it however it burns. That single fact explains its distribution indoors. Homes burning coal, heating oil or unrefined kerosene have their own source; homes on gas or electricity do not, and their indoor concentration is outdoor air minus what the building removes.
Being highly water-soluble, it is absorbed readily on damp surfaces and in the upper airway, which has two consequences. Indoor-to-outdoor ratios are usually well below one, and the gas acts on the nose and throat rather than reaching deep into the lung.
Its history is the history of urban air: the smoke-and-sulfur episodes that drove the first clean air legislation were mixtures of this gas and soot.
What the studies report
| Linked to | Effect | Population | Study design | Source | Checked |
|---|---|---|---|---|---|
| Gestational diabetes | OR 1.18 (1.10–1.26) | pregnant women | systematic review and meta-analysis of 35 epidemiological studies (33 cohort, 1 cross-sectional, 1 case-control) covering 6,939,725 pregnant women | F-0080 Association of air pollution and fine particulate matter (PM… (2023) | machine |
| Dry eye disease | RR 1.174 (1.036–1.330) per 10 | outpatients of a megacity · city (ambient) | time-series study of daily outpatient visits for dry eye disease in Guangzhou, 1 January 2014 to 31 December 2020 (2557 days, 27,828 visits), quasi-Poisson generalized linear model with distributed lag non-linear model | F-0075 Cao Association between traffic-related air pollution and risk o… (2025) | machine |
| Dermatitis | difference 2.22 (1.27–3.16) per 10 % | dermatology outpatients · city (ambient) | time-series analysis of daily outpatient visits for eczema at a dermatology department in Shanghai against ambient air pollutants and meteorological factors, generalized additive models with single-day and cumulative lags | F-0197 Li et al. Ambient Air Pollution, Meteorological Factors and Outpatient… (2016) | machine |
| — | mean 42 | dermatology outpatients · city (ambient) | time-series analysis of daily outpatient visits for eczema at a dermatology department in Shanghai against ambient air pollutants and meteorological factors, generalized additive models with single-day and cumulative lags | F-0200 Li et al. Ambient Air Pollution, Meteorological Factors and Outpatient… (2016) | machine |
| — | mean 264.8 | pupils aged 11 to 15 · classroom | cross-sectional study in a coal-burning city in northern China: a questionnaire on respiratory health and home environment was answered by 1,993 pupils aged 11 to 15 in ten urban schools of Taiyuan, and indoor and outdoor air pollutants and climate factors were measured in the same schools in winter | F-1280 Lotz Asthmatic Symptoms among Pupils in Relation to Winter Indoor… (2008) | machine |
| — | the sentence writes the ratio in words and covers all four measured pollutants together | pupils aged 11 to 15 · classroom | cross-sectional study in a coal-burning city in northern China: a questionnaire on respiratory health and home environment was answered by 1,993 pupils aged 11 to 15 in ten urban schools of Taiyuan, and indoor and outdoor air pollutants and climate factors were measured in the same schools in winter | F-1284 Lotz Asthmatic Symptoms among Pupils in Relation to Winter Indoor… (2008) | machine |
| Wheeze | a stated direction without a coefficient; the sentence names the three pollutants together and ozone is not among them | pupils aged 11 to 15 · classroom | cross-sectional study in a coal-burning city in northern China: a questionnaire on respiratory health and home environment was answered by 1,993 pupils aged 11 to 15 in ten urban schools of Taiyuan, and indoor and outdoor air pollutants and climate factors were measured in the same schools in winter | F-1291 Lotz Asthmatic Symptoms among Pupils in Relation to Winter Indoor… (2008) | machine |
Each row is one Finding — a sentence as printed in one study, recorded with its page in the Coridum Knowledge Base. Follow the Finding number for the exact wording and the citation. Checked says who verified the row: machine means every automatic check passed and the surrounding text was read; person means someone read the sentence in the document. Rows are re-checked by a person over time. The studies are curated in the Coridum Knowledge Base; the reading of them together is a Claim, shown separately.
Identifiers
Cite this page
Coridum Research. Sulfur dioxide (SO₂). Coridum Knowledge G-0134, 16 September 2026. https://coridum.com/k/G-0134/