Indoor environment factor · measured in µg/m³
Benzene
Also: C6H6
A volatile aromatic hydrocarbon and confirmed human carcinogen. Indoors it comes mainly from tobacco smoke, attached garages, vehicle exhaust entering from outside, solvents and some consumer products. No safe level of exposure has been identified.
Why it matters indoors
Benzene is a building block of the petrochemical industry and a natural component of petrol and crude oil. It evaporates readily, which is why it is present wherever fuel is stored, burned or spilled. Its toxicity is well established: the International Agency for Research on Cancer classifies it as carcinogenic to humans, and the WHO treats it as a compound without a safe threshold.
Where it comes from indoors
Tobacco smoke is the dominant source in homes where people smoke. Others: attached or integral garages, petrol and solvent storage, vehicle exhaust infiltrating from busy streets, wood and coal burning, gas cooking, and consumer products containing solvents. Building materials contribute little compared with formaldehyde.
Health effects
Chronic exposure damages bone marrow, causing reduced blood-cell counts and acute myeloid leukaemia; associations with other blood cancers are reported. Acute exposure to high concentrations depresses the central nervous system — drowsiness, dizziness, headache — but such levels are rare outside industrial accidents.
Exposure limits
| Jurisdiction | Value | Basis | Source |
|---|---|---|---|
| World Health Organization | no safe level; unit risk 6 × 10⁻⁶ per µg/m³ (1.7 µg/m³ ≈ 1 in 100 000 lifetime leukaemia risk) | carcinogenic, no threshold | WHO indoor air quality guidelines 2010 |
| European Union (ambient) | 3.4 µg/m³ from 2030 (currently 5 µg/m³) | annual | Directive (EU) 2024/2881 |
Slovak, UAE and Hong Kong values are being compiled in the indoor air quality limits table.
How it is measured
Benzene is identified and quantified by gas chromatography of air samples collected on sorbent tubes or in canisters, usually over hours to days. Real-time sensors cannot single it out; a persistently elevated total VOC reading in a room with a garage, fuel storage or smoking is the practical cue to sample for it.
What the studies report
12 of 23 Findings — those with the strongest study design.
| Linked to | Effect | Population | Study design | Source | Checked |
|---|---|---|---|---|---|
| Cardiovascular disease (CVD) | RR 1.09 (0.99–1.21) · borderline | — | systematic review and meta-analysis of 36 studies of volatile organic compound exposure and cardiovascular disease: random-effects and fixed-effects pooled estimates for volatile organic compound mixtures, for toluene, ethylbenzene and xylene, and for benzene against cardiovascular death | F-1195 Exposure to volatile organic compounds and cardiovascular di… (2026) | machine |
| Indoor plants (phytoremediation) | mean 0.3 | — · university laboratory | study of plant-based biofiltration in a pharmaceutical teaching laboratory: benzene and toluene removal by ornamental species measured against the laboratory background, with a health risk assessment for staff and students | F-1116 Sustainable indoor air quality via plant-based biofiltration… (2026) | machine |
| Atopic dermatitis symptoms | difference 12.0 (-0.9–26.6) per 1 ppb of indoor benzene % · borderline | children with atopic dermatitis · home | panel study of children with atopic dermatitis in Korea: indoor volatile organic compounds and other pollutants measured in the homes alongside daily symptom scores, analysed in unlagged and lagged models | F-1125 Kim et al. Indoor air pollution aggravates symptoms of atopic dermatiti… (2015) | machine |
| Gas stoves | share-above 29 | — · kitchen | measurement of benzene emissions from gas and propane stoves in homes: emission factors measured for 33 distinct stove and oven settings in a subset of 17 homes, with the kitchen benzene concentration measured after use | F-1560 Gas and propane combustion from stoves emits benzene and inc… (2023) | machine |
| Atopic dermatitis symptoms | difference 12.0 (-0.9–26.6) per 1 % · borderline | children · day-care centre | prospective longitudinal (panel) study in a newly built day-care centre | F-0005 Kim et al. Indoor air pollution aggravates symptoms of atopic dermatiti… (2015) | machine |
| — | a detection frequency, not a concentration | — · office | analysis of the volatile organic compound measurements the Finnish Institute of Occupational Health made in offices, schools, kindergartens and healthcare buildings between 2010 and 2019: detection frequencies, 95th and 99th percentiles and maxima of 42 compounds against German and European guideline values | F-1061 Wallenius et al. Volatile Organic Compounds in Finnish Office Environments in… | machine |
| Adhesives and sealants | mean 10.59 | — · test chamber | chamber study of 21 volatile pollutants emitted by white emulsion and silicone adhesives: chemical concentrations, odour contributions and cancer and non-cancer health risks of each compound | F-1075 Zhao et al. Characterizing Key Volatile Pollutants Emitted from Adhesive… (2022) | machine |
| — | median 1.6 (1.5–1.7) | children and adolescents aged 3 to 14 years · home | analysis of repeated cross-sectional data from the German Environmental Survey and the KiGGS health survey: benzene, toluene, xylene, limonene and formaldehyde measured in the homes of children and adolescents aged 3 to 14 against equivalized disposable income, socioeconomic status and parental history of migration, in fifteen random-intercept models | F-1079 Indoor air pollution inequalities among children and adolesc… (2025) | machine |
| — | ratio 0.95 (0.91–0.99) per one standard deviation of equivalized disposable income ratio of concentrations | children and adolescents aged 3 to 14 years · home | analysis of repeated cross-sectional data from the German Environmental Survey and the KiGGS health survey: benzene, toluene, xylene, limonene and formaldehyde measured in the homes of children and adolescents aged 3 to 14 against equivalized disposable income, socioeconomic status and parental history of migration, in fifteen random-intercept models | F-1081 Indoor air pollution inequalities among children and adolesc… (2025) | machine |
| — | ratio 0.90 (0.87–0.94) per one standard deviation of socioeconomic status ratio of concentrations | children and adolescents aged 3 to 14 years · home | analysis of repeated cross-sectional data from the German Environmental Survey and the KiGGS health survey: benzene, toluene, xylene, limonene and formaldehyde measured in the homes of children and adolescents aged 3 to 14 against equivalized disposable income, socioeconomic status and parental history of migration, in fifteen random-intercept models | F-1082 Indoor air pollution inequalities among children and adolesc… (2025) | machine |
| — | ratio 0.78 (0.68–0.89) per a parental history of migration against none ratio of concentrations | children and adolescents aged 3 to 14 years · home | analysis of repeated cross-sectional data from the German Environmental Survey and the KiGGS health survey: benzene, toluene, xylene, limonene and formaldehyde measured in the homes of children and adolescents aged 3 to 14 against equivalized disposable income, socioeconomic status and parental history of migration, in fifteen random-intercept models | F-1086 Indoor air pollution inequalities among children and adolesc… (2025) | machine |
| — | other 24.2 | children and adolescents aged 0 to 19 years | health risk assessment of volatile organic compounds for children in Ulaanbaatar, Mongolia: benzene, toluene, m,p-xylene and formaldehyde sampled at 144 sites in kindergartens, schools, apartments, houses, traditional gers, hospitals, offices and shopping centres, with lifetime dose and cancer risk calculated by age group | F-1089 Otgonbyamba et al. Health Risk Assessment of Volatile Organic Compounds for Chi… (2023) | 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.
How Coridum measures it: Coridum devices do not measure benzene specifically; the total VOC sensor responds to it as part of the overall load. Benzene is identified in laboratory analysis of sorbent-tube samples.
Identifiers
- Molecular formula
- C₆H₆
- IUPAC name
- benzene
- CAS Registry Number
- 71-43-2 · PubChem · CTD
- InChIKey
- UHOVQNZJYSORNB-UHFFFAOYSA-N
- MeSH
- D001554
- SMILES
c1ccccc1
Frequently asked questions
Why is there no safe level for benzene?
Benzene causes leukaemia through a mechanism without a threshold — any exposure carries some risk. The WHO therefore gives a unit risk instead of a limit: a lifetime exposure to 1.7 µg/m³ corresponds to roughly one additional case of leukaemia per 100 000 people.
What is the biggest indoor source of benzene?
Tobacco smoking, where it occurs. Otherwise attached garages, petrol stored indoors, vehicle traffic outside, wood and gas combustion, and solvent-containing products such as paint strippers and adhesives.
How does indoor benzene compare to outdoors?
In homes without smoking, indoor benzene is typically similar to or slightly above outdoor levels — around 1–5 µg/m³ in European cities. Smoking or an attached garage can multiply that several times.
Sources
- WHO guidelines for indoor air quality: selected pollutants. World Health Organization Regional Office for Europe, 2010.
- IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 120: Benzene. International Agency for Research on Cancer, 2018.
- Directive (EU) 2024/2881 on ambient air quality and cleaner air for Europe.
- Gas and propane combustion from stoves emits benzene and increases indoor air pollution… (2023). Environmental science & technology. doi:10.1021/acs.est.2c09289 CKB 0959
- Sparks et al. Benzene and other hazardous air pollutants in consumer-grade natural gas in Europe… (2026). Environ Res Lett. doi:10.1088/1748-9326/ae499f CKB 1208
- Fiore et al. The Presence of Aromatic Substances in Incense: Determining Indoor Air Quality and Its Impact on Human Health. Applied Sciences. doi:10.3390/app13127344 CKB 0964
CKB = document number in the Coridum Knowledge Base, our curated library of peer-reviewed studies. Follow the DOI for the original paper.
Cite this page
Coridum Research. Benzene. Coridum Knowledge G-0009, 16 September 2026. https://coridum.com/k/G-0009/