Indoor environment factor · measured in µg/m³ or ppb
Toluene (C₇H₈)
Also: C7H8, methylbenzene, BTEX
A clear aromatic solvent used in paints, adhesives, printing inks and cleaning products, and released by tobacco smoke and traffic. Indoors it is one of the most consistently detected volatile organic compounds, usually measured together with benzene, ethylbenzene and the xylenes.
Why it matters indoors
Toluene rarely appears alone. It belongs to the group usually written as benzene, toluene, ethylbenzene and the xylenes, which are measured together because they share sources — solvents, adhesives, fuels and combustion — and because a single analysis reports all of them. That grouping matters for reading studies: a health effect attributed to one of them was often measured in a room where all four were present.
What it tells you about a room
Because it evaporates quickly and comes mostly from products rather than from the building itself, a raised concentration usually points at something recent and identifiable: fresh paint, new adhesive, a hobby with solvents, or smoking. That makes it more useful as a marker of an activity than as a long-term property of a building.
What the studies report
12 of 13 Findings — those with the strongest study design.
| Linked to | Effect | Population | Study design | Source | Checked |
|---|---|---|---|---|---|
| Indoor plants (phytoremediation) | mean 4 | — · 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-1117 Sustainable indoor air quality via plant-based biofiltration… (2026) | machine |
| Atopic dermatitis symptoms | difference 12.7 (-0.01–27.1) per 1 ppb of indoor toluene % | 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-1126 Kim et al. Indoor air pollution aggravates symptoms of atopic dermatiti… (2015) | machine |
| Atopic dermatitis symptoms | difference 12.7 (-0.01–27.1) per 1 % · borderline | children · day-care centre | prospective longitudinal (panel) study in a newly built day-care centre | F-0006 Kim et al. Indoor air pollution aggravates symptoms of atopic dermatiti… (2015) | machine |
| — | p95 265.30 | — · office | cross-sectional measurement and questionnaire study in 31 offices in Korea (three building groups, July to September 2016): indoor and outdoor air pollutants and subjective symptoms of office workers, with health risk assessment | F-0303 Jung et al. Risk Assessment of Indoor Air Quality and Its Association wi… | machine |
| — | ratio 0.94 (0.89–0.99) 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-1083 Indoor air pollution inequalities among children and adolesc… (2025) | machine |
| — | ratio 0.98 (0.92–1.04) per one standard deviation of socioeconomic status ratio of concentrations · borderline | 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-1087 Indoor air pollution inequalities among children and adolesc… (2025) | machine |
| — | mean 73.9 | 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-1092 Otgonbyamba et al. Health Risk Assessment of Volatile Organic Compounds for Chi… (2023) | machine |
| — | other 73.19 | — · beauty salon | preliminary measurement study of benzene, toluene, ethylbenzene and xylenes in beauty salons in Poland: nail styling, hairdressing and cosmetics salons sampled on Tenax tubes with a children's hairdresser as the indoor background and outdoor air as the outdoor background | F-1096 BTEX occurrence in the indoor air of beauty salons - prelimi… (2023) | machine |
| Printers and photocopiers | other 37.7 | — · test chamber | chamber measurements of volatile organic compounds emitted by office printers and copiers in Poland: seven devices tested, with aromatic and halogenated compounds and total volatile organic compounds determined per device and per printed page | F-1100 Measurements of chlorinated volatile organic compounds emitt… (2014) | machine |
| — | other 78.3 | — · car cabin | measurement study of 24 car cabins in Japan: volatile organic compounds and aldehydes sampled inside the cabins with outdoor air for comparison, against the advisable values of the Japanese Ministry of Health, Labour and Welfare, with a screening-level risk assessment | F-1123 Car indoor air pollution by volatile organic compounds and a… (2016) | machine |
| — | mean 5.76 | university students | measurement study on a Chinese university campus: volatile organic compounds sampled in a dormitory, a canteen, a classroom and a library across four seasons and at different times of day, with time-activity data from a questionnaire for a health risk assessment | F-1165 Jin et al. Indoor Volatile Organic Compounds: Concentration Characteris… (2023) | machine |
| — | other 371.0 | — · dwelling without ventilation | measurement study of formaldehyde, acetaldehyde and five volatile organic compounds in residences of different types with and without ventilation | F-1183 Concentration of Formaldehyde, Acetaldehyde, and Five Volati… (2017) | 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
- Molecular formula
- C₇H₈
- IUPAC name
- methylbenzene
- CAS Registry Number
- 108-88-3 · PubChem · CTD
- InChIKey
- YXFVVABEGXRONW-UHFFFAOYSA-N
- MeSH
- D014050
- SMILES
Cc1ccccc1
Frequently asked questions
Where does indoor toluene come from?
Solvent-based paints and varnishes, adhesives used in flooring and furniture, printing inks, some cleaning and hobby products, tobacco smoke, and traffic entering from outside. Concentrations rise sharply during and after painting or gluing and then decay over days to weeks.
Is toluene as dangerous as benzene?
No. Benzene is a recognised human carcinogen with no safe level; toluene is not classified as carcinogenic to humans and its concern is different — irritation at higher concentrations and effects on the nervous system in occupational exposure. That is why the two are regulated differently even though they are measured together.
How is it measured indoors?
Usually by passive sampling over days to weeks, or by active sampling onto a sorbent tube analysed in a laboratory. General volatile organic compound sensors respond to it but cannot separate it from the rest of the mixture.
In the literature
- Kamani Health risk assessment of BTEX compounds (benzene, toluene, ethylbenzene and xylene) in different indoor air using Monte Carlo simulation in zahedan city, Iran (2023). doi:10.1016/j.heliyon.2023.e20294 CKB 0213
- Systematic review and meta-analysis of toluene concentration a comparative assessment of… (2026). BMC Public Health. doi:10.1186/s12889-026-26939-8 CKB 1234
- Gonçalves Passive sampling of toluene (and benzene) in indoor air using a semipermeable membrane device (2021). Ecotoxicology and environmental safety. doi:10.1016/j.ecoenv.2020.111707 CKB 0186
Studies in the Coridum Knowledge Base in which this term is used. The definition follows standard usage in WHO, ISO and textbook sources; it is not quoted from these papers.
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. Toluene (C₇H₈). Coridum Knowledge G-0091, 16 September 2026. https://coridum.com/k/G-0091/