At a glance
| Chemical family | A hindered-phenol antioxidant (2,6-di-tert-butyl-4-methylphenol); semi-volatile |
| CAS number | 128-37-0 (food additive E321) |
| Classification | IARC Group 3 — not classifiable as to carcinogenicity to humans (limited animal evidence; no human evaluation). A sensory irritant in laboratory assays |
| Where you encounter it | An antioxidant/heat stabiliser in polyurethane foam, rubber and plastics; and — the same molecule — a preservative in foods, fats, oils and cosmetics |
| Sleep micro-environment relevance | Sublimes slowly from fresh foam and has been measured emitting from every urethane cushion tested — but predicted indoor air levels sit well below the irritation threshold |
| Activated carbon capture | As a semi-volatile organic, BHT is readily adsorbed; airing and ventilating new foam handles most of it |
Regulatory & certification status
Where BHT stands across the major regulatory systems and the certifications a bedroom product might carry. Each row links to the governing instrument; where a jurisdiction has no specific measure, that is stated plainly rather than left blank.
| European Union | Not a REACH Substance of Very High Concern and not on the Authorisation List (Annex XIV) or the Restriction List (Annex XVII). BHT is registered under REACH (registration 01-2119555270-46) and has been listed for substance evaluation under the Community Rolling Action Plan (CoRAP). It has no harmonised CLP classification in Annex VI — 2,6-di-tert-butyl-4-methylphenol carries no index number there — so its hazard classification comes from industry self-notification, most commonly Aquatic Chronic 1 (H410, 'very toxic to aquatic life with long-lasting effects'), the dominant statement among ECHA C&L Inventory notifications. Separately, it is restricted in cosmetics by Commission Regulation (EU) 2022/2195, which adds BHT to Annex III of the Cosmetics Regulation (entry 325) at 0.001% in mouthwash, 0.1% in toothpaste and 0.8% in other leave-on and rinse-off products. Regulatory — EUR-Lex · ECHA C&L Inventory (aggreg |
| United States | BHT is listed on the TSCA Inventory but is not the subject of any EPA TSCA risk evaluation or regulatory action, and it is not listed on the U.S. National Toxicology Program Report on Carcinogens. It is not on the California Proposition 65 list. The related antioxidant BHA (butylated hydroxyanisole) is Prop 65-listed for cancer (listed 1990), but BHT, CAS 128-37-0, is not. Regulatory — OEHHA · U.S. CPSC Hazard Assessmen |
| Canada | BHT is on the Domestic Substances List. In the DRAFT Substituted Phenols Group screening assessment (notice in Canada Gazette, Part I, 12 January 2024), Environment and Climate Change Canada / Health Canada propose that BHT meets the CEPA paragraph 64(a) criterion (harmful to the environment), finding it persistent but not bioaccumulative, while proposing it does not meet the human-health criterion at current exposures. On that basis BHT is proposed for addition to Part 2 of Schedule 1 of CEPA. This conclusion is proposed, not final — the assessment is a draft and BHT is not yet added to Schedule 1. Regulatory — Government of Canada |
| Australia | BHT was assessed by NICNAS (now AICIS) under the IMAP programme. The Environment Tier II assessment concluded that BHT is not a Persistent, Bioaccumulative and Toxic (PBT) substance under domestic environmental-hazard criteria, finding it unstable in water and soil (not expected to be persistent). The assessment recommended no further assessment and did not recommend specific import, manufacture or use controls. Regulatory — AICIS |
| United Kingdom | Under GB CLP, BHT mirrors the EU position: it has no GB-harmonised classification and is most commonly self-classified Aquatic Chronic 1 (H410), and it is not a UK REACH SVHC / Annex XIV / Annex XVII substance. The UK separately restricted BHT in cosmetics through SI 2024 No. 455, which adds it to Annex III of the GB Cosmetics Regulation (entry 322) following the Final Opinion of the GB Scientific Advisory Group on Chemical Safety of non-food and non-medicinal consumer products (SAG-CS), aligning with the EU cosmetics limits (0.1% toothpaste, 0.001% mouthwash and leave-on oral care, 0.8% other products). Regulatory — UK legislation · GB SAG-CS Final Opinion on |
| International | IARC evaluated BHT and placed it in Group 3 — not classifiable as to its carcinogenicity to humans — on the basis of limited evidence in experimental animals and no data to evaluate carcinogenicity in humans (Monographs Vol. 40, 1986; re-evaluated in Supplement 7, 1987). No global treaty restricts it: BHT is not listed as a Stockholm Convention persistent organic pollutant, and the Minamata Convention (mercury) does not apply. Regulatory — IARC Monographs Vol. 40 / |
| Certifications | CertiPUR-US: does not name BHT — its foam programme prohibits certain flame retardants, heavy metals, formaldehyde, phthalates and ozone depleters and caps total VOC emissions, so BHT would only be addressed indirectly through the emissions cap, not by a content limit. OEKO-TEX Standard 100: a textile content-limit certification that does not set a BHT-specific limit. GREENGUARD / GREENGUARD Gold: low-emission certifications that test total VOCs and a list of individual chemicals of concern rather than screening for BHT by name. In short, no major mattress-relevant certification names BHT by name. Industry — CertiPUR-US · OEKO-TEX |
| The 72-hour test window | Partially captured at best. BHT is semi-volatile — as a solid it slowly sublimes, and the U.S. CPSC measured it off-gassing from every urethane carpet-cushion sample it tested, at 24-hour emission rates of 0.024–0.648 mg/m2/h — so a short ~72h chamber test can detect some of it. But its low volatility means much of the BHT stays in the foam and migrates onto dust and surfaces rather than fully off-gassing, so a brief VOC test understates the total reservoir. Inferred — from the compound's volatility/emission profile versus the VOC focus of short chamber tests |
What it is
BHT is a hindered-phenol antioxidant — a molecule whose job is to stop other molecules from oxidising. It has been used since 1947 in rubber, petroleum products and plastics, and since 1949 as an antioxidant in fat-containing foods, edible oils and cosmetics, which is why human exposure to it is so widespread. Regulatory — IARC Monographs Vol. 40 In polyurethane foam it plays the same protective role: a heat stabiliser that keeps the polymer from degrading during manufacture and use. Regulatory — U.S. CPSC
On hazard, BHT is one of the calmer entries in the Atlas. IARC places it in Group 3 — not classifiable as to carcinogenicity to humans — on the basis of limited and inconsistent animal evidence and no data adequate to evaluate humans. Regulatory — IARC Group 3 Tellingly for an antioxidant, when BHT was tested alongside known carcinogens it often reduced their activity rather than adding to it. Regulatory — IARC Vol. 40 European cosmetic regulators reached a similarly measured conclusion: the EU Scientific Committee on Consumer Safety judged BHT safe in cosmetics at up to 0.8% in leave-on and rinse-off products. Regulatory — EU SCCS Opinion
How it relates to the bedroom
The molecule you eat and sleep on
The most useful thing about BHT is the perspective it offers. The compound stabilising your mattress foam is chemically identical to the E321 keeping a box of cereal fresh. Regulatory — IARC Vol. 40 That does not make either use automatically safe or automatically suspect; it means the honest questions are always the same two — how much, and by what route — rather than whether a scary-sounding chemical is "present." Presence is not exposure, and exposure is not dose.
It does off-gas — and here is how much
BHT is semi-volatile: as a solid it slowly sublimes into the vapour phase, and it leaves fresh foam the same way. The U.S. Consumer Product Safety Commission measured BHT emitting from every prime and bonded urethane carpet-cushion sample it tested, with twenty-four-hour emission rates ranging from 0.024 to 0.648 milligrams per square metre per hour. Regulatory — CPSC In a standardised mouse bioassay BHT also behaved as a relatively potent sensory irritant. Regulatory — CPSC Taken alone, those two facts sound concerning.
The calibration is what matters, and CPSC did it. The indoor air concentrations predicted from those emission rates came out several-fold to dozens-fold below the level associated with sensory irritation — the irritation data were roughly seven times higher than the highest predicted residential air concentration and twenty-five times higher than the median. Regulatory — CPSC CPSC's conclusion was that BHT emitted from these cushions would not be expected to cause sensory irritation in the home. Emission rates had also fallen about three-fold over a few years of manufacturing change. Regulatory — CPSC
Why this is the reassuring shape of an Atlas page
BHT is a model of a low-concern off-gassing compound done honestly: it is genuinely emitted, it genuinely has an irritant property in the lab, and the measured-and-modelled dose at home is still comfortably under the line where that property would matter. Inferred — combining the measured emission rates with the irritation threshold Saying so plainly is more useful than either ignoring the emission or inflating it.
What the research says
- Low carcinogenicity concern. IARC Group 3; limited animal evidence; frequently anticarcinogenic alongside other agents. Regulatory — IARC Vol. 40
- It does off-gas from foam. Measured emitting from every urethane cushion tested, 0.024–0.648 mg/m²/h. Regulatory — CPSC
- Predicted home levels are below the irritation threshold. 7–25× margin in CPSC's assessment. Regulatory — CPSC
- Judged safe in cosmetics to 0.8%. Regulatory — EU SCCS
- An emerging, unsettled question — BHT's breakdown products. Recent reviews note that some of BHT's metabolites can be more reactive than the parent compound and have been linked, in mechanistic and animal work, to oxidative stress and possible endocrine effects, with attention focused on pregnancy and early childhood. This remains active debate rather than established risk: a 2022 toxicogenomic assessment found no endocrine activity for BHT or its close analogues. Peer-reviewed — Pu 2025; De Abrew 2022
What helps reduce it
Air out new foam. Because BHT leaves foam by slow sublimation, unwrapping and ventilating a new product, and keeping the room aired for the first days to weeks, removes most of what would otherwise drift into bedroom air.
Favour newer, low-emission foam. Measured BHT emission rates fell about three-fold across a few years of manufacturing change, so lower-emission formulations release less. Regulatory — CPSC
Ventilate. Ordinary fresh-air exchange clears BHT along with the wider new-foam mixture.
What does NOT help
- Treating "it off-gasses" as the whole story. Emission is real, but the dose predicted at home is well below the threshold for the one effect (irritation) that BHT is known to cause at higher levels. Regulatory — CPSC
- Avoiding it on cancer grounds. BHT is Group 3 and is often protective against other carcinogens; cancer is not the concern here. Regulatory — IARC Vol. 40
Open research questions
- Long-term, low-level inhalation of BHT and other semi-volatile foam additives across years of bedroom use. Speculation
- How BHT partitions between foam, bedroom air, and settled house dust over a mattress's life. Speculation
The Embr Exposure Ledger: Butylated hydroxytoluene (BHT)
One chemical, several public questions, answered from independent datasets and joined here — the environment it shows up in, the body burden it carries, how it is regulated, and what actually reduces it.
Detection and body-burden figures are occurrence data, not a personal measurement or a health diagnosis. Part of the Embr Exposure Ledger — an open, cross-dataset chemical join (download the data), reusable with attribution.
Citations
- IARC (1986/1987). Butylated hydroxytoluene (BHT). IARC Monographs Vol. 40 (p. 161) and Supplement 7 (1987, p. 59) — Group 3 (not classifiable); limited evidence in experimental animals, no evaluation possible in humans. inchem.org — IARC Vol. 40 summary Regulatory
- U.S. Consumer Product Safety Commission. Hazard Assessment of Butylated Hydroxytoluene Emitted from Urethane Carpet Cushions (BHT as a polyurethane-foam heat stabiliser; 24-hour emission rates 0.024–0.648 mg/m²/h; sensory-irritant mouse bioassay; predicted residential air levels 7–25× below the irritation threshold). cpsc.gov Regulatory
- EU Scientific Committee on Consumer Safety. Opinion on Butylated Hydroxytoluene (BHT) (SCCS) — concluded safe as a cosmetic ingredient up to 0.8% in leave-on and rinse-off products (0.1% toothpaste, 0.001% mouthwash). health.ec.europa.eu Regulatory
- Pu M, et al. (2025). Research progress on the human exposure levels and health risks of butylated hydroxytoluene and its metabolites. Zhonghua Yu Fang Yi Xue Za Zhi (Chinese Journal of Preventive Medicine) — review noting that BHT metabolites can be more toxic than the parent compound, with proposed endocrine-disruption, oxidative-stress and DNA-damage mechanisms and a focus on pregnant women and children. PMID 41287337 Peer-reviewed
- De Abrew KN, et al. (2022). A New Approach Methodology (NAM)-Based Assessment of Butylated Hydroxytoluene (BHT) for Endocrine Disruption Potential. Toxicological Sciences — toxicogenomic assessment finding that neither BHT nor its close analogues connected to estrogen, androgen, thyroid, or steroidogenesis endocrine activity. DOI 10.1093/toxsci/kfac099 Peer-reviewed
Frequently asked questions
Is the BHT in my mattress the same as the BHT in food?
Yes — it is the same molecule. Butylated hydroxytoluene (E321) has been used since the late 1940s as an antioxidant in fats, oils, cereals and cosmetics, and the same compound is added to polyurethane foam as a heat stabiliser to keep the polymer from oxidising. The molecule is identical; what differs is the amount and the route of exposure. That is a useful reminder that "a chemical in your mattress" and "a chemical you eat" can be one and the same.
Is BHT a carcinogen?
IARC places BHT in Group 3 — not classifiable as to carcinogenicity to humans. The animal evidence is limited and inconsistent, there was no basis to evaluate human carcinogenicity, and in many experiments BHT actually reduced the activity of other carcinogens, consistent with its role as an antioxidant. It is one of the lower-concern compounds in this Atlas.
Does BHT off-gas from foam, and is that harmful?
It does. BHT is semi-volatile and slowly sublimes from fresh polyurethane foam; the U.S. CPSC measured it emitting from every urethane carpet-cushion sample it tested. BHT is also a sensory irritant in a standardised mouse assay. The reassuring part is the dose: CPSC concluded that the indoor air concentrations predicted from those emission rates sit several-fold to dozens-fold below the level that would cause sensory irritation, so home exposure would not be expected to cause it. Airing out new foam reduces it further.
How do I reduce BHT from new foam?
Because BHT leaves foam by slow sublimation, the same airing-out routine that handles other new-foam emissions works here: unwrap and ventilate a new product, and keep the bedroom aired for the first days to weeks. Measured emission rates from cushions also fell roughly three-fold over a few years of manufacturing change, so newer low-emission foam tends to release less.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-06-27. If you find a factual error, contact us.