At a glance
| Chemical family | Organotin — biocide / endocrine disruptor |
| CAS number | 56-35-9 |
| Classification | EU SVHC (PBT and endocrine disruptor); REACH restricted; Canada SOR/2025-270 prohibited; IMO International Convention bans in marine paints |
| Where you encounter it | Anti-fungal treatment on textiles (especially imported); wood preservative; PVC heat stabiliser; historically in marine anti-fouling paints |
| Sleep micro-environment relevance | May be present as an anti-fungal residue on imported textiles (sheets, covers, pillow fills). Detected in household dust. OEKO-TEX restricts organotins in certified textiles |
Regulatory & certification status
| European Union | SVHC (Candidate List — PBT). REACH Annex XVII Entry 20 restricts organostannic (organotin) compounds in articles: TBT must not be used in articles ≥0.1% by mass of tin. Biocidal Products Regulation: TBT not approved as an active substance. Regulatory — European Union authority |
| Canada | Prohibited under the Prohibition of Certain Toxic Substances Regulations, 2025 (SOR/2025-270), in force 30 June 2026. Tributyltins listed with a threshold of 30,000 mg/kg for tetrabutyltin impurities. Regulatory — Canada authority |
| International | IMO International Convention on the Control of Harmful Anti-fouling Systems (AFS Convention, 2008) bans TBT in ship anti-fouling paints globally. WHO drinking-water guideline: no formal guideline value set (insufficient data for humans). Regulatory |
| Certifications | OEKO-TEX Standard 100 restricts total organotins (including TBT) to 0.5 mg/kg (product class I, baby) to 1.0 mg/kg (other classes). AFIRM RSL restricts organotins. GOTS prohibits organotin compounds. Industry |
What it is
Tributyltin compounds (TBT — primarily the oxide TBTO, CAS 56-35-9, and the chloride TBTCl) are organotin biocides. They are extraordinarily toxic to aquatic invertebrates and are potent endocrine disruptors, disrupting normal hormonal function at extremely low concentrations. The most famous effect is imposex — the development of male sex organs in female gastropod snails — which was documented at parts-per-trillion ambient water concentrations. TBT's anti-fouling, anti-fungal, and antimicrobial properties led to widespread use across marine, industrial, and consumer applications before bans took effect.
Where it shows up in bedding
TBT enters the bedroom primarily through treated textiles. Organotin compounds have been used as anti-fungal and anti-bacterial treatments on fabrics during manufacturing and shipping — preventing mold during ocean transport of textile goods. They have also been used as heat stabilisers in PVC, which appears in some mattress protectors and covers. Studies have detected organotins, including TBT, in household dust, with textiles and PVC products as suspected sources. OEKO-TEX Standard 100 restricts total organotins (including TBT) to 0.5–1.0 mg/kg depending on product class.
Citations
- ECHA. Substance Information: Bis(tributyltin) oxide (TBTO). Source Regulatory
- Government of Canada. SOR/2025-270. Source Regulatory
- IMO. International Convention on the Control of Harmful Anti-fouling Systems. Regulatory
Frequently asked questions
Can TBT be in my sheets?
Possibly, if they were imported from supply chains that use organotin anti-fungal treatments during manufacturing or ocean shipping. The concentrations are typically low, but TBT is biologically active at very small doses. Textiles certified under OEKO-TEX Standard 100 or GOTS are tested for organotins and restricted to levels well below those associated with biological effects.
How is TBT an endocrine disruptor?
TBT disrupts the aromatase enzyme system, which converts androgens to oestrogens. At extremely low concentrations (nanograms per litre in water), it causes imposex in marine gastropods — the development of male sexual characteristics in females. In mammals, TBT disrupts adipocyte differentiation, immune function, and reproductive development. It is one of the most potent endocrine disruptors measured, with effects documented at concentrations orders of magnitude below those of better-known EDCs like BPA or phthalates.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-07-07. If you find a factual error, contact us.