Pet Safety / Compounds / Tributyltin oxide

Is Tributyltin oxide safe for dogs and cats?

Moderate risk for pets

Potential exposure if consuming contaminated shellfish or fish from harbor areas.

What is tributyltin oxide?

The IUPAC name is Tributylstannane oxide.

Also known as: Tributylstannane oxide, BIS(TRIBUTYLTIN) OXIDE, Hexabutyldistannoxane, Bis(tributyltin)oxide.

IUPAC name
Tributylstannane oxide
CAS number
56-35-9
Molecular formula
C12H27OSn
Molecular weight
310.98 g/mol
SMILES
CCCC[Sn](CCCC)(CCCC)O[Sn](CCCC)(CCCC)CCCC
PubChem CID
16682746

Risk for dogs

Moderate risk

Potential exposure if consuming contaminated shellfish or fish from harbor areas.

Risk for cats

Moderate risk

Same as dogs. Seafood-based pet food could contain trace TBT.

Regulatory consensus

4 regulatory and scientific bodies have classified Tributyltin oxide. The classifications differ — that's the data.

AgencyYearClassificationNotes
EPA—All antifouling registrations cancelled. Listed in TRI (Toxic Release Inventory). TSCA restrictions
IMO—BANNED under International Convention on the Control of Harmful Anti-fouling Systems (AFS Convention, 2008)
EU—Banned in antifouling. REACH Annex XVII restriction. CLP: Acute Tox 2, Repr 2, STOT RE 1, Skin Corr 1B, Aquatic Acute 1, Aquatic Chronic 1
Stockholm Convention—Under consideration for POPs listing. Already effectively banned through maritime regulations

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where pets encounter tributyltin oxide

  • biocide in antifouling paints (historical)
  • wood preservative (restricted)
  • industrial catalyst
  • Legacy Contamination — Marine sediments at harbors, shipyards, drydocks worldwide, Contaminated dredge spoils, Former wood treatment sites
  • Historical Use (Banned) — Ship hull antifouling paint (banned 2008), Marine structure protection, Wood preservative (some uses banned)
  • Remaining Uses — Industrial biocide in some non-marine applications (limited), PVC stabilizer (being phased out)

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Tributyltin oxide:

  • Copper-based antifouling paints (cuprous oxide)
    Trade-offs: Lower efficacy against slime-forming organisms. Copper accumulation in harbors. Requires more frequent repainting.
    Relative cost: 0.5-0.8×
  • Silicone-based foul-release coatings (Intersleek)
    Trade-offs: Requires vessel speed >15 knots for self-cleaning. Higher initial cost. Mechanical cleaning for slow vessels.
    Relative cost: 3-5× initial; lower lifecycle
  • DCOIT (Sea-Nine)
    Relative cost: 1.2-2×

Frequently asked questions

Is tributyltin oxide safe for pets?

Potential exposure if consuming contaminated shellfish or fish from harbor areas.

What products contain tributyltin oxide?

Tributyltin oxide appears in: biocide in antifouling paints (historical); wood preservative (restricted); industrial catalyst.

Why do regulators disagree about tributyltin oxide?

Tributyltin oxide has been classified by 4 agencies including EPA, IMO, EU, Stockholm Convention, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.

See Tributyltin oxide in the pets app

Look up products containing tributyltin oxide, compare to alternatives, and explore the full data record.

Open in pets View raw API data

Sources (1)
  1. ATSDR Toxicological Profile — CAS 56-35-9 — reference

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →