Octylisothiazolinone (OIT)CAS 26530-20-1
Wood preservative isothiazolinone — added to oil stains and exterior sealers for fungal resistance.
Toxic Chemical Databases
Substance-specific listings — these flags are for Octylisothiazolinone alone, not for the broader family.
Chemical Type
Oil-Soluble Isothiazolinone Fungicide
Chemical Description
OIT is the long-chain (octyl) variant of MIT, used primarily as a fungicide in oil-based wood preservatives, exterior paints, and stains. The octyl side chain makes it oil-soluble, suiting it to solvent-based applications where MIT (water-soluble) doesn't work. Same isothiazolinone sensitization concerns apply, plus persistence on weather-exposed surfaces — OIT-treated wood is still measurably biocidal years after application, with residual exposure to maintenance workers and re-coating crews.
Biological Activity
Severity scores specific to this substance, NOT the parent family average. Differences between siblings are real and meaningful.
Top Health Consequences
- Skin sensitization with rising clinical incidence
- REACH SVHC for sensitization endpoints
- Persistent on exterior wood for years post-application
- Aquatic toxicity in stormwater runoff
Pathways of Exposure
- Skin contact with treated decks, fences, and exterior wood
- Inhalation during oil-based stain application
- Off-gassing from recently-treated wood
Building Materials with Octylisothiazolinone
Listed alphabetically — product categories where this specific substance appears.
Deck Preservatives
Exterior Wood Stains
Oil-Based Wood Sealers
Pressure-Treated Wood (Some Lines)