Baby Safety / Compounds / DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211)

Is DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211) safe for babies and kids?

Moderate risk for kids

Infants are more vulnerable to DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211) than children or adults due to immature hepatic/renal clearance, higher intake-to-body-weight ratio, rapid organ development, and increased gastrointestinal absorption.

What is dcoit (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one / sea-nine 211)?

The IUPAC name is 4,5-dichloro-2-octyl-1,2-thiazol-3-one.

Also known as: 64359-81-5, Kathon 930, dcoit, 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one.

IUPAC name
4,5-dichloro-2-octyl-1,2-thiazol-3-one
CAS number
64359-81-5
Molecular formula
C11H17Cl2NOS
Molecular weight
282.23 g/mol
SMILES
CCCCCCCCN1C(=O)C(=C(S1)Cl)Cl
PubChem CID
91688

Risk for babies

Moderate risk

Infants are more vulnerable to DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211) than children or adults due to immature hepatic/renal clearance, higher intake-to-body-weight ratio, rapid organ development, and increased gastrointestinal absorption.

Neonates and infants up to 12 months have incomplete blood-brain barrier development, immature Phase I/II metabolic enzymes (particularly CYP3A4, UGT1A1), and higher gastrointestinal permeability. Equivalent doses produce higher internal concentrations and longer residence times.

What to do: Minimize infant exposure through source control. For breastfeeding mothers: reduce maternal exposure. For formula-fed infants: use certified low-migration bottles and verified water sources. Consult pediatrician regarding any concerns.

Risk for pregnant and nursing people

Context-dependent

Pregnancy alters the metabolism and distribution of DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211), potentially increasing fetal exposure. The developing embryo/fetus is vulnerable during organogenesis (weeks 3-8) and neurological development. Placental transfer should be assumed.

No specific reproductive toxicity data identified, but pregnancy-specific safety data is limited for most chemicals. Precautionary minimization of exposure is recommended.

What to do: Minimize exposure during pregnancy and lactation. Consult healthcare provider regarding specific risks. Consider alternative products with lower hazard profiles.

Regulatory consensus

3 regulatory and scientific bodies have classified DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211). The classifications differ — that's the data.

AgencyYearClassificationNotes
IMO—Listed in AFS Convention as permitted antifoulant (unlike TBT which is banned)
EU BPR—Approved for Product Type 21 (antifouling). Under review for environmental risk
Japan—Registered for antifouling use. Subject to environmental monitoring requirements

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 kids encounter dcoit (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one / sea-nine 211)

  • Marine Antifouling — Antifouling boat hull paint (Sea-Nine 211), Ship bottom coatings, Marina infrastructure protection
  • Industrial Preservatives — Paint and coating preservative (in-can), Adhesive and sealant preservative, Metalworking fluid biocide
  • Cooling Water — Industrial cooling system biocide

Safer alternatives

Lower-risk approaches that achieve a similar outcome to DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211):

  • Copper-free foul-release coatings
    Trade-offs: Zero point-of-use emissions; shifts emissions to power generation (grid-dependent); lower operating cost; higher capital cost; infrastructure requirements (charging, grid capacity); rapidly improving economics.
    Relative cost: Lower (ingredient elimination)
  • Ultrasonic antifouling
    Trade-offs: Zero point-of-use emissions; shifts emissions to power generation (grid-dependent); lower operating cost; higher capital cost; infrastructure requirements (charging, grid capacity); rapidly improving economics.
    Relative cost: 1.2-2×
  • Tralopyril
    Trade-offs: Alternative approach; specific tradeoffs depend on application context, scale, and regulatory requirements. Full hazard assessment of alternative recommended before adoption to avoid regrettable substitution.
    Relative cost: 1.2-2×

Frequently asked questions

Is dcoit (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one / sea-nine 211) safe for kids?

Infants are more vulnerable to DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211) than children or adults due to immature hepatic/renal clearance, higher intake-to-body-weight ratio, rapid organ development, and increased gastrointestinal absorption.

What products contain dcoit (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one / sea-nine 211)?

DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211) appears in: Antifouling boat hull paint (Sea-Nine 211) (Marine antifouling); Ship bottom coatings (Marine antifouling); Paint and coating preservative (in-can) (Industrial preservatives); Adhesive and sealant preservative (Industrial preservatives); Industrial cooling system biocide (Cooling water).

What should I do if my child is exposed to dcoit (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one / sea-nine 211)?

Minimize infant exposure through source control. For breastfeeding mothers: reduce maternal exposure. For formula-fed infants: use certified low-migration bottles and verified water sources. Consult pediatrician regarding any concerns.

Why do regulators disagree about dcoit (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one / sea-nine 211)?

DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211) has been classified by 3 agencies including IMO, EU BPR, Japan, 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 DCOIT (4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one / Sea-Nine 211) in the baby app

Look up products containing dcoit (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one / sea-nine 211), compare to alternatives, and explore the full data record.

Open in baby View raw API data

Sources (1)
  1. — expert_curation

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 →