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CarCareTruthProducts · Ranked

CMIT/MIT Preservative

  • Biocides
  • CAS 55965-84-9
  • IUPAC: Mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one

CMIT/MIT Preservative (CAS 55965-84-9) appears in 2 of the 1,812 car-care products CarCareTruth tracks (as of June 2026), 1 of which carry a DANGER signal word on their published Safety Data Sheet. It is classified as a respiratory sensitizer (asthmagen).

Known skin sensitizer (H317 Cat 1) and respiratory sensitizer (H334 Cat 1 asthmagen) at higher concentrations. In car-care products it typically appears at <0.01% — at this concentration the clinical sensitization risk during consumer use is low, but it remains a regulatory sensitizer ingredient. Banned or restricted in some rinse-off cosmetics in the EU at concentrations that could be inhaled.

CMIT/MIT (the Kathon CG preservative system) is a blend of methylchloroisothiazolinone (CMIT) and methylisothiazolinone (MIT) widely used as a broad-spectrum preservative in water-based industrial and consumer formulations. It prevents bacterial and fungal contamination in emulsion systems.

The isothiazolinone class is a known skin sensitizer (H317) and respiratory sensitizer (H334) in occupational settings at higher concentrations. In car-care consumer products, CMIT/MIT typically appears at <0.01% (0.1 g/L or less), well below the concentrations that drive acute sensitization in normal use. However, it retains the chemical classification.

The primary regulatory concern in recent years has been aquatic toxicity and environmental persistence — the compound is highly toxic to aquatic organisms and shows poor biodegradability. Its use in rinse-off consumer products is restricted in the EU. In car polishes and waxes applied to painted surfaces (leave-on products), the environmental pathway is primarily via pad-cleaning water rather than direct rinse-off.

Health & environment profile

VOC
no
Prop 65 listed
no
Asthmagen
yes
EPA Safer Choice
no
Aquatic toxicity
yes
Biodegradable
no
Bioaccumulative
no
Persistent
yes
Ozone depleting
no
Microplastic
no
PFAS
no
Env. score
2/5
Purpose: Preservative — prevents microbial growth in water-based formulations

Common questions about CMIT/MIT Preservative

What is CMIT/MIT Preservative used for in car care?
Preservative — prevents microbial growth in water-based formulations
Is CMIT/MIT Preservative a VOC?
No. CMIT/MIT Preservative is not classified as a volatile organic compound (VOC).
Is CMIT/MIT Preservative on California's Proposition 65 list?
No. CMIT/MIT Preservative is not on California's Proposition 65 list.
Is CMIT/MIT Preservative a respiratory sensitizer?
Yes. CMIT/MIT Preservative is classified as a respiratory sensitizer (asthmagen).

2 products contain this

Related

Health and environment notes translate the manufacturer Safety Data Sheet, the GHS classification, and authoritative regulatory listings (California Prop 65, EPA). Not medical advice. They describe the ingredient itself; whether a hazard applies to a finished product depends on its concentration and how it's used.