Filippo Busolo – CHEMLER
1,2-benzisothiazol-3(2H)-one; 1,2-benzisothiazolin-3-one (BIT) (INDEX: 613-088-00-6; EC: 220-120-9; CAS: 2634-33-5) is an isothiazolinone, widely used in the world of paints and varnishes as a bactericidal and fungicidal active ingredient, weakly active against Pseudomonas. It is a very stable substance with low volatility, stable at basic pH values and combinable with other active ingredients.
CLP CLASSIFICATION OF THE BIT
The Delegated Regulation (EU) 2024/197 (XXI ATP to the CLP Reg.), in application from 1th September 2025, will change the CLP classification of 1,2-benzisothiazol-3(2H)-one (BIT). The most important change for paint and varnish formulators is the specific concentration limit, which will increase from the current 500 ppm to 360 ppm for triggering the classification as a skin sensitiser, H317. The two CLP classifications, before and after the introduction of the 21st ATP CLP, are compared in this article.
BIT AS TREATED ARTICLE
According to Regulation (EU) 528/2012 as amended (BPR), a treated article is any substance, mixture or article treated with, or intentionally containing, one or more biocidal products. A treated article that has a primary biocidal function is considered a biocidal product.
Article 58 of the BPR provides the rules for placing treated articles on the market, i.e. treated articles that are not biocidal products.
With Implementing Regulation (EU) 2025/929, BIT was approved as an active substance for use in biocidal products of product type 6 (PT6), i.e. preservative for products during storage.
The placing on the market of treated articles is subject to the conditions:
a) the person responsible for the placing on the market of a treated article that has been treated with BIT or that contains BIT shall ensure that the label of that treated article bears the information listed in the second subparagraph of Article 58(3) of the BPR Regulation;
b) the person responsible for placing on the market for use by non-professional users of a mixture (other than varnishes) treated with or containing BIT shall ensure that the mixture does not contain BIT at a concentration leading to the classification of the mixture as a skin sensitiser category 1A, unless exposure can be prevented by other means than the use of personal protective equipment;
c) the person responsible for placing on the market for use by non-professional users a paint treated with or containing BIT at a concentration leading to the classification of the mixture as a skin sensitiser category 1A shall ensure that:
i. the paint is supplied with suitable protective gloves complying with European standard EN 374 or equivalent;
ii. the label ndicates that protective gloves must beworn during use.
