Candidate for substitution: what it means for a biocidal product dossier

Article 10(1) lists six criteria, and meeting any one makes a substance a candidate. It meets an exclusion criterion in Article 5(1) but is approved by derogation under Article 5(2). It is a respiratory sensitiser under CLP. Its acceptable daily intake, acute reference dose or acceptable operator exposure level is significantly lower than most approved substances for the same product type and use. It meets two of the three PBT criteria. Its critical effects and use pattern still give cause for concern even with very restrictive risk management. Or it contains a significant proportion of non-active isomers or impurities.

The European Chemicals Agency (ECHA) examines the criteria in its opinion, and the Commission records the result in the approval or renewal regulation (Article 10(5)). Read the Annex of that regulation for each product type in the product, not a secondary list. It states whether the substance is a candidate, under which point of Article 10(1), and the approval and expiry dates. Then check for later acts, such as a decision postponing the expiry date while a renewal is assessed.

Status also sets the substance's approval period. A candidate's approval, and each renewal, lasts seven years at most (Article 10(4)), against the usual ten for a first approval and fifteen for a renewal. A substance that meets an exclusion criterion is limited to five years for its first approval (Article 4(1)). Some older substances received ten years under the transitional rules for Directive 98/8/EC, even as candidates.

Comparative assessment works use by use, so define each use the dossier will claim. Product type 6 in Annex V of the BPR covers preservatives for products during storage, often called in-can preservatives. These are products that control microbial spoilage of manufactured products to give them a shelf life, excluding food, feed, cosmetics, medicines and medical devices.

Take a fictional supplier, Brellin Additives, preparing a national application for a PT6 preservative based on glutaraldehyde, for water-based paints made by industrial users. Implementing Regulation (EU) 2015/1759 approved glutaraldehyde for PT6 and other product types from 1 October 2016, and names it a candidate for substitution under Article 10(1)(b), as a respiratory sensitiser. It received ten years under the Directive 98/8/EC transitional rule. Implementing Decision (EU) 2026/1109 then moved the expiry date from 30 September 2026 to 31 March 2029 while its renewal is assessed. Brellin records each use by the product treated, the target organisms, the user category and the application rate, because alternatives are compared on those terms.

Newer PT6 candidates show the other routes to the status. DBNPA is approved for PT6 from 1 November 2026 to 31 October 2031 as a candidate under points (a) and (e), for short-term preservation by industrial users of named materials only, and its products can be authorised only in Member States that meet the condition in Article 5(2)(c) (Implementing Regulation (EU) 2025/937).

Article 23(1) requires a comparative assessment as part of every application for authorisation, or renewal, of a product containing a candidate. The receiving competent authority runs it for a national authorisation. For a Union authorisation, the evaluating competent authority runs it and the Commission decides. The authority must restrict or prohibit the product only when both conditions in Article 23(3) are shown. First, another authorised product or a non-chemical method for the same uses presents a significantly lower overall risk, is sufficiently effective and has no other significant economic or practical disadvantages. Second, the chemical diversity of the active substances is adequate to minimise resistance in the target organism.

The method is set out in the Commission's technical guidance note on comparative assessment, agreed with Member State competent authorities in May 2015. It starts with a screening phase that checks chemical diversity. As a general rule, at least three different active substance and mode of action combinations should remain available for a use. Where diversity is inadequate, the assessment can usually stop there. Tier I compares authorised alternative products, first from their summaries of product characteristics and then in detail. Tier II compares non-chemical methods. Economic and practical disadvantages are judged at the level of the user. The note adds that a restriction carries the burden of proof, so an inconclusive assessment leads to a five-year authorisation. The note is guidance, and Member States aren't legally bound by it.

Recent PT6 decisions show the usual outcome. Three Union authorisations for glutaraldehyde products of product types 6, 11 and 12, granted in 2025 and 2026, each found that chemical diversity was insufficient for substitution and set a five-year term. The Regulation also allows, in exceptional cases, authorisation for up to four years without a comparative assessment where experience must first be gained from using the product (Article 23(4)).

The authority searches for alternatives itself, but the dossier should make that search easy. For each use, list the authorised products with the same use from the Register for Biocidal Products, their active substances and modes of action, and any non-chemical methods in use in the sector. The guidance note invites applicants to include a critical review of the information on alternatives that ECHA gathered in its public consultation under Article 10(3). For a substance already approved, that consultation runs again only at renewal, so the review covers the alternatives known to the applicant.

Back the review with data the authority can compare. That means efficacy data for the claimed uses, resistance information and a management strategy (Annex III, point 6.8.1), and the practical constraints of the uses. For Brellin, a practical constraint could be compatibility with the paint formulation or the time the preservative needs to act. Record them as evidence, not assertion, because disadvantages count only if they are significant for the user.

Mutual recognition needs its own preparation. The guidance note says the reference Member State should identify alternatives authorised in its own market and in other Member States. Under Article 37(1), each concerned Member State may propose to refuse or adjust the authorisation for a product containing a candidate for substitution, with a 60-day period to agree with the applicant before the Commission decides. List the alternatives authorised in each target country, not only the reference one.

Build the plan around five dates. The product evaluation runs for up to 365 days from validation, with the clock stopped while the authority waits for extra information (Article 30). An authorisation for a product with a candidate lasts five years at most, not the usual ten, and each renewal the same (Article 23(6)). A renewal application is due at least 550 days before expiry (Article 31(1)), and the comparative assessment is repeated. If an assessment leads to a prohibition or restriction, it takes effect four years after the decision, or earlier if the substance's approval ends first (Article 23(7)).

Track the substance as well as the product. For glutaraldehyde, Finland, as the evaluating authority, expects to send its renewal assessment report to ECHA in the third quarter of 2027. A renewal of a candidate is capped at seven years, and ECHA's public consultation on potential candidates runs before its opinion, which is the moment to submit information on the uses Brellin needs. A change in the substance's conditions or status should restart the product timeline.

Watch proposals separately from adopted law. The Commission's food and feed safety omnibus proposal, COM(2025) 1030, would make most active substance approvals unlimited in time while keeping approvals of candidates for substitution limited to seven years. It wasn't adopted on 14 October 2026, and the European Parliament's indicative plenary date was 23 November 2026.