Substitution Warning

Chemicals which are hazardous to the marine environment are subject to substitution warnings under the Harmonised Mandatory Control Scheme (HMCS).

The UK  follow and apply the OSPAR harmonised Pre-screening scheme and comply with REACH recommendation to replace chemical substances identified as candidates for substitution. These substances are flagged with a substitution warning on the product template

Find out more about the substitution warning for chemicals used and discharged offshore.


An offshore chemical has a substitution warning if:

  1. it is, or contains a substance that is on the OSPAR List of chemicals for priority action; or

  2. it is, or contains a substance that is on the Authorisation List established pursuant to REACH (Annex XIV) and the Sunset Date in that Annex has passed, or

  3. its offshore use is covered by restrictions under Annex XVII to REACH; or

  4. it is considered by the authority, to which the application has been made, to be of equivalent concern for the marine environment as the substances covered by the previous sub-paragraphs; based for example on its inclusion on the REACH Candidate List of Substances of Very High Concern for Authorisation, or

  5. it is inorganic and has a LC50 or EC50 less than 1 mg/l; or

  6. it has an ultimate biodegradation (mineralization) of

less than 20% in OECD 306, Marine BODIS or any other accepted marine protocols; or

less than 20% in 28 days in freshwater (OECD 301 and 310); or

  1. half-life values derived from simulation tests submitted under REACH (EC 1907/2006) are greater than 60 and 180 days in marine water and sediment respectively (e.g. OECD 308, 309 conducted with marine water and sediment as appropriate); or

  2. it meets two of the following three criteria:
    1. biodegradation: less than 60% in 28 days (OECD 306 or any other OSPAR-accepted marine protocol); or in the absence of valid results for such tests:
      • less than 60% (OECD 301B, 301C, 301D, 301F, Freshwater BODIS); or
      • less than 70% (OECD 301A, 301E);
    2. bioaccumulation: BCF > 100 or log Pow ³ 3 and molecular weight <700; or if the conclusion of a weight of evidence judgement under Appendix 3 of OSPAR Agreement 2008-5 is negative; or
    3. toxicity: LC50 < 10mg/l or EC50 < 10mg/l; if toxicity values <10 mg/l are derived from limit tests to fish, actual fish LC50 data should be submitted;

  and a less hazardous (or preferably non-hazardous) substitute is available


Recommendations for the chemical supplier and operator in relation to offshore chemicals with a substitution warning

Operators are required:

  • to consider the selection of products during the risk-assessment process, in terms of the magnitude of their Risk Quotient (RQ) and the presence of hazardous substances, (including candidates for substitution),
  • to provide a robust defence for the continued use of products that have a high RQ or contain candidates for substitution

Operators are encouraged to select products without a substitution warning.

Chemical suppliers:

  • must consider any advice they provide to operators that justifies continued use of any product containing candidates for substitution,
  • should consider a managed approach to the replacement of any undesirable components, leading to the reformulation and re-certification of products.

If there are good technical reasons why a substance cannot immediately be substituted, the supplier should highlight these to operators so that they can include this information in their justification for continued use of the product.

The OCNS team is happy to explain any substitution warning assigned to a product, and to discuss any approach you may be considering in addressing these issues.