Testing of chemicals

OECD Test Guidelines for Chemicals


What's new

Guideline on Defined Approaches for Skin Sensitisation On 14 June 2021, the OECD published a new Guideline on Defined Approaches for Skin Sensitisation (OECD GL No. 497). This is a new type of OECD Guideline that uses several types of combined information to provide chemical safety information and can replace the need for animal test data. The project to develop this new Guideline started in 2017 and was led by the United States, the European Commission Joint Research Centre and Health Canada, supported by a group of nominated experts. The Defined Approaches (DAs) were validated using an extensively curated large set of human and mouse reference data on skin sensitisation. A supporting document providing details on the data curation and performance characteristics of the DAs on skin sensitisation will be published soon in the OECD Series on Testing and Assessment

What is a Defined Approach? 

A Defined Approach (DA) consists of selected information sources (e.g. in silico predictions, in chemicoin vitro data) used in a specific combination, and resulting data are interpreted using a fixed data interpretation procedure (DIP) (e.g. a mathematical, rule-based model). DAs are intended to overcome some limitations of the individual methods. 

What does the new OECD Guideline contain?

The first three DAs included in this Guideline use combinations of OECD validated in chemico and in vitro test data, in some cases along with in silico information.  The DAs included in this Guideline have shown to either provide the same level of information or be more informative than the LLNA (OECD TG 429) for hazard identification (i.e. sensitiser versus non-sensitiser).  In addition, two of the DAs provide information for sensitisation potency categorisation that is equivalent to the potency categorisation information provided by the LLNA.


This new Guideline is intended to be the first of more harmonised defined approaches adopted across OECD member countries and countries adhering to the Mutual Acceptance of Data system to 1) address regulatory needs, 2) enhance the utility of individual methods when used in testing strategies, and 3) reduce use of animal testing.


Test No. 249: Fish Cell Line Acute Toxicity - The RTgill-W1 cell line assay

The OECD published Test Guideline No. 249: Fish Cell Line Acute Toxicity: The RTgill-W1 cell line assay on 14 June 2021.

This is another significant step in the implementation of the 3Rs-principles (Reduction, Replacement, Refinement), the guiding principles for more ethical use of animals in testing.

The project to develop this test guideline was led by Switzerland and Norway and resulted in a method that identifies chemicals that are toxic to fish by testing cell cultures instead of whole animals.

Watch Switzerland’s video on the fish cell line assay:

In line with scientific progress and the commitment of OECD member, the OECD continues the further development of methods and approaches to improve animal welfare in chemical testing. 

On 14 June, OECD member countries and countries adhering to the Mutual Acceptance of Data system adopted the following new, updated and corrected Guidelines for the testing of chemicals.




All of these Guidelines were elaborated with the assistance of lead countries and/or expert groups providing input (i.e. experimental/validation work, (statistical) analysis, data collection and curation). Draft documents have been reviewed multiple times by country experts to improve the final product. All of these Guidelines enable the production of results that are covered by the Mutual Acceptance of Data system, when used in laboratories that are GLP certified.

A number of supporting documents (validaiton reports, peer-review reports, guidance documents) will be published in Q3 2021 in the OECD Series on Testing and Assessment.


OECD Test Guidelines 

‌The OECD Guidelines for the Testing of Chemicals are a unique tool for assessing the potential effects of chemicals on human health and the environment. Accepted internationally as standard methods for safety testing, the Guidelines are used by professionals in industry, academia and government involved in the testing and assessment of chemicals (industrial chemicals, pesticides, personal care products, etc.). These Guidelines are continuously expanded and updated to ensure they reflect the state-of-the-art science and techniques to meet member countries regulatory needs. The Guidelines are elaborated with the assistance of experts from regulatory agencies, academia, industry, environmental and animal welfare organisations. 

OECD Test Guidelines are covered by the OECD Mutual Acceptance of Data (MAD) system. Under this system, laboratory test results related to the safety of chemicals that are generated in accordance with OECD Test Guidelines and OECD Principles of Good Laboratory Practices are accepted in all OECD countries and adherent countries for the purpose of safety assessment and other uses relating to the protection of human health and the environment.


The OECD Guidelines for the Testing of Chemicals are split into five sections:

The full list of adopted Test Guidelines, the draft TGs under public commenting rounds, the draft Guidance and review documents are available on the Test Guidelines Programme


Publications in the Series of Testing and Assessment

This Series includes publications related to testing and assessment of chemicals; some of them support the development of OECD Test Guidelines (e.g. validation reports, guidance documents, detailed review papers).

Find out more about our work 

Find out about our areas of work, upcoming webinars, programme of work and the Council Acts related to Test Guidelines. 


Test Guidelines that have been deleted or replaced by updated versions

The Test Guidelines that have been deleted should not be used for new testing. They are included here because it may be useful to consult them in the framework of the assessment of substances based on old study reports. The guaranties of Mutual Acceptance of Data (MAD) would not apply if these Test Guidelines were used for new testing.

In November 2012, the Joint Meeting of the Chemicals Committee and Working Party on Chemicals, Pesticides and Biotechnology decided on a transition period of 18 months, between the Council Decision and the effective deletion, for Test Guidelines that have been updated or deleted. For more information, please read the presentation: Update of Test Guidelines and the Mutual Acceptance of Data.


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