OECD Test Guidelines Update 

On 25 June 2025, the OECD (Organisation for Economic Co-operation and Development) released 56 new, updated and corrected test guidelines related to chemical testing.

 

These revisions reflect the latest scientific developments and encourage best practices in the field, particularly by supporting the 3Rs principles (Replacement, Reduction, and Refinement) of animal use in experiments. Many of the new guidelines emphasise in vitro testing methods and structured approaches designed to minimise or eliminate the need for animal testing. These updates reflect the latest scientific progress and enhance global harmonisation through mutual acceptance of data across OECD member and adhering countries. 

Key updates include: 

New Test Guideline: 

  • Test No. 254: Mason bees (Osmia sp.), Acute Contact Toxicity Test. This introduces a new scientifically robust method for solitary bee risk assessment, to complement the existing honeybee and bumblebee protocols (Test No. 214 and 246). 

The following test guidelines were updated to allow collection of tissue samples for ‘omics’ analysis: 

  • Test No. 203: Fish Acute Toxicity Test 
  • Test No. 210: Fish Early-life Stage Toxicity Test 
  • Test No. 236: Fish Embryo Acute Toxicity Test 
  • Test No. 407, 408, 421, 422: oral toxicity and reproduction/developmental toxicity rodent studies 

Some test guidelines were updated to clarify or correct protocols: 

  • Test No. 239: Toxicity on Myriophyllum spicatum, improved analytical requirements, calculations and statistical analyses. 
  • Hydrolysis and transformation studies (Test No. 111, 307, 308, 316) were corrected for radioactive labelling position. 
  • Test No. 506 on pesticide residue stability was updated based on global use in pesticide storage stability studies, giving now more explicit information about how these studies should be performed and the data interpreted.  

Contact us to discuss how these changes could influence your regulatory approach or risk assessment strategies. In addition, we offer support with study monitoring to ensure your studies aligns with the highest scientific and regulatory standards.