Research and analysis

Applicability of OECD Test Guideline 201 validity criteria to algae in the genus Skeletonema: summary

Published 20 July 2022

Applies to England

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This publication is available at https://www.gov.uk/government/publications/applicability-of-oecd-test-guideline-201-validity-criteria-to-algae-in-the-genus-skeletonema/applicability-of-oecd-test-guideline-201-validity-criteria-to-algae-in-the-genus-skeletonema-summary

1. Chief Scientist’s Group report summary

This project examined whether the validity criteria specified by a widely used standard method for algal growth inhibition studies are relevant for Skeletonema species. The results will help the Environment Agency to understand the reliability and relevance of such data for chemical hazard assessment.

1.1 Background

Algae are a key trophic group in chemical risk assessment, so regulations frequently require algal growth inhibition studies to measure how toxic a substance is to one or more representative algal species. Most studies use freshwater algae and follow the Organisation for Economic Co-operation and Development (OECD) test guideline (TG) 201. However, data may sometimes be available from an International Organisation for Standardization (ISO) method for marine algae in the genus Skeletonema. These two methods have slightly different validity criteria for controls.

Some regulatory assessments have compared Skeletonema data from ISO studies with the OECD TG validity criteria. This species forms chains of cells, which is different to the unicellular freshwater algae for which the OECD TG is validated. Often the OECD’s section-by-section growth rate criterion is not met for Skeletonema, which has resulted in some Skeletonema studies being rejected as unreliable.

1.2 Method

To assess whether the section-by-section growth rate criterion is relevant or achievable for Skeletonema, this project reviewed historical control data from studies performed in academic and commercial laboratories and generated new laboratory data.

1.3 Results

Overall, there is high section-by-section growth variability for Skeletonema meaning around half of all tests do not meet the OECD validity criterion. However, tests that fail this criterion are not necessarily unreliable and careful review of cell culturing and test design (particularly biomass assessment) is needed to reach a decision. The report makes specific recommendations for cell culturing/counting and test design to produce optimum controls and reduce the number of tests that would be rejected.

1.4 Next steps

This work will inform UK regulatory review of algal studies using Skeletonema species under the UK REACH (Registration, Evaluation, Authorisation and restriction of Chemicals) Regulation to conclude if the data can be used in hazard assessment and classification or to fulfil algal toxicity information requirements. The full report is available from UKREACH@environment-agency.gov.uk.

1.5 Project details

This summary relates to information from the following project:

  • Title: Applicability of OECD Test Guideline 201 validity criteria to algae in the genus Skeletonema

  • Project manager: Audrey Pearson, Chemicals Assessment Unit, part of the Chief Scientist’s Group

This project was commissioned by the Environment Agency’s Chief Scientist’s Group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.

Enquiries: research@environment-agency.gov.uk

© Environment Agency

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