1. Chief Scientist’s Group report summary

This project reviewed bioaccumulation studies for chemical substances using the water flea (scientific name, Daphnia magna) to explore the test methods used and consider the implications of these for regulatory assessments.

1.1 Background

Bioaccumulation results from the movement of a substance into an organism from its environment and is important for both hazard and risk assessment. It is usually measured in a laboratory test with fish. A reduction in the use of vertebrate species in chemical testing is desirable from an animal welfare and resource perspective. Water fleas (an aquatic invertebrate) are already widely used for toxicity testing, and they could be an option for preliminary bioaccumulation measurements to reduce reliance on fish.

1.2 Approach

A search of published academic literature and regulatory databases was carried out to identify bioaccumulation studies using the water flea as the test species. The methods used in those studies were summarised and compared, then discussed in terms of the water flea’s life cycle. The bioaccumulation data for water fleas were compared with those for fish for each substance investigated, where possible.

1.3 Results

Twenty-two laboratory-based bioaccumulation tests were identified. The water fleas were generally kept according to well established standard procedures. Experiments used a variety of ages, from < 24 hours old to sexually mature adults. The length of substance exposure was usually between 24 and 48 hours, although some were shorter and one test lasted 40 days. Other variations in test conditions included the number of water fleas used, whether they were fed or not, and the number of replicates. There were also differences in how bioaccumulation was calculated and the units used. The extent of bioaccumulation in water fleas and fish was comparable for some substances, but not all.

The project concludes that bioaccumulation potential can be determined by exposing water fleas to substances for short time periods (a few days). It uses findings from the analysis of the published studies to provide some preliminary guidance for the interpretation of this type of test. The report also recommends further work that would be needed to support the development of a standardised test method.

1.4 Publication details

This summary relates to information from the following:

• Title: The water flea as an alternative to fish for bioaccumulation testing.
• Project manager: Richard Gibson, Chemicals Assessment Unit, Chief Scientist’s Group
• Contractor: Vitis Regulatory Limited, Saxon House, John Roberts Business Park, Whitstable, Kent, CT5 3BJ

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