Earthworms provide information on chemical-effects in soils
Earthworms are an important indicator of soil fertility. They aerate the soil, promote root growth, improve water absorption, produce humus and contribute to soil fertility: the new standard test method examines the impact of chemicals on individual species and the earthworm community in field trials.
The new OECD Test Guideline No. 256 examines the short- and long-term effects of chemicals on earthworm communities in soil under field conditions. It is used in particular for the European authorisation of plant protection products and is based on ISO-Standard 11268-3, which has been in use since 1999 and was last updated in 2014. An earthworm field study is primarily conducted during the higher-tier risk assessment of plant protection products, where a risk to earthworms has been identified in the standard test procedures for chronic toxicity and exposure assessment based on the proposed application rate. It is therefore important that the field study on earthworms employs a test design with sufficient statistical power to reliably identify effects on the earthworm community.
An analysis of the data collected to date from studies conducted in accordance with the ISO standard revealed very low statistical power: effects of less than 50 per cent were not reliably detected. Consequently, an improved and more complex test design was developed for the new OECD Test Guideline. Furthermore, the suitability of available statistical methods for analysing data from field studies was tested and adapted to ensure an optimised statistical analysis of the data. In order to be able to link the effects observed in the field to the actual residues of the test substances applied, additional analytical measurements of chemical residues were included throughout the course of the study. The new OECD Test Guideline is a valuable contribution to the updating of the guidance document on terrestrial risk assessment of plant protection products, which is currently being revised.
The OECD Test Guidelines for the testing of chemicals comprise a series of standardised, internationally harmonised and accepted test methods and guidelines, which can be used to characterise chemicals and investigate their potentially harmful behaviour and effects on humans and the environment. The Test Guideline now adopted was retrospectively validated by ECT Ökotoxikologie GmbH, RWTH Aachen and Darwin Statistics on behalf of the Federal Environment Agency and with funding from the Federal Ministry for the Environment, and a pilot study was carried out to develop an improved test design. The data collected from the pilot study were analysed alongside data from field studies on earthworms held by the Federal Environment Agency.