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OECD 207 is a standard method designed to examine the toxicity of chemicals to earthworms, including two methods: a paper contact toxicity test and an artificial soil test.
The recommended specie is Eisenia foetida (Michaelsen).
The initial screening test (filter paper contact test) involves exposing earthworms to test substances on moist filter paper in order to identify potentially toxic chemicals to earthworms in soil. Five or more treatment levels in a geometric series and, at least, ten replicates (one worm per vial) for each treatment should be used. Tests are done in the dark and for a period of 48 hours.
The artificial soil test gives toxicity data more representative of natural exposure of earthworms to chemicals. It involves keeping earthworms in samples of a precisely defined artificial soil. Five concentrations, in a geometric series, of the test substance have been applied. One concentration resulting in no mortality and one resulting in total mortality should be used. Four replicates for each treatment are recommended. Mortality is assessed 7 and 14 days after application..
▶ Materials that can be tested:
➢ General chemicals, biocides and crop protection products, and so on;
▶ Earthworm species: Eisenia foetida;
▶ Test validity criteria: The mortality in the controls should not exceed 10 per cent at the end of either test.
Filter paper contact test (initial screening) (optional):
▶ Test substance incorporation: The test substance is dissolved in water or in a suitable organic solvent to give a range of known concentrations. One mL of solution is pipetted into each vial and evaporated to dryness, the vial being rotated horizontally as it dries. The control vial should be treated with 1 mL of deionized water or appropriate organic solvent. After drying, 1 mL of deionized water is added to each vial to moisten the filter paper. Each vial is sealed with a cap or plastic film with a small ventilation hole;
▶ Reactor: Flat-bottomed glass vials approximately 8 cm in length and 3 cm in diameter, whose sides are lined with filter paper cut to a suitable size so it does not overlap appreciably;
▶ Test substance dosage: A preliminary range-finding test may be done optionally using five different dosages ranging from 0.0001 mg/cm2 to 1.0 mg/cm2;
▶ Number of tests: for each dosage, ten replicates, each consisting of one worm per vial;
▶ Testing conditions: vials are laid on their sides at 20° ± 2°C in the dark;
▶ Duration: 48 hours.
Artificial soil test:
▶ Test substance incorporation: If soluble in water, the test substance is dissolved in water and the mixture is mixed with the artificial soil. If insoluble in water, the mixture can be prepared using a suitable organic solvent;
▶ Test setup: Place ten earthworms in each glass container that contains 750 g test medium. Cover the container with perforated plastic film to prevent the test medium from drying and kept under the test conditions for 14 days;
▶ Test substance dosage: A preliminary range-finding test may be done optionally using five different dosages at 0.01, 0.1, 1.0, 10, 100, 1000 mg/kg (dry weight of soil);
▶ Number of tests: for each dosage, use four replicates, each consisting of 10 worms;
▶ Testing conditions: 20° ± 2°C in continuous light;
▶ Duration: 14 days.
To learn more about different types of biodegradation tests, their applicability, biodegradation mechanisms, and many other information such as case studies, publications, and blogs, please check our Aropha Resource Center