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Toxicity to aquatic plants other than algae

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Description of key information

EC50 = 100 mg/L

Key value for chemical safety assessment

EC50 for freshwater plants:
100 mg/L

Additional information

From Section 13.5.3 of the EU Manual of Decisions dated July 2006:

Alternatives to the algae growth inhibition test with coloured substances

In the Annex VI of Directive 67/548/EEC an exemption clause is mentioned on algae growth inhibition tests with coloured substances. The clause emphasises that “where it can be demonstrated in the case of highly coloured substances that algal growth is inhibited solely as a result of a reduction in light intensity, then the 72h EC50 for algae should not be used as a basis for classification.”

In order to make a distinction between shading and toxic inhibition effects, in 1994 some modifications to the algae growth inhibition test, known as the ETAD (Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers) method (also known as the double flask method), were suggested. Advanced insights revealed that the ETAD method is too simplistic to allow evaluation of both toxic and light absorption effects of the coloured substances and should not be used any more.

Instead, a modified standard algae growth inhibition test, which applies the recommendations in the OECD Guidance Document on Testing and Assessment, number 23 (2000), is recommended for testing light absorbing substances The following adjustments to the standard algae growth inhibition test, Annex V method C.3 (or OECD guideline 201) have to be applied:

• The irradiation (light intensity) should be in the highest end of the range prescribed in the method C.3 (or (draft revised) OECD guideline 201): 120μE m-2 s-1 or higher.

• The light path should be shortened by reduction of the volume of the test solutions (in the range of 5 - 25 ml).

• Sufficient agitation (for example by moderate shaking) should be performed in order to obtain a high frequency of exposure of the algae to high irradiation at the surface of the culture.

 

For highly light absorbing substances, the modified standard algae growth inhibition test is not recommended. With these particular substances, a modified standardLemna-test (draft OECD guideline 221) is recommended. The following modification to the standardLemnatest has to be applied: the test has to be performed on a black, non-reflecting surface.