# Commission Regulation (EC) No 761/2009 of 23 July 2009 amending, for the purpose of its adaptation to technical progress, Regulation (EC) No 440/2008 laying down test methods pursuant to Regulation (EC) No 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) (Text with EEA relevance), Division 2.2.4: ECx estimation

Extent: E+W+S+N.I.

Estimates of the ECx (e.g. EC50) should be based upon both average specific growth rate (ErCx) and yield (EyCx), each of which should in turn be based upon frond number and one additional measurement variable (total frond area, dry weight, or fresh weight). This is because there are test substances that impact frond number and other measurement variables differently. The desired toxicity parameters are therefore four ECx values for each inhibition level x calculated: ErCx (frond number); ErCx (total frond area, dry weight, or fresh weight); EyCx (frond number); and EyCx (total frond area, dry weight, or fresh weight).

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Source: https://www.legislation.gov.uk/eur/2009/761/annex/VI/division/2/division/2.2/division/2.2.4 (the official version)
Page: https://openlegislation.uk/eu-regulation-2009-761/annex-VI/division-2/division-2.2/division-2.2.4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.