User Guide to Thresholds and Classification - Environmental ...

396User Guide for Thresholds and Classifications0.0001 < EC 50 0.001 1,0000.00001 < EC 50 0.0001 10,000(continue in factor 10 intervals)Note: EC 50 = median effect concentration. [where appropriate, ie for microbial function data, the EC 25 value can beused]Table 20.6: Example calculation for soil hazard classification of mixture Y containing one highly toxic componentComponentL(E)C 50(mg/kg)Soilclassificationof individualcomponentComponentwith DT 50>30 days*Concentration ofcomponent inmixture(%)Multiplyingfactor (M)(from Error!Referencesource notfound.)B 5 9.2B No 5 1 5P 0.02 9.2A Yes 0.05 10 0.5Q 0.9 9.2A No 1 1 1T 50 9.2C Yes 40 1 40U 200 Not classified No 53.95 1 53.95Adjustedconcentrationof componentin mixture(M x %)Note:*where no data on degradation, the default applies, ie the substance is considered to have DT 50 >30 daysL(E)C 50 = median lethal concentration or median effect concentration. [where appropriate, ie for microbial functiondata, the EC 25 value can be used]The steps to follow in applying the summation approach to soil hazard classification for mixtures with highlytoxic components are set out below, using the information from Table 20.6.Step 1Component P is highly ecotoxic and attracts a multiplier of 10, resulting in a weighted concentration ofthat component of 0.5%.Component Q, although classified as 9.2A does not attract a multiplier, that is:(10 x P) + Q(10 x 0.05%) + 1% = 1.5%, which is < 25%Therefore mixture Y is not classified as 9.2A.Step 2: Consider components classified as 9.2A and 9.2B.10((10 x P) + Q) +B10((10 x 0.05%) +1%) + 5% = 15% + 5% = 20%which is