User Guide to Thresholds and Classification - Environmental ...

295User Guide for Thresholds and ClassificationsTable 19.5: Example calculation for aquatic classification of mixture Z containing one highly toxic componentComponentL(E)C 50(mg/L)AquaticclassificationofindividualcomponentComponentnot rapidlydegradable orbioaccumulatesConcentrationofcomponent inmixture (%)Multiplyingfactor M(from table19.4.)B 5 9.1B No 5 1 5P 0.002 9.1A Yes 0.05 100 5Q 0.9 9.1A No 1 1 1T 50 9.1C No 40 1 40Adjustedconcentration ofcomponentinmixture(M x %)UNotclassifiedNot classified No 53.95 1 53.95Note: L(E)C 50 = median lethal concentration or median effect concentration.The steps to follow in applying the summation approach to aquatic hazard classification for mixtures withhighly toxic components are set out below, using the information in Table 19.5.Step 1Component P is highly ecotoxic and attracts a multiplier of 100, resulting in a weighted concentration ofthat component of 5%.Component Q, although classified as 9.1A, is not given addition weighting, that is:(100 × P) + Q(100 × 0.05%) + 1% = 6%which is < 25% therefore mixture Z is not classified as 9.1A.Step 2a: Consider components classified as 9.1A and 9.1B10((100 × P) + Q) +B10((100 × 0.05%) +1%) + 5% = 60% + 5% = 65%which is ≥ 25% therefore mixture Z is classified as 9.1B unlessStep 2b: Consider components that are not rapidly degradable or are bioaccumulativeComponent P is not rapidly degradable in the aquatic environment and attracts a multiplier of 100 due toits high toxicity, resulting in an adjusted concentration for that component of 5%. As mixture Z is notclassified as 9.1A, an additional weighting is given to component P at Step 2, i.e. 10((100 × 0.05%) =50%.Mixture Z retains the 9.1B classification based on the weighted presence of ≥25% of components in themixture that are not rapidly degradable.January 2012 EPA0109