User Guide to Thresholds and Classification - Environmental ...

392User Guide for Thresholds and ClassificationsNotes:*where no data on degradation, the default applies, ie the substance is considered to have DT50 >30 days;EC 50 = median effect concentration;DT 50 = time required to reduce the concentration of the original substance by 50%. [where appropriate, ie formicrobial function data, the EC25 value can be used]Figure 20.1: Soil classification of a single substance20.3. Classification of mixturesTo make use of all available data to classify the hazards of the mixture to the soil environment, the followingassumption has been made and is applied where appropriate.The ‗relevant components‘ of a mixture are those that are present in a concentration of 1% (by weight – w/w)or greater, unless there is a presumption (for example, in the case of highly toxic components) that acomponent present at less than 1% can still be relevant for classifying the mixture for aquatic environmentalhazards.January 2012 EPA0109