User Guide to Thresholds and Classification - Environmental ...

280User Guide for Thresholds and ClassificationsTermmajor metaboliteMATCmaximum acceptable toxicantconcentrationDefinitionAll metabolites that are formed in amounts of equal to or more than 10% of theapplied amount of substance at any time-point evaluated during the degradationstudies in the appropriate compartment under consideration (soil or water).The maximum acceptable toxicant concentration, being the geometric mean ofthe NOEC and LOEC where the NOEC and LOEC are derived from the samestudy.See Schedule 6 to the Hazardous Substances (Minimum Degrees of Hazard)Regulations 2001. See also LOEC, NOEC.See MATC.median effect concentration See EC 50.median lethal concentration See LC 50.median lethal dose See LD 50.metaboliteminor metaboliteno observed effectconcentrationNOECAll breakdown products of a substance that are formed in the environment bybiotic or abiotic processes.All metabolites, degradation and reaction products that are formed in amountsof less than 10% of the parent substance at any time during the degradationstudies under consideration.See NOEC.The no observed effect concentration, being the highest concentration of asubstance that does not produce a significant ecotoxic effect in an organism ororganism population.See Schedule 6 to the Hazardous Substances (Minimum Degrees of Hazard)Regulations 2001.In relation to a substance in water, means:a. 28 days after a solution containing the substance is inoculated with microorganisms,there is at least a:i. 70% reduction in dissolved organic carbon in the solution; orrapidly degradableii.iii.60% depletion of oxygen in the solution, when compared with themaximum depletion of oxygen that would occur if the substance werecompletely degraded; or60% generation of carbon dioxide in the solution, when compared withthe maximum generation of carbon dioxide that would occur if thesubstance were completely degraded; orb. if only COD and BOD 5 data are available, the ratio of BOD 5 to COD isgreater than or equal to 0.5:1; orc. at least 70% of the substance can be degraded biotically or abiotically, in theaquatic environment within 28 days.January 2012 EPA0109