User Guide to Thresholds and Classification - Environmental ...

310User Guide for Thresholds and ClassificationsChronic testing involves an exposure that is lingering or continues for a longer time; the term can signifyperiods from days to a year, or more depending on the reproductive cycle of the aquatic organism. Chronictests can be done to assess certain endpoints relating to growth, survival, reproduction, and development.Chronic toxicity data are less available than acute data and the range of testing procedures lessstandardised. Data generated according to the OECD Test Guidelines 210 (Fish Early Life Stage), 202or 211 (Daphnia Reproduction) and 201 (Algal Growth Inhibition) can be accepted. Other validatedand internationally accepted tests could also be used. The NOECs or other equivalent L(E)Cx shouldbe used.It should be noted that several of the OECD guidelines cited as examples for classification are being revisedor are being planned for updating. Such revisions may lead to minor modifications of test conditions.Therefore, the expert group that developed the harmonised criteria for classification intended some flexibilityin test duration or even species used.Guidelines for conducting acceptable tests with fish, crustacea, and algae can be found in Appendix 19A.The OECD‘s (1998) Detailed Review Paper on Aquatic Toxicity Testing for Industrial Chemicals andPesticides is a good compilation of pelagic test methods and sources of testing guidance. This document isalso a source of appropriate test methodologies.Fish testsAcute testingAcute tests are generally performed with young juveniles 0.1–5 g in size for a period of 96 hours. Theobservational endpoint in these tests is mortality. Fish larger than this range and/or durations shorter than 96hours are generally less sensitive. However, for classification, they could be used if no acceptable data withthe smaller fish for 96 hours are available or the results of these tests with different size fish or test durationswould influence classification in a more hazardous category. Tests consistent with OECD Test Guideline 203(Fish 96-hour LC50) or equivalent should be used for classification.Chronic testingChronic or long-term tests with fish can be initiated with fertilised eggs, embryos, juveniles, or reproductivelyactive adults. Tests consistent with OECD Test Guideline 210 (Fish Early Life Stage), the fish life-cycle test(US EPA 850.1500), or equivalent can be used in the classification scheme. Durations can vary widelydepending on the test purpose (anywhere from 7 days to over 200 days). Observational endpoints caninclude hatching success, growth (length and weight changes), spawning success, and survival. Technically,the OECD 210 Guideline (Fish Early Life Stage) is not a ‗chronic‘ test, but a sub-chronic test on sensitive lifestages. It is widely accepted as a predictor of chronic toxicity and is used as such for purposes ofclassification in the harmonised system. Fish early life stage toxicity data are much more available than fishlife cycle or reproduction studies.January 2012 EPA0109