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Reliable proprietary studies for 2-methylbut-2-ene on the acute freshwater toxicity of the three trophic levels (fish, Daphnia and algae) and toxicity towards micro-organisms were identified. The studies were conducted to standard guidelines and according to GLP and so are considered fully reliable for use as key studies. Algae were found to be less sensitive than either invertebrates or fish which had similar sensitivity to the test substances (EC50 3.84 mg/L and LC50 4.99 mg/L respectively). The substance was not toxic to micro-organisms at a concentration of 2.1 mg/L.

The information gathered indicates that 2-methylbut-2-ene is of low toxicity to environmental receptors. In the PBT assessment, none of the studies evaluated meet the acute LC50/EC50 toxicity (T) screening criteria of <0.1 mg/L or the chronic criteria of <0.01 mg/L for marine or freshwater organisms based on Annex XIII of the REACH Regulation. The lowest results for each trophic level are a 96 hour LC50 for fish of 4.99 mg/L, a 48 hour EC50 forDaphniaof 3.84 mg/L, a 72 hour EC50 for algae of 12.0 mg/L based on growth rate as well as a NOEC for algae of 7.22 mg/L based on growth rate. Therefore, 2-methylbut-2-ene is not considered to be T on the basis of the environmental screening criterion.