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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

Short-term toxicity to fish, invertebrate, and algae

Reliable experimental results from acute toxicity testing of two trophic levels (daphnids, algae) are available; no experimental data are available for fish. Due to the low toxicity of L-tryptophan to daphnids and algae it is to be expected that the acute toxicity to fish will be low as well. Therefore the acute toxicity to fish was calculated using ECOSAR which supports this assumption (96 h LC50>850 mg/L). The toxicity of L-tryptophan to Daphnia magna and Desmodesmus subspicatus was investigated in guideline studies. The 48h LC50 and 72 h EC50 for Daphnia magna and Desmodesmus subspicatus were determined to be >100 mg/L nominal each.

Long-term toxicity to fish and invertebrate, and algae

In Annex IX of Regulation (EC) No 1907/2006, it is laid down that chronic toxicity tests shall be proposed by the registrant if the chemical safety assessment indicates the need to investigate further the effects on aquatic organisms. According to Annex I of this regulation, the chemical safety assessment triggers further action when the substance or the preparation meets the criteria for classification as dangerous according to Directive 67/548/EEC or Directive 1999/45/EC or is assessed to be a PBT or vPvB. The hazard assessment of L-tryptophan reveals neither a need to classify the substance as dangerous for the environment, nor is it a PBT or vPvB substance, nor are there any further indications that the substance may be hazardous to aquatic organisms. According to reliable study results, L-tryptophan is considered to be rapidly degraded in the environment and the bioaccumulation potential is regarded to be insignificant. For the algae Desmodesmus subspicatus a 72 h NOEC=100 mg/L (nominal) was determined in a guideline study. Based on the available information the performance of chronic studies with fish and invertebrates is assumed to be not justifiable.

Toxicity to microorganisms

According to REACH Regulation (Annex VIII, 9.1.4, column 2) the study on respiration inhibition of activated sludge does not need to be done if the substance is readily biodegradable. L-Tryptophan proved to be readily biodegradable and fulfilling the 10-d-window criterion (77% biodegradation after 28 d). In the toxicity control containing both test and reference item (20 mg/L each) 75% biodegradation based on ThCO2 occurred within 14 d thus indicating that the test item was not inhibitory at the concentration tested. Based on these results, the study on respiration inhibition of activated sludge is assumed to be not justifiable.