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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

The toxicity to the aquatic environment of butoxystyrene was investigated in accordance with Annex VII of REACH by performing GLP-compliant short-term toxicity studies to freshwater aquatic invertebrates and algae.

Short-term toxicity to aquatic invertebrates (Daphnia magna): the acute toxicity of butoxystyrene was assessed in a GLP-compliant study according to OECD202. No acute immobilisation was induced by butoxystyrene at 1.1 mg/l after 48h of exposure (NOEC). The 48h-EC50 was 3.8 mg/l based on average exposure concentrations. 

Toxicity to aquatic algae: a GLP-compliant fresh water algal growth inhibition study was performed with butoxystyrene according to OECD201. The 72h ErC50 was >4.8 mg/l and the NOEC for growth rate reduction was 1.2 mg/l.


Considering that the lowest EC50 for butoxystyrene is above 1 mg/L, the substance does not meet the criteria for EU CLP classification as Aquatic Acute 1.


A GLP-compliant study was conducted to determine the ready biodegradability of butoxystyrene according to OECD301B (CO2 evolution test). The relative degradation values calculated from the measurements performed during the test period revealed no significant degradation of butoxystyrene. Butoxystyrene was considered to be not readily biodegradable.

Considering that the lowest EC50 for butoxystyrene is between 1 and 10 mg/L and the substance is not readily biodegradable, butoxystyrene meets the criteria for EU CLP classification as Aquatic Chronic 2.


Additional information