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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

48h-ErC50 and NOEC green algae (Pseudokirchneriella subcapitata): 16 mg/L and 1.5 mg/L, respectively (OECD201/EU C.3, GLP, read-across from structural analogue)

Key value for chemical safety assessment

EC50 for freshwater algae:
16 mg/L
EC10 or NOEC for freshwater algae:
1.5 mg/L

Additional information

The read-across hypothesis is based on the assumption that source substance and target do have comparable aquatic toxicity. Source substance and target are both alkyltriphenylphosphonium halogen salts with an almost identical organic moiety and an identical counterion. Target substance n-Butyltriphenylphosphonium bromide differs from source substance Ethyltriphenylfosfonium bromide only in the length of the saturated alkyl chain - n-butyl instead of ethyl. As it is not expected that this minor deviation has a major impact on aquatic toxicity, this read-across is justified.

The toxicity of source Ethyltriphenylfosfonium bromide to Pseudokirchneriella subcapitata was studied under static conditions according to OECD Guideline 201 (adopted March 23, 2006), EU Method C.3 (December 1992) and ISO International Standard 8692 (October 2004)Exponentially growing cultures were exposed to a control and Ethyltriphenylfosfonium bromide concentrations of 0.60, 1.5, 3.8, 9.5, 24 and 60 mg/L. Test concentrations were based on the result of a preceding range-finding test. The total test period was 48 hours and the initial algal cell density was 104 cells/mL. Samples for determination of actual exposure concentrations were taken at the start, after 24 and 48 hours of exposure. Analyses showed that measured concentrations were in agreement with nominal throughout the 48-hour test period (97-104%).

Ethyltriphenylfosfonium bromide reduced growth rate and inhibited the yield of this fresh water algae species significantly at 3.8 mg/L and higher.

The EC50 for growth rate reduction (ErC50: 0-48h) was 16 mg/L with a 95 % confidence interval ranging from 9.8 to 25 mg/L.

The EC50 for yield inhibition (EyC50: 0-48h) was 4.3 mg/L with a 95 % confidence interval ranging from 3.1 to 6.1 mg/L.

The NOEC for both growth rate reduction and yield inhibition was 1.5 mg/L.

These values are read across to n-Butyltriphenylphosphonium bromide without molecular correction.