Registration Dossier
Registration Dossier
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EC number: 273-386-3 | CAS number: 68959-00-2
Toxicity to aquatic plants other than algae
Administrative data
Link to relevant study record(s)
Description of key information
EC50 > 100 mg/l a.i. for growth rate inhibition of both frond number and biomass (dry weight).
Key value for chemical safety assessment
- EC10 or NOEC for freshwater plants:
- 25.1 mg/L
Additional information
No data on the substance in itself was available. Therefore, a read across approach was followed, using data on Similar Substance 01, as detailed in section 13.
The substance was tested for toxicity on freshwater aquatic plants, i.e. Lemna minor, according to OECD Guideline 221 under static exposure conditions.
Initial measured concentrations were 0.818, 2.67, 8.90, 29.1 and 95.4 mg/l a.i., corresponding to a nominal loading of 1.00, 3.16, 10.0, 31.6 and 100 mg/l a.i.. Concentrations decreased over the whole test period to 57 %, 66 %, 66 %, 71 % and 67 % of initial value, respectively. In order to account for the decrease of test concentrations, geometric means over 7 days of measured concentrations were used in the assessment.
Plants in control and at concentrations up to 10.0 mg/l were similar, in terms of number of fronds and length of roots. At higher doses, plants were healthy with green fronds, but fronds were slightly smaller and roots were shorter as compared to controls.
Effects concentrations (EC10 and EC50), based on growth rate and yield, were determined using Logit regression model, for bot frond number and dry weight.
No observed effect concentrations (NOEC) were estimated by Dunnett's test.
After 7 days, observed effects were:
- 7 % and 18 % growth rate inhibition of frond number, at measured concnetrations of 25.1 mg/l and 78.4 mg/l a.i..
- 5 % and 16 % growth rate inhibition of biomass (dry weight), at measured concnetrations of 25.1 mg/l and 78.4 mg/l a.i..
For the purpose of classification, based on both limited effects at the highest concentration as well as the flat response curve, EC50 values were reasonably assumed to be > 100 mg/l a.i..
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