Registration Dossier
Registration Dossier
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EC number: 203-632-7 | CAS number: 108-95-2
Toxicity to aquatic plants other than algae
Administrative data
Link to relevant study record(s)
Description of key information
The most sensitive enpoint was the 7 day EC50 of 61.82 mg/L nominal for the endpoint yield based on dry weight obtained in a study conducted with Lemna minor.
Key value for chemical safety assessment
- EC50 for freshwater plants:
- 61.82 mg/L
- EC10 or NOEC for freshwater plants:
- 5 mg/L
Additional information
It is stated that the lowest available valid EC50 value obtained with the aquatic plant Lemna minor is 171 mg/L and the NOEC is 5 mg/L, based on the effects on the number of plants. The data were taken from the study of Cowgill et al.(1991).
In the study of Cowgill et al. (1991), the effects of phenol on aquatic plants were investigated with Lemna gibba and four strains of Lemna minor in 7 day growth inhibition tests under static conditions. Measured parameters were number of plants, frond number and dry weight. The EC50 values ranged between 157 and 312 mg/L and the NOEC values between 5 and 108 mg/L. Dry weight was the most sensitive parameter and Lemna minor strain 7136 was found to be most sensitive Lemna strain. The EC50 for dry weight was 157 mg/L and the NOEC was 5 mg/L for all parameters in Lemna minor strain 7136.
Though the test concentrations were not analytically verified, the phenol concentrations are considered to be stable due to the findings in the studies from Colgan et al. (1982) and Lewis et al. (1983), where after a 2 day static exposure period the measured phenol concentrations were > 80 % of the nominal concentrations.
In a report finished recently (SLOVNAFT 2009), the toxicity of phenol towards the duckweed Lemna minor was investigated in a GLP-study conducted according to OECD Guideline 221 (Lemna sp. Growth Inhibition test) for seven days under static conditions. The stability of the test solutions over a period of 5 days was proven via TOC analysis (after 5 d 92.1% of the initial test substance concentration was found). The 7 d EC10 values were determined to be 37.10 (growth rate based on dry weight), 30.62 (growth rate based on number of fronds), 17.48 (yield based on dry weight), and 5.92 mg/L nominal (yield based on number of fronds), respectively. The correspnding 7 d EC50 values were found to be 160.51 (growth rate based on dry weight), 1981.80 (growth rate based on number of fronds), 61.82 (yield based on dry weight), and 195.23 mg/L nominal (yield based on number of fronds), respectively. In this study the lowest EC10 value (5.92 mg/L) was determined for the endpoint yield based on number of fronds and the lowest EC50 value (61.82 mg/L) was determined for the endpoint yield based on dry weight. As this EC50 value is the lowest available, this value will be used for assessment.
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