Reaction mass of (R)-cyano(3-phenoxyphenyl)methyl rel-(1R,3R)-3-((1Z)-2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethylcyclopropanecarboxylate and (R)-cyano(3-phenoxyphenyl)methyl rel-(1S,3S)-3-((1Z)-2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethylcyclopropanecarboxylate

Toxicity to aquatic algae and cyanobacteria

Description of key information

EC50>51 mg/L, 72h, (growth rate), NOEC=0.0044 mg/L, 72h, (growth rate), Pseudokirchneriella subcapitata, OECD 201, Volz 2005

Key value for chemical safety assessment

EC50 for freshwater algae:

51 mg/L

EC10 or NOEC for freshwater algae:

0.004 mg/L

Additional information

The influence of the test item Cyhalothrin on the growth green alga (Pseudokirchneriella subcapitata) was investigated in a 72-hour static test under GLP according to the EU Commission Directive 92/69/EEC, C.3, 1992, and the OECD Guideline No. 201, 1984, as well as according to the JMAFF Test Guidelines, 2-7-3 (2001). The study is considered valid and conclusive.

The study was performed with test concentrations mostly above the water solubility of the test item (i.e. 0.004 mg/L).

The test organisms were 72 h exposed to nominal test concentrations of 0.0032, 0.010, 0.032, 0.10, 0.32, 1.0, 3.2, 10, 32 and 100 mg/L in parallel with a control and a solvent control group.

The measured test item concentrations at the start of the test ranged from 50 to 119% of the nominal. At the end of the test 21 to 61% of the nominal values were found. The mean measured test concentrations (calculated as the geometric mean of all measurements per test concentration) varied in the range of 42 to 76% of the nominal values. The reported biological results are based on the mean measured test item concentrations.

A very flat concentration-effect relationship was observed. Down to the lowest test concentration a very small, but statistically significant inhibitory effect on the growth (biomass) after the exposure period of 72 hours at concentrations of 0.0022 mg/L and above (results of Dunnett-tests, one-sided, α = 0.05). Thus, the 72-hour LOEC (lowest concentration tested with toxic effects) for algae biomass was determined to be ≤ 0.0022 mg/L. The 72-hour NOEC (highest concentration tested without toxic effects after a test period of 72 hours) for algae biomass was determined to be <0.0022 mg/L

The growth rate of the algae was statistically significantly inhibited at 0.014 mg/L and above after the exposure period of 72 hours (results of Dunnett-tests one-sided,  α  = 0.05). Thus, the test concentration of nominal 0.014 mg/L was determined to be the 72-hour LOEC for algae growth rate. The NOEC for algae growth rate after 72 hours of exposure was determined to be 0.0044 mg/L, since at this test concentration, the algae growth rate was not statistically significantly lower than in the solvent control.

Nevertheless, up to 100 mg/L the inhibition (growth rate and biomass) was always <50%.

The EC values as well as the NOEC and LOEC were determined for both parameters, the algal biomass (b) and the growth rate (r), after 72 hours test duration. The 72-hour EC50 and EC90 of the test item could not be calculated because none of the responses exceeded 50%. The 72-hour EC10 was not calculable, since no monotonous concentration-effect relationship was obtained.