Amitrole

Long-term toxicity to aquatic invertebrates

Description of key information

Key study, following OECD 202 part b (previously the OECD chronic daphnid study prior to renumbering OECD 211 and EEC-Draft (EEC XI/681/86, GLP:

21d-NOEC (Daphnia magna) = 0.32 mg/L based on body length data and on nominal concentrations further to analytical confirmation that concentrations remained within + or - 20% of the nominals

21d-NOEC (Daphnia magna) = 0.56 mg/L based on reproduction data and on nominal concentrations further to analytical confirmation that concentrations remained within + or - 20% of the nominals

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.32 mg/L

Additional information

In accordance with GLP-regulations, Amitrole was tested for inhibition of reproduction of water fleas according to the method OECD-guideline No. 202 (1984) and EEC-Draft (EEC XI/681/86) (1987).

In the semi-static test, for each concentration, 10 female water fleas (Daphnia magna)(1 daphnia/vessel) were transferred three times a week to freshly prepared test medium and fed with defined numbers of green algae (Scenedesmus subspicatus).

Nominal concentrations of 0.032 ; 0.10 ; 0.18 ; 0.32 ; 0.56 ; 1.0 and 3.2 mg AI/L were tested.

No mortality was observed in the parent animals of the control. The average number of offspring determined in the control was 80 % daphnia in the three broods during the study period.

The numbers of offspring were not significantly reduced at the test concentrations from 0.032 and 0.56 mg/L as revealed by the statistical comparison of offspring numbers from the individual test concentrations with those of the control. At the concentration of 1.0 mg/L some offsprings were dead at the evaluation of the study.

The mean body length of the parent animals of 4.37 mm in the control represents well nourished and developed adult females of the species Daphnia magna of normal body length. The statistical evaluation of the body length of the parent animals showed statistically significant differences at the test concentrations 0.56 and 1.0 mg/L compared to the control.

The following effects of the test substance on mortality, reproduction rate and body length of parent animals of Daphnia magna during the 21 day period, were evaluated :

- for the reproduction, the highest test concentration without effect (no observed effect concentration, NOEC) was 0.56 mg AI /L ; the lowest test concentration with effect (lowest observed effect concentration, LOEC) was 1.0 mg AI/L ; the threshold effect concentration  (TEC, geometric mean) was 0.75 mg AI /L

- for the body length of the parent animals : the highest test concentration without effect (NOEC) was 0.32 mg/L ; the lowest test concentration with effect (LOEC) was 0.56 mg/L ; the threshold effect concentration (TEC, geometric mean) was 0.42 mg AI/L.