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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

Key study, guideline FIFRA 72 -3 (equivalent OECD 203), K2:

LC50 (96h)> 1000 mg/L

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
1 000 mg/L

Marine water fish

Marine water fish
Effect concentration:
1 000 mg/L

Additional information

Two acute fish studies have been performed to assess the toxicity of amitrole. Both studies showed no lethal effects to fish with a LC50(96h) greater than 1000 mg/L.

- The first study (Collins, 1993) was performed on seawater to assess the acute effects of Amitrole technical to the sheephead minnow (Cyprinodon variegatus). This study was conducted according to FIFRA guideline 72 -3 (equivalent to OECD 203) in a semi-static acute test. The test conditions were as follows:

- dilution water: natural filtered seawater, pH 7.9, salinity 32 °/oo

- test temperature: 21 -23 °C

- nominal test concentration: 130, 220, 360, 600 and 1000 mg a.i./L

- mean measured test concentrations: 130, 220, 370, 620 and 1000 mg a.i./L, mean measured concentrations averaged 101 % of nominal concentrations.

The 96-hour LC50 value was estimated to be greater than 1000 mg a.i./L, the highest mean measured concentration tested.

- The second study (McAllister, 1985) was performed according to the methods outlined by the Committee on Methods for toxicity tests with aquatic organisms on rainbow trout (Salmo gairdneri).Water quality parameters of temperature, dissolved oxygen and pH were measured throughout the test and were within acceptable limits. Culture and acclimation records indicated the fish were in good condition for testing.

The study was conducted at the following nominal concentration of Aminotriazole: 62.5, 125, 250, 500 and 1000 mg/L. Ten fish, with a mean weight of 0.36 (± 0.10) g and a mean standard length of 30 (± 2.3) mm, were exposed to each test concentration and control.

The results of the four day static fish toxicity study using Aminotriazole are summarized below. The 24- and 48 -hour LC50values were also determined


96-hour LC50

(95% C.I.)


> 1000 mg/L

Also, the results indicated a 96-hour no-observed effect concentration could be estimated at 1000 mg/L, which was based on the lack of mortality and abnormal effects at the highest level tested.

The missing analytical analysis in the supporting study is not considered as a blocking point as key study results were based on mean measured concentrations (representing more than 80 % of nominal concentrations).