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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Triquat Monomer inhibited the growth of the freshwater green algae Scenedesmus subspicatus with an EC10 and EC50 value for the test parameter "growth rate" of 9.0 mg/L (4.5 mg/L dry matter) and 87 mg/L (44 mg/L dry matter), respectively.
Therefore, TRIQUAT monomer should be considered as harmful to the aquatic organisms tested.

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
87 mg/L
EC10, LC10 or NOEC for freshwater algae:
9 mg/L

Additional information

One reliable key study is available (Baetscher, 2008) as described below:

The influence of the test substance Triquat Monomer on the growth of the freshwater green algal species Scenedesmus subspicatus was investigated in a 72 hour static test according to EEC Directive 92/69, C.3 (1992), the OECD Guideline No. 201 (2006) and the GLP.

Due to the high water content of the test substance (50%), the highest test substance concentration tested was 200 mg/L to yield results corresponding to a dry matter concentration of the test substance of 100 mg/L.The nominal concentrations of the test substance of 0.63, 2.0, 6.3, 20, 63 and 200 mg/L were tested in parallel with a control. The test concentrations corresponded to the following concentrations of the test substance dry matter:0.32,1.0, 3.2, 10, 32 and 100 mg/L.

The measured concentrations of the test substance in the test media were between 90 and 120% of the nominal values at the start of the test and between 43 and 106% of the nominal values at the end of the test. The biological results were related to the mean measured concentrations (geometric means) which were between 67 and 107% of the nominal values.

The test substance had a statistically significant inhibitory effect on the growth rate and yield of the algae after the test period of 72 hours at the concentration of 21 mg/L (11 mg/L dry matter) and at all higher test concentrations. In addition, the yield after 3 days was statistically significantly lower than in the control at the two lowest test concentrations of0.47and 1.3 mg/L (0.24 and 0.78 mg/L dry matter, respectively). The average growth rate was significantly lower than the control at the concentration of 1.3 mg/L (0.78 mg/L dry matter) as well. Thus, no clear concentration-effect relationship was determined for low growth inhibition at the concentration range of0.47to 6.1 mg/L (0.24 to 3.1 mg/L dry matter).

Using Probit Analysis, the 72 hour EC10, EC20 and EC50 values for the test parameter "growth rate" were determined to be 9.0 mg/L (4.5 mg/L dry matter), 20 mg/L (9.9 mg/L dry matter) and 87 mg/L (44 mg/L dry matter), respectively. For the test parameter "yield", the 72 hour EC10, EC20 and EC50 values were calculated as 1.2 mg/L (0.61 mg/L dry matter), 2.8 mg/L (1.4 mg/L dry matter) and 14 mg/L (6.9 mg/L dry matter), respectively.

The 72 hour NOEC and LOEC could not be reliably determined by means of the statistical tests. Instead, the 72-hour EC10 or EC20 can be regarded as threshold effect concentration for the algal growth inhibition.

The validity criteria requested by the OECD Guideline No. 201 were fulfilled.

Based on these results, TRIQUAT Monomer should be considered as harmful to the aquatic organisms tested.