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Ecotoxicological information

Toxicity to soil microorganisms

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Description of key information

In a reliable study (reliability category 1) assessing long-term effects of the supporting substance HYEQS on nitrogen transformation rate of terrestrial microorganisms, after 28 days no inhibitory effects were determined (NOEC ≥ 1000 mg/kg soil dry weight). 

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
1 000 mg/kg soil dw

Additional information

Long-term effects on nitrogen transformation rate of terrestrial microorganisms after single exposure to the supporting substance HYEQS was assessed in a reliable (category 1) study performed according to OECD 216 and compliant to GLP over a period of 28 days. The validity criterion of the guideline was met.

HYEQS is of high similarity to C12-14 DMA in that it has essentially the same alkyl chain distribution and – like DMA category members - two methyl substituents at the amino group. The only difference is an additional hydroxyethyl substituent at the amino group rendering it a quaternary amine being permanently positively charged. This is however a minor difference as due to protonation at environmentally relevant pH values also DMA category members are predominantly positively charged at the amino group.

HYEQS was tested at five different application rates between 25.6 and 1000 mg/kg soil dry weight. The NOEC, EC50 and EC25 for nitrogen transformation rate in soil measured as nitrate on day 7 was 400, > 1000 and 782 mg/kg soil dry weight, respectively.

The NOEC, EC50 and EC25 for nitrogen transformation rate in soil measured as nitrate on day 14 was 400, 908 and 562 mg/kg soil dry weight, respectively.

The NOEC for nitrogen transformation rate in soil measured as nitrate on day 28 was≥1000 mg/kg soil dry weight.

In conclusion,no long-term inhibitory effects of DMA category members on the nitrogen transformation rate of terrestrial microorganisms are expected, even at high exposure concentrations.