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Ecotoxicological information

Toxicity to soil microorganisms

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Description of key information

In a study using several endpoints to measure toxicity to soil micro-organisms, EDDS at 1.0 g/kg dw soil for 3 days (considered the study NOEC) did not affect substrate-induced respiration (used as an indicator of potential biomass activity) or the activity of four enzymes (considered important for the breakdown of organic matter), although it did cause a significant inhibition of soil basal respiration (Epelde et al. 2008).

Key value for chemical safety assessment

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

Additional information

Ethylenediamine disuccinate (EDDS) was studied for its effects on soil micro-organisms (microbial biomass, activity and diversity and community structure), using soil samples from a natural grassland in Larrauri, Northern Spain. After the addition of 1.0 g EDDS/kg dw soil, basal respiration (as an indicator of overall microbial activity) was measured and compared to substrate-induced respiration (as a measure of potentially active biomass) after the addition of glucose. Metabolic quotient (qCO2) was then calculated as the ratio of these two measurements to determine the effect of the test substance on the soil ecosystem. The activity of dehydrogenase, acid phosphatase, beta-glucosidase, and arylsulphatase were analyzed as representatives of four different classes of enzymes important for the breakdown of organic matter. Potentially mineralizable nitrogen was also measured as an indicator of the biological soil activity. Finally, substrate profiles were assessed to determine the functional diversity of the soil microflora.

Basal respiration was reduced slightly (by about 10%), whilst substrate-induced respiration was unaffected by the addition of the test substance. The qCO2 was significantly reduced compared to the control value, indicating development of the ecosystem. There were no significant changes in enzyme activities or potentially mineralizable nitrogen when compared to the controls. Functional diversity was actually increased by the presence of EDDS. In conclusion, 1 g EDDS/kg dw soil had no significant detrimental effect on the soil microflora; this value is considered the study 3-d NOEC (Epelde et al. 2008).