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Toxicity to soil microorganisms

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Description of key information

In a reliable guideline compliant study, the activity of the microorganisms transforming nitrogen in the soil was slightly inhibited by the test substance at 50 mg a.i./kg soil dw. The EC50 was 130 mg a.i./kg soil dw. Furthermore C12-16 ADBAC had no long-term influence on nitrogen and carbon transformations in sandy loam and low humic content sandy soils. The same behaviour is expected for C12-14 ADMAES.

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil microorganisms:
130 mg/kg soil dw
Long-term EC10, LC10 or NOEC for soil microorganisms:
70 mg/kg soil dw

Additional information

A guideline compliant nitrogen transformation test was conducted with the read-across substance C12 -16 ADBAC. Analytical determination of the test substance was performed. The concentrations ranged from 0, 50, 100, 200, 400, 800, 1,600, 3,200 and 6,400 mg a.i./kg soil dw. The activity of the microorganisms transforming nitrogen in soil was slightly inhibited at 50 mg a.i./kg soil dw. The EC50 was 130 mg a.i./kg soil. The EC10, EC20 and EC80 were 70, 90 and 200 mg a.i./kg soil dw, respectively. Denitrifying microorganisms were not affected at concentrations ranging from 400 to 3,200 mg a.i./kg soil dw whereas the microorganisms responsible of the formation of nitrate were inhibited at these concentrations. The denitrifying microorganisms were inhibited at 6,400 mg a.i./kg soil dw because after 28 days only a limited amount of the nitrate was removed (van Ginkel CG and van der Togt B, 2004).

The effects of C12-16 ADBAC on carbon mineralization and nitrogen transformation activity of soil micro-organisms in a sandy loam soil and a low humic content sand soil were investigated in a 28 day guideline study. Fifty grams dry weight of soil samples were mixed with lucerne meal and placed in 100 mL bottles. The samples were incubated in the dark at 20±2°C for 28 days. The moisture content of the samples was checked weekly. Samples were treated with test substance at concentrations 0, 10, 100 and 1,000 mg a.i./kg soil dw. No analytical determination of the test substance was performed. CO2evolution was determined on Days 5-8 and 25-28. The difference in CO2 production and nitrogen transformation between the treated and untreated soil samples did not exceed 25% after 28 days of incubation. The highest inhibition recorded was 82.5% in the nitrite formation rate at 10 mg a.i./kg soil dw in the sandy loam soil. After 28 days of incubation however, no relevant effect was observed (i.e., less than 25% reduction). Test substance is therefore considered to have a low potential to adversely affect the microbial functions of sandy loam and low humic content sandy soils. The test substance can be characterised as having no long-term influence on nitrogen and carbon transformations in soils (de Vette HQM et al., 2001).