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Ecotoxicological information

Toxicity to soil microorganisms

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Description of key information

Based on a reliable guideline study, the activity of the micro-organisms transforming nitrogen in the soil was slightly inhibited by the C12-C16 ADBAC at 50 mg a. i. /kg. The EC50 calculated was 130 mg a. i. /kg. Furthermore, C12-C16 ADABC had no long-term influence on nitrogen and carbon transformations in sandy loam and low humic content sand soils.

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:
0.7 mg/kg soil dw

Additional information

An OECD guideline 216 study (nitrogen transformation test) was conducted using structurally similar C12-C16 ADBAC. Analytical determination was performed for the test substance and the method of analysis: The content of the test substance in the stock solutions was analysed with Dr Lange cuvettes (LCK 331) and Dr Lange apparatus (CADAS 30) and cuvettes were purchased from Dr Lange, Dusseldorf, Germany. The concentrations ranged from 0, 50, 100, 200, 400, 800, 1,600, 3,200 and 6,400 mg a. i. /kg of the test substance. The activity of the micro-organisms transforming nitrogen in soil was slightly inhibited at 50 mg a. i. /kg. The EC50calculated was 130 mg a. i. /kg with 95% confidence limits of 80 mg a. i. /kg and 190 mg a. i. /kg. The EC10, EC20and EC80of the test substance were 70, 90 and 200 mg a. i. /kg respectively. Denitrifying microorganisms were not affected by the test substance at concentrations ranging from 400 to 3200 mg a. i. /kg whereas the microorganisms responsible for the formation of nitrate are inhibited at these concentrations. The denitrifying microorganisms are inhibited at 6,400 mg a. i. /kg because after 28 days only a limited amount of the nitrate was removed (van Ginkel and van der Togt, 2004).

The effects of the structurally similar C12-C16 ADBAC on the carbon mineralization and nitrogen transformation activity of soil micro-organisms in sandy loam soil and low humic content sandy soil was investigated in a 28 day guideline study. Fifty±0.5 g dry weight of soil samples were mixed with lucerne meal and placed in 100 mL Schott Duran 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 dosed with test substance at concentrations 0, 10, 100 and 1,000 µg a. i. /g soil dw. No analytical determination was performed for the test substance. Nitrogen and carbon transformations were determined. Samples were taken to determine nitrogen metabolite content on Days 5 and 28. CO2evolution was determined on Days 5 – 8 and 25 – 28. The difference in CO2production 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 after 5 at 10 µg a. i. /g 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 for adversely affecting the microbial functions of sandy loam and low humic content sand soils. The test substance can be characterised as having no long-term influence on nitrogen and carbon transformations in soils (de Vette et al.,2001).