C8-18 alkylampho(di)propionates

Toxicity to soil microorganisms

Description of key information

The EC50 for soil nitrogen transformation was concluded to be >648 mg test item/kg dry soil (>248 mg solids/kg dry soil). The NOEC was determined to be 81 mg/kg soil dw for the registered substance and 31 mg/kg soil dw for the solid content of the registered substance.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

81 mg/kg soil dw

Additional information

The effects of the substance on nitrogen transformation in a LUFA standard field soil (type 2.3) were investigated according to OECD216 and GLP.

 

There were two parallel test: One parallel test with soil amended with lucerne and one parallel test with soil not amended with lucerne (= nitrogen control) as the test item contained nitrogen and was known to breakdown in soil. The lucerne was added at a rate of 2.5 g of lucerne/500 g of soil (dry weight equivalent) to the deionised water control amended with lucerne and treatment groups amended with lucerne.

 

The following nominal test concentration were tested: 40, 81, 162, 324 and 648 mg test item/kg dry weight soil (15, 31, 62, 124, and 248 mg solids/kg dry weight soil).

 

Triplicate samples per concentration were incubated for 28 days in the dark at room temperature.

 

As soon as possible after dosing, a sub-sample of soil was taken from each replicate for the determination of nitrate, nitrite and ammonium concentration. The samples were extracted and analysed for nitrate, ammonium and nitrite in two sets (Day 0 and 7, Day 14 and 28).

 

The nitrate concentration in the amended soil treatments was adjusted to account for the nitrate produced by the breakdown of the test item (using the data from the unamended treatments at both Day 0 and Day 28). After adjustment of the nitrate produced in the unamended treatment set, the percentage variation from the control for each treatment was calculated and the higher rates of 162, 324 and 648 mg product/kg dry soil, showed statistically significant differences from the control, in terms of nitrate produced (Dunnett’s two tail,α=0.05). The no effect concentration (NOEC) was determined at 81 mg/kg dry soil (31 mg solids/kg dry soil) and the lowest effect concentration (LOEC) at 162 mg test item/kg dry soil (62 mg solids/kg dry soil). After 28 days exposure, the test substance significantly stimulated the production of nitrate at concentrations 162, 324 and 648 mg product/kg dry soil, but the stimulation was insufficient in order to derive effects concentration at 10% maximal value (EC10), 25% maximal value (EC25) and 50% maximal value(EC50). The EC50was concluded to be >648 mg test item/kg dry soil (>248 mg solids/kg dry soil).

 

Nitrite values, determined to confirm that theTotal Oxidisable Nitrogen (TON, sum of nitrate and nitrite)measured was derived from nitrate alone, have not been reported as no nitrite-N was detected.

 

The percentage variation within the amended control vessels for nitrate concentration (mg/kg dry soil) ranged from -7.5 % to 4.8 % on Day 28; these data fulfil the validity criterion that the variation between control replicates from the average should not be greater than 15%.