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Toxicity to soil microorganisms

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Description of key information

No adverse effects, OECD 216 and 217,  Perina 2000
No adverse effects, OECD 216 and 217, BBA Part VI 1-1, SETAC, Grade 2000

Key value for chemical safety assessment

Additional information

Two studies have been provided to address the toxicity of the test material to soil microorganisms on a weight of evidence basis.

Both studies assess the adverse effects on the nitrogen cycle by quantifying the amount of ammonium, nitrate and nitrate produced after incubation with the test material. Effects on the carbon cycle were assessed by measuring the CO₂ evolution through respiration.

Perina (2000) tested two different soil samples, Typic Hapludox and Rhodic Hapludox. They were exposed to the test material at nominal concentrations of 0.042 and 0.084 kg/ha (equivalent to 0.042 and 0.084 mg/kg soil dry weight), representing 1 fold and

2-fold the maximum used rate respectively. Samples were incubated for 28 days at 20 ± 2 ºC and then sampled for analysis at 0, 14 and 28 hours. Under the conditions of the test, no significant adverse effects were observed on soil microflora when comparing effects to blank controls.

Grade (2000) used a loamy sand soil which was exposed to concentration of the test material equivalent to 1 and 10-fold the maximum field application rate. The proposed maximum field application rate was 60 g/ha 3 times per year, thus the 10- fold application would be 600 g/ha corresponding to 0.08 and 0.8 mg/kg soil dry weight. Samples were incubated with the test material at 20 ± 1 ºC for 102 days in the nitrogen fixation test and 101 days in the respiration test. Samples were collected for analysis at 0-3 hours, Days 14, 28, 61 and at termination. Results obtained from blank and positive controls confirmed adequate microbial activity and the viability of the test system. Under the conditions of the test no adverse effects on organic matter turnover, and hence on soil fertility, was observed under exposure to the test material up to the highest concentration tested 0.8 mg/kg soil dry weigh or 600 g/ha.

Both studies were performed according to GLP, in line with standardised guidelines, with a high standard of reporting and have thus been assigned a reliability score of 1 in line with the principles for assessing data quality set out by Klimisch (1997).

The available data are considered to be complete and test material is concluded to be non-toxic to soil microorganisms up to > 0.084 mg/kg soil dry weight.