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Ecotoxicological information

Toxicity to soil microorganisms

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Description of key information

Tetrabutane has no effect on carbon transformation by soil micro-organisms. NOEC (28-days) ≥ 1000 mg/kg soil dw. (OECD 217). The EC50 value for nitrogen transformation by soil micro-organisms has been determined to be 743 mg/Kg dw.

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The effect of Tetrabutane on the metabolic activity of soil micro-organisms was determined in a carbon transformation test according to the guideline OECD 217. The test was conducted at concentrations of 500 and1000 mg/kg soil dw, over a duration of 28 days. The effect of the test substance on glucose induced respiration of the microbial biomass was determined on the day of treatment (day 0) and after 7, 14 and 28 days. On each occasion glucose was added to aliquots of soil (4000 mg/kg soil) and oxygen consumption measured over a subsequent 24 hour period. Tetrabutane caused no effect on the soil micro-organisms at 500 or 1000 mg/kg soil dw. No inhibition of stimulation was observed and therefore Tetrabutane is not expected to lead to any long-term detrimental effects on the carbon transformation in soil under normal conditions. The NOEC was determined to be1000 mg/kg soil dw.

In an additional test, the metabolic activity of soil micro-organisms were determined according to OECD Guideline 216 (January 2000) and 68/548/EEC, Annex V, Method C.21 (2004) with Tetrabutane. The test item was applied via quartz sand with the test concentrations 2000 - 1000 - 500 - 250 - 125 mg/kg soil dry weight (DW). After incubation for 28 days, effects on the nitrogen transformation were observed and resulted in an EC50 value (28 days) of 743 mg/kg dw and a NOEC <125 mg/kg dw. However, high test substance concentrations were used in the study, which are above the limit of solubility. Therefore, physical effects in this study cannot be excluded.