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Ecotoxicological information

Toxicity to soil microorganisms

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Description of key information

Nitrate formation inhibition test: TEP A stimulated nitrate formation at all concentrations  and at all timepoints  

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
500 mg/kg soil dw

Additional information

The effects of Tetraethylenepentamine, TEPA on the metabolic activity of the nitrogen-N formation rate (nitrate) soil micro-organisms were determined according to OECD Guideline 216 (2000) over a 28 day period. Nominal test concentrations were 31.3, 62.5, 125, 250 and 500 mg/kg soil dry weight. Effects were recorded on the day of treatment (day 0) and after 7, 14 and 28 days. Untreated soil was tested as the control under the same test conditions as the test item replicates.The rates of nitrate formation were consistently higher in all the TEPA treatments than in the untreated control at all timepoints throughout the study. Consequently, there was no evidence that exposure to TEPA inhibited the nitrogen transformation activity of soil microflora at the range of concentrations applied. The 28 day EC50 value was >500 mg/kg soil dry weight. The corresponding no-observed effect concentration (NOEC) was 500 mg TEPA/kg soil dry weight. Test validity criteria were

Data from the analogue TETA were initially used, since TETA is structurally similar to TEPA , the relevant physochemical properties are comparable , as well the metabolism by aquatic mico-organisms, as shown by the behavior as sole nitrogen source in a modified SCAS test. The effects of the test item on nitrogen transformation by soil microflora were determined by comparing rates of formation of the terminal transformation product, nitrate-nitrogen (NO3--N), in soil treated with TETA against the rate observed in the untreated control. Measurements of nitrate-nitogen concentrations in soil were made in all treatments and the control on the day of treatment application (day 0) and after 7, 14 and 28 days.

 

The rates of nitrate formation were consistently higher in all the TETA treatments than in the untreated control at all timepoints throughout the study. Consequently there was no evidence that exposure to TETA inhibited the nitrogen transformation acivity of soil microflora at the range of concentrations applied. The EC50based on inhibition of nitrogen transformation processes could therefore not be determined reliably, but it exceeded 100 mg TETA/kg soil dry weight, the highest concentration applied in the definitive test. The corresponding no-observed effect concentration (NOEC) was 100 mg TETA/kg soil dw, 

The test resutls with TEPA confirm that read-across from TETA would haven possible and would not have underestimated the risk.