2,2',6,6'-tetrabromo-4,4'-isopropylidenediphenol

Toxicity to soil microorganisms

Description of key information

28 d Soil nitrogen transformation test.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

1 000 mg/kg soil dw

Additional information

In order to determine the effects of Tetrabromobisphenol A on soil microorganisms, a nitrogen transformation test was performed according to OECD Guideline 216. Natural soil was field-collected and amended with powdered alfalfa as an organic substrate. TBBPA was added directly to soil to give nominal concentrations of 10, 32, 100, 316 and 1000 mg/kg soil dw. Soils were incubated at 20 °C for 28 days, with ammonium, nitrite and nitrate generation measured on days 0, 7, 14, and 28. As a clear concentration-response relationship between TBBPA treatment and nitrogen transformation could not be established using these measures, the 28-day EC10 value for inhibition of nitrogen transformation was established as greater than 1000 mg TBBPA/ kg soil d.w. Consequently, based on these findings, it is unlikely that TBBPA exerts any significant toxic effects on soil microorganisms.

In a supporting study, an investigation of the toxicity of the test material to nitrifying bacteria was carried out as part of a series of bioassays that also determined the test material toxicity to a plant species and a soil invertebrate. The study was conducted using methodology similar to that in the standardised guideline ISO 14238.

An inoculum was prepared from a sandy loam soil collected at Askov, Jutland and was exposed to the test material at concentrations of 1, 10, 100 and 1000 mg/kg soil dw for 4 weeks.

Under the conditions of the test, at 1000 mg/kg there was a significant effect on soil nitrification and the estimated corresponding EC10 value was 295 mg/kg (95 % CL 210 – 390 mg/kg).