Indeno[4,3a-b]furan, decahydro-2,2,7,7,8,9,9-heptamethyl-

Toxicity to soil microorganisms

Description of key information

The influence of the test substance on soil microorganisms was determined by measuring the soil nitrification processes (NO2-N and NO3-N formation) according to the OECD TG 216. The study was conducted in compliance with GLP criteria. The test substance was directly applied onto quartz sand for all test item concentrations and additionally 0.5% lucerne meal (related to soil dry weight) was added to the soil. As the controls should be treated in the same way, the same amount of quartz sand and Lucerne meal was added to the controls. Throughout the application the soil was ventilated and the soil water content for the test item treatments were adjusted to 47% of WHC with ultrapure water. The soil water content of the control was adjusted to 47% of WHC. The test item was applied to the total soil amount for each treatment and soil from each treatment was divided into three replicates after application. The sandy loam soil had pH of 7.4, 0.88% OC and microbial biomass 288.63 mg C/kg (i.e. 3.28 % of the total soil organic carbon)). The Nominal treatment rates were 10, 32, 100, 320, 1000 mg test item/kg soil d.w. Effects of sodium chloride as reference item were determined at a rate of 16 g/kg dry soil in a separate study once a year. The test was conducted in 20 °C ± 2 °C, in the dark and the moisture was 47% to 48% of maximum water holding capacity (WHCmax).

At day 28, dose-response related stimulating effects could be measured starting from test item concentrations of 32 mg test item /kg soil s.w. for nitrate-N contents. A test item concentration of 1000 mg/kg soil dry weight caused strong stimulating effects on nitrate content in soil. At day 28, the differences to the control were 5.12%, 10.21%, 16.14%, 43.47% and 66.95% for test rate 1 (10 mg test item/kg soil dry weight) up to test rate 5 (1000 mg test item/kg soil dry weight). For the interval between day 0 and day 28, dose-response related effects could be measured starting from test item concentrations of 32 mg test item /kg soil dry weight. A test item concentration of 1000 mg/kg soil dry weight caused strong positive effects on the cumulative nitrate formation rate in soil. Differences to the control were 8.88%, 17.87%, 26.39%, 71.36% and 109.70% for test rate 1 (10 mg test item/kg soil dry weight) up to test rate 5 (1000 mg test item/kg soil dry weight). The variation between the replicate control samples did not exceed the validity criterion of 15% throughout the study. No ECx evaluation could be performed since the test item had stimulating effects on nitrogen transformation (nitrate-N content, nitrate-N formation rate) of soil microorganisms. Therefore it can be concluded, that the test item has no negative impact on soil microflora (N transformation).

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

1 000 mg/kg soil dw