3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate

Endpoint summary

Additional information

According to claimed uses of 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate and to its lyfe cycle, terrestrial exposure is likely.

Therefore, long-term toxicity studies on soil organisms covering plants, invertebrates and micro-organisms have been performed with the substance. PNEC for the terrestrial compartment has been derived using the lowest determined effect concentration from these studies applying an assessment factor of 10.

A study was designed to assess potential effects of 3-hydroxy-1,1-dimethyl-butylperoxyneodecanoate on seedling emergence and seedling growth of six non-target terrestrial plant species following a pre-emergence application of the product on soil surface according to OECD 208 guideline and GLP requirements (Piskorski, 2015). Seeds of six different species (two monocotyledonae, four dicotyledonae) were exposed to soil treated with the test item at five treatment rates: 20, 50, 125, 312 and 780 mg a.i./kg dry soil.. The test item was applied to soil before sowing. The inhibition of the plant emergence and early growth was compared to the control plants over a study period of 21 days, after 50% emergence in the control group. At test termination, shoot fresh weight was determined. Out of the six plant species tested, lettuce (Lactuca sativa) showed to be the most tolerant as deduced from high values of ER50 and NOER based on seedling emergence, plant survival and fresh weight (ER50 and NOER values of > 780 and ≥ 780 mg a.i./kg dry soil for all three endpoints, respectively). Overall, wheat (Triticum aestivum) was the most susceptible with the lowest values of NOER based on emergence and fresh weight (50 and 20 mg a.i./kg dry soil, respectively). The study fulfilled all validity criteria from the OECD Guideline 208.

Adult earthworms of the species Eisenia fetida were used in a earthworm reproduction test according to OECD 222 and GLP requirements (Odemer, 2015).

Exposure to 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate of earthworms to treated soil for four weeks with mortality assessment and subsequent counting of offspring (number of juveniles + cocoons) after an additional four weeks of exposure was carried out. The Study consisted of seven treatments: One control, five test item concentrations (3.2, 10, 32, 100 and 320 mg active ingredient (a.i.) test item/kg dry soil) and one reference item (Carbendazim).

The validity criteria of the test were fulfilled.

After 56 days of exposure to 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate, the EC20 and EC50 calculated for earthworm reproduction (juveniles) were determined to be 1.752 and 12.085 mg a.i. test item/kg dry soil, respectively (corresponding to 3.5 and 23.8 mg test item/L, respectively).

It was not possible to extrapolate an EC10 for earthworm reproduction related to the results obtained. Therefore the EC20 has been used as the key value for this long-term study. Indeed, as indicated in the Table R.10 -1 Chapter R.10 of REACH guidance (May 2008 version), ECx where x is a low effect percentile (e.g. 5 -20%) is recommended to express long-term effects.

One valid experiment has been carried out according to OECD 216 guideline and GLP requirements (Bangert, 2015) in order to assess the effects of 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate on the activity of the soil microflora (nitrogen transformation).

The study was performed using 5 concentrations 100 / 180 / 320 / 560 / 1000 mg/kg dry soil.

Sieved soil was exposed to the test item for 28 days. After 0 days (start of the test) and 28 days, the nitrate content of the soil of each treatment was determined. A blank control was tested.

The following concentrations showed inhibition of Nitrate production compared to the control: 1000 / 560 / 320 mg/kg

The following results were determined: 28d-EC50 = 190 mg/kg a.i. and 28d-EC10 = 130 mg/kg a.i..

The relative standard deviation between the replicates of the blank control was 1.2 %, indicating the small difference between the replicates. No observations were made which might cause doubts concerning the validity of the study outcome.

The result of the test can be considered valid.