1-[4-(1,1-dimethylethyl)phenyl]-3-(4-methoxyphenyl)propane-1,3-dione

Endpoint summary

Additional information

Stability

Hydrolysis

Study on hydrolysis waived due to the extremely poor water solubility of the test item of 0.027 mg/L.

 

Biodegradation:

Biodegradation in water: screening tests

Both a study on anaerobic biodegradability and a study on (aerobic) inherent biodegradability revealed that the substance is not readily biodegradable. Based on ECHA Guidance "R.11 PBT Assessment", if the test item is not degradable in an inherent biodegradability study, the substance shall be considered as non biodegradable and further testing shall not be considered. 

 

Ultimate degradation in surface water (OECD 309)

The half-life, DT50, of the parent compound in natural water at 12 °C was determined to be 10.8 days at high dose (0.015 mg/L) and 10.2 days at low dose (0.005 mg/L). Under sterile conditions the parent compound degraded slower than in a non-sterile conditions. The half-life at 12 °C was 54.7 days at a concentration of 0.015 mg/L. The parent compound degraded to two major metabolites, depending on the placement of the radiolabel and a common metabolite for both labels.

 

Biodegradation in sediment (OECD 308)

The half-life, DT50, of the parent compound in freshwater sediment was determined to be 111 days at 12 °C in a river water/sediment system. The half-life in the water phase was 0.13 days at 12 °C and from the entire river water/sediment system the DT50 was determined to be 72.1 days at 12 °C. Using a pond water/sediment system, the DT50 for the parent compound in the sediment phase was 139 days at 12 °C, for the pond water phase 1.4 days at 12 °C and for the entire pond water/sediment system, the DT50 was 99 days at 12 °C.

 

Bioaccumulation

Bioaccumulation: aquatic / sediment 

In a dietary study according to OECD TG 305 under flow-through conditions with Oncorhynchus mykiss the lipid normalized BMF was calculated to be 0.1218. The half-life (DT 50) for elimination of BMDBM during the depuration phase was 3.83 days. The growth corrected rate constant K2 for depuration was calculated to be 0.1811. In compliance with the guidance document to OECD TG 305 (2^nd draft, 2016) the kinetic BMF value obtained from the OECD 305 study was translated into BCF values by using the excel spreadsheet published by OECD (version 2, as provided on 10 December 2020). Based on the experimental data and current guidance the BCF of the test item is considered to be in the range between 2000 and 3000. An in-depth assessment on the bioaccumulation potential of the substance is attached to IUCLID section 13.2.

 

Transport and distribution

Adsorption/desorption

The computational approach (QSPR) for deriving the Koc is based on the real physical properties of the test item, i.e. the experimentally derived log Kow of 6.1. When using the geometric mean of the results of four different QSPR models, the resulting log Koc is 4.65 (Koc = 44242 L/kg). Based on this result BMDBM has to be considered as "immobile" in sediments or soil.