Pyrrolo[3,4-c]pyrrole-1,4-dione, 3,6-bis[4-(1,1-dimethylethyl)phenyl]-2,5-dihydro-

Bioaccumulation: aquatic / sediment

Description of key information

The substance does not significantly accumulate in organisms.

Additional information

A flow-through Dietary Bioaccumulation Study in the Rainbow Trout (Oncorhynchus mykiss) was conducted following GLP and OECD 305 (Dietary exposure, Draft revised Guideline 31 Aug 2010) with radiolabeled test substance (BASF SE 2012b). The fish were fed a diet spiked with radiolabeled [¹⁴C] test substance at 500 mg test substance/kg food at a rate of 3% mean body weight/day over an uptake period of 14 days followed by a depuration period of 4 days. Additionally, hexachlorobenzene was used as reference substance.

Over the entire test no toxic effects like increased mortality in comparison to the control group or changes in behavior or appearance were observed in the test organisms.There was a slight but statistically significant difference in fish growth rate during the study between the control and treatment group. However this was not considered a toxic effect since there was practically no uptake of test substance in fish tissue and the growth rates in both test groups were within the normal range for trout fed at 3%. The growth rate of the treatment group was used as the kg value for “growth-corrected” calculations.The lipid content of control fish sampled over the test period increased from 3.2% to 6.3% over the test period.

The depuration rate constants (k₂ and k_2g) derived from measured values of HCB in the fish tissues were similar to the values in the OECD 305 ring test for the fish dietary bioaccumulation test and the HCB BMF_KgLwas > 1 providing confidence in the data quality of this study.

The mean measured concentration in fish during the uptake period was 7.46 µg/g. Dividing this concentration by the measured concentration in the diet (503 µg/g) gives an estimated biomagnification factor (BMF) of 0.014. On test day 14, fish were dissected and the radioactivity present in the gastrointestinal (GI) tract was measured separately from the rest of the fish. 98.8% of the radioactivity was present in the GI tract, most likely due to remaining undigested spiked food. The measured radioactivity in the fish carcass (-GI tract) was minor yet highly variable (especially day 14) likely due to cross contamination during the dissection procedure. The measured data fit very well to a first order kinetic model which was used to estimate rate constants and BMF values. Since the majority of substance remained within the GI tract, there was practically no accumulation in fish tissues and the application of a lipid correction does not provide greater accuracy to estimate BMF. In conclusion,the most relevant BMF value in this study is the growth corrected dietary kinetic BMF (BMF_Kg) which was 0.0151. This value is far below the generally accepted threshold of concern (BMF = 1). Therefore, the test substance does not significantly accumulate in organisms.

The results are supported by a bioaccumulation study according to OECD 305C using Japenese carp (Gakushuin University 1995). Due to the low solubility of the test substance a dispersing agent was used. The BCF after 8 weeks was estimated to be below 25. The test substance does not significantly accumulate in fish. However, the used test concentrations of 1 ppm and 0.1 ppm are above the water solubility.