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

Bioaccumulation: aquatic / sediment

Description of key information

The test substance does not significantly accumulate in organisms.

Additional information

The bioaccumulation potential of the substance was tested in a guideline study following OECD 305 C (Institute of Ecotoxicology 1996). Japanese carp (Cyprinus carpio) were exposed to the test substance for 8 weeks. Due to the low solubility of the test item an emulsifier has been used. The determined bioconcentration factor was <40 and the test item does not significantly accumulate in fish. Despite the use of an emulsifier the test is regarded as valid in a weight of evidence since the low exposure level was at the water solubility of the test item.

To support these findings a test with an analogue substance is used as read-across. The analogue substance (EC 416-250-2) is also a DPP-pigment. Both substances share the same common functional group, the 2,5-dihydro-pyrrolo(3,4-c)pyrrole-1,4-dione core. They only differ in the moiety. The analogue substance has a tert-butyl moiety in para-position of both phenyl rings instead of a methyl moiety.

Both substances are not readily biodegradable and due to the inert structure no break-down products will occur in the environmental compartment. Additionally, both substances have a very low solubility in water and a similar molecular weight. Due to their similar PC properties the behavior within the environmental compartment is comparable. Furthermore, since the read-across substance has a slightly higher logKow the read-across can be regarded as worst case. Additional, both substances show same results in the aquatic toxicity test and no toxic effects occur within the range of solubility for all trophic levels. Therefore, the read-across is justified.

	EC 419-370-3	EC 416-250-2 (read-across substance)
Physico-chemical data
Mol. weight	316.353	400.521
Melting point	>300°C	>500°C
Relative density	1.38	1.202
Water solubility (mg/L)	< 0.1	< 0.1
LogKow (HPLC)	3.38	5
Dmax average (nm)	1.799	2.066
Environmental fate data
Hydrolysis	Not expected, low water solubility	Not expected, low water solubility
Biodegradation in water	0% after 28 d	No biodegradation observed
Adsorption/desorption (logKoc)	4.1356	6.639
Ecotoxicity data
Short-term toxicity to fish	No acute toxic effects within the range of solubility	No acute toxic effects within the range of solubility
Short-term toxicity to aquatic invertebrates	No acute toxic effects within the range of solubility	No acute toxic effects within the range of solubility
Short-term toxicity to aquatic algae and cyanobacteria	No acute toxic effects within the range of solubility	No acute toxic effects within the range of solubility
Toxicity to micro-organisms	EC50 > 100 mg/L	EC50 > 100 mg/L

 

 

The flow-through Dietary Bioaccumulation Study using EC 416-250-2 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 2012). 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.

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 (k₂andk_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.

Furthermore, to complete the weight of evidence several QSAR calculations have been used to assess the bioaccumulation potential. In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met. Furthermore according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

 

For the assessment of the test substance additional (Q)SAR results were used for bioaccumulation. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.Therefore, and for reasons of animal welfare, further experimental studies on bioaccumulation are not provided.

 

The different QSAR calculations gave following results:

US EPA T.E.S.T v4.1 using the consensus method resulted in a BCF of 4.78. The test substance is within the applicability domain.

US EPA EPISuite v4.10 (BCF BAF v3.01; submodel BCF according to Meylan) revealed a BCF of 9.76 L/kg wet-wt. The test substance is within the applicability domain. The two other submodels “Biotransformation rate in fish (kM; Arnot et al., 2008a/b)” and “Arnot & Gobas BAF and steady-state BCF Arnot & Gobas, 2003” resulted also in BCF values below 12. However, since the test substance is a pigment both submodels are not within the applicability domain.

CATALOGIC v5.11.5 (BCF base-line model v2.05) resulted in a BCF of 5.96 with all mitigating factors applied. Even though the structural domain was correct with only 8.33% (91.67% unknown) the results support the overall conclusion in a weight of evidence.

Summarizing the results of the two bioaccumulation studies (test-substance and read-across substances) and all QSAR calculations it can be concluded regarding all available information the test item does not significantly accumulate in organisms and the BCF is below 100.