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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The ready biodegradability of the read across substance Reaction products of γ-butyrolactone, naphthalene-1,6-diol and phthalic anhydride (EC 946-798-2) was determined according OECD 301 B under GLP conditions. The read across substance is not readily biodegradable according to OECD criteria, but poorly biodegradable (15% CO2/ThCO2 after 28 days).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

No data on biodegradability were available for the substance itself. Therefore, a read across to the close structural analogue Reaction products of γ-butyrolactone, naphthalene-1,6-diol and phthalic anhydride (EC 946-798-2) was conducted.

Key study

To assess the ready biodegradability of the close structural analogue (EC 946-798-2), a CO2 Evolution Test according to OECD 301 B, EU Method C.4 -C, US EPA OPPTS 835.3110 and ISO 9439 was conducted in compliance with GLP principles (BASF SE, 2018). Activated sludge of a municipal sewage treatment plant (30 mg/L dry weight per test bottle) was exposed to 20 mg/L TOC of the test item (equivalent to to approx. 30 mg/L test item, 2 assays; TOC of the test item: 670 mg/g) over a test duration of 28 days. In addition, a blank control (without the test item, 2 assays) and a positive control with the reference substance aniline (1 assay, 20 mg TOC/L) as well as an inhibition control (test item: 20 mg/L TOC; aniline: 20 mg/L TOC; 1 assay) was performed. The used mineral medium complied with the test guideline OECD 301 B. The test vessels were aereated with CO2 free air at a flow of approximately 800 mL per hour by connecting the test bottles with an aeration unit. The incubation bottles were stirred during the experimental duration on a magnetic stirrer. Each test bottle was connected to two serial scrubbing bottles filled with 100 mL of 0.05 mol sodium hydroxide (NaOH) solution as CO2 trap. Formed carbon dioxide was measured (twice a week in triplicates) in a TOC-analyzer unit using the infrared gas analysis method. A separate determination of total inorganic carbon (TIC) was not necessary with the test substance. The overall biodegradation was calculated as the mean of the maximum values of biodegradation observed in the plateau phase, instead of at the end of exposure period. The biodegradation of the reference substance after 14 days was determined to be 83% CO2/ThCO2, confirming the suitability of the test item. In the inhibition control test assay no toxic effects to the microorganisms were observed. Maximum degree of biodegradation of the test item averaged 15% CO2/ThCO2 (standard deviation = 2.1%) after an exposure period of 28 days. Hence, the required pass level for ready biodegradability in accordance to the OECD guideline 301 B i.e., > 60% CO2/ThCO2 was not reached. As the test item is a mixture of structure similar compounds (UVCB), the 10 days window was not applied. In conclusion, the test item was determined to be not readily biodegradable in this test, but poorly biodegradable. All validity criteria of the guidelines were fulfilled.