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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Tert-butyl acrylate is not readily biodegradable according to OECD criteria. Tert-butyl acrylate is partly or moderately biodegradable.

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In a CO2-Headspace test according to ISO 14593 which is identical to OECD 310 (Ready Biodegradability - CO2 in sealed vessels) tert-butyl acrylate was moderately or partly biodegradable. The inoculum used in this study was municipal activated sludge from the domestic wastewater treatment plant of the City of Mannheim. The assay was conducted at a test substance concentration of 30.5 mg/L equivalent to 20 mg/L TOC at 22 °C in the dark. After 28 days a biodegradation degree of 50 - 60 % (range of three test assays: 53 - 63 %; mean value: 59 % TIC/TOC) was determined. The 10-day-window criterion for ready biodegradability was not fulfilled (BASFSE, 2008).

The biodegradability of tert-butyl acrylate was also investigated in several batch tests for ready biodegradability. In a manometric respirometry test (OECD 301 F) with non-adapted domestic sludge the biodegradation of tert-butyl acrylate was 32 % within 28 days and 38 % within 43 days (range of six test assays: 30 - 50 %), respectively (BASF 1993). Performing this test with adapted domestic sludge increased the degradation to 56 % within 28 days (range of six test assays: 38 - 67 %) (BASF 1994).

Primary degradation products predicted for tert-butyl acrylate by Q(SAR) modeling (OASIS, Catalogic v5.10.5) are acrylic acid and tert-butanol. Acrylic acid is readily biodegradable according to OECD criteria (Huels, 1995; BAMM, 1991). The biodegradability of tert-butanol was investigated in a CO2-Headspace test according to ISO 14593 (non-GLP). After 28 days a biodegradation degree of 70 - 80 % was determined (BASFSE 1997). Due to a longer lag-phase, the 10-day-window criterion for ready biodegradability was not met. Based on these test results, tert-butanol was considered to be biodegradable.

All other acrylates that are included in the read-across justification regarding ecotoxicity, are readily biodegradable with the exception of tert-butyl acrylate. Due to its branched molecular structure, slower biodegradation than observed for the other members is expected. Based on the presented test results, tert-butyl acrylate is considered to be not readily biodegradable according to OECD criteria. Tert-butyl acrylate is partly or moderately biodegradable. Since its degradation products acrylic acid and tert-butanol are readily biodegradable and biodegradable, respectively, ultimate biodegradation of tert-butyl acrylate in the environment is indicated. Formation of persistent breakdown products is not expected.