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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Mequinol is readily biodegradable in water screening tests (OECD 301C). It should also degrade under anaerobic conditions.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Among the biodegradation data available in water, two have been chosen as key studies:

-  the first one was generated by Japanese Competent Authorities (CERI), according to OECD guideline301C. The inoculum was activated sludge (30 ppm) in contact with 100 ppm test substance for 28 days. Based on BOD, 86% degradation of test substance occured in 28 days. Based on TOC removal, it was 99%. And based on test material analysis (HPLC), 100% disapeared in 28 days. No data were given concerning the validity criteria.  Based on the results of this test, PMP is readily biodegradable.

-  the second one (Boyd et al., 1983), was performed before OECD TG on anaerobic biodegradation was available. However, the procedure used in the study is similar to the one of the OECD TG 311, except that the additional  measurement of the dissolved inorganic carbon (DIC)  was not performed.

The CH4 production was calculated and more than 90% of CH4 was produced in 4 weeks. The parent compound, PMP, needed one week for complete disappearance. The degradation products were determined; PMP was presumably transformed to 1,4 -dihydroxybenzene (hydroquinone), although it was not observed by HPLC, it is assumed to be a transient intermediate.

Based on this study, PMP should be degraded under anaerobic conditions.

Two other data of reliability 2 have been chosen as supporting studies:

-  Shelton and and Tiedje, 1984: the study was conducted using the OECD guideline 311 method under anaerobic conditions. The result was expressed as percentage of theoretical methane production, based on stoichiometry of degradation. In 56 days, the ultimate degradation of PMP in CH4 was > 75%.

Based on this study, PMP should be degraded under anaerobic conditions.

-  Wellens VH, 1990: this study is an inherent biodegradability test, conducted according to OECD

guideline 302B, under aerobic conditions. Based on DOC removal, 100% of the substance is

degraded in 6 days.

Based on this study, PMP is inherently biodegradable.