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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Palmitic acid is readily biodegradable

Key value for chemical safety assessment

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Palmitic acid was tested according to the ISO 10708 (BODIS test) which is apparently similar to the “closed bottle test”, OECD 301 D. Three replicates with palmitic acid at concentrations of 100 mg/L COD were incubated with non-adapted activated sludge. The oxygen consumption was monitored during the 28 day test period. The results clearly showed that palmitic acid was degraded by 65% in average at day 28 (Börner,1994).
According to the opinion of the SCIENTIFIC COMMITTEE ON HEALTH AND ENVIRONMENTAL RISKS on “Compatibility of the ISO standard 10708 (biodegradability test method) with the ultimate biodegradability requirements imposed through Annex III of Regulation 648/2004 of Parliament and of the Council”, the BODIS-Test/ISO 10708 shows the same variability and biodegradation results obtained with other OECD screening tests (SCHER, 2005). Since the pass criterion of 60% degradation within 28 days of the ISO 10708 is consistent with those obtained with the OECD ready biodegradability methods, palmitic acid can be regarded as readily biodegradable.

The well anaerobic biodegradability of palmitic acid is shown in the following tests.

Wierich (1992) showed in an anaerobic biodegradation study with 98% pure palmitic acid according to ECETOC Technical Report no 28 (today ISO 11734) a 77% degradation in 69 days.

The anaerobic degradation of palmitic acid was investigated by Nuck and Federle (1995) in an mixture of anaerobic sewage sludge and mineral salts. The radioactive labeled test substance was monitored for the production of labeled carbon dioxide and methane over the time (30 d). Palmitic acid was significantly mineralized: At test end 67.5% of the labeled test substance was recovered as carbon dioxide and 20.9% as methane. In sum, palmitic acid was mineralized in sludge up to 88.4% under anaerobic conditions within 30 days.