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Environmental fate & pathways

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The ready biodegradability of methyl polyhydroxymethyl stearate was evaluated using the OECD Guideline No. 301F: Manometric Respirometry Test. This test employed biodegradation reaction mixtures containing a non-adapted activated sludge inoculum, which was suspended in a defined mineral medium at a concentration of 30 mg/L (dry solids). The water-insoluble test substance was coated onto silica gel to facilitate its dispersion in the reaction mixtures at a concentration of 40 mg/L (100 mg/L theoretical oxygen demand). Biodegradation of the substance began almost immediately upon addition to the reaction mixtures, and reached 112.1 ± 5.7% and 80.8 ± 4.0% (mean ± 1 SD) based on biological oxygen demand (BOD) and CO2 evolution, respectively, at the end of the 28-day test. Dissolved organic carbon (DOC) analyses also showed that biodegradation of the test substance did not result in accumulation of soluble, persistent degradation products. Since the pass level of 60% biodegradation was achieved within the 28-day test period, the substance meets OECD criteria for ready biodegradability in the Manometric Respirometry test. 

The results of this test met or exceeded each of the OECD-specified criteria for validation of its ready biodegradability tests. These include parameters such as viability of the inoculum, control of pH and temperature, and precision in percentage biodegradation recorded among replicate test mixtures. Biodegradation of a reference substance (sodium benzoate) exceeded 60% within only 3.1 days, and thus verified the viability of the inoculum employed in this test. A Toxicity Control mixture, containing both sodium benzoate (120 mg/L) and the test substance, showed no evidence for inhibition of the microbial inoculum. An Abiotic Control mixture, containing the test substance and a chemical sterilant (HgCl2), verified that the observed test substance degradation was due solely to biological activity. 

The results of ready biodegradability tests for the Natural Oil Monomer, sodium stearate, and 1-methylpyrrolidin-2-one, as well as BIOWIN- and CATABOL-predicted biodegradabilities for the known/expected components of the Natural Oil Monomer substance, provide a conclusive weight of evidence showing that all components of this UVCB substance would be rapidly and ultimately biodegradable in the environment