2,2,3,3,5,5,6,6-octafluoro-4-(trifluoromethyl)morpholine

Biodegradation in water: screening tests

Description of key information

Perfluoromethylmorpholine is not biodegradable. 

Additional information

Perfluoromethylmorpholine (PMM) is a member of the Perfluorinated Organic Chemicals, C5-C18, category. Biodegradation of PMM is addressed by readacross from category members. PMM was studied in a closed bottle test, but due to an invalid result the study was disregarded (BOD was greater than COD). The category member Hydrofluoric acid, reaction products with 4-(1-methylethyl) morpholine (FC-770, CAS# 1093615-61-2) was studied in an assay performed according OECD method 310. This method is specifically designed for volatile, insoluble materials and is appropriate for members of this category. This study included a toxicity control having both reference substance and FC-770, each in the same amounts used in positive controls or test flasks. No biodegradation was observed of FC-770. Assuming that all biodegradation in a toxicity control was due to the reference substance and none due to FC-770, the toxicity control was not significantly different than the positive control, and FC-770 had no inhibitory effect on biodegradation. In addition, none of the other category members tested showed signs of biodegradation in reliable closed bottle tests. PMM is not readily biodegradable in water or sediment.

All of the members of this category stem from the same manufacturing process, have similar physicochemical properties including high vapor pressure and low water solubility relative to the hydrocarbon analogs (e.g., hexanes v. perfluorohexanes), and also lack any chemically reactive groups, which forms the technical basis for the category. Members of this category are fully fluorinated, meaning that fluorine, rather than hydrogen, is bonded to all carbon atoms in the molecule. Fluorine is the most electronegative of the elements (fluorine has an electronegativity of 3.98 on the Pauling scale, as compared to 2.55 for carbon or 2.20 for hydrogen). This electronegativity is expected to dominate over all other aspects of substance chemistry and is the underlying basis for similarity of substances in this category. Because these substances exhibit similarity in their physicochemical properties and toxicological properties in mammals, and because available data indicates that parent molecules are not reactive toward biological molecules and cannot undergo bioactivation or indeed any reaction by normal enzymatic processes, they are considered to constitute a chemical category. Data gaps for biodegradation can therefore be addressed by read-across between category members. Please see IUCLID section 13 for the category justification and a matrix of biodegradation data for members of the Perfluorinated Organic Chemicals C5-C18 category.