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Environmental fate & pathways

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The biodegradability of monomethylamine has been investigated within different experimental settings.

In the key study (Official Bulletin of Economy, Trade and Industry, 1988), the biodegradability of monomethylamine hydrochloride was determined according to MITI-I (OECD 301C). This experiment was conducted with the almost identical substance methylamine hydrochloride. 30 mg/L activated sludge and 100 mg/L of the test substance were used in this test. The time duration was 2 weeks, whereby the indirect analysis showed a result of 84 % degradation, based on BOD (NH3). Direct analysis results are given as 96 %, based on TOC and 100 %, based on HPLC, respectively. The substance was, thus, considered as readily biodegradable.

In a supporting study (Chudoba et al., 1969), the oxygen consumption of activated sludge exposed to methylamine was studied using respirometers (aerobic conditions). The oxygen consumption by endogenous respiration was recorded whereby two different sets of tests were set up (non-adapted sludge; adapted sludge). The exposure period in both sets was 13 days. The test substance concentration amounts to 66.7 mg/L. The removal of methylamine from the test samples by biodegradation was also determined by studying the chemical oxygen demand. Within 13 days the following results are reported for methylamine: BOD/ThOD = 67.8 % (non-adapted sludge); BOD/COD = 93.5 % (adapted sludge).

 

In another supporting study (BASF AG, 1990), monomethylamine was investigated in a study similar to OECD 301F. The exposure duration was 28 days and the test substance concentration was 400 mg/L, based on test material. Degradation of 55 % occurred within 28 days under aerobic conditions. The authors report that ammonia or ammonium release may lead to an impaired degradation due to a shift in pH. If this shift in pH does not occur, biological degradation is possible. As inoculum domestic, activated sludge (without adaption) was used. According to this test, the substance is not readily biodegradable. However, due to high substance concentration (400 mg/L), it is assumed that the pH of the test solutions has been influenced leading to a decreased degradation rate as mentioned by the authors. pH values are only reported for the end of the test. Neither additional pH values for other points in time nor information about pH adjustments are available.

 

In another supporting study (Chemservice S.A., 2010), the biodegradability of the substance monomethylamine was calculated based on QSAR methods by using EPIWIN (BIOWIN v4.10). Seven different models are used by this tool to predict an overall result if the substance is readily biodegradable or not. As newest model, Biowin 7 predicts additionally the biodegradation ability under anaerobic conditions. According to the Linear and also Non-linear Model monomethylamine is biodegrading fast. The Ultimate Biodegradation Timeframe is given in weeks, whereas the Primary Biodegradation Timeframe shows days. Both MITI Models predict that the substance is readily biodegradable, which is also the overall conclusion of the calculation. Under anaerobic conditions monomethylamine is suspected to be biodegraded fast as well.