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Environmental fate & pathways

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PACM (4,4’-methylenebis(cyclohexylamine) is soluble in water (12.3 g/L) and is poorly degraded in water (neither readily biodegradable nor inherently biodegradable). It undergoes rapid phototransformation in the atmosphere (half-life of 3.3 h; at 0.5E-06 molecules OH/cm³, 24 h daylight).

The substance will not evaporate into the atmosphere from the water surface based on the pH-corrected Henry's Law constant of 3.65E-8 Pa m³/mol at pH 7 (range pH 5 to 9: 3.65E-10 to 3.63E-06 Pa m³/mol; BASF, 2012).

The Koc for PACM was calculated for the environmetally relevant pH range according to Franco and Trapp (2008, 2009, 2010). This resulted in a log Koc of 4.23 at pH 5 to 8 (Koc = 17047 at pH 5 to Koc = 17034 at pH 8). Therefore adsorption to solid soil phase is expected.

The log Kow value indicates that PACM has a low potential for bioaccumulation in aquatic and terrestrial habitats; the bioconcentration factor was estimated as BCF = 10.15 L/kg ww. This is supported by further QSAR data and the experimental result from a structurally similar substance (DMDC, CAS 6864 -37 -5; BCF < 60 according to OECD 305).

 

According to a Mackay Level I (static equilibrium) fugacity calculation, the main target compartments for PACM (as uncharged molecule) will be the hydrosphere (98.3 %), followed by sediment and soil (0.85 % each) and air (0.032 %). Assuming equal emissions to the air, water and soil compartments, a Mackay Level III (dynamic steady-state) fugacity calculation predicted a distribution of 75.1 %, 24.8 %, 0.09 % and 0.06 % to the soil, water, sediment and air compartments, respectively.