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Environmental fate & pathways

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DCDPS is hydrolytically stable (Boelhouwers 2007). Studies on direct phototransformation in water are not available but it is assumed the substance is not degraded by direct photolysis due to its chemical structure. It is concluded, therefore, that abiotic processes do not contribute significantly to the depletion of the substance in the aquatic environment.

DCDPS is not readily biodegradable (NITE 1999). Additionally, a 100-day simulation test of two water-sediment systems (Talken, 2014) showed that aerobic transformation in aquatic/sediment systems is not a major pathway of degradation of the substance, which increasingly migrates from the water column to the sediment layer over time. Therefore, the substance is expected to be persistent in the aquatic environment.

The low vapour pressure and the Henry constant (see Table 4, p 6 and Table16, p 27) indicate that DCDPS is characterized by a low volatilisation potential and no significant transport from water to air is expected. Indirect photolysis by hydroxyl-radicals (Meylan & Howard 1993) is assumed to contribute to the depletion of any atmospheric DCDPS from the troposphere.

Based on a Kocof 3162 (log Koc= 3.5) DCDPS is classified as slightly mobile in soil (according to the mobility classes of McCall et al 1981).

Concluding from its octanol-water and octanol-air fugacity properties (Kow, Koa) DCDPS is expected not to bioaccumulate in water breathing organisms. This conclusion is in line with an experimental BCF of 75 L/kg (whole fish body ww). But accumulation in air breathing biota is suggested (Gobas et al 2009, Kelly et al 2004). Further investigations are required for assessment on possible biomagnification since the relevance of available measured environmental concentration data can not be finally assessed yet.

Measurements from environmental samples found an annual decrement of 1.6% of the DCDPS levels in replacement eggs from the Baltic guillemot (Uria aalge) collected between 1971 and 2001 (Jörundsdóttir et al 2006). Assuming that historical emissions are the relevant source for the observed levels, this indicates that some degradation in the environmental compartments may occur.

Final conclusions on the biomagnification of DCDPS in the environment are not possible based on the available information. Therefore, further investigations on biomagnification of DCDPS are indicated. A testing proposal is presented in the relevant section.