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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

Biodegradation in sediments
Discussion (sediment testing)
Studies are not available to assess the biodegradability of DIUP in sediment. Although there are no data specifically for the diester, there are biodegradation data for the monoester of DIDP (mono-isodecyl phthalate, MIDP) that showed an average half-life of 23 hours in marine sediments based on results from two studies (Otton et al., 2008). Research suggests that the formation of the monoester occurs as the first step in the biotic degradation of DIDP (Staples et al., 1997). Because this step does not appear to be rate limiting, as evidenced by the high extent of biodegradation demonstrated by DIDP in a ready test, the degradation of the diester in sediment is expected to occur at a similar high rate. Because Di-isodecyl phthalate ester (DIDP) is an analog to DIUP, the mono ester of DIUP is expected to biodegrade in sediment at approximately the same rate as was exhibited by the mono ester of DIDP.

Key value for chemical safety assessment

at the temperature of:
295 K

Additional information

Studies are not available to assess the biodegradability of DIUP under simulated conditions (i.e., wastewater treatment). However, there are data for di-n-decyl phthalate (CAS No. 84-77-5; DnDP), an analog to DIUP, using treated wastewater that suggest DIUP would demonstrate a high extent of biodegradation under sewage treatment plant (STP) conditions (Furtmann, 1993). DnDP biodegraded 82% after 7 days based on the disappearance of the parent compound from the test system. The initial DnDP concentration was 7.8 μg/l and the DT50 was <1 day.

The elimination of DIUP in a STP through biodegradation and distribution, as reported by the European Commission (2003), was estimated using the SIMPLETREAT model. The model calculated that 94% of DIUP would be eliminated in a STP, which is consistent with the high loss reported by Furtmann (1993). The measured data for DnDP and the modeled data suggest that DIUP will be largely eliminated in a STP.