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Environmental fate & pathways

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DIUP has a low potential to bioaccumulate in the environment based on results from a calculated bioconcentration factor value, and results from a bioaccumulation food-web field study, a biomagnification dietary lab study with a fish, and a measured biota-soil accumulation factor (BSAF) for a soil-dwelling invertebrate.

Conclusion:Potential of DIUP to bioaccumulate is low.

I5 Summary:

Biomagnification:High molecular weight phthalate esters (di-C8 PEs to di-C10 PEs) have been shown not to biomagnify through the food web, but rather decrease in tissue concentration with increasing trophic position. The results of a study to assess the bioaccumulation of high molecular weight phthalate diesters in an aquatic food-web that included 18 marine species, showed that DIDP did not biomagnify, but rather decreased in tissue concentration in organisms of increasing trophic position. Decreasing concentrations, also referred to as biodilution, can be quantified by food-web magnification factors (FWMFs). A FWMF that is greater than 1.0 is an indication of chemical biomagnification within a food-web, whereas a value of less than 1.0 indicates biodilution or dilution from lower to higher trophic levels. Study results showed that lipid equivalent concentrations of the high molecular weight phthalate diesters significantly declined with increasing trophic level and that the FWMF for di-isodecyl phthalate was0.44. Similar results would be expected with DIUP, an analog of DIDP.

Biomagnification:The finding above is consistent with a laboratory fish bioaccumulation study in which rainbow trout were fed a DIUP spiked diet for 9 days. The low water solubility and high Kow of DIUP prevent conducting an aqueous exposure BCF (bioconcentration factor) study. At the end of the exposure period, fish were sampled after different depuration times (1, 3 days). Results demonstrated limited bioaccumulation with a lipid normalized biomagnification factor (BMF, concentration ratio in tissue to that in diet) of 0.0045 and rapid subsequent depuration with a tissue elimination half-life of less than 1 day. The half-life of less than 1 day was used to calculate a BCF in fish of less than 1 L/kg for DIUP.

Bioconcentration:Calculated BCF data for di-isoundecyl phthalate (DIUP) suggest that it has a low potential to bioconcentrate in the aquatic environment.

BSAF:Data to assess the potential for terrestrial bioaccumulation of DIDP were reported in a 14-day earthworm (Eisenia fetida) toxicity study. The biota-soil accumulation factor (BSAF) as measured in a natural soil was 0.015 based on a DIDP concentration in the earthworm of 120 mg/kg (wet weight) and in soil of 7829 mg/kg (dry weight). A BSAF value of 1 indicates a lack of bioaccumulation. Similar results would be expected with DIUP, an analog of DIDP.