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Additional information

The acute and chronic aquatic toxicity studies with DIUP summarized in this report exhibit a range of maximum test substance concentrations achieved under the specific conditions of the studies. In those studies that did not use surfactants to increase aqueous solubility of DIUP, differences in the reported measured water solubilities are a result of several factors including different media composition, test substance spiking methods influenced by partitioning between test system and organism, different analytical techniques, and improvements in analytical procedures that have produced greater analytical sensitivity.

Some of the data used to characterize DIUP are for diundecyl phthalate (DUP; CAS #3648-20 -2) ester and di-isodecyl phthalate ester (DIDP), which are analogs to DIUP. Both DIUP and DUP contain undecyl alkyl groups. Whereas DUP contains linear undecyl alkyl groups, the alkyl groups in DIUP are branched. DIDP contains isodecyl alkyl groups. Therefore, because of the structural similarity between these substances and the similar biological behavior of high molecular weight phthalate esters in general, data for the analogs can be used to characterize the biological effects of DIUP for aquatic toxicity.

DIUP does not produce acute or chronic aquatic toxicity in fish, invertebrates, and algae. It has also been shown not to adversely impact the population parameters evaluated in a multi-generation study with a fish species, demonstrating that DIUP does not have the potential to cause endocrine disruption in the aquatic environment. The absence of toxicity demonstrated by DIUP is, at least in part, due to its low water solubility, resulting in low exposure potential, as well as the ability of organisms to metabolize DIUP at a rate that prevents a critical body burden from being reached. The data for DIUP show that it is not toxic at its maximally attainable water solubility level, which varies dependent on the conditions of study. Since DIUP does not cause acute or chronic aquatic toxic effects at the limits of water solubility, it is not possible to derive NOEC or PNEC values needed for quantitative risk assessment. However, it is possible to qualitatively conclude based on low solubility and the results of acute and chronic aquatic toxicity tests that DINP does not pose an unacceptable risk to the aquatic compartment.