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The acute and chronic aquatic toxicity studies with DTDP and with analogs of DINP 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 DTDP, 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.

DTDP does not produce acute or chronic aquatic toxicity in fish, invertebrates, and algae. Analogs of DTDP (DIDP and DUP) have also been shown not to adversely impact the population parameters evaluated in a multi-generation study with a fish species, demonstrating that DTDP does not have the potential to cause endocrine disruption in the aquatic environment. The absence of toxicity demonstrated by DTDP 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 DTDP at a rate that prevents a critical body burden from being reached. The data for DTDP show that it is not toxic at its maximally attainable water solubility level, which varies dependent on the conditions of study. Since DTDP 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 DTDP does not pose an unacceptable risk to the aquatic compartment.

Justification for read-across:

The High Molecular Weight Phthalate Ester (HMWPE) Category consists of phthalate esters with an alkyl carbon backbone with 7 carbon (C7) atoms or greater. The category is formed on the principle that substances of similar structure have similar toxicological properties. The data available on high molecular weight phthalates demonstrate that members of this category have similar biological activities and toxicological properties; verifying the use of read-across data as an appropriate approach to characterize endpoints. Both substances named DTDP are high molecular weight phthalate esters (C13), diisotridecyl phthalate (CAS number 27253-26-5, EC number 248-368-3) and 1,2-Benzenedicarboxylic acid, di-C11-14-branched alkyl esters, C13-rich (CAS number 68515-47-9, EC number 271-089-3). Both are isomeric mixtures of C13 branched alkyl esters, the starting material being different but both starting materials consisting of various isomers of multibranched C13 alcohols. Where data maybe lacking for DTDP, DINP (C9) and DIDP (C10), which are also high molecular weight phthalate esters, are used as read-across substances to provide toxicological information.

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