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Long-term toxicity to fish

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Long-term toxicity to fish:
Conclusion: Results of studies with two analog substances suggest that DTDP will not produce chronic toxicity to fish at or below its maximum attainable water solubility.

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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.

The result of a long-term toxicity study is reported as a NOEC value for chronic fish toxicity. The NOEC value from these studies represents the highest concentration tested and measured under the conditions of the study. Results from a long-term fish toxicity studies show that DIDP and Diundecylphthalate (DUP), analogs to DTDP, do not cause toxicity (ExxonMobil, 2002; Rhodes et al., 1995). Additionally, the results can be used to assess the potential for endocrine disruption in fish.

The multi-generation feeding study with Oryzias latipes (Medaka, 284-days) was conducted by adding DIDP to dry flake food at 20 mg/kg. Evaluation of F1 and F2 embryos showed normal development except for a transient decrease in red blood cell pigmentation, which was observed in both the acetone control and DIDP treatment groups. The male to female ratios (3:1) in all groups were similar. Phenotypic gender classification of male and female fish was histopathologically confirmed to be 100% correct. The gonadal and liver somatic indices were not significantly different in the DIDP treated group. There were no statistically significant changes in mortality, fecundity, or egg production in the treatment groups.

DUP showed no effect on egg hatchability, egg survival, fry survival, or growth (length and weight) at its highest achievable water solubility (0.30 mg/L) under the conditions of this test. No compound-related physical and behavioral effects were noted at any test concentrations.

I5 Summary

The data used to characterize the fish chronic toxicity of di-isotridecyl phthalate (DTDP) ester are consistent with the data for several high molecular weight phthalate diesters summarized by Staples et al. (1997). These data show that high molecular weight phthalate diesters do not produce chronic toxicity to fish at or below their maximum attainable solubliity. The data used to characterize DTDP are for diundecyl phthalate ester (DUP) and di-isodecyl phthalate ester (DIDP), which are analogs to DTDP. Results of studies with two analog substances suggest that DTDP will also not produce chronic toxicity to fish at or below its maximum attainable solubility. 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 DTDP for this endpoint. The chronic fish dataset includes results for two species of freshwater fish, Oncorhynchus mykiss and Oryzias latipes.

Staples et al. (1997). Aquatic toxicity of eighteen phthalate esters. Environ. Toxicol. Chem. 16(5): 875 -891.