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Long-term toxicity to aquatic invertebrates

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Long-term toxicity to aquatic invertebrates:
Results of two studies with di-isoundecyl phthalate ester (DIUP) and an analog substance suggest that DIUP will not produce chronic toxicity to invertebrates at or below its maximum attainable water solubility.

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The results of long-term toxicity studies are reported as EC50and NOEC values for chronic invertebrate toxicity. The NOEC values represent the highest concentration measured in these studies that did not demonstrate effects. In all cases this was the highest concentration attainable and measured under the conditions of the study. The use of the NOEC values in the results overview table to derive values for quantitative risk assessment is inappropriate as they are not true NOEC values.

Results from long-term toxicity studies with an invertebrate show that DIUP does not cause chronic toxicity at the maximum achievable aqueous concentrations investigated in these tests (i.e.in excess of water solubility). The study conducted by Rhodes (1995) tested DUP up to its solubility limit under the conditions of the study. In comparison, the Brownet al.(1998) study used a surfactant to achieve an exposure solution with a stable emulsion of DIUP at a level that far exceeded its water solubility. The use of a surfactant in comparison to the study that did not use a surfactant explains the large difference in the reported EC50and NOEC values.

I5 Summary

The data used to characterize the invertebrate chronic toxicity of di-isoundecyl phthalate (DIUP; CAS #85507-79-5) 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 weig

These data suggest that DIUP will not produce chronic toxicity in invertebrates. The data used to characterize DIUP are for DIUP and diundecyl phthalate (DUP) ester, which is an analog to DIUP. Both DIUP and DUP contain undecyl alkyl groups. Where phthalate diesters do not produce chronic toxicity to invertebrates at or below their maximum attainable solubliity. The chronic invertebrate dataset includes results for one species, Daphnia magna.as DUP contains linear undecyl alkyl groups, the alkyl groups in DIUP are branched. 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 analog can be used to support the biological effects of DIUP for this endpoint.

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