Acute Toxicity of Diisoheptyl Phthalate and Diisononyl Phthalate to Oryzias latipes

Abstract

Phthalates are industrial chemicals used primarily as plasticizers to increase the flexibility of high molecular-weight polymers. These compounds are not covalently bound to the polymeric matrix but are instead distributed between the macromolecules of the polymer. Therefore, it is highly possible for them to leach out, inducing subsequent environmental contamination. It is important to learn more about how these toxicants are affecting the environment and vertebrate health. Diisoheptyl phthalate (DIHepP) and diisononyl phthalate (DINP) are among the list of substances that are being assessed by Environment Canada’s Chemical Management Plan. This study examines the effect of DIHepP and DINP on the Asian fish Oryzias latipes because it is subject to phthalate contamination in its natural habitat when phthalates leach out of plastic substances into the surrounding environment. At 1 day post hatching, fish were exposed to a range of environmentally relevant, low concentrations of DIHepP (0.037-0.3 µL/L) and DINP (0.012-0.1 µL/L) under semi-static conditions for 7 d. None of the treatments significantly induced mortality or malformation. Gene expression analysis was performed to assess possible endocrine disruption of these compounds. The transcripts of interest include deiodinase iodothyronine type 1 (dio1), thyroid hormone receptor β (trβ), steroidogenic acute regulatory protein (star), steroid 5-alpha reductase type 2 (srd5α2), and cytochrome P450 aromatase (cyp19β). The exposure did not have a statistically significant effect on gene expression. Taken together, these results indicate that exposure to DIHepP and DINP do not significantly affect mortality, malformation, or endocrine disruption in O. latipes at the tested concentrations.