Mitochondrial Toxicity of Phosphorus Based Flame Retardants

Abstract

Flame retardants (FRs) are added to various substances so that when exposed to an open flame the parent material combusts at a slower rate. However, there is concern over the safety of these chemicals. In this study the mitochondrial toxicity of Triphenyl Phosphate (TPP), Isopropylated Triphenyl Phosphate (IPP), and Tert-Butylphenyl Diphenyl Phosphate (TBDP) were assessed using the model organism Caenorhabditis elegans. The first experiments were growth assays utilizing mitochondrial regulation (fusion, fission, mitophagy) knock down mutants (eat-3, fzo-1, drp-1, dct-1, pdr-1, and pink-1). In the second set of experiments, relative ATP levels were measured using a luciferase reporter strain (PE255). The results were that eat-3, fzo-1, drp-1, and dct-1 were more sensitive to TPP than the control (defined as growth decrease greater than 10%) at the mid to high dose range; there was decreased sensitivity to pdr-1. IPP and TBDP caused less toxicity in eat-3 and pdr-1. There was no significant change in ATP levels after exposure to TPP, while there was a concentration-dependent decrease with IPP and a slight increase with TBDP. Overall the results of this study are consistent with the possibility that TPP is a mitochondrial toxicant; future research is needed to fully understand that relationship.