Advanced Morphological — Behavioral Test Platform Reveals Neurodevelopmental Defects in Embryonic Zebrafish Exposed to Comprehensive Suite of Halogenated and Organophosphate Flame Retardants

Abstract

The increased use of flammable plastics and electronic devices along with stricter fire safety standards has led to the heavy use of flame retardant chemicals in many consumer, commercial, and industrial products. Although flame retardant use has increased, a great deal of uncertainty surrounds their safety with some evidence showing toxicity and risk to human and environmental health. Recent efforts have focused on designing high-throughput biological platforms with nonmammalian models to evaluate and prioritize chemicals with limited hazard information. To complement these efforts, this study used a new morphological and behavioral testing platform with embryonic zebrafish to characterize the developmental toxicity of 44 halogenated and organophosphate flame retardants, including several of their known metabolites. Zebrafish were exposed to flame retardants from 6 to 120 h post fertilization (hpf) across concentrations spanning 4 orders of magnitude (eg, 6.4 nM to 64 µM). Flame retardant effects on survival and development were evaluated at 24 and 120 hpf, and neurobehavioral changes were measured using 2 photomotor response (PMR) assays. Compared to controls, 93% (41/44) of flame retardants studied elicited adverse effects among one or more of the bioassays and concentrations tested with the aryl phosphate ester (APE)-based mono-isopropylated triaryl phosphate and the brominated-bisphenol-A analog tetrabromobisphenol-A producing the greatest array of malformations. Hierarchical clustering showed that APE flame retardants with isopropyl, butyl, and cresyl substituents on phenyl rings clustered tightly and were particularly potent. Both PMR assays were highly predictive of morphological defects supporting their use as nonlethal means of evaluating teratogenicity that could allow for additional evaluations of long-term or delayed effects in older animals. Taken together, evidence presented here indicates that zebrafish neurodevelopment is highly sensitive to many flame retardants currently in use and can be used to understand potential vulnerabilities to human health.

Developmental exposure to organophosphate flame retardants causes behavioral effects in larval and adult zebrafish

“…Instead, it was found that exposures an order of magnitude higher decreased larval activity in both the light and dark (Dishaw et al, 2014). Another study also failed to find that TPHP exposure during the same time period produced behavioral effects up to a dose two orders of magnitudes higher, at which point TPHP also depressed locomotion (Noyes et al, 2015). The same study, however, found that TDCIPP increased locomotion at doses near the higher dose tested here, but attenuated it at higher doses (Noyes et al, 2015).…”

“…Another study also failed to find that TPHP exposure during the same time period produced behavioral effects up to a dose two orders of magnitudes higher, at which point TPHP also depressed locomotion (Noyes et al, 2015). The same study, however, found that TDCIPP increased locomotion at doses near the higher dose tested here, but attenuated it at higher doses (Noyes et al, 2015). Variations between these results may partially be explained by differences in testing protocol (eg, beginning with a light phase as opposed to a dark phase) or differences in strain of zebrafish (5D in both Dishaw et al, 2014 and Noyes et al, 2015 compared to the AB* strain used here).…”

“…Zebrafish larvae exposed developmentally to doses of OPFRs such as TDCIPP and TPHP below those that cause overt physiological toxicities display abnormal locomotor behavior in light and dark environments (Dishaw et al, 2014; Noyes et al, 2015). One study found that, although developmental exposure to TDCIPP did not cause behavioral effects or alter monoamine levels in larval zebrafish, females exposed through to adulthood showed depressed levels of both dopamine and serotonin later in life (Wang et al, 2015).…”

Ecotoxicity of the insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO) and its reduced metabolite 3-amino-1,2,4-triazol-5-one (ATO)

“…Importantly, the critical processes of zebrafish neurodevelopment are homologous to those in humans [14]. Neuronal effects of developmental chemical exposure on embryo and larval photomotor activity can be easily measured in zebrafish, widening the potential field of bioactivity that can be detected [15, 16]. It was found that developmental mortality/morphology endpoints, combined with the larval photomotor response, serve as a robust biological sensor for chemical hazard potential.…”

Tris(pentafluoroethyl)trifluorophosphate-basd ionic liquids as advantageous solid-phase micro-extraction coatings for the extraction of organophosphate esters in environmental waters

“…Moreover, some halogenated OPEs, such as tris(2-chloroethyl)phosphate (TCEP), tris(chloroisopropyl)phosphate (TCPP) and tris(1,3-dichloro-2-propyl)phosphate (TDCP), are quite recalcitrant to naturally degradation or biodegradation [1,3], suggesting that they are likely to enter the aquatic environment and persistent in environment. In addition, extensive studies have showed that exposure to several OPEs pose a potential health risk for animals and humans [12][13][14].…”