In ovo exposure to organophosphorous flame retardants: survival, development, neurochemical, and behavioral changes in white leghorn chickens

Abstract

Organophosphorous flame retardants (OPFRs) are contaminants of emerging concern. There is growing evidence of environmental contamination and exposures to both humans and wildlife. Here, the objective was to increase understanding of the potential neurodevelopmental effects of two relevant OPFRs, TMPP (tri (methylphenyl) phosphate; a non-halogen-containing OPFR) and TDCIPP (tris (1,3-dichloro-isopropyl) phosphate; a halogen-containing OPFR) in an avian embryo/chick model. We injected white leghorn chicken eggs with a range of TMPP (0, 10, 100, and 1000ng/g) or TDCIPP (0, 10, 100, 1000, 50,000ng/g) concentrations at incubation day 0 exposing embryos throughout the ~21-day in ovo period. Hatching success was unaffected by TMPP, but TDCIPP-exposed chicks had higher early-incubation mortality in 100 and 50,000ng/g groups. On 7–9-day-old chicks, we assessed behavior via tests concerning righting reflex, angled balance beams, gait patterns, wing flap reflex, and open field movements. Chicks exposed to 100ng/g TDCIPP achieved 40% lower maximum velocity in the open field test than vehicle-exposed controls, while those exposed to 1000ng/g TDCIPP achieved 20% higher maximum velocity than vehicle-exposed controls. Chicks exposed to 50,000ng/g TDCIPP showed reduced righting response success. There were no dose- or treatment-related differences in angled beam, gait analysis, or wing flap reflex tests. Cerebrum hemispheres from 10-day-old chicks were examined for neurochemistry (acetylcholinesterase [AChE] activity and both nicotinic [nACh] and muscarinic [mACh] acetylcholine receptor levels) and cerebellums were examined for histopathology. TDCIPP-exposed chicks had reduced number of degenerate Purkinje cells (TDCIPP, 1000ng/g), possibly indicating disruption of neurodevelopment. No neurochemical effects were found in TMPP- or TDCIPP-exposed chicks. In general this study shows some possible neurodevelopmental effects in chicks exposed to TDCIPP when levels greatly exceeded those measured in wild bird eggs and no clear changes in TMPP-exposed chicks. This study builds upon previous in vitro studies as well as work on adult birds showing that toxic responses in avian models can vary among species and OPFRs.