Organophosphorus flame retardants induce malformations in avian embryos

Tris(2-chloroisopropyl) phosphate (TCIPP) is one of the organophosphorus flame retardants that has been detected in the environment, and in the eggs, feathers, and liver of birds. Early developmental avian embryos are known to be sensitive to chemical exposure, but  knowledge regarding the effects of TCIPP on avian embryonic development is limited. In this study, a shell-less embryo incubation system was used to investigate the toxicity of TCIPP in early chicken (Gallus gallus domesticus) embryos.

Fertilized chick embryos were exposed to 50 nmol TCIPP/g, 500 nmol TCIPP/g, or vehicle control, dimethyl sulfoxide (DMSO) on day 0 of incubation. Embryos were observed on days 3-9 of incubation, and expression levels of several genes were measured in embryos on day 4.

Survival was significantly reduced in both groups exposed to TCIPP. Imaging analysis showed that body length, head and bill length, eye diameter, and forelimb and hindlimb length were significantly reduced in both groups exposed to TCIPP. In addition, TCIPP exposure significantly inhibited extraembryonic vascular length and red blood cell production. The heart rate decreased in a dose-dependent manner, particularly on days 4-7, and the somitic angle was significantly increased on days 4-6 in the TCIPP-exposed group, inducing asymmetrical somite formation. The significant correlation between somitic angle and FGF8 expression suggested that TCIPP exposure affects somite formation through an altered FGF signaling pathway.

These results indicate that TCIPP exposure exerts toxic effects on development, including vascularization, cardiac function, and somite formation in avian embryos.