Evaluation of interactive effects of UV light and nano encapsulation on the toxicity of azoxystrobin on zebrafish

The use of nanotechnology to enhance pesticide formulations holds the promise of reduced pesticide use, reduced mobility in soils, and overall improvements in agricultural practices while simultaneously maintaining yields. However, the toxicity of nano-enabled pesticides, including azoxystrobin (Az), has not been well studied compared with their conventional form. This study investigates both lethal and sub-lethal endpoints in zebrafish embryos up to 120 h post-fertilization (hpf) under either laboratory light or simulated UV light. The median lethal concentration (LC50) value of nano-enabled Az (nAz) was significantly lower than the conventional form (Az). Interestingly, artificial UV light significantly increased toxicity (decreased LC50) of both Az and nAz. Malformations were not observed but the remaining yolk sac volume was significantly increased in both types of Az at both light conditions. This decreased yolk consumption is in agreement with reduced oxygen consumption and heart rate. Catalase enzyme activity was only reduced to UV light while superoxide dismutase activity was significantly reduced by co-exposure of UV light, and either type of Az at a nominal concentration of 100 μg L^-1. The co-exposure of Az at 100 μg L^-1 and UV light significantly upregulated sod1, sod2, and gpx1b expression and both types of Az significantly reduced gpx1a expression. Lipid peroxidation was significantly increased in nAz and Az at 100 μg L^-1 under laboratory light, while UV light induced even higher level of lipid peroxidation. The results will provide important information on the toxicity of nAz under ecologically realistic conditions.