Effects of 16.8–22.0 T High Static Magnetic Fields on the Development of Zebrafish in Early Fertilization

Despite some existing studies on the safety of high static magnetic fields (SMFs), the effects of ultra-high SMFs above 20.0 T for embryonic development in early pregnancy are absent. The objective of this study is to evaluate the influence of 16.8–22.0 T SMF on the development of zebrafish embryos, which will provide important information for the future application of ultra-high field magnetic resonance imaging (MRI). Two-hour exposure to homogenous (0 T/m) 22.0 T SMF, or 16.8 T SMFs with 123.25 T/m spatial gradient of opposite magnetic force directions was examined in the embryonic development of 200 zebrafish. Their body length, heart rate, spontaneous tail-wagging movement, hatching and survival rate, photomotor response, and visual motor response (VMR) were analyzed. Our results show that these ultra-high SMFs did not significantly affect the general development of zebrafish embryos, such as the body length or spontaneous tail-wagging movement. However, the hatching rate was reduced by the gradient SMFs (p < 0.05), but not the homogenous 22.0 T SMF. Moreover, although the zebrafish larva activities were differentially affected by these ultra-high SMFs (p < 0.05), the expression of several visual and neurodevelopmental genes (p < 0.05) was generally downregulated in the eyeball. Our findings suggest that exposure to ultra-high SMFs, especially the gradient SMFs, may have adverse effects on embryonic development, which should cause some attention to the future application of ultra-high field MRIs. As technology advances, it is conceivable that very strong magnetic fields may be adapted for use in medical imaging. Possible dangers associated with these higher Tesla fields need to be considered and evaluated prior to human use.