Keywords: 
• Methylisothiazolinone /
• zebrafish embryos /
• acute toxicity /
• apoptosis staining

Abstract: Personal care products, daily necessities and coatings are widely used in daily life, and in most of them methylisothiazolinone (MIT) is used as a preservative. As a widespread pollutant in surface water, however, few toxicologic studies on MIT to aquatic organisms are reported. Acute toxicity test was conducted to study the effects of MIT on zebrafish embryos. 3 hours post-fertilization (3 hpf) zebrafish embryos were exposed to a gradient of concentration of MIT solutions. Meanwhile we used acridine orange (AO) staining to detect cell apoptosis in vivo and observed embryonic morphologic change after 24 h, 48 h, 72 h and 96 h exposure to MIT under a stereoscopic microscope. Results show that the embryo hatching rate and heart rate was significantly decreased under the concentration higher than 1.0 mg·L^-1 after 48 h and 1.52 mg·L^-1 after 72 h respectively. We found that 96 h half lethal concentration (96 h-LC₅₀) and 96 h half teratogenic concentration (96 h-TC₅₀) were 6.15 mg·L^-1 and 3.89 mg·L^-1 respectively. The 96 h minimum growth inhibitory concentration (MCIG) was found to be 2.31 mg·L^-1. In addition, the results of acridine orange (AO) staining showed that in the concentration of 1.0 and 2.0 mg·L^-1 cell apoptosis appeared mainly in brain and tail after 72 h. Microscopic observation also found that the malformation included caudal dysplasia syndrome, spinal curvature, yolk edema and pericardial edema, most of which were body axis curving. Moreover, in the concentrations greater than 1.52 mg·L^-1 independent twitch in 24 h embryos treatment groups increased significantly compared to control group. Furthermore, the embryos locomotion decreased, and touch response became sluggish when exposed to MIT up to 72 h and 96 h. It is concluded that MIT has both developmental toxicity and neurotoxicity on zebrafish embryos.