Toxicity assessment of artificially added zinc, selenium, and strontium in water

The present research was to study the toxicology of artificially added Zn, Se and Sr in water. Specifically, we investigated the mortality and liver toxicity in zebrafish (Danio rerio), caused by different water concentrations of zinc sulfate (ZnSO4), sodium selenite (Na2SeO3), and strontium chloride hexahydrate (6H2O·SrCl2). Adult and embryo-larval zebrafish were used in the experiment. Analysis was performed of mortality, liver area and impermeability, delayed absorption area of the yolk sac, and liver tissue structure. The concentration change of sodium selenite exerted the most significant effect on the mortality of adult zebrafish, followed by that of strontium chloride hexahydrate, and zinc sulfate. Elevated strontium chloride hexahydrate concentration was associated with liver toxicity in zebrafish in the preliminary experiment. However, embryo-larval zebrafish were observed to die when the concentration of Zn2+ or Se4+ increased to a certain extent, without obvious liver toxicity. Our results indicated strontium chloride hexahydrate was hepatotoxic to embryo-larval zebrafish, which was manifested mainly as hepatomegaly and delayed absorption of the yolk sac. In addition, the artificially added strontium chloride hexahydrate destroyed liver tissue structure, resulting in hepatocyte enlargement, cell nucleus enlargement, blurred cytoplasmic boundaries, and formation of a vacuolar liver. These findings suggest the amount of strontium chloride hexahydrate added in soft drinks should be limited to certain levels.