Toxic effects of nano-TiO2 in bivalves—A synthesis of meta-analysis and bibliometric analysis

Since the beginning of the 21st century, the increasing production and application of nano-TiO2 in consumer products have inevitably led to its release into aquatic systems and therefore caused the exposure of aquatic organisms, resulting in growing environmental concerns. However, the safety of nano-TiO2 in aquatic environments has not been systematically assessed, especially in coastal and estuary waters where a large number of filter-feeding animals live. Bivalves are considered around the world to be a unique target group for nanoparticle toxicity, and numerous studies have been conducted to test the toxic effects of nano-TiO2 on bivalves. The aim of this review was to systematically summarize and analyze published data concerning the toxicological effects of nano-TiO2 in bivalves. In particular, the toxicity of nano-TiO2 to the antioxidant system and cell physiology was subjected to meta-analysis to reveal the mechanism of the toxicological effects of nano-TiO2 and the factors affecting its toxicological effects. To reveal the cooperation, hot keywords and co-citations in this field, bibliometric analysis was conducted, and the results showed that the toxicological molecular mechanisms of nano-TiO2 and the combined effects of nano-TiO2 and other environmental factors are two major hot spots. Finally, some perspectives and insights were provided in this review for future research on nano-TiO2 toxicology in bivalves.