Titanium dioxide nanoparticles (nano‐TiO2) are widely used in consumer products, raising environmental and health concerns. An overview of the toxic effects of nano‐TiO2 on human and environmental health is provided. A meta‐analysis is conducted to analyze the toxicity of nano‐TiO2 to the liver, circulatory system, and DNA in humans. To assess the environmental impacts of nano‐TiO2, aquatic environments that receive high nano‐TiO2 inputs are focused on, and the toxicity of nano‐TiO2 to aquatic organisms is discussed with regard to the present and predicted environmental concentrations. Genotoxicity, damage to membranes, inflammation and oxidative stress emerge as the main mechanisms of nano‐TiO2 toxicity. Furthermore, nano‐TiO2 can bind with free radicals and signal molecules, and interfere with the biochemical reactions on plasmalemma. At the higher organizational level, nano‐TiO2 toxicity is manifested as the negative effects on fitness‐related organismal traits including feeding, reproduction and immunity in aquatic organisms. Bibliometric analysis reveals two major research hot spots including the molecular mechanisms of toxicity of nano‐TiO2 and the combined effects of nano‐TiO2 and other environmental factors such as light and pH. The possible measures to reduce the harmful effects of nano‐TiO2 on humans and non‐target organisms has emerged as an underexplored topic requiring further investigation.

This review provides the updated information and analysis of research development on horseshoe crabs over the past 30 years and raises some suggestions for future studies on horseshoe crabs. Horseshoe crab is a unique marine species and attracts many scholars in various research fields. However, to date, the development of horseshoe crab research has not been analyzed and reported from a bibliometric perspective. Bibliometric analysis is a unique tool for evaluating the development of a specific research area by analyzing relevant publications and researchers from all over the world. In this study, Web of Science, Google Scholar, and PubMed were used to collect relevant data on horseshoe crabs. VOSviewer software was used to visualize cooperation and major keywords in horseshoe crab research. From 1989 to 2019, scholars emphasized the physiological characteristics, medical value, and ecological conservation of horseshoe crabs. Some topics in this field have gradually developed because of some reasons explained in this review. Some important or recent studies have been discussed, and some potential research topics for future research have been suggested.

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