Background
As emerging environmental contaminants with ecological risks, flame retardants (FRs) exhibit obvious toxicity and persistence. In recent years, as FRs have been widely detected in indoor environments and human samples, the human health risks after FRs exposure are of great concern.
Objective
To systematically understand the topic evolution, research status, progress, and development trends on the toxicity and health effects of FRs on humans worldwide.
Methods
We retrieved the literature regarding toxicity of FRs and their effects on human health through the Web of Science database from 2000 to 2020, screened and processed the literature using Endnote software, and analyzed annual publications, important citations, and authors. CiteSpace and VOSviewer were employed to draw co-citation network, keyword co-occurrence network, and keyword clustering map for bibliometric visualization analysis.
Results
From 2000 to 2020, 472 international papers on toxic effects and human health impacts of FRs were published. In terms of publication years, FRs-related research was mainly divided into three stages: the infancy and exploration stage (2001—2006), when the research on the toxic effects of FRs was just starting; the growth stage (2007—2015), when the risk assessments of FRs on human health were conducted; and the acceleration stage (2016—), when the studies have shifted to the mechanism of FRs damage to human health. In this field, China published the largest number of published articles in the world (177 papers), but the intermediary centrality (reflecting academic influence) was only 0.19, far lower than that of European and American countries such as the Netherlands (0.78), Britain (0.51), and Germany (0.44). Among the top 10 research institutions in terms of the number of articles published, the Chinese Academy of Sciences topped the list with 49 articles. Van der Veen and other researchers had a strong influence on the research of the toxic effects of phosphorous FRs since their papers published in 2012 were cited 1319 times and in the most prominent node in the literature co-citation network. The high-frequency keywords in the literature on the human health effects of FRs were polybrominated diphenyl ethers (217 times), brominated FRs (166 times), toxicity (147 times), FRs (102 times), exposure, polychlorinated biphenyls, in vitro experiment, plasticizer, etc. Through keyword clustering and co-occurrence analyses, it was found that current research is systematically exploring the toxic mechanism of FRs from a perspective integrating pollution source-exposure route-final receptor of pollutants, and is evaluating the environmental health risks via different exposure routes. The visualized bibliometric analysis findings suggested that future studies understand the underlying mechanisms of various cell damage caused by FRs toxicity, identify the key factors of change and their relationships, aiming to provide a scientific basis for targeted prevention of health effects of FRs.
Conclusion
The research hotspots on the toxic effects of FRs and their effects on human health have changed over time, and the breadth and depth have been increasing. The toxic effects of brominated/phosphorus FRs have always been the mainstream direction in this field. Further studies will focus on the molecular mechanisms of human toxicity after FRs exposure.
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