Comparative bibliometric trends of microplastics and perfluoroalkyl and polyfluoroalkyl substances: how these hot environmental remediation research topics developed over time.

Microplastics (MPs) and per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment due to consumer and industrial use. These compounds are very persistent in the environment and human body, which has made them hot environmental topics in recent years; but how this did come about? What factors have been driving the trends of their publication records, the public concern over environmental and public health issues caused by these pollutants, and the collaboration between scientists, regulators, and policymakers to solve these problems? In this paper, to understand these factors and contrast them between the two hot topics ("PFAS" and "MPs"), the changes in the bibliometric and scientometric trends of their publication records (extracted from the Web of Science from 1990 to 2020) have been visualized over time based on different classification perspectives, such as year, country, source, and organization. According to the analyses performed on these records, utilizing publication ratios and principal component and cluster analyses, in recent years (beginning in 2018) research topics related to MPs have surpassed PFAS topics. In addition, the economic, social, and geographical conditions of the top 20 countries with the highest number of publications in MPs and PFAS were explored to identify which countries are most concerned about each of these topics and why. For instance, PFAS research topics were more prevalant in countries with larger water areas compared to land area; while MPs topic were more prevelant in countries that produced more plastic wastes, and had higher landfilling and recycling rates and greater proportion of treated wastewater.