Coupled Bibliometric and Systematic Review on the Molecular Effects of Estrogenic Endocrine Disrupting Chemicals and Microplastics in Mollusks

Estrogenic endocrine disrupting chemicals (EEDCs) and microplastics (MPs) are ubiquitous pollutants in aquatic systems. This study performed a bibliometric analysis, coupled with a systematic review, of 72 articles that used omics approaches to evaluate the molecular effects of these pollutants on mollusks. Cluster and co-occurrence analyses mapped research themes, and relative frequency and temporal analysis of keywords were used to identify and recommend research directions. One theme of EEDC research, involving 11 articles, addressed a controversy about whether EEDC exposure induces vitellogenin and estrogen receptor mRNA expression. An additional theme for both pollutants was induction of oxidative stress, frequently evaluated through transcriptomics in mussels. Transcriptomics was the dominant omics approach, but metabolomics is emerging. The most frequently selected EEDCs were 17α ethynylestradiol (EE2, 28%), 17β estradiol (E2, 26%), and bisphenol A (BPA, 21%). From 2006 to 2024, the most common concentration of EE2 and E2 was 0.05 μg/L, representing the high end of their environmental range. Acute and chronic exposure durations were consistently selected over time for both pollutants. The most common physical types of MPs were virgin MPs (85%) and microbeads (69%), likely due to their uniformity and availability. Only 14% of EEDC studies and 41% of MPs studies evaluated co-exposures with other chemicals, microcystein, climatic factors or pathogens. To make future studies environmentally relevant, researchers should select low concentrations, chronic exposures, aged or biodegradable plastics, and co-exposures. Thus, this study provides a basis for future environmentally relevant experimental designs.