Microplastics (MPs) and mesoplastics are able to sorb harmful substances and often contain additives, e.g.,
endocrine disrupting chemicals (EDCs), that can cause adverse effects to organisms. The present study aims to
determine EDC concentrations and their endocrine activities in leachates of field-collected marine MPs and
mesoplastics under stress conditions that are known to occur during the plastic life cycle. Estrogens were the
dominant EDCs on plastic particles and were either concentrated from the surrounding water or originated from
plastic manufacturing. Bisphenol A had the highest detection frequency (75%) with an average concentration of
475 ± 882 μg/kg, followed by bisphenol S, octylphenol and nonylphenol. Moreover, smaller marine MPs leached
greater quantities of EDCs because the sorption from surrounding seawater is more efficient for smaller
particles. It was found that normal life stresses such as microwaving (MW) and autoclaving (AC) can decrease
EDC concentrations, but solar irradiation (solar) can increase EDC concentrations in leachates. Even though
organisms with higher metabolic ability exhibited greater estrogenic effects, the comprehensive toxicity of
plastic leachates after common life treatments was still limited (below the EC10 value) if 0.1% is taken as the EDC
uptake from plastic. In future studies, the accurate contribution of plastic bound EDCs needs to be further
explored, and the monitoring of MPs and mesoplastics in the human diet remains important because the concentrations
of these plastics may change in the future.