Study on the toxic effect of seawater-aged microplastics on Philippine curtain clams.

This study delved into the impact of aging on the properties of five common microplastic types, including polymethylmethacrylate (PMMA), polystyrene (PS), polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP). The aging process significantly altered the particle size distribution: PS, PP, and PMMA underwent a contraction, with average sizes decreasing by 6.8%, 3.2%, and 1.7%, respectively, whereas PE and PVC experienced an expansion, with increases of 3.1% and 1.7%. Notably, aging generally increased the specific surface area of all microplastics by more than 20%, a change that could influence their environmental interactions. Scanning electron microscopy revealed marked surface cracks and depressions in aged PE and PVC, in contrast to minor surface alterations in PS and PMMA. Fourier transform infrared spectroscopy further indicated modifications in the characteristic peaks of aged PMMA, PP, and PE microplastics. Exposure experiments demonstrates that increasing microplastic concentrations from 100 mg/L to 5000 mg/L accelerated mortality rates in clams, with juveniles exhibiting slower mortality onset compared to adults. Prolonged exposure led to rising mortality rates across all groups, suggesting a cumulative toxic effect from long-term microplastic exposure. These findings underscore the environmental ecological risks associated with the altered physicochemical properties of aged microplastics, particularly for the Philippine clam. This study provides an essential insight for advancing our understanding of microplastic behavior and their ecological impacts, highlighting the need for further research to mitigate these environmental threats.