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Microplastic co-exposure increases PFAS bioaccumulation without universally amplifying toxicity in aquatic organisms: A multi-endpoint meta-analysis
Summary
Scientists found that microplastics and "forever chemicals" (PFAS) often build up together in water animals, with microplastics helping PFAS accumulate more in their bodies. But this didn't always mean worse health effects: some issues like nerve damage and digestion problems got worse, while others like reproduction and hormone effects didn't change, showing that risk depends on the specific chemical and situation, not one blanket rule.
Aquatic ecosystems are important sinks for microplastics (MPs) and per- and polyfluoroalkyl substances (PFASs), while their combined toxic effects on aquatic organisms vary across biological endpoints. This quantitative meta-analysis was performed based on 810 datasets from 29 laboratory studies, to explore MPs-mediated changes in PFASs toxicity and identify key influencing factors. MPs-PFASs co-exposure significantly increased PFASs bioaccumulation, indicating enhanced particle-mediated transport, co-ingestion, or altered internal retention. However, this increase of bioaccumulation did not translate into a universal enhancement of toxicity across endpoints. MPs exacerbated PFAS-associated toxicity in photosynthesis, neurotoxicity, and alimentary and excretory endpoints, whereas no significant effects were observed for oxidative damage, pathway-specific gene expression, reproductive toxicity, growth and development, endocrine disruption, immune-inflammatory responses, hepatotoxicity and metabolic responses. Subgroup and interaction analyses suggested that the effects of MPs-PFASs co-exposure were governed by endpoint identity and exposure context. Categorical MPs size classes did not show a significant effect, but partial correlation analysis indicated weak significant negative association between particle size and effect size. GeoDetector analysis indicated that factor interactions explained more variation in toxic responses than individual factors. PFASs type, MPs size, and exposure time were the dominant drivers of PFASs bioaccumulation, neurotoxicity, and photosynthetic toxicity, respectively. Notably, MPs co-exposure may produce stronger toxicity enhancements for emerging PFAS alternatives than for legacy PFASs. Overall, MPs reshape PFASs toxicological profiles in aquatic organisms in an endpoint- and context-dependent manner. These findings provide quantitative evidence for mechanism-based, multi-endpoint ecological risk assessment of MPs-PFASs co-contamination under environmentally relevant conditions.