Sex-based differences in toxicity after exposure to microplastics or nanoplastics in aquatic and terrestrial organisms: A systematic review

Microplastics (MPs) and nanoplastics (NPs) have attracted increasing attention due to their widespread presence in the environment and their detrimental effects on organisms. MPs are defined as particles smaller than 5 mm, while NPs are smaller than 1000 nm. These pollutants primarily result from the degradation of plastic waste, industrial processes, and everyday consumer products. This review systematically investigated sex-based differences in toxicity following exposure to MPs and/or NPs in aquatic and terrestrial organisms. Three databases (PubMed, Web of Science, and Scopus) were searched up to September 10, 2024, to identify studies following PRISMA guidelines. A total of 26 original articles published between 2020 and 2024 were included in the review. Among these, 19 studies focused on MPs, five on NPs, and two on MNPs (MPs and NPs) separately. Polystyrene (PS) and polyethylene (PE) were the most commonly investigated types. Fish and mice were the most frequently used animal models in exposure studies. The results revealed sex-specific divergences across physiological systems. Males exhibited higher mortality, elevated oxidative stress, and greater susceptibility to immune suppression, whereas females showed increased particle accumulation and a more pronounced decrease in body weight. These effects varied between species, reflecting species-specific differences in response to MNPs. Toxicological outcomes were additionally influenced by particle properties, exposure duration, and concentration. Collectively, these findings underscore the importance of integrating sex as a biological variable and species identity in toxicological assessments, and highlight the need for further research to elucidate the mechanisms underlying differential susceptibility to MNPs.