Beyond concentration: Particle traits shape the toxicity of microplastics in fish - A global meta-analysis

Microplastics (MPs) are widespread contaminants, but their biological effects on fish remain inconsistent across studies. Through a systematic review and meta-analysis of 114 experiments (2015-2025), we show that MPs impair key biological functions, with effects strongly shaped by particle properties. Fertility was little affected, but hatching success declined significantly, particularly under exposure to blue particles. Growth and mobility were severely compromised, reflecting metabolic disruption, while feeding behavior showed little change. Mortality risk increased across species, with more pronounced effects associated with the fibrous MPs of PE and PP polymers. This study provides the first quantitative synthesis demonstrating that physicochemical traits of MPs-color, shape, and polymer type-are critical determinants of toxicity, beyond exposure duration or concentration. These findings highlight serious ecological risks and potential One Health implications, reinforcing the urgency for standardized protocols, environmentally realistic experiments, and stronger mitigation policies.