Global assessment of microplastics: Leveraging MP-TOX scale for predicting ecological risk in aquatic ecosystems

Microplastics (MPs) are omnipresent in nature. This investigation provides a comprehensive global meta-analysis of MPs with 3515 field datapoints from 62 countries (water: 2167; sediments: 738; biota: 610), along with 216 laboratory data points. MP concentrations standardized to particle-based units revealed freshwater systems as MP hotspots, with significantly higher median MP concentrations (5.40 × 10² MPs/m³) compared to marine waters (3.23 MPs/m³; p < 0.0001). The Atlantic Ocean exhibits the highest MP contamination at 3.99 × 10² MPs/m³. Fibrous particles are more prevalent in water, sediment, and biota with polyethylene (PE) and polypropylene (PP) as the dominant polymers. Biota analysis showed significant geographic variation, with Antarctica and Canada having the highest invertebrate contamination. Filter feeders showed elevated MP burdens compared to carnivores, implicating feeding ecology as a major driver of MP accumulation. Interestingly, significant correlation has been observed for biota PLI (pollution load index) and PHI (polymer hazard index) despite lower MP burden. A novel MP-Tox scale developed and validated with D. magna bioassays provide a standardized framework that link environmental MP occurrence with biological outcomes. The predicted no-effect concentration (6.70 × 10⁸ MPs/m³) exceeded maximum reported environmental concentration (1.54 × 10⁸ MPs/m³) by 0.77-fold, indicating existing environmental MPs are unlikely to cause acute toxicity in freshwater filter-feeders but induce significant decline in the zooplankton reproduction, a primary ecological concern. These findings bridge the fragmented, region-specific MPs risk assessment and provide evidence- based tools for global monitoring and management. Future studies warrant MP-Tox scale validation across additional taxa and assess combined toxicological assessment with chemical stressors.