Soil-dwelling species-based biomarker as a sensitivity-risk measure of terrestrial ecosystems response to microplastics: A dose-response modeling approach.

Microplastics (MPs) dispersed throughout terrestrial ecosystems is a growing global concern, yet their potential risks on terrestrial ecosystems are poorly understood from a mechanistic viewpoint. A novel empirical approach to assess relative sensitivity-risk of terrestrial ecosystems to MPs-posed potential impacts was presented. The risk metrics based on soil-dwelling organism responses-derived biomarkers that could identify whether study regions have sensitivity-risk to MPs were developed. The recently published datasets covering geographic areas worldwide with toxicity endpoints from major soil organism groups (snail, potworm, springtail, nematode, and earthworm) were used to build relationships between species physiological alterations and MPs based on a toxicodynamic-based dose-response model. The regional pollution and species sensitivity distributions combined with a probabilistic risk model were used to compare relative ranks with MPs-associated risks using predicted thresholds. The results found that ecologically sensitive regions with severe responses to soil MPs appeared in areas polluted by sewage sludge and plastic mulching. The results also showed that ~25% of study regions suffered significant MPs-associated ecological risks. This work provides a baseline measurement tool of soil species biomarker-based thresholds for comparing regional sensitivity-risk that highlights why some regions appear to be more sensitive than others and what potential risk impact this has on MPs-polluted terrestrial ecosystems globally.