Beyond Particle Effects: Leachate-Induced Duckweed Toxicity from PBAT and PLA under Global Warming

Area of Science:

• Environmental toxicology
• Ecotoxicology
• Polymer science

Background:

• Microplastics (MPs) are a growing environmental concern, posing ecological risks.
• Understanding the toxicity of aged MPs, especially under warming conditions, is crucial.
• Distinguishing between particle and leachate toxicity is essential for accurate risk assessment.

Purpose of the Study:

• To mechanistically quantify the contributions of microplastic particles versus leachates to toxicity.
• To investigate polymer- and endpoint-specific effects in the duckweed *Spirodela polyrhiza*.
• To identify and prioritize high-risk chemical leachates from aged microplastics.

Main Methods:

• Exposure of *Spirodela polyrhiza* to aged microplastics (PVC, PS, PBAT, PLA) at varying concentrations (10-500 mg L^-1).
• Quantification of particle versus leachate toxicity contributions.
• Nontarget screening using HPLC-MS and the Toxicological Priority Index (ToxPi) framework to identify leachate components.

Main Results:

• Particle toxicity dominated for polyvinyl chloride (PVC) and polystyrene (PS).
• Leachate toxicity was primary for poly(butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA).
• High-risk leachates (e.g., docosanamide, pyrene, adipic acid) were identified in PLA and PBAT; elevated temperatures increased leaching but not proportionally toxicity.

Conclusions:

• Microplastic toxicity is polymer-specific, driven by either particles or leachates.
• Leachates from PLA and PBAT contain high-risk chemicals, necessitating further investigation.
• This study provides critical insights for mechanism-driven microplastic risk assessment under warming.