Tris(2,4-di-tert-butylphenyl) Phosphate Is the Key Toxicant in Aged Polyvinyl Chloride Microplastics to Wheat (Triticum aestivum L.) Roots

Abstract

Polyvinyl chloride microplastics (PVC-MPs) pollution is drawing increasing attention, especially due to concerns about the environmental safety of the diverse additives that they contain. To date, few ecotoxicity data are available for PVC MP-derived chemicals. Here, wheat (Triticum aestivum L.) seedling roots were used to comparatively evaluate the toxicity of three commonly studied PVC MP-derived chemicals (2,4-dimethyl-6-s-hexadecylphenol─Irganox 1076 and tris (2,4-ditert-butylphenyl) phosphate─Irgafos 168-ox, and erucamide─Eru). These chemicals were evaluated individually and in combination. Exposure to these chemicals caused dose-dependent reductions in root dry weight (0.39%–19.29%) and root length (0.11%–8.15%). While Irganox 1076 and Eru had minimal impact on root activity and the antioxidant system, Irgafos 168-ox and its mixture induced significant elevations of antioxidant enzymes (SOD, CAT, and APX) activities and antioxidants (AsA and GSH) concentrations in the roots, enhancing the antioxidant level. Our findings indicate that the coexposure of PVC MP-derived chemicals exerts an additive effect on antioxidant response inhibition. Irgafos 168-ox showed stronger effects with the maximum toxic concentration of 10 mg L^–1, whether alone or in additive mixtures, due to its higher potential for root accumulation and oxidative stress induction. These results highlight the need for further research into ecological risks of PVC MP-derived chemicals, particularly under combined exposure scenarios.