Ageing affects microplastic toxicity over time: Effects of aged polycarbonate on germination, growth, and oxidative stress of Lepidium sativum.

Plastic has been an environmental pollutant far longer than claimed by the first reports surfacing in 1979, meaning some plastic materials have been decaying in nature for decades. Nevertheless, the threat posed to biota is not fully understood, especially from aged microplastic. The question considered in this study was whether the adverse effects of new plastic differ from those of old plastic material. Therefore, the morphological and physiological effects on Lepidium sativum with exposure to both new and aged polycarbonate were considered against a known stressor leaching from polycarbonate with time, bisphenol-A. Exposure to new and short-term aged polycarbonate (up to 80 days) elicited the most severe effects such as germination inhibition, reduced seedling growth, decreased chlorophyll concentrations, and increased catalase activity. These adverse effects in L. sativum associated with polycarbonate exposure were reduced as a function of the ageing time applied to the polycarbonate. The chemical substances that lend new polycarbonate material its toxicity were likely leached with time during the ageing process. Based on the results obtained, temperature and humidity based artificial ageing significantly reduced the phytotoxicity of the microplastic particles.