Combined effects of P25 TiO2 nanoparticles and disposable face mask leachate on microalgae Scenedesmus obliquus: Analysing the effects of heavy metals

Disposable surgical masks have been extensively employed as protective medical equipment due to the widespread breakout and transmission of the COVID-19 virus across the globe. These masks were made up of plastic polymer materials that would emit microplastics after entering the environment. Therefore, their careless disposal might lead to new and bigger microplastic contamination. The impacts of plastics that seep into waterways and their subsequent interactions with aquatic life are yet largely unexplored. In this study, we determined the quantity and kind of microplastics that were discharged from disposable surgical face masks. Furthermore, we also quantified heavy metals leached from the face masks (HML). In contrast, the increasing usage of nTiO2 in consumer items has led to its ubiquitous presence in freshwater systems. Four different concentrations of nTiO2, 0.5, 1, 2, and 4 mg L-1 were mixed with face mask leachates (FML) to perform the mixture toxicity test on freshwater algae, Scenedesmus obliquus. Reduced cell viability and photosynthetic activity were noticed in the treatment groups containing nTiO2 and FML. This was accompanied by increased oxidative stress and antioxidant activities. Furthermore, the heavy metals leached from the face masks were also tested for toxicity. In addition to that, changes in the cellular morphology were also studied with the help of FE-SEM and FTIR analysis. Our study reveals that leachates from disposable surgical face masks along with nTiO2 possess a serious threat to the environment. Environmental significanceDuring COVID-19, surgical face masks were widely used and discarded. These discarded face masks end up in lakes, rivers, and ponds. The facemasks were composed of polypropylene and other polymers. These masks release microplastics and heavy metals when discarded into water bodies. The current research focuses on assessing the environmental toxicity of the microplastics and heavy metals leached from the masks using algae as a model system. Our work further demonstrates the combined toxic effects of nTiO2 in the presence of the face mask leachate. Algae plays a crucial role as the primary producer in the freshwater ecosystem. These emerging contaminants may act as environmental stressors to the microalgae, and this may impair the ecosystems structure and function.