Phthalate acid esters contribute to the cytotoxicity of mask leachate: Cell-based assay for toxicity assessment

After the COVID-19 outbreak, masks have become an essential part of people lives. Although several studies have been conducted to determine the release of hazardous substances from masks, how their co-presence poses a potential exposure risk to human health remains unexplored. In this study, we quantitatively compared the leaching of substances from six different common types of masks, including phthalate acid esters (PAEs), metals, and microplastics (MPs), and comprehensively evaluated the potential cytotoxicity of different leachates. MPs smaller than 3 µm were quantified by Py-GC-MS, and reusable masks showed greater releasing potentials up to 1504 µg/g. We also detected the prevalence of PAEs in masks, with the highest release reaching 42 μg/g, with dibutyl phthalate (DBP), diisobutyl phthalate (DiBP) and bis (2-ethylhexyl) phthalate (DEHP) being the predominant types. Moreover, the antimicrobial cloth masks released 173.0 µg of Cu or 4.5 µg of Ag, representing 2.7% and 0.04% of the original masks, respectively. Our cell-based assay results demonstrated for the first time that mask leachate induced nuclear condensation with DNA damage, and simultaneously triggered high levels of glutathione and reactive oxidative stress production, which exacerbated mitochondrial fragmentation, eventually leading to cell death. Combined with substance identification and correlation analysis, PAEs were found to be the contributors to cytotoxicity. Masks containing Cu or Ag led to acidification of lysosomes and alkalinization of cells. These results strongly suggested that the levels of PAEs in the production of regulatory masks should be strictly controlled.