A threat or not? A global-scale investigation on microplastics inhalation during the first-ever worldwide face-mask wearing against the COVID-19 pandemic

A spike in public attention on whether wearing masks will increase microplastics (MPs) inhalation has recently been triggered by the major transformation in widespread masking in public ever since the pandemic. To timely address this question and provide reliable insights for public health recommendations, mask users, and producers, we developed a platform based on a custom inhalation simulator, and conducted comparative measurements to investigate masks as both a source of MP release and a barrier to MP inhalation. We examined 209 mask brands from 46 countries/regions, covering multiple filtration and quality levels. Our kinetic study revealed that MP leaching primarily occurs during the initial period of wearing a new mask. Subsequently, masks act as a barrier, reducing MP inhalation compared to not wearing a mask. Hence, frequently changing masks or using masks from unproper manufacture process may not be a wise choice. We also observed significant variations in MP inhalation character among different quality levels and brands, indicating the need of future safety standards to this end. Overall, the estimated worldwide inhalation of MPs during the pandemic office hours is 1.16 times that of the pre-pandemic era. However, the impact of MP inhalation could be changed by wearing masks with higher filtration grade (and better quality). For instance, if everyone were to wear FFP-3 masks, a 28.8% reduction in MP inhalation would be expected compared to not wearing a mask.