Microplastics (MPs) are ubiquitous in the environment, including the atmosphere. Yet, the size detection limit in measuring airborne MPs undermines the determination of the human MP exposure level through inhalation and also restricts the understanding of airborne MPs pollution behavior. To comprehensively and accurately assess the MPs pollution features in air, we demonstrate a qualitative and quantitively method using Raman microscopy to characterize the suspended atmospheric MPs. Our methodology has achieved detailed characterization of MPs down to 1 μm and ensured all the MPs to be counted regardless of their transparency. Further, a case study of indoor and outdoor samples from eight sampling sites were conducted in Shanghai, China. Inhalable MPs prevails in all samples with higher concentrations occur indoors. Indoor MPs varied strongly in composition compare to outdoor. Ventilation played an important role in lowering indoor MPs concentrations, and MPs in better ventilated indoors displayed similar distribution patterns as outdoors. MPs detected were mainly Polyethylene, Polyester, Phenolic Resin and Polyvinyl chloride. 77% of the Polyethylene detected were transparent films, suggesting the fragmentation from PE film products, such as plastic bags and cling films. Our work confirmed the widespread existences of inhalable MPs in air and provides solid foundations for future studies to understand the realistic MPs exposure conditions through inhalation.

Microplastic particles (MP) are prevalent in both industrial production and the natural environment, posing a significant concern for human health. Daily diet, air inhalation, and skin contact are major routines of MP intake in human. The main injury target systems of MPs include the digestive system, respiratory system, and cardiovascular system. However, the study on MPs' adverse effects on the heart is less than other target organs. Previous in vivo studies have demonstrated that MPs can induce heart injuries, including abnormal heart rate, apoptosis of cardiomyocytes, mitochondrial membrane potential change, and fibrin overexpression. To address animal welfare concerns and overcome inter-species variations, this study employed a human pluripotent stem cell-derived in vitro three-dimensional cardiac organoid (CO) model to investigate the adverse effects of MPs on the human heart. The distinct cavities of COs allowed for the observation of MPs' aggregation and spatial distribution following polystyrene-MP (PS) exposure in a dynamic exposure system. After exposure to various concentrations of PS (0.025, 0.25 and 2.5 µg/mL, with the lowest concentration equivalent to human internal exposure levels), the COs exhibited increased oxidative stress, inflammatory response, apoptosis, and collagen accumulation. These findings were consistent with in vivo observations, in terms of increases in the interventricular septal thickness. The expression of hypertrophic-related genes of COs (MYH7B/ANP/BNP/COL1A1) changed noticeably and the cardiac-specific markers MYL2/MYL4/CX43 were also markedly elevated. Our findings revealed the PS could induced cardiac hypertrophy in vivo and in vitro, indicating that MP may be an under-recognized risk factor for cardiovascular system.