Microplastics

Micro- and nanoplastics are human made environmental contaminants that pose a growing concern for our health, particularly through airborne exposures. Although human autopsy studies confirm that micro- and nanoplastics are retained in lung tissue, our understanding of their short- and long-term effects on the pulmonary system is limited. We reviewed the existing literature to evaluate the effects of micro- and nanoplastics on the respiratory system and how their downstream effects may induce respiratory disease. In vivo and in vitro studies demonstrate that micro- and nanoplastics appear to have the capacity to disrupt pulmonary homeostasis through oxidative stress, immune activation, epithelial remodeling, and surfactant interference. Unfortunately, most available micro- and nanoplastics exposure studies are conducted using environmentally irrelevant plastics at high doses, which limits the accuracy and validity of conclusions regarding biological mechanisms that may contribute to chronic lung disease. To close this gap, future studies must adopt standardized, human-relevant models and realistic exposure scenarios. This includes using advanced in vitro and ex vivo platforms, and environmentally representative micro- and nanoplastics (rather than polystyrene spheres) to improve clinical relevance and support effective prevention and risk mitigation strategies.

Children are vulnerable to exposure to airborne microplastics (MPs) because of their developing lungs and prolonged time spent indoors. Therefore, this study employed a computational fluid–particle dynamics framework to simulate the posture-dependent transport and deposition of MPs in a realistic airway model of a 2-year-old child extending to the 8th bronchial generation. A steady inhalation breathing flow rate of 5 L/min was used for both postures. Subsequently, a discrete-phase model was used to predict the transportation and deposition of MPs, which employed an appropriate drag coefficient model. MP configurations were selected from the field survey, identifying the diameters of 4.785, 9.797, and 15.731 µm with aspect ratios of 3, 5, and 10. The results showed that posture significantly altered the deposition patterns of small- and low-aspect-ratio MPs. Specifically, the total deposition fraction was higher in the upright position than in the supine position. Local deposition analyses revealed that hotspots of deposited MPs varied across the airways under the effects of posture, especially in the upper respiratory tract. These findings provide mechanistic insights into how posture shapes regional fiber deposition in children and highlight the need to consider body orientation in pediatric inhalation exposure assessments.

The settling and rising of spherical microplastic particles with different Reynolds numbers, $Re$, were studied using a fully coupled large eddy simulation–discrete element method (LES-DEM) model, where the particles were treated using the immersed boundary method. Twelve different simulations were performed to find the drag coefficient $C_D$, particle trajectories, and wake patterns of both settling and rising microplastic particles. Results were compared to experimental findings from the literature and the comparisons show that the present LES-DEM model produces accurate values for $C_D$ when $Re\lesssim 310$ and qualitatively captures both wake patterns and particle trajectories for .