) using atmospheric humidity caused by plant leaf transpiration*

Removal of particulate matter (PM) reduction is one of the most significant challenges in public health and environment protection. To mitigate PM-related problems and effectively remove PM_2.5, tree planting and afforestation have been proposed as eco-friendly strategies. However, the PM removal effect of plants and its primary mechanism remains uncertain. In this study, we experimentally investigated the PM removal performance of five species in a closed chamber and the effects of relative humidity (RH) caused by plant evapotranspiration, as a governing parameter. Based on the PM removal tests, we selected Scindapsus as a representative plant among the tested plants to identify the PM removal efficiency depending on evapotranspiration and particle type. As a result, Scindapsus showed a high PM removal efficiency for smoke-type PM_2.5 under active transpiration. We examined the correlation between PM removal and relative humidity (RH) and evaluated the effect of increased RH on PM_2.5 removal by using a plant-inspired in vitro model. These results support that the increase of RH due to plant evapotranspiration is crucial for the reduction of PM_2.5.