Influence of Air Conditioning on the Vertical Deposition and Inhalation Risk of Indoor Microplastics
Keywords:
Air conditioning, Indoor, Inhalation risk, Microplastics, Passive samplingAbstract
Indoor environments are important pathways of
microplastic (MP) exposure because people spend long
periods indoors and are surrounded by synthetic textiles and
plastic-based furnishings. This study examined how airconditioning (AC)-induced air recirculation affects the
vertical deposition and inhalation risk of MPs in a closed,
furnished bedroom. Passive samplers were placed at floor
level (0.2 m) and breathing height (1.2 m) under stagnant air
(SA), low-temperature AC (LTA), and high-temperature AC
(HTA) conditions. Results showed that AC transformed the
indoor atmosphere from a settling-dominant to a
recirculating-suspension state. Under SA, larger MPs (>500
µm) settled mainly to the floor, whereas AC increased MP
deposition at breathing height and redistributed particles
into the inhalation zone. Smaller fractions (<100 µm) and
more diverse polymers, including polypropylene,
polystyrene, and polyvinyl acetate, were also detected under
AC operation. Overall, AC may improve comfort while
unintentionally increasing indoor inhalation exposure to
MPs.
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