Concentrations of particulate matter (PM) and contributions of tire wear particle to PM in an indoor parking garage: Comparison with the outside and the differences according to the sampling sites.

Particulate matter (PM) is increasingly affecting the social-economic development of countries. An increase in PM concentration increases susceptibility to cardiovascular and respiratory diseases and cancer. Tire wear particles (TWP) contribute to airborne PM. In the present work, we investigated the variation in the concentration of TWP of <2.5 μm in aerodynamic diameter (TWP) in an indoor parking garage depending on the sampling sites. PM samples were collected at four sites in an indoor parking garage of a college campus: the entrance of the parking garage (Ent), the second floor toward the third floor (2F), the front of the parking zone on the second floor (2FP), and the third floor toward the fourth floor (3F). Each PM sampling was performed for 4 days during the fall season. The PM concentrations at the 2F and 2FP were similar to the outside PM concentrations, whereas those at the Ent and 3F were higher than the outside PM concentrations. The TWP concentrations in the indoor parking garage were 0.61-0.73 μg/m. The differences in the TWP concentrations depending on the sampling sites were due to the differences in traffic volumes. The TWP concentration at the 2FP was higher than those at the other sampling sites owing to air stagnation and TWPs produced by the high friction when parking and exiting a car in the parking zone. The contributions of TWP to the PM concentrations were 3.9-11.7%, in the order of 2FP ≫ Ent > 3F > 2F. A good air ventilation system can be recommended to reduce TWP concentrations in indoor parking garages.