Exercise in Thermal Inversions: PM_2.5 Air Pollution Effects on Pulmonary Function and Aerobic Performance

Wintertime thermal inversions can lead to the accumulation of small particulate matter (PM_2.5). Despite an association between respiratory hospital admissions and elevated PM_2.5 levels, many people continue to exercise outdoors during inversions. This study compared pulmonary function and exercise performance during periods of low and high ambient PM_2.5 concentrations.

Forced vital capacity and forced expiratory volume in 1 s were measured outdoors before and after two 3200 m running time trials: one with low ambient PM_2.5 (0.6-14.7 microgram·m^-3), and the other during high PM_2.5 (19.1-42.5 micrograms·m^-3). A 10 cm visual analog scale (VAS) administered postexercise quantified subjective ratings of respiratory discomfort.

The PM_2.5 differential between trials was ≥18 micrograms·m^-3 for 10 healthy runners. Despite feeling more respiratory discomfort (P=0.044) during the bad air trial (VAS: 4.6±1.8 cm) compared with the good air trial (VAS: 2.9±1.8 cm), the 3200 m run time (low PM_2.5: 13:54±1:34 min:s; high PM_2.5: 14:07±1:44 min:s) was not different (P=0.261) between trials. Postexercise forced vital capacity was not significantly different (P=0.846) between the low (4.86±1.00 L) and high (4.84±0.95 L) PM_2.5 conditions. Similarly, the difference in postexercise forced expiratory volume in 1 s was not significant (P=0.750) between trials (4.22±0.89 L vs 4.23±0.85 L).

Neither run time nor pulmonary function of healthy adults were adversely affected by an acute bout of exercise in elevated ambient PM_2.5, equivalent to yellow or orange on the air quality index.