Synergistic Effects of Ozone Reaction Products and Fine Particulate Matter on Respiratory Pathophysiology in Children with Asthma

Abstract

After being transported from outdoor to indoor environments, a large portion of ozone (O₃) reacts with indoor chemicals to generate O₃ reaction products. A fraction of these products can partition to fine particulate matter (PM_2.5). Hence, we hypothesize that PM_2.5 serves as a carrier to deliver O₃ reaction products to the deep lung, leading to synergistic adverse pulmonary effects. In a panel study involving 43 children with asthma, each was assessed 4 times (2-week interval) for biomarkers of respiratory pathophysiology and personal exposures to PM_2.5 and O₃. We also assessed O₃ loss exposures, calculated by taking the difference between the outdoor and indoor O₃ concentrations, which was proportional to the net exposure to O₃ reaction products. We found the adverse effects of O₃ loss exposure on biomarkers of pulmonary inflammation, airway (especially lower airway) mechanics, and spirometry lung function were greater at higher PM_2.5 exposure levels. We also found that the adverse effects of PM_2.5 exposure were greater at higher O₃ loss exposure levels. This suggests an additional mechanism for the synergistic pulmonary effects: PM_2.5 predisposes the lung to be more susceptible to O₃ reaction products and vice versa. However, our data is limited in differentiating the two potential mechanisms.

Little is known regarding the health impacts of O₃ reaction products. This study presents mechanistic explanations for the synergistic effects of O₃ reaction products and PM_2.5 on respiratory pathophysiology.