Indoor ozone reaction products: Contributors to the respiratory health effects associated with low-level outdoor ozone

Low-level outdoor ozone (O3) exposure has been associated with adverse respiratory health effects, whereas substantially higher O3 concentrations have been required to exert measurable effects in controlled studies. This discrepancy remains poorly understood. After entering indoors, a substantial portion of O3 reacts with indoor chemicals to generate ozone reaction products that are potentially more toxic than O3 itself. We hypothesize that ozone reaction product exposures contribute to the adverse respiratory effects associated with low-level outdoor O3 exposure. In a panel study of 70 healthy adults, each was measured four times during a low-ozone season (maximum 8-h average: 29 ± 13 ppb). We found that higher average outdoor O3 concentrations, irrespective of whether participants were outdoors or indoors, were significantly associated with worsened spirometric lung function (i.e., FVC, FEV1, FEF25-75) and airway mechanics (i.e., R5, R20) indicators. Per interquartile range (IQR) increase in average outdoor O3 exposure when participants were indoors with windows closed (exposure proxy for ozone reaction products + indoor O3) was significantly associated with worsening of multiple respiratory function indicators including FVC, FEV1, FEF25-75, Z5, R5, and R20 by 0.56–3.08%. In contrast, per IQR increase in average outdoor O3 exposure when participants were outdoors or indoors with windows open (exposure proxy for O3 without ozone reaction products) was only significantly and adversely associated with worsening of one respiratory function indicator X5 by 1.4%. These findings support our hypothesis and suggest further evaluation of indoor ozone reaction products' contribution to adverse health effects induced by outdoor O3 exposure.

Duke Scholars

Author Junfeng Zhang Environmental Sciences and Policy