Indoor Exposure to Ozone-Derived Carbonyls: Association with Indicators of Blood and Cardiovascular Physiology among Healthy Young Adults

Ozone is a globally important outdoor air pollutant. When transported indoors, where people spend most of their time, ozone is largely consumed through chemical reactions; yet the health effects of its major volatile products, carbonyls, remain unclear. In a panel study of 110 healthy Tibetan college students, we repeatedly measured week-long concentrations of seven selected carbonyls in participants’ dormitories and assessed biomarkers related to cardiovascular health. Carbonyl concentrations were generally higher indoors than outdoors, with the median indoor-to-outdoor ratio for decanal reaching 15. Further analyses suggest that the elevated indoor carbonyl concentrations likely result from ozone reactions, particularly with skin oil. Due to substantial ventilation variations across dormitories, indoor carbonyl concentrations showed no substantial correlations with outdoor ozone levels (r = −0.08∼0.20), enabling the evaluation of ozone-independent carbonyl health effects. Increased carbonyl exposure was significantly associated with the elevation of multiple red blood cell indices. Carbonyl associations with the red blood cell count, hemoglobin level, and hematocrit remained robust in ozone-adjusted models. These associations were further corroborated by additional analyses based on outdoor ozone levels and air-change rates. Increases in these red blood cell indices represent adverse cardiovascular effects in hypoxia-acclimated Tibetans and may contribute to the pathogenesis of chronic mountain sickness.