Determinants of personal exposure to fine particulate matter in the retired adults – Results of a panel study in two megacities, China

This study aimed to investigate the relationship between outdoor, indoor, and personal PM2.5 exposure in the retired adults and explore the effects of potential determinants in two Chinese megacities. A longitudinal panel study was conducted in Nanjing (NJ) and Beijing (BJ), China, and thirty-three retired non-smoking adults aged 43–86 years were recruited in each city. Repeated measurements of outdoor-indoor-personal PM2.5 concentrations were measured for five consecutive 24-h periods during both heating and non-heating seasons using real-time and gravimetric methods. Time-activity and household characteristics were recorded. Mixed-effects models were applied to analyze the determinants of personal PM2.5 exposure. In total, 558 complete sets of collocated 24-h outdoor-indoor-personal PM2.5 concentrations were collected. The median 24-h personal PM2.5 exposure concentrations ranged from 43 to 79 μg/m3 across cities and seasons, which were significantly greater than their corresponding indoor levels (ranging from 36 to 68 μg/m3, p