Abstract:
Background The global disease burden studies show that particulate matters seriously affect the elderly population. Therefore, it is critical to identify risk factors and propose protective measures accordingly based on accurate exposure risk assessment.
Objective This study assesses the individual exposure levels of fine particulate matters (PM2.5) in the elderly in Shanghai, and explore the potential influencing factors by comparing with concurrent ambient PM2.5.
Methods We implemented a panel study with four repeated follow-ups in four seasons (once in a season with three months of interval) in 2017-2018, respectively. A total of 83 elderly volunteers were recruited in the Gumei Community Health Center Affiliated to Fudan University in Minhang District, Shanghai. In each follow-up, seven consecutive days of measurements on individual PM2.5 exposure, individual ambient temperature, and relative humidity were collected. Information on time activity patterns and household environment was also collected by questionnaire. Outdoor PM2.5 levels were retrieved from the closest fixed-site monitoring station (less than 3 km).
Results The daily average concentration of individual PM2.5 was 38.0 μg·m-3 in the study year, higher than that of ambient PM2.5 (35.7 μg·m-3, P < 0.05) by the fixed-site monitoring station in Shanghai during the same time period. The individual PM2.5 levels were higher than those in ambient air in spring, summer, and autumn, but lower in winter (35.3 μg·m-3 vs. 41.3 μg·m-3). The linear mixed-effect regression model results showed that ambient PM2.5, individual ambient temperature, and home cooking frequency were positively associated with individual PM2.5 exposure level (P < 0.05), while the time spent indoors was inversely associated (P < 0.05). By analyzing the hourly variation, individual PM2.5 showed peak levels during lunch and dinner periods in four seasons. The multiple regression analysis results found that ambient PM2.5 had a higher impact on individual PM2.5 between dawn and noon (an increase of 0.6-0.8 μg·m-3 of individual PM2.5 per 1 μg·m-3 increase of ambient PM2.5), compared with other time periods in a day (an increase of 0.4-0.6 μg·m-3 of individual PM2.5 per 1 μg·m-3 increase of ambient PM2.5).
Conclusion In conclusion, the individual PM2.5 exposure levels have different seasonal variation patterns in comparison with ambient PM2.5 levels in the elderly people in Shanghai. Higher ambient PM2.5, higher individual ambient temperature, more frequent cooking indoors might increase the individual PM2.5 exposure levels, while more time spent indoors might have a decreasing effect.