Activity pattern and personal exposure to nitrogen dioxide in indoor and outdoor microenvironments
People are exposed to air pollution from a range of indoor and outdoor sources. Concentrations of nitrogen dioxide (NO2), which is hazardous to health, can be significant in both types of environments. This paper reports on the measurement and analysis of indoor and outdoor NO2 concentrations and their comparison with measured personal exposure in various microenvironments during winter and summer seasons. Furthermore, the relationship between NO2 personal exposure in various microenvironments and including activities patterns were also studied. Personal, indoor microenvironments and outdoor measurements of NO2 levels were conducted using Palmes tubes for 60 subjects. The results showed significant differences in indoor and outdoor NO2 concentrations in winter but not for summer. In winter, indoor NO2 concentrations were found to be strongly correlated with personal exposure levels. NO2 concentration in houses using a gas cooker was higher in all rooms than those with an electric cooker during the winter campaign, whereas there was no significant difference noticed in summer. The average NO2 levels in kitchens with a gas cooker were twice as high as those with an electric cooker, with no significant difference in the summer period. A time-weighted average personal exposure was calculated and compared with measured personal exposures in various indoor microenvironments (e.g. front doors, bedroom, living room and kitchen); including non-smokers, passive smokers and smoker. The estimated results were closely correlated, but showed some underestimation of the measured personal exposures to NO2 concentrations. Interestingly, for our particular study higher NO2 personal exposure levels were found during summer (14.0 ± 1.5) than winter (9.5 ± 2.4).