Human exposure to carbon monoxide and inhalable particulate in Beijing, China.

Twenty nonsmoking volunteers were selected from the staff members of the Institute of Health according to their housing conditions. Carbon monoxide (CO) and particulate matter in the outdoor and indoor air and personal exposure were monitored simultaneously for 1 week in summer and 1 week in winter. At the same time some public areas, such as workplaces and shopping and traffic areas, were also monitored. The average outdoor concentration for CO was 1.5 ppm in summer and 3.9 ppm in winter; indoors it averaged 2.8 ppm in summer and 20.1 ppm in winter. Personal exposure fluctuated between these values. The level of COHb averaged 0.2% in summer and 1.9% in winter. The level of inhalable particles was higher in winter than in summer, but the difference was not as marked as that for CO. The activity diary showed that the time spent at home was around 66% and that total indoor (home and workplace) time was over 90%. This indicates the importance of studying indoor pollution and personal exposure.