ASSESSMENT OF THE RELATIONSHIP BETWEEN OUTDOOR AND INDOOR CONCENTRATIONS OF AIRBORNE PARTICULATES IN RESIDENTIAL BUILDINGS IN SINGAPORE

A small-scale comprehensive indoor, outdoor and personal particle characterization study was conducted in a non-smoking apartment for a period of 2 to 10 days during April, 2003 to May, 2003. Concurrent indoor, outdoor and personal particle number measurements were recorded using a handheld condensation particle counter (CPC TSI 3700). Direct reading of the CPC provided near real-time data of suspended particulate matter (PM) with the instrument at fixed locations. An activity-time log was strictly adhered to in order to relate changes in particle number concentrations to the various activities within the apartment. The results indicated that activities like cooking, cleaning and general human activities contributed to the elevation of particulate matter indoors. The elevation of indoor (1) and personal (P) particle concentrations were also due to other factors like ventilation, wind direction and the location of the apartment. The outdoor particle number concentrations were lower than that indoors, which was in turn lower than that of personal PM levels. Observed indoor and personal concentrations were more varied, because of household activities that took place inside the apartment and the natural ventilation that prevailed. During the same period, personal particle number concentration measurements were also carried out for a typical day of an individual. An activity-time log was kept to record all events that might have an effect on the personal particle number concentration. Personal particle concentration was highly variable due to the diverse human activity, occupational and environmental dust that the individual was exposed to during the course of his day. Personal exposure measurements made using the Condensation Particulate Counter (TSI 3007) clearly showed that exposure to particulate matter varies according to the activities transpired and the surrounding environment. Personal particle concentrations were found to be exceptionally high when traveling by public transport and walking on the roads. Vehicular emissions and dust from the road are reasons for the higher personal exposure to particulate matter. In addition, the paper discusses concepts that have been used to quantify exposure to particles, as well as error analysis methodology. It also examines the spatial and temporal variability within and between outdoor samples, factors associated with variability in indoor and personal samples, and implications of these results for assessing PM exposure in the general population.

Author dc:creator

• MATHEW THOMAS THOMAS