The Relationships between Indoor and Outdoor Respirable Particulate Matter: Meteorology, Chemistry and Personal Exposure

Abstract

Respirable particulate matter was collected inside and outside of a building located in Wolverhampton city centre during the same time period between 19/9/00 and 1/5/01. A total of 103 pairs of indoor and outdoor measurements were made using Casella personal dust monitors. The building monitored was located in a small street canyon produced by 4- and 5-storey buildings on both sides of the road. The road is the main approach road to a major bus station and is used by large numbers of heavy-duty diesel vehicles each day. The mean concentration for outdoor samples was 27.6 and 9.8 µg·m^–3 for indoor samples. The mean indoor/outdoor ratio for this period was 0.4 (±0.02 SE). Meteorological variables including wind speed, wind direction and precipitation were measured at a nearby urban monitoring station. A greater wind speed caused an increase in the quantity of outdoor generated particulates penetrating indoors. Wind direction affected both indoor and outdoor particulate concentrations, with lower concentrations being observed when the wind direction was parallel to the street canyon. The indoor/outdoor ratio also showed a decrease during parallel wind conditions. During days with high amounts of precipitation, the concentration of particulates, both indoors and outdoors, decreased significantly. The personal exposure of a building occupant was measured for 20 working days in conjunction with outdoor and indoor measurements. Personal exposure concentrations were well correlated with indoor concentrations (r² = 0.98). Forty of the indoor and outdoor particulate samples of dust were chemically analysed for sulphate, nitrate, chloride, zinc, copper, manganese and aluminium to determine any indoor/outdoor relationships of particulate chemistry and any interrelationships between the analytes.