Ljs. Liu et al., ASSESSMENT OF OZONE EXPOSURES IN THE GREATER METROPOLITAN TORONTO AREA, Journal of the Air & Waste Management Association [1995], 45(4), 1995, pp. 223-234
An ozone (O-3) exposure assessment study was conducted in Toronto, Ont
ario, Canada during the winter and summer of 1992. A new passive O-3 s
ampler developed by Harvard was used to measure indoor, outdoor, and p
ersonal O-3 concentrations. Measurements were taken weekly and daily d
uring the winter and summer, respectively. Indoor samples were collect
ed at a total of 50 homes and workplaces of study participants. Outdoo
r O-3 concentrations were measured both at home sites using the passiv
e sampler and at 20 ambient monitoring sites with continuous monitors.
Personal O-3 measurements were collected from 123 participants, who a
lso completed detailed time-activity diaries. A total of 2,274 O-3 sam
ples were collected. In addition, weekly air exchange rates of homes w
ere measured. This study demonstrates the performance of our O-3 sampl
er for exposure assessment. The data obtained are further used to exam
ine the relationships between personal, indoor (home and workplace), a
nd outdoor O-3 concentrations, and to investigate outdoor and indoor s
patial variations in O-3 concentrations. Based on home outdoor and ind
oor, workplace, and ambient O-3 concentrations measured at the Ontario
Ministry of the Environment (MOE) sites, the traditional microenviron
mental model predicts 72% of the variability in measured personal expo
sures. An alternative personal O-3 exposure model based on outdoor mea
surements and time-activity information is able to predict the mean pe
rsonal exposures in a large population, with the highest R(2) value of
0.41.