CSIRO, July 2008
- Assessment of different approaches for determining personal exposure (PDF - 947 KB) | (RTF - 6,578 KB)
The primary aim of this Clean Air Research Programme (CARP) project is to evaluate methodologies for estimating personal exposure from ambient monitoring data and from simulation data from complex ambient air quality models. We focussed our efforts on nitrogen dioxide (NO2), but also present measurements and modelling of fine particulate matter (PM2.5).
Following a literature search, we developed a conceptual model of personal exposure to NO2 based on time-weighted sums of exposure in the microenvironments of home, transit and work. In this model, personal exposure in each microenvironment is linked to ambient concentration by indoor-outdoor concentration ratios. Previous studies indicated that gas cooking appliances and house ventilation rates are strong influences on indoor NO2 concentrations, and thus on indoor-outdoor ratios. Unflued gas heaters are also significant contributors, but there are restrictions on the installation of such heaters operating on Natural Gas in Victoria and consequently their use is not widespread. There were none in any of the homes in which measurements were taken in our study. To allow us to both develop and evaluate our model, we designed a measurement program involving volunteers across Melbourne wearing personal samplers. Participants' diaries were designed to record details of time and activities in each microenvironment, especially those associated with cooking and ventilation. Measurement of house ventilation rates was also conducted at five dwellings.
The field-work for the project entailed the measurement of NO2 concentrations (cumulative) across Melbourne for 15 - 17 volunteers wearing personal passive samplers in each of four events (each of two days). In addition, PM2.5 concentrations were continuously measured over the same periods by four volunteers with portable DustTrakTM monitors (TSI inc.). Both working and non-working participants were included in the study. All participants were non-smokers. The study was done for a total of four separate two-day events, in April 2007, May 2006, May 2007 and June 2006. These times of year were chosen for the stable light-wind conditions to maximize concentrations and the spatial variation in concentrations across the city and suburbs. Participants also wore additional samplers for sub-periods of each 48-hour exposure, at home, at work and in transit between work and home. Outdoor concentrations were also measured in these microenvironments, except for travel on public transport, allowing indoor-outdoor ratios to be calculated.