Environmental Engineering Reference
In-Depth Information
1. A Conceptual Model for Personal Exposure
and the Measurement Program
This paper presents results from a study to investigate the extent to which NO 2
data from ambient network monitoring, air quality modelling, or a combination of
both, can improve estimates of personal exposure across a city. We link ambient
and personal exposure via an indoor-outdoor (I/O) ratio, and follow the approach
outlined in Monn (2001) in which total personal exposure (PE) to a particular
pollutant is estimated by weighting exposures in different microenvironments (C i )
according to the time spent in each microenvironment (t i ). Such an approach is
based on easy-to-use time-activity diaries. Algebraically, this is expressed as
n
n
∑∑
=
PE
=
C
t
t
.
(1)
i
i
i
i
1
i
=
1
To allow us to both develop and evaluate the above model, we designed a
measurement program involving volunteers across Melbourne (Australia) wearing
small Ferm-type passive gas samplers (about 2.5 cm diameter) attached to chest
clothing (Keywood et al., 1998). The study was done for a total of four separate
2-day events, in April 2007, May 2006, May 2007 and June 2006. These times of
year were chosen for the stable light-wind conditions, in order to maximize
concentrations and the spatial variation in concentrations across the city and suburbs.
The NO 2 data (cumulative) were gathered by between 15 and 17 volunteers
wearing the personal samplers for each of the 2-day periods and maintaining a
diary of their activities over these periods. Both working and non-working
participants were included in the study. All participants were non-smokers and no
dwellings with unflued gas heaters were used.
Participants wore two sets of NO 2 passive samplers at all times, each set
containing two samplers to enable precision checking to be done. One set was
worn at all times throughout the 48-h period and the second set depended on
which microenvironment (home, work or transit between work and home) was
being experienced. When in none of the above environments, volunteers wore a
set of samplers labelled 'other' for their second set. 'Other' included such activities
as shopping, visiting friends, attending the cinema etc. When not being worn, a
sampler was closed by returning it to a canister fitted with a lid. An additional pair
of samplers was placed outside a participant's home and workplace and opened
only while the volunteer was in that environment. In this way, ratios of indoor to
outdoor concentrations were obtained. For vehicles, a sampler was placed on the
mirror-side of the side mirror to enable ratios of in-car to out-car concentrations.
Activity diaries were kept by each person, noting times of arrival and exit in
the different environments. At home, details of heating and cooking appliances
and usage times were recorded, as were age of house, materials, floor area and
volume. Open doors and windows were also noted. The infiltration rate (ventilation
rate of a house in a closed-up state) was measured for five selected houses using a
CO 2 release method similar to that described in Dunne et al. (2006).
 
Search WWH ::




Custom Search