| dc.description.abstract | The study of exposure to nitrogen dioxide (NO2) is important because of its
significant health effects. As it is associated with combustion processes, road traffic is
one of the main outdoor sources and gas cookers and gas heaters are the main indoor
sources. Indoor NO2 is a significant health problem due to people spending most of
their time indoors. Activity patterns and lifestyles vary and, consequently, people may
be exposed NO2 from several different sources during a typical day. In order to
understand and quantify total personal exposure, it is, therefore, important to
determine both the indoor and outdoor concentration levels.
This thesis reports on two pilot studies, spring and summer 2000 and three full
campaigns, autumn, winter 2000 and summer 2001 to investigate the relationship
between NO2 personal exposure of office workers in relation to indoor and outdoor
sources and activity patterns. The study has been carried out in the area of
Hertfordshire, UK. This region is adjacent to London and has a population of just over
one million people. It consists of several major commuter routes connecting medium
sized towns to London.
Volunteers using gas cookers and electric cookers in their kitchens were asked
to fill in activity patterns records and questionnaires. At the same time, weekly
average personal exposure to N02 and indoor (bedroom, living room, kitchen and
office) and front door N02 concentrations were measured by using passive diffusion
tubes. Correlation between weekly personal exposures and mean indoor and outdoor
concentrations during the same periods were examined.
The results show significant differences in indoor and outdoor concentrations
of NO2 in autumn and winter. The data indicated that NO2 concentrations in all rooms
in houses with gas cookers were significantly higher than those with electric cookers
especially in kitchens where levels of NO2 were 3 to 4 times greater. Interpretation of
time activity daily diaries showed that the subjects spent on average 80% of their time
indoors. Despite the very high concentrations in kitchens with gas cookers, personal
exposure did not increase similarly as volunteers only spent a small amount of time
cooking over the 7 day period.
Good correlation was observed between the average indoor NO2
concentrations, especially in bedrooms and living rooms, and personal exposure. This
indicated that indoor levels in areas like the bedroom and living rooms could be used as
a proxy for NO2 personal exposure for this group of volunteers. An empirical time
weighted average concentration model was developed based on the NO2
concentrations measured in the microenvironments and the data on time spent in each
microenvironment. This was tested by comparison between time weighted average
calculations and the personal exposure measurements of NO2 concentrations. The
comparison yielded good relationships for most of the campaign periods despite the
fact that NO2 concentrations were not similar in the different micro environments and
the fact that subjects spent varying times in these places. Statistical tests were
performed for time weighted average concentrations of N02 and the personal
exposure to NO2 concentrations and differences were found to be non-significant. | en_US |
