Conclusions
We have presented the results of a localised study aimed at
enhancing our understanding of the connections between individual
perception and exposure to different environmental stimuli; microclimate,
noise and especially particulate matter. People were asked to
evaluate environmental quality at the same time and location as
highly time-resolved physical measurements were carried out, so the
objective and subjective parameters could be directly linked. Since
our sample size is relatively small (260 interviews), the results should
be regarded as indicative of the trends in actual perception of pollution
and the relative importance of various other factors.
The surveys took place in daytime on sidewalks next to a road
construction site (CS) and a medium density traffic site (TS). The
meteorological conditions were generally sunny, warm, moderately
humid, and with light winds. At both sites the environment was noisy.
The particulate matter concentration was generally low, but the CS
was burdened with higher PM counts (presumably from dust) and
higher sound levels.
The overall comfort was determined primarily by the thermal
environment, with no correlation between comfort and sound or PM
levels. Overall air quality is considered to be clean by more than 50%
of the participants. Air quality vote distribution is strongly correlated
to the Air Clean/Dusty votes, and both of these perception votes
are correlated with the PM count. Overall as the concentration of
PM increases the number of ‘clean air’ and ‘good air quality’ votes
decreases, whereas the number of ‘dusty air’ and ‘poor air quality’
votes increases. Through the exposure–response relationships between
the various perception votes and PM, it was possible to predict
air cleanness using the PM count. The model performed fairly well for
the three middle categories, where the majority of the votes existed
and less well for the two extreme categories.
Surprisingly, these perception votes also present a significant
negative correlation with solar radiation, suggesting that the way
people perceive PM is through the visual effect of particles that
inevitably becomes more noticeable under low irradiation conditions.
Hyslop (2009) suggests that impaired visibility is the result
of air pollution due to light scattering on particles or more extreme
cues such as smoke from chimneys or car motor exhausts.
The effect of medical or smoking history on the perceived air
quality was also evaluated. People with a medical history of hay fever
voted more frequently for poor air quality conditions than those
without, whereas current smokers were the least sensitive to air
quality. Medical history affects the occurrence of specific symptoms
as can be expected, e.g. symptoms of blocked nose for those suffering
of hay fever, dry throat for smokers. The analysis also suggests that
there appears to be no statistically significant differentiation of the
PM-related sensitivity according to the existing medical history —
although the sample with such history is small.
This work shows promising results but the confidence of these
results is affected by the small number of responses. An extensive
study investigating different levels of air pollution in different urban
settings would help us to disentangle the effect of these parameters.
Furthermore, it would help us to identify threshold levels that different
air pollutants need to reach for them to be perceived by
individuals, while investigating the means by which these pollutants
are being perceived (e.g. sensory irritation to eyes, nose, throat; visual
appearance, etc.).
Understanding the role of air quality in the overall satisfaction
with the environment will open new dimensions for urban planning
and the development of urban spaces. Individuals' perception of
ambient environmental conditions, in particular microclimate, noise
and air quality, can influence the ‘liveability’ of a city. An in-depth
analysis of the human parameter will open new horizons for
evaluating the use of physical intervention through urban and built
form in urban design to improve environmental quality and increase
adaptive capacity to climate change. The impact on urban design, in
relation to the allocation of uses and activities in the urban context
could also be significant. Finally, it can indirectly inform air quality
management schemes and outreach campaigns by addressing the
public's interaction with the environment and motivation for change,
to induce environmentally sustainable behaviour. As Uzzell and
Moser (2006) highlight “it is not the quality of the environment, but
how people interact with it that may be a principal explanatory factor
in well-being”.