Abstract:
Exposure to traffic-related air pollution may threaten children’s health. Due to proximity to traffic, children, whilst foot commuting to school, are at higher risk of exposure to air pollution. The children’s exposure is influenced by many factors, some of the most important of which are socioeconomic status (SES) (e.g, in low SES areas, the vehicle fleet may be older and can lead to a higher emission rate per vehicle), the characteristics of the neighbourhood (the width of footpath and roads and density of traffic lights), and route choice. To our knowledge, there are a limited number of studies that have investigated these factors in children’s exposure to traffic-related air pollution. Therefore, this study will answer the following questions: 1) How do the socioeconomic status of the neighbourhood and route characteristics influence the mean exposure and the frequency of 'spikes' in concentrations of ultrafine particles (UFP) on the walk to primary school? 2) What are the health benefits of choosing an optimum route regarding exposure to air pollution for active commuters (cyclists and walkers)? 3) Can any reduction be achieved in pedestrian’s mean exposure to UFP and duration of elevated exposure to UFP by choosing the low exposure route to school?
To answer the first question, five pairs of schools, each including a low and a high SES school, were selected. The routes to schools were traversed by the researcher while measuring UFP concentration and recording videos (to measure traffic flow, capturing fleet characteristics and finding reasons for spikes) and GPS data in the morning commute to school. To answer the second question, a health impact analysis was carried out to estimate the health benefits of choosing an optimised route for active commuters. This was done using literature found through a systematic review. Afterwards, fieldwork was conducted to compare three routes from an origin to a school; two routes went through a high trafficked road (with different traffic flows on the sides of the road) and the third one went through quiet streets (the background route). Three operators walked the three routes simultaneously while recording UFP concentration.
The results showed both the mean age of cars and the percentage of old cars (> 14 years) were lower in the high SES neighbourhoods. However, vehicle age was not associated with a significant difference in either the estimated emission from the sample of cars or the pedestrian’s exposure to UFP (even after adjusting for traffic flow). Other factors such as width of sidewalks and the density of intersections and traffic lights had a significant role in the children’s exposure to pollution. The results also suggested that active commuters’ route choice can have a sigficant role in their exposure to air pollution. Based on a literature review and a post-analysis of the mean exposures to black carbon (BC) extracted from reviewed articles, it was estimated up to 36 out of 10,000 deaths could be prevented if the active commuters choose the optimised route. Furthermore, the results of the fieldwork showed that the operator in the background route, compared to the high trafficked routes, experienced a lower daily exposure and duration, on average, of elevated pollutant exposure. The pedestrian on the low traffic side of the road experienced less than half of the duration of exposure to elevated exposure. Consequently, pedestrians should avoid roads with intense traffic and traffic lights. If choosing low traffic routes is not possible, pedestrians should choose the low traffic side of the road.
In conclusion, although SES of the neighborhoods may not be a contributory factor in pedestrian exposure to air pollution, it can be suggested to active commuters to avoid the high traffic roads, the roads with high number of traffic lights, and narrow foothpaths to expose to lower concentration of air pollution. If avoiding the low traffic roads is not possible, choosing the low traffic side of the road may decrease the duration of exposure to elevated concentrations. The findings in this study enhance our understanding of the pedestrian’s exposure to traffic-related air pollution whilst travelling to school. Governments may use these findings to support ‘walk to school’ initiatives and provide the relevant infrastructure.