Abstract
BackgroundThe Democratic National Convention (DNC) in Boston, Massachusetts in 2004 provided an opportunity to evaluate the impacts of a localized and short-term but potentially significant change in traffic patterns on air quality, and to determine the optimal monitoring approach to address events of this nature. It was anticipated that the road closures associated with the DNC would both influence the overall air pollution level and the distribution of concentrations across the city, through shifts in traffic patterns.MethodsTo capture these effects, we placed passive nitrogen dioxide badges at 40 sites around metropolitan Boston before, during, and after the DNC, with the goal of capturing the array of hypothesized impacts. In addition, we continuously measured elemental carbon at three sites, and gathered continuous air pollution data from US EPA fixed-site monitors and traffic count data from the Massachusetts Highway Department.ResultsThere were significant reductions in traffic volume on the highway with closures north of Boston, with relatively little change along other highways, indicating a more isolated traffic reduction rather than an across-the-board decrease. For our nitrogen dioxide samples, while there was a relatively small change in mean concentrations, there was significant heterogeneity across sites, which corresponded with our a priori classifications of road segments. The median ratio of nitrogen dioxide concentrations during the DNC relative to non-DNC sampling periods was 0.58 at sites with hypothesized traffic reductions, versus 0.88 for sites with no changes hypothesized and 1.15 for sites with hypothesized traffic increases. Continuous monitors measured slightly lower concentrations of elemental carbon and nitrogen dioxide during road closure periods at monitors proximate to closed highway segments, but not for PM2.5 or further from major highways.ConclusionWe conclude that there was a small but measurable influence of DNC-related road closures on air quality patterns in the Boston area, and that a low-cost monitoring study combining passive badges for spatial heterogeneity and continuous monitors for temporal heterogeneity can provide useful insight for community air quality assessments.
Highlights
The Democratic National Convention (DNC) in Boston, Massachusetts in 2004 provided an opportunity to evaluate the impacts of a localized and short-term but potentially significant change in traffic patterns on air quality, and to determine the optimal monitoring approach to address events of this nature
Analytical methods To determine if the DNC resulted in significant changes in traffic volumes and/or air pollutant concentrations, we evaluated integrated nitrogen dioxide concentrations and traffic volumes by calculating the ratio of the level during the week of the DNC to the average of levels the weeks before and afterwards
There are significant changes on I93 and Route 1 north of Boston, both of which had road closures associated with the DNC, with the precise diurnal patterns and impacts varying by direction and proximity to downtown Boston
Summary
It was anticipated that the road closures associated with the DNC would both influence the overall air pollution level and the distribution of concentrations across the city, through shifts in traffic patterns. Holidays, and road construction can all influence traffic volume on selected roadways, less transient changes that can be anticipated in advance are less common. In one such example, reductions in traffic volume associated with the 1996 Summer Olympics in Atlanta were associated with significant improvements in ambient air quality and reductions in childhood asthma events [4]. Construction of a bypass in North Wales was shown to reduce heavy goods traffic and particulate matter concentrations by 23–29%, with some concurrent reductions in rhinitis and rhinoconjunctivitis [5]
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