Identification of Neighborhood Hotspots via the Cumulative Hazard Index: Results From a Community-Partnered Low-Cost Sensor Deployment

The Strathcona neighborhood in Vancouver is particularly vulnerable to environmental injustice due to its close proximity to the Port of Vancouver, and a high proportion of Indigenous and low-income households. Furthermore, local sources of air pollutants (e.g., roadways) can contribute to small-scale variations within communities. The aim of this study was to assess hyperlocal air quality patterns (intra-neighborhood variability) and compare them to average Vancouver concentrations (inter-neighborhood variability) to identify possible disparities in air pollution exposure for the Strathcona community. Between April and August 2022, 11 low-cost sensors (LCS) were deployed within the neighborhood to measure PM2.5, NO2, and O3 concentrations. The collected 15-min concentrations were down-averaged to daily concentrations and compared to greater Vancouver region concentrations to quantify the exposures faced by the community relative to the rest of the region. Concentrations were also estimated at every 25 m grid within the neighborhood to quantify the distribution of air pollution within the community. Using population information from census data, cumulative hazard indices (CHIs) were computed for every dissemination block. We found that although PM2.5 concentrations in the neighborhood were lower than regional Vancouver averages, daily NO2 concentrations and summer O3 concentrations were consistently higher. Additionally, although CHIs varied daily, we found that CHIs were consistently higher in areas with high commercial activity. As such, estimating CHI for dissemination blocks was useful in identifying hotspots and potential areas of concern within the neighborhood. This information can collectively assist the community in their advocacy efforts. Historically marginalized communities can experience environmental injustice due to disproportionately high air pollution relative to other communities. The Strathcona neighborhood in Vancouver is of particular concern due to its proximity to the Port of Vancouver, major roads and railways, and a high proportion of Indigenous and low-income households. Here, we assess hyperlocal air quality patterns in Strathcona and compare them to average Vancouver concentrations to assess potential air quality inequity. Between April and August 2022, 11 low-cost sensors (LCS) measuring PM2.5, O3, and NO2 were deployed in community backyards. The daily average concentrations were compared to those in other Vancouver neighborhoods. Concentrations were also estimated at every 25m grid within the neighborhood using ordinary kriging, a relatively simple spatial interpolation technique. Using Census population data, cumulative hazard indices (CHIs, which combine PM2.5, O3, and NO2 in a single metric) were computed for every dissemination block. We found that daily NO2 concentrations and summer O3 concentrations consistently higher than in other Vancouver neighborhoods. Although CHIs varied daily, CHIs were consistently higher in areas with high commercial activity. The kriging model was more easily implemented than traditional land use regression models, and may be useful to communities struggling to interpret LCS network data. Mapping the cumulative hazard index (CHI) is a useful way for communities to summarize complex outputs from low-cost air quality sensors The NO2 concentrations in the study area were consistently higher than other Metro Vancouver neighborhoods The western and eastern peripheries (high commercial density) of the study domain were the dominant hotspots, depending on wind direction