Assessing the impact of increased traffic-related air pollution associated with a proposed development in a densely populated urban area

Proposed development plans for Assembly Square in Somerville, Massachusetts, the most densely populated city in New England (5th in the U.S.), have the potential to further increase traffic related air pollution in this community. The development is adjacent to a portion of I-93 with the highest traffic volumes in Massachusetts (143,000 vehicles per day), with post-construction traffic counts projected to increase by an additional 24,000 vehicles per day. Examining the implications of commercial development and the impact on the local community is a public health priority, particularly in diverse communities like Somerville where approximately 30% of the Somerville residents are foreign born and 4,000 residents live within 200m of I-93. To assess the impact of traffic related pollution to residents nearby I-93, 40 passive diffusion tubes were deployed within 500m of I-93 to measure the averaged NO₂ concentration over 2 weeks in October and November, 2007. NO₂ has been shown to be a reliable surrogate for traffic-related air pollution. Preliminary results show samples collected adjacent to I-93 (<30m) have approximately 10 – 50% higher NO2 concentration than samples collected 100m away from the highway. Projected traffic counts after development indicate that air pollution may increase by 20% in the most affected communities. Additional analyses are being conducted to further examine if socio-economic status is associated with NO₂ concentrations.