Most of us move around cities every day and are exposed to air pollution during our commutes. Our daily travel patterns – a complex yet significant factor in measuring pollution exposure – are considered in a recent PolyU study, offering new insights to authorities worldwide. The study highlights disparities in pollution exposure and calls for targeted mitigation measures.

Led by Professor An Wang, Assistant Professor of the Department of Civil and Environmental Engineering, a PolyU research team collaborated with international experts to study urban air pollution in the Bronx, New York City, utilising big mobility data and advanced sensor technology. Known for its dense population and ethnic diversity, the Bronx faces severe air pollution issues and has the poorest air quality among the New York City boroughs. 

The team tracked three months of daily mobility data from over 500,000 mobile device users, collecting 600,000 valid data. They developed an empirical model to predict air quality levels and assess differences in pollution exposure among Bronx residents.

Key findings include:

1) Impact of land use and infrastructure planning 

The area where expressways and industries meet most intensively experiences the highest levels of particulate matter. 

2) Exposure based on mobility

Citizens working long hours or living on highly polluted streets are more exposed to fine particulate matter (PM2.5). This analysis uniquely considered both air pollutant concentrations and mobility patterns in places like restaurants, schools, and malls.

3) Race and ethnicity are stronger indicators of exposure disparity than income

Hispanic-majority and low-income neighbourhoods faced the most severe and disproportionate exposure, with the greatest differences in exposure by ethnic groups observed in Hispanic-majority communities. 

The study highlighted the significance of daily travel patterns as a factor in assessing air pollution exposure. The research team suggests developing granular plans to address high-exposure individuals from socially disadvantaged groups, alongside general air quality improvements.

Professor Wang said, “By quantifying air pollution exposure, we can develop cost-effective strategies for targeted emission control, health impact assessment, clean air action and urban design, helping Hong Kong and other cities worldwide to achieve the vision of ‘One Health’.”

PolyU collaborated with scientists from the Senseable City Lab of the Massachusetts Institute of Technology and Brown University in the USA, the Norwegian University of Science and Technology, and University College Cork in Ireland. Their findings have been published in the international journal Nature Cities. Click here to read the paper.