PolyU collaborates with international experts to study urban air pollution, revealing disparities in pollution exposure and advocating for targeted mitigation measures

To foster a sustainable public health environment, a research team from The Hong Kong Polytechnic University (PolyU) Department of Civil and Environmental Engineering has collaborated with experts from international universities, utilising big mobility data and advanced sensor technology to study urban air pollution. Their study has highlighted the significance of daily travel patterns, and race and ethnicity in assessing differences in residents’ exposure to air pollution, offering new insights for authorities worldwide when developing air pollution mitigation measures. The findings have been published in the international journal Nature Cities.

Dr An WANG, Assistant Professor of the PolyU Department of Civil and Environmental Engineering, 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, to measure air pollution exposure across different areas and ethnic groups in the Bronx, New York City. The Bronx, known for its dense population and ethnic diversity, faces severe long-standing air pollution issues and has the worst air quality among the New York City boroughs with asthma cases 2.5 times higher than in other boroughs.

The health effects of air pollution depend on the concentrations of air pollutants and the duration of exposure. The study tracked three months of daily mobility data from over 500,000 mobile device users, utilising 500 million anonymous location records from the Bronx. The team also installed solar-powered, Internet-of-Things-enabled environmental sensing platforms on government service vehicles, which travelled over one-third of major roads in the Bronx, measuring the concentration of fine particulate matter (PM_2.5) in the air and successfully collecting 600,000 valid data. Based on these mobility and air pollution data, the team trained an empirical model for air quality prediction to extrapolate the air quality levels across the region and differences in pollution exposure among Bronx residents.

The study revealed that the southeast Bronx, where expressways and industries meet most intensively, has the highest levels of particulate matter, indicating the impact of land use and infrastructure planning on air pollution. Unlike previous studies, the team’s analysis considered both air pollutant concentrations and people’s mobility patterns in places like restaurants, schools, and malls to more comprehensively assess their exposure to air pollution. The results showed that citizens who work long hours or live on highly polluted streets have higher exposure to PM_2.5. Among these, people from Hispanic-majority and low-income neighbourhoods were the most severely and disproportionately exposed to the pollution. The greatest differences in exposure by ethnic groups were found in Hispanic-majority communities. The results highlighted that race and ethnicity are much stronger indicators of air pollution exposure disparity than income. The team suggested developing more granular mitigation plans to target high-exposure individuals from socially disadvantaged groups, alongside general air quality improvement efforts.

Dr An Wang said, “Our long-term goal is to utilise composite environmental sensing technologies to address urban environmental problems such as vehicle emissions, noise pollution, urban heat island effects and lack of greenery. The findings of this study can be applied to public health research in dense urban environments like Hong Kong. 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’.”

Looking ahead, Dr Wang will expand the research by developing new data sources and sensing technologies. This will broaden its scope to include a wider range of air pollutants, lay the groundwork for more precise toxicity analyses, advance future air quality research, and provide innovative solutions to urban environmental challenges.

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