“Cairo Air Pollution with smog - Pyramids1” by Nina Hale is licensed under CC BY 2.0

TRAP: Traffic Related Air Pollution Linked to Millions of Pediatric Asthma Cases Worldwide

MedicalResearch.com Interview with:
Ploy Pattanun Achakulwisut, PhD
Postdoctoral Scientist in Climate change, Air pollution, and Public Health
Milken Institute School of Public Health (Anenberg Group
The George Washington University, D.C 

MedicalResearch.com: What is the background for this study?

Response: Dozens of epidemiological studies have found positive and generally statistically significant associations between long-term exposure to traffic-related air pollution (TRAP) and asthma development in children. The evidence is most robust for nitrogen dioxide (NO2), a major component of and commonly used surrogate for the complex TRAP mixture. Recent reviews conducted by the US Environmental Protection Agency and Health Canada concluded that there is “likely a causal relationship” between long-term NO2 exposure and pediatric asthma development.

Using NO2 as a proxy for TRAP, our study provides the first global estimate of the number of new asthma cases among children that are attributable to traffic pollution, using fine spatial-scale global datasets that can resolve within-city and near-roadway NO2 exposures.

 MedicalResearch.com: What are the main findings?

Response: We estimate that in 2010-2015, more than one in ten paediatric asthma cases may be linked to TRAP, resulting in 4 million new cases of asthma worldwide each year. The majority of this impact occurs in urban areas.

Within 125 major cities we investigated, the percentage of new paediatric asthma cases attributable to traffic pollution ranged from 6% in Orlu, Nigeria, to 48% in Shanghai, China. This percentage exceeded 20% in 92 cities located in both developed and developing countries. The top 10 highest contributions estimated for eight cities in China (37-48% for Shanghai, Tianjin, Beijing, Shenyang, Xi’an, Taiyuan, Zhengzhou, and Harbin) alongside Moscow, Russia (40%), and Seoul, South Korea (40%).

We also estimated that ~97% of children lived, and ~92% of NO2-attributable pediatric asthma incidence occurred, in areas below the current World Health Organization (WHO) guideline of 21 ppb (40 µg m-3) for annual average NO2.

MedicalResearch.com: What should readers take away from your report?

Response: Traffic pollution appears to be a substantial risk factor for childhood asthma incidence in both developed and developing countries, and especially in cities, and should therefore be a target for exposure-mitigation policies. Initiatives to reduce traffic pollution and improve access to cleaner forms of transportation, like electrified public transport and active commuting by cycling and walking, would not only bring down NO2 pollution levels and improve children’s health, but would also help reduce greenhouse gas emissions.

If NO2 proves to be the causative agent of asthma development within the TRAP mixture, our findings suggest that the World Health Organization guideline for annual average NO2 concentrations may need to be re-evaluated. 

MedicalResearch.com: What recommendations do you have for future research as a result of this work?

Response: Due to limited data availability, the NO2 levels used in this study are for 2010-2012, whereas the population and asthma incidence rates are for 2015. Given recent global changes in NO2 levels (generally, decreases in US and European cities, and increases in Asia), the estimates may not be exact and further research with the latest NO2 levels is needed.

Additionally, it would be useful for future epidemiological studies to identify the putative agents within the TRAP mixture and target understudied populations, especially in Africa and central and southeast Asia. This effort, along with more air pollution monitoring in data-limited countries outside of North America, Europe, and east Asia, will help to refine our estimates of the burden of paediatric asthma incidence attributable to traffic-related air pollution.

Any disclosures? This research was funded by The George Washington University


Pattanun Achakulwisut, Prof Michael Brauer, Perry Hystad, Susan C Anenberg. Global, national, and urban burdens of paediatric asthma incidence attributable to ambient NO2 pollution: estimates from global datasets. The Lancet Planetary Health, 2019 DOI: 10.1016/S2542-5196(19)30046-4



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Last Updated on April 12, 2019 by Marie Benz MD FAAD