Epidemiology and Population Health

The association of air pollution with body mass index: evidence from Hong Kong’s “Children of 1997” birth cohort




Child overweight and obesity have increased substantially in many countries. Physical and psychological effects of childhood obesity endure throughout adulthood. Much attention has been paid to energy intake and expenditure in childhood adiposity, but less to environmental factors, such as outdoor air quality. Here we assessed prospectively the association of exposure to air pollution with body mass index (BMI) in late childhood and early adolescence.


We assessed the association of air pollutants (particulate matter with a diameter of 10 µm or less (PM10), sulfur dioxide (SO2), nitric oxide (NO), and nitrogen dioxide (NO2)) at different growth phases (in utero, in infancy, and in childhood) with BMI at ~9, ~11, ~13, and ~15 years in a population-representative birth cohort from Hong Kong, “Children of 1997.” We used partial least square regression to account for colinearity between pollutants and exposure periods. We also assessed whether associations varied by sex from model fit.


Associations were sex-specific based on better model fit when including sex interaction terms. Among boys, higher SO2 in utero was associated with lower BMI at ~13 and ~15 years, higher SO2 in childhood with lower BMI at ~15 years, and higher NO2 in childhood with higher BMI at ~9, ~13, and ~15 years using a multi-pollutant model.


These findings of air pollutant- and sex-specific associations with adiposity should give impetus to the investigation of their physiological effects, possibly operating as endocrine disruptors or via mitochondria, so as to protect the next generation of boys.

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This work is a sub-study of the “Children of 1997” birth cohort study, which was initially supported by the Health Care and Promotion Fund, Health and Welfare Bureau, Government of the Hong Kong Special Administrative Region (HCPF grant no. 216106) and reestablished in 2005 with support from the Health and Health Services Research Fund (grant nos. 03040771, 07080751 and 07080841), and the University Research Committee Strategic Research Theme (SRT) of Public Health, University of Hong Kong. This sub-study builds on information added to the birth cohort by Research Fund for Control of Infectious Diseases (grant no. 04050172), Government of the Hong Kong Special Administrative Region. The authors thank the late Dr. Connie O for coordinating the project and all the fieldwork for the initial study in 1997–1998.

Author information


  1. School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, People’s Republic of China

    • Jian V Huang
    • , Gabriel M Leung
    •  & C Mary Schooling
  2. Graduate School of Public Health and Health Policy, City University of New York, New York, USA

    • C Mary Schooling


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Conflict of interest

The authors declare that they have no conflict of interest.

Corresponding author

Correspondence to C Mary Schooling.

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