Early-life particulate exposure and increased risk of childhood asthma

Published: March 5, 2021

Childhood asthma gives rise to a great health burden from chronic respiratory diseases and substantially affects quality of life among children across the globe. Exposure to ambient particulate air pollution, particularly during early-life, has been identified as an important environmental determinant of asthma onset and exacerbation in population-based studies. Emerging evidence suggested stronger associations of children’s respiratory health with smaller particle exposure, but no studies have investigated the potentially differential effects of submicron particulate exposure on development of asthma in early childhood.

In a recent research article in The Journal of Allergy and Clinical Immunology (JACI), Zhang et al examined the associations of in-utero and first-year exposures to size-specific particulate air pollution with childhood asthma and wheezing. They conducted a retrospective investigation among 5,788 preschool children aged 3–5 years in central China, playing as a part of the Phase II CCHH (the China, Children, Homes, Health) study. Information on first-ever incidence of asthma and wheezing was ascertained by surveying children’s caregivers through a standard questionnaire. Individual residential exposures at a 1×1 km-resolution were assessed by taking advantage of satellite-based space-time models using machine learning methods.

Zhang et al found significant evidence for increased risk of childhood asthma due to particulate exposure in early life, particularly during the prenatal stage. They linked 24–62% greater risks of asthma in early childhood with per 10-µg/m3 increase in in-utero exposure to particulate pollution. These associations were only observed among boys and children who experienced a longer breastfeeding duration. For example, for each 10-µg/m3 increase in in-utero exposure, children with 0–5 months’ breastfeeding had an excess risk of 42–126%, while those longer breastfed were at much lower risks (7–16%).

This study highlighted stronger associations of early-life exposure to ambient submicron particulate pollution with development of childhood asthma than larger particles. Suggestive evidence indicated that longer breastfeeding may lower asthma risk in children exposed to particulate air pollutants. These findings may have significant public health implications in informing environmental and healthcare policy makers to make greater efforts in clean air actions, particularly in highly-polluted megacities, so as to reduce burden of childhood asthma associated with ambient particulate air pollution.

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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