Early-life exposure to air pollution and childhood allergic diseases: an update on the link and its implications

ABSTRACT

Introduction

Although mounting evidence has linked environmental factors with childhood allergies, some specific key issues still remain unclear: what is the main environmental factor? what is the critical timing window? And whether these contribute to the development of disease?

Areas covered

This selective review summarizes recent epidemiological studies on the association between early-life exposure to indoor/outdoor air pollution and childhood allergic diseases. A literature search was conducted in the PubMed and Web of Science for peer-reviewed articles published until April 2020. Exposure to the traffic-related air pollutant, NO₂, exposure during pregnancy and early postnatal periods is found to be associated with childhood allergies, and exposure during different trimesters causes different allergic diseases. However, exposure to classical air pollutants (PM₁₀ and SO₂) also contributes to childhood allergy in developing countries. In addition, early-life exposure to indoor renovation and mold/dampness significantly increases the risk of allergy in children. A synergistic effect between indoor and outdoor air pollution is found in the development of allergic diseases.

Expert opinion

Early-life exposure to outdoor air pollution and indoor environmental factors plays an important role in the development of childhood allergic diseases, and the synergy between indoor and outdoor exposures increases allergy risk. The available findings support the hypothesis of the ‘fetal origins of childhood allergy,’ with new implications for the effective control and early prevention of childhood allergies.

KEYWORDS:

• Asthma and allergy
• children
• early-life
• ambient air pollution
• indoor air pollution
• cohort study

Article highlights

1. Early-life exposure to the traffic-related air pollutant, NO2, during pregnancy and early postnatal periods, particularly the first years of life, plays a key role in the development of childhood allergic diseases including asthma, allergic rhinitis, and eczema.

2. Exposure to classical air pollutants (PM10 and SO2) during early-life in low- and middle-income countries is also shown to contribute to an increased risk of childhood asthma and allergies, and thus cannot be overlooked.

3. Children living in buildings with new furniture and mold/dampness during early-life have a higher risk of developing allergic diseases.

4. There is a synergistic effect between early-life exposure to outdoor air pollution and indoor environmental factors on childhood allergic diseases.

5. There is a synergistic effect between early-life exposure to outdoor air pollution and indoor environmental factors on childhood allergic diseases.

6. Findings from the available literature support the role of air pollution in the ‘fetal origins of childhood allergy’, suggesting a straightforward strategy for the effective reduction and early prevention of the risk of childhood asthma and allergies: To avoid early-life exposure to indoor and outdoor pollutants for pregnant mothers and young children.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (No. 21777193, 81861138005 and 41977369).