Effect of Early Life Exposure to Air Pollution on Development of Childhood Asthma

TLDR

Early environmental exposures, including outdoor air pollution, are increasingly recognized as important factors in childhood asthma, yet it remains unclear whether such exposure influences disease incidence. The study aimed to determine whether in utero and first‑year exposure to ambient air pollution increases the risk of later asthma diagnosis in a large population‑based cohort. Researchers matched asthma cases to five controls and estimated each child’s exposure to multiple pollutants during gestation and the first year using high‑resolution monitoring data and land‑use regression, then applied logistic regression to assess associations. Higher early‑life exposure to CO, NO, NO₂, PM₁₀, SO₂, black carbon, and proximity to point sources was associated with a significantly increased risk of asthma, with traffic‑related pollutants showing the strongest associations (e.g., OR 1.08 per 10 µg/m³ NO).

Abstract

There is increasing recognition of the importance of early environmental exposures in the development of childhood asthma. Outdoor air pollution is a recognized asthma trigger, but it is unclear whether exposure influences incident disease. We investigated the effect of exposure to ambient air pollution in utero and during the first year of life on risk of subsequent asthma diagnosis in a population-based nested case-control study.We assessed all children born in southwestern British Columbia in 1999 and 2000 (n = 37,401) for incidence of asthma diagnosis up to 34 years of age using outpatient and hospitalization records. Asthma cases were age- and sex-matched to five randomly chosen controls from the eligible cohort. We estimated each individual's exposure to ambient air pollution for the gestational period and first year of life using high-resolution pollution surfaces derived from regulatory monitoring data as well as land use regression models adjusted for temporal variation. We used logistic regression analyses to estimate effects of carbon monoxide, nitric oxide, nitrogen dioxide, particulate matter <or= 10 microm and <or= 2.5 microm in aerodynamic diameter (PM10 and PM2.5), ozone, sulfur dioxide, black carbon, woodsmoke, and proximity to roads and point sources on asthma diagnosis.A total of 3,482 children (9%) were classified as asthma cases. We observed a statistically significantly increased risk of asthma diagnosis with increased early life exposure to CO, NO, NO2, PM10, SO2, and black carbon and proximity to point sources. Traffic-related pollutants were associated with the highest risks: adjusted odds ratio = 1.08 (95% confidence interval, 1.041.12) for a 10-microg/m3 increase of NO, 1.12 (1.071.17) for a 10-microg/m3 increase in NO2, and 1.10 (1.061.13) for a 100-microg/m3 increase in CO. These data support the hypothesis that early childhood exposure to air pollutants plays a role in development of asthma.