Thesis Abstract

Abstract
Childhood asthma is a significant public health concern worldwide, with environmental factors playing a crucial role in its development. Air pollution, in particular, has been implicated as a major risk factor for the onset and exacerbation of asthma. This study aimed to investigate the effect of early life exposure to air pollution on the development of childhood asthma. A systematic review of existing literature was conducted to analyze the relationship between air pollution exposure in early life and the subsequent development of asthma in children. Various air pollutants, including particulate matter (PM), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and carbon monoxide (CO), were examined for their effects on asthma development. The findings revealed a strong association between early life exposure to air pollution and an increased risk of developing childhood asthma. Exposure to PM2.5 and PM10 during infancy and early childhood was consistently linked to a higher prevalence of asthma in children. Similarly, elevated levels of NO2 and O3 were significantly associated with an increased incidence of asthma in young individuals. Furthermore, the study highlighted the importance of considering the timing and duration of air pollution exposure in relation to asthma development. Prenatal exposure to air pollution was found to have long-lasting effects on respiratory health, predisposing children to asthma later in life. Additionally, prolonged exposure to high levels of air pollution was shown to exacerbate asthma symptoms and increase the risk of asthma-related hospitalizations. The mechanisms through which air pollution influences asthma development were also explored in this study. It was observed that air pollutants can trigger airway inflammation, oxidative stress, and immune dysregulation, leading to the development and progression of asthma in susceptible individuals. Genetic factors were found to interact with environmental exposures, further influencing the risk of asthma in children exposed to air pollution early in life. In conclusion, early life exposure to air pollution is a significant risk factor for the development of childhood asthma. Efforts to reduce air pollution levels, especially in urban areas, may help mitigate the burden of asthma in children. Public health interventions focusing on improving air quality and reducing exposure to environmental pollutants are essential for preventing and managing childhood asthma effectively.

Thesis Overview

BACKGROUND

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.

METHODS:

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.

RESULTS:

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.