Estimating the Relationships Between Early-Life Air Pollution Exposures and Wheezing From Birth Into Adulthood

Abstract

Half of children in the United States experience wheezing incidents before their 6th birthday, and while most outgrow this condition, those who do not are at increased risk for irreversible decrements in lung function and development of asthma. During early life, lungs are more susceptible to environmental insults, however, findings on the association between ambient air pollution exposures in this time and wheezing outcomes are mixed, and effects on later wheezing outcomes have only been studied to age 11. To better understand these relationships, I took advantage of respiratory health data from the Tucson Children’s Respiratory Study (TCRS), one of the oldest on-going, prospective respiratory birth cohorts in the world, with 32 years of follow-up data (enrolled from 1980-1984, n=1246). I also utilized air pollution measures from two independent, spatially-representative air pollution studies in the Tucson, AZ area, the Pima County Workers Study (1987-1991) and the Tucson Air Pollution Study (2015-2016), to build and validate land use regression (LUR) models for NO2, NOx, PM2.5, and PM10, and then estimate exposures for TCRS participants at birth and age 6. Air pollution measurements from the Pima County Workers and Tucson Air Pollution Studies were well below ambient air quality standards, and concentrations decreased between the study periods, owing to regulations and controls enacted during this time. More sampling sites better characterized the relationships among predictors and pollutant concentrations, as shown by external validation, while the opposite was shown by internal validation. Decreased external validation capacity of LUR models can attenuate the effect of estimated air pollution exposures in health models. Despite relatively low concentrations of pollutants, PM2.5 exposures at birth significantly increased the risk of having wheezing in the first 3 years of life, which has been associated with reduced lung function and later development of asthma. Children born to mothers <25 years of age were more susceptible to NO2 and NOx exposures at birth for wheezing by age 3. NO2 exposures at birth also increased the risk of more frequent wheezing from age 8-32 years. Further reducing ambient concentrations of these pollutants through regulations or emissions controls could reduce the risk of these outcomes and future, long-term respiratory health implications.