Critical review of long-term ozone exposure and asthma development

Abstract

Asthma, a chronic respiratory disorder with complex etiology and various phenotypes, is a considerable public health concern in the USA and worldwide. While there is evidence suggesting ambient ozone exposure may exacerbate asthma, information regarding the potential role of ozone in asthma development is more limited. Thus, we conducted a critical review of observational epidemiology studies to determine whether long-term ambient ozone exposure is a risk factor for asthma development. We identified 14 relevant studies; 11 evaluated asthma development in children, while three studies, based on a single cohort, assessed this outcome in adults. Studies of childhood asthma and long-term ozone exposure – including exposure in utero, during the first year of life and during early childhood – reported inconsistent findings, which were further weakened by critical methodological limitations in statistical analyses and in exposure and outcome assessments, such as exposure measurement error and a lack of adjustment for key confounders. For adult-onset asthma, long-term ozone exposure was associated with an increased risk in men but not women. In addition to considerable uncertainties due to potential exposure measurement error and a lack of adjustment for key confounders, this study has limited generalizability to the US general population. While experimental evidence indicates that it may be biologically plausible that long-term ozone exposure could contribute to asthma development, it does not provide insight regarding an established mode of action. Future research is needed to address the uncertainties regarding the role of long-term ambient ozone exposure in asthma development.

Keywords:

• Ozone
• asthma development
• childhood asthma
• adult-onset asthma
• long-term exposure
• review

Acknowledgments

The authors gratefully acknowledge the editorial review provided by Ms. Carla Walker (Gradient).

Disclosure statement

The authors are employed by Gradient, a private environmental consulting firm.

Additional information

Funding

The work reported in this article was conducted by the authors during the normal course of employment with financial support provided to Gradient by the Electric Power Research Institute (EPRI). This article was reviewed by members of EPRI while in preparation, but the authors retain sole responsibility for the writing, content and conclusions in this article.