The Role of Ambient Ozone in Epidemiologic Studies of Heat-Related Mortality

• Published in: Environmental health perspectives Vol. 120; no. 12; pp. 1627 - 1630
• Main Authors: Reid, Colleen E., Snowden, Jonathan M., Kontgis, Caitlin, Tager, Ira B.
• Format: Journal Article
• Language: English
• Published: United States National Institute of Environmental Health Sciences 01.12.2012
• Subjects: Air Pollutants - toxicity; Air pollution; Ambient temperature; Analysis; Commentaries; Computer Graphics; Confounding Factors (Epidemiology); Data Interpretation, Statistical; Directed acyclic graphs; Epidemiologic studies; Epidemiology; Extreme heat; Extreme Heat - adverse effects; Graphs; Health; Health aspects; Heat; Heat tolerance (Biology); High temperature; Mathematical analysis; Mortality; Ozone; Ozone - toxicity; Pollutants; Risk factors; Temperature control; Volatile organic compounds
• ISSN: 0091-6765; 1552-9924; 1552-9924
• DOI: 10.1289/ehp.1205251

Background: A large and growing literature investigating the role of extreme heat on mortality has conceptualized the role of ambient ozone in various ways, sometimes treating it as a confounder, sometimes as an effect modifier, and sometimes as a co-exposure. Thus, there is a lack of consensus about the roles that temperature and ozone together play in causing mortality. Objectives: We applied directed acyclic graphs (DAGs) to the topic of heat-related mortality to graphically represent the subject matter behind the research questions and to provide insight on the analytical options available. Discussion: On the basis of the subject matter encoded in the graphs, we assert that the role of ozone in studies of temperature and mortality is a causal intermediate that is affected by temperature and that can also affect mortality, rather than a confounder. Conclusions: We discuss possible questions of interest implied by this causal structure and propose areas of future work to further clarify the role of air pollutants in epidemiologic studies of extreme temperature.