Concentration-response of short-term ozone exposure and hospital admissions for asthma in Texas. (July 2017)

• Record Type: Journal Article
• Authors: Zu, Ke; Liu, Xiaobin; Shi, Liuhua; Tao, Ge; Loftus, Christine T.; Lange, Sabine; Goodman, Julie E.
• Is Part Of: Environment international. Volume 104(2017)
• Page Start: 139
• Page End: 145
• Publication Date: 2017-07
• Subjects: CI confidence interval -- C-R concentration-response -- DV design value -- ED emergency department -- edf effective degrees of freedom -- ELF extracellular lining fluid -- HA hospital admission -- ICD-9 International Classification of Disease, 9th Revision -- IRB Institutional Review Board -- NAAQS National Ambient Air Quality Standard -- NO2 nitrogen dioxide -- PM2.5 fine particulate matter -- ppb parts per billion -- RR relative risk -- SD standard deviation -- SO2 sulfur dioxide -- TCEQ Texas Commission on Environmental Quality -- TDSHS Texas Department of State Health Services -- US United States -- US EPA United States Environmental Protection Agency; Ozone -- Air pollution -- Asthma -- Hospital admissions -- Epidemiology -- Concentration-response -- Exposure science; Environmental protection -- Periodicals; Environmental health -- Periodicals; Environmental monitoring -- Periodicals; Environmental Monitoring -- Periodicals; Environnement -- Protection -- Périodiques; Hygiène du milieu -- Périodiques; Environnement -- Surveillance -- Périodiques; Environmental health; Environmental monitoring; Environmental protection; Periodicals; 333.705
• DOI: 10.1016/j.envint.2017.04.006
• Languages: English
• ISSNs: 0160-4120

Abstract

Abstract: Background: Short-term exposure to ozone has been associated with asthma hospital admissions (HA) and emergency department (ED) visits, but the shape of the concentration-response (C-R) curve is unclear. Methods: We conducted a time series analysis of asthma HAs and ambient ozone concentrations in six metropolitan areas in Texas from 2001 to 2013. Using generalized linear regression models, we estimated the effect of daily 8-hour maximum ozone concentrations on asthma HAs for all ages combined, and for those aged 5–14, 15–64, and 65 + years. We fit penalized regression splines to evaluate the shape of the C-R curves. Results: Using a log-linear model, estimated risk per 10 ppb increase in average daily 8-hour maximum ozone concentrations was highest for children (relative risk [RR] = 1.047, 95% confidence interval [CI]: 1.025–1.069), lower for younger adults (RR = 1.018, 95% CI: 1.005–1.032), and null for older adults (RR = 1.002, 95% CI: 0.981–1.023). However, penalized spline models demonstrated significant nonlinear C-R relationships for all ages combined, children, and younger adults, indicating the existence of thresholds. We did not observe an increased risk of asthma HAs until average daily 8-hour maximum ozone concentrations exceeded approximately 40 ppb. Conclusion: Ozone and asthma HAs are significantly associated with each other; susceptibility to ozone is age-dependent, with children at highest risk. C-R relationships between average daily 8-hour maximum ozone concentrations and asthma HAs are significantly curvilinear for all ages combined, children, and younger adults. These nonlinear relationships, as well as the lack of relationship between average daily 8-hour maximum and peak ozone concentrations, have important implications for assessing risks to human health in regulatory settings. Highlights: Ambient ozone levels are positively associated with total asthma hospitalizations in Texas. The associations between ozone and asthma hospitalization are strongest in school-aged children. The concentration-response relationships are nonlinear, suggestive of a threshold. The results have important implications for assessing human health risks in regulatory settings.