Association of ambient ozone with pneumonia hospital admissions in Hong Kong and Taipei: A tale of two Southeast Asian cities

Ozone (O-3) is a reactive oxidant exerting both inflammatory and oxidative damages to the respiratory system. With the ground-level O-3 progressively increasing in the past decade, the reevaluation of the pneumonia hospitalization risk from exposure to O-3 is of public health interest. We conducted an ecological time-series study to examine the city-specific association between short-term O-3 exposure and pneumonia hospitalizations in Hong Kong and Taipei, respectively. We linked the daily pneumonia hospitalization count to air pollution concentrations and weather conditions according to the date of admission during 2010-2017. We applied a generalized additive distributed lag model to examine the association while adjusting for time-varying covariates. Stratified analysis by age group and the potential harvesting effect of O-3 were evaluated. We observed the harvesting effects of O-3 on pneumonia hospitalizations in children in both cities and adults in Taipei. The short-term effect of O-3 lasted for around one week. An interquartile range (IQR) increment of daytime 8-hour mean concentration of O-3 distributed over 0-6 lag days in Hong Kong (42.4 mu g/m(3)) was associated with a 7.04% (95% CI: 5.35-8.76%) increase in hospital admissions for elderly pneumonia, while the corresponding cumulative excess risk per IQR increment of O-3 in Taipei (38.7 mu g/m(3)) was 3.41% (95% CI: 1.63-5.22%). Different O-3 metrics, varying degrees of freedom for filtering the temporal trend, and three-pollutant models supported the robustness of the associations. We concluded that short-term O-3 exposure was associated with pneumonia hospitalizations in the elderly population. Understanding the pneumonia hospitalization risk of O-3 will help to inform public health policies in the planning of ozone control strategies and intervention measures to prevent ozone-related pneumonia in vulnerable elderly populations.

Automated summary

The study reveals that short-term O-3 exposure is associated with pneumonia hospitalizations, with harvesting effects observed in different age groups and cities. An increase in the daytime 8-hour mean O-3 concentration by an interquartile range over 0-6 lag days in Hong Kong is linked to a 7.04% increase in elderly pneumonia hospital admissions, while the corresponding increase in Taipei is 3.41%.