Alternative ozone metrics and daily mortality in Suzhou: The China Air Pollution and Health Effects Study (CAPES)

Controversy remains regarding the relationship between various metrics of ozone (O-3) and mortality. In China, the largest developing country, there have been few studies investigating the acute effect of O-3 on death. We used three exposure metrics of O-3 (1-hour maximum, maximum 8-hour average and 24-hour average) to examine its short-term association with daily mortality in Suzhou, China. We used a Generalized Additive Model (GAM) with penalized splines to analyze the mortality, O-3, and covariate data. We examined the association by season, age group, sex and educational level. We found that the current level of O-3 in Suzhou is associated with death rates from all causes and cardiovascular diseases. Among various metrics of O-3, maximum 8-hour average and 1-hour maximum concentrations seem to be more strongly associated with increased mortality rate compared to 24-hour average concentrations. Using maximum 8-hour average, an inter-quartile range increase of 2-day average O-3 (lag 01) corresponds to 2.15% (95%CI, 0.36 to 3.93), 4.47% (95%CI, 1.43 to 7.51), -1.85% (95%CI, -6.91 to 3.22) increase in all-cause, cardiovascular, and respiratory mortality, respectively. The associations between O-3 and daily mortality appeared to be more evident in the cool season than in the warm season. In conclusion, maximum 8-hour average and 1-hour maximum concentrations of O-3 are associated with daily mortality in Suzhou. Our analyses strengthen the rationale for further limiting levels of O-3 pollution in the city. (C) 2012 Elsevier B.V. All rights reserved.