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 (O3) and mortality. In China, the largest developing country, there have been few studies investigating the acute effect of O3 on death. We used three exposure metrics of O3 (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, O3, and covariate data. We examined the association by season, age group, sex and educational level. We found that the current level of O3 in Suzhou is associated with death rates from all causes and cardiovascular diseases. Among various metrics of O3, 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 O3 (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 O3 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 O3 are associated with daily mortality in Suzhou. Our analyses strengthen the rationale for further limiting levels of O3 pollution in the city.

► Controversy remains regarding various metrics of O3 and health hazards.
► Maximum 8-hr average and 1-hr maximum were better health predictors of O3.
► The health impact of O3 was more evident in the cool season in Suzhou.