[Modification effects of ozone on the relationship between PM10 and daily mortality in three cities, China]

To estimate the modification effects of ozone on the relationship between PM10 and daily mortality.

Daily total non-accidental, cardiovascular and respiratory motality data in Beijing, Shanghai and Suzhou from 2001 to 2008 were collected from the Center for Disease Control and Prevention of each city. The concentration of PM10 and ozone and other Meteorology data during the study period were abtained from the national air quality monitoring network. A generalized additive model (GAM) were used to estimate the acute effects of air pollution on daily mortality in the three cities. The time-series method were applied to analyze the association between air pollution and daily mortality. In order to analyze the interaction effect between PM10 and ozone, ozone were stratified into three levels (≤5% . as low from 5% - 95% . as moderate, >95%, as high) and then analyzed the effect of PM10. A Meta analysis was used to describe the effect of PM10 in all the cities.

With the increment of ozone, PM10 corresponded to an increase of total, cardiovascular and respiratory mortality in Beijing, Shanghai and Suzhou. The result of the Meta analyses showed that on the days of "low" ozone, a 10 µg/m3 increment in PM10 corresponded to a 0.47% (95% CI - 0. 74%, 1. 67%) decrease in total mortality, 0. 36% (95% CI - 0. 59%, 1. 31%) decrease in cardiovascular mortality, and 0. 69% (95% CI - 0. 52%, 1. 90%) decrease in respiratory mortality. When it was moderate, the increment was 0.45% (95% CI 0. 26%, 0. 63%), 0. 16% (95% CI - 2. 26%, 1. 95%) and 0. 57% (95% CI 0. 13%, 1. 02%). The increment was 0. 82% (95% CI 0. 24% , 1. 39%), 0. 37% (95% CI 0. 07%, 0. 66% ) and 1. 13% (95% CI - 0. 67% , 2. 92%) while the.zone was high.

Ozone could modify the effect of PM10 on the daily mortality.