The authors conducted a time-series analysis to examine seasonal variation of mortality risk in association with particulate matter less than 2.5 μm in aerodynamic diameter (PM(2.5)) and chemical species in Xi'an, China, using daily air pollution and all-cause and cause-specific mortality data (2004-2008). Poisson regression incorporating natural splines was used to estimate mortality risks of PM(2.5) and its chemical components, adjusting for day of the week, time trend, and meteorologic effects. Increases of 2.29% (95% confidence interval: 0.83, 3.76) for all-cause mortality and 3.08% (95% confidence interval: 0.94, 5.26) for cardiovascular mortality were associated with an interquartile range increase of 103.0 μg/m(3) in lagged 1-2 day PM(2.5) exposure. Stronger effects were observed for the elderly (≥65 years), males, and cardiovascular diseases groups. Secondary components (sulfate and ammonium), combustion species (elemental carbon, sulfur, chlorine), and transition metals (chromium, lead, nickel, and zinc) appeared most responsible for increased risk, particularly in the cold months. The authors concluded that differential association patterns observed across species and seasons indicated that PM(2.5)-related effects might not be sufficiently explained by PM(2.5) mass alone. Future research is needed to examine spatial and temporal varying factors that might play important roles in modifying the PM(2.5)-mortality association.

Objective To study associations between daily mortality and exposure to air pollution.Methods A time-series analysis was conducted to assess the acute mortality effects of respirable particulate matter(PM10),nitrogen dioxide(NO2)and sulfur dioxide(SO2) in urban Xi'an residents,using Poisson regression.Temperature,relative humidity,age,gender and day of week were controlled in the models.Results Per 10 μg/m3 increases in 2-day average concentrations of air pollution,significant increases were observed in all-cause mortality of 0.35%(95%CI: 0.11%-0.58%) for PM10,2.42%(95%CI: 1.57%-3.27%) for NO2,and 0.60%(95%CI: 0.16%-1.05%) for SO2.Stronger effects of air pollution were observed on cardio-respiratory mortality.Seasonal variations in pollution associated mortality effects were found between centralized heating(November 15 to March 15) and non-heating(March 16 to November 14) periods.Conclusion Exposure to ambient pollution was significantly associated with the increases in excess risk of total and cardio-respiratory mortality in Xi'an residents.

[Objective]To compare the causes of death in residents living in different areas in Xi'an.[Methods]Standard mortality rate(SMR),sequence of cause of death,average years of life lost(AYLL)and life lost rate were used to analyze causes of death in urban,fringe and rural areas in Xi'an from 2007 to 2008.[Results]SMR of the residents living in fringe area from 2007 to 2008 was 569.87/105,which was higher than the SMR in urban and rural areas;the comparison result of SMRs of malignant tumor showed significant difference(fringe area﹥urban area﹥rural area),the comparison result of SMRs of lung cancer also showed significant difference(fringe area﹥urban area﹥rural area);SMRs of traffic accidents,poisoning,suffocation,crash to death and electric shock etc.in fringe area were significant higher than those in urban and rural areas,while the SMRs of falling,drowning and suicide in rural area were significant higher than those in urban and fringe areas.Accidental death took a lead in fringe and rural areas with the life lost rate of 17.69% and 9.97% respectively.[Conclusion]In order to reduce mortality rate of the residents in Xi'an,it is necessary to strengthen the administration of both natural and social environment.