| Objectives:1.To understand the impact of air pollution controlling policies on air quality by analyzing daily average concentration of air pollutants in Lanzhou from 2004to 2017.2.To explore the changes of non-accidental mortality risks associated with air pollutants during the two periods by using the death data of residents before（2004-2009）and after（2014-2017）the implement of air pollution controlling policies.3.To evaluate the changes of air pollutants attributable mortality and life expectancy loss quantitatively during the two periods.4.To explore the impact of air pollution controlling policies on air quality and related health benefit in Lanzhou through the above analysis.Methods:1.The data of daily average concentration of air pollutants from 2004 to2017,the daily meteorological data,and the daily death data in Lanzhou during the study phases（2004-2009,2014-2017）were collected;2.Spearman Order Correlation methods were employed to analyze the interannual trends of air pollutants and air quality composite index;3.The generalized additive models were utilized to explore the short-term effects on daily mortality of air pollutants;4.Mortality burden indicators,including attributable mortality and attributable fraction,were evaluated with Poisson Regression Proportional Risk Model;5.To obtain the life expectancy and life expectancy of death removal,the abridged life table and cause eliminated life table were established with Excel 2016,and then life expectancy loss was calculated.Results:1.The annual average concentrations of sulfur dioxide（SO2）and respirable particulate matter(PM10)showed a decreasing trend in the whole period from2004 to 2017 in Lanzhou.While the nitrogen dioxide（NO2）remained stable over time.The average concentrations of SO2,NO2 and PM10 were 61.58,45.47,154.97μg/m3respectively in Lanzhou before the air pollution control（2004-2011）,as well as 24.03,50.59,130.01μg/m3 after treatment（2012-2017）.The average concentrations of SO2and PM10 dropped by 60.98%and 16.11%,while the NO2 increased by 11.26%,and all of the differences were significant（P<0.05）.2.Compared with the period of 2004-2009,the annual average concentrations of SO2 and PM10 dropped,while NO2 increased in the period of 2014-2017 in Lanzhou.By fitting generalized additive model,the effects of air pollutants on daily non-accidental deaths were evaluated and the results were as follows:（1）Each 10-μg/m3increase of SO2 was associated with an increment of 0.55%（95%CI:0.22,0.87）in2004-2009 and 2.09%（95%CI:0.85,3.34）in 2014-2017.Although the concentration of SO2 decreased significantly,the mortality risks did not improve accordingly.（2）Each10-μg/m3 increase of PM10 was associated with a death-increment of 0.12%（95%CI:0.01,0.22）in 2004-2009,but there was no significant association between PM10 and daily non-accidental deaths in the period 2014-2017.The implement of air pollution controlling strategies has successfully reduced PM10 pollution and the mortality risks due to PM10 in Lanzhou.（3）Each 10-μg/m3 increase of NO2 was associated with an increment of 0.92%（95%CI:0.46,1.38）in 2004-2009 and 0.85%（95%CI:0.18,1.51）in 2014-2017.Our findings might suggest non-distinctive change of NO2 on non-accidental death from 2004-2009 to 2014-2017,even if there was a rise trend for NO2level.3.Regarding the World Health Organization’s Air Quality Guidelines as the reference concentration,the mortality burdens of air pollutants before and after the air pollution control were as follows:（1）The proportion of deaths attributable to atmospheric SO2 in total mortality in Lanzhou was 2.23%in 2004-2009,and 0.85%in2014-2017.Although there was no significant change in the mortality risk of SO2 after the implement of air pollution controlling strategies,the estimated SO2 attributable fraction decreased,which indicated that the proportion of deaths due to SO2 decreased.（2）The attributable fraction of PM10 was 1.51%in 2004-2009 in Lanzhou.The data of attributable deaths was not calculated in 2014-2017 since no significant associations were found between non-accidental total deaths and PM10.（3）The attributable fraction of NO2 was 0.62%in 2004-2009,and 1.15%in 2014-2017.Although there was no significant change in the mortality risk of NO2 over two periods,the NO2 attributable fraction increased which meant the proportion of deaths due to NO2 pollution increased.4.After the causes of deaths on SO2,NO2 and PM10 removed,the life expectancy of residents in main urban areas of Lanzhou increased to varying degrees,and the overall life expectancy increased most after removing the cause of SO2 death from 2004to 2009.The life expectancy loss attributable to SO2 was higher in 2004-2009 than2014-2017（0.26>0.10 years）;the loss of life expectancy caused by atmospheric NO2pollution was slightly lower in 2004-2009 than 2014–2017（0.07<0.12 years）;and the PM10 pollution in 2004–2009 resulted in a loss of life expectancy of 0.17 years.Conclusions:1.The pollution situation of SO2 and PM10 improved obviously after the implement of air pollution controlling policies,while the pollution of NO2 increased.2.After the implement of air pollution controlling policies,the mortality risk of PM10was greatly reduced,while the changes of risks due to NO2 or SO2 were not significant.3.Air pollution control in Lanzhou city has reduced the mortality burden and life loss caused by air pollutants SO2 and PM10,while the mortality burden and life loss caused by NO2 increased,which is still an urgent environmental problem to be solved in recent years. |
