| Objective:The number of the studies on the adverse effects of air pollution on human health has increased rapidly.Among them many have indicated that short-term exposure to particulate matter(including PM2.5.5 and PM10),ozone?O3?,carbon monoxide?CO?,nitrogen dioxide?NO2?,and sulfur dioxide?SO2?will increase the population mortality.However,some other studies failed to find any associations between air pollution and population mortality.Some studies reported that these differences across studies were mainly due to spatial differences,including differences in ambient temperature,pollutant concentrations,and socio-economic factors.There are also some evidences suggesting extreme temperature,seasons,age and gender may be the reasons of the divergences.Therefore,in order to sort out the factors of exposure-response between air pollution and population mortality as well as to provide evidences for policy making,it is necessary to study the influences of the variables mentioned above.In addition,China's current limits of some kind of air pollutants are not as strict as those of developed countries,so exploring the limits that can both avoid health risks and be available to carry out is an urgent task.Meanwhile,exploring the effect thresholds of exposure-response relationship of air pollution and its influencing factors can provide theoretical basis for the development of environmental standards,which is of great significance.The City of Shenyang is Regional Centre of Northeastern China as well as the capital of the Liaoning Province.It is a metropolitan city with both characters of heavy pollution and cold.However,few studies on the relationship between air pollution and population mortality have been performed in such cities.We perform a retrospective analysis with a time series analysis approach to explore the short-term air pollution(including PM2.5,PM10,O3,CO,NO2 and SO2)exposure and circulatory diseases deaths in Shenyang during 2014 to 2017.The purpose of this study is:?1?to explore the association between the daily deaths of circulatory diseases and the short-term air pollution(PM2.5,PM10,SO2,NO2,CO and O3)exposure in cold areas like Shenyang,and screen the disease groups that are more sensitive to air pollution;?2?to analyze the interaction between season as well as extreme temperature and short-term air pollution exposure,and to determine whether they are the influencing factors of thses exposure-response relationships;?3?to explore the exposure-response relationship between air pollution and circulatory diseases?including cardiovascular disease and cerebrovascular disease?deaths in Shenyang,and to discriminate their influencing factors;?4?to explore the effect thresholds and the specific impacts of the factors on the exposure-response relationships.Methods:We selected Shenyang as the location.With a population of more than7.3 million,Shenyang is an important heavy industrial city in China.It has been listed as one of the World Bank's“world's top ten polluted cities”.The average concentration of PM2.5 and PM10 is 61.86?g/m3 and 103.56?g/m3 respectively.The data after 2014 is selected for analysis,and the research period is 2014-2017.From the Shenyang Environmental Protection Bureau and the Ministry of Environmental Protection,daily average concentration of PM2.5,PM10,O3,CO,NO2 and SO2 were obtained.1455 days'data were retrieved?data missing in 2015/4/4-2015/4/9?;meteorological data including daily average temperature,humidity of Shenyang City?site number 543420?were downloaded through R statistic from the NOAA website;Through Shenyang Centers of Disease Control and Prevention,we collected daily deaths data for circulatory diseases?ICD-10:I0-I99?during the study period,including cardiovascular disease?ICD-10 code:I0-I59.9?,including coronary heart disease?ICD-10?Coding:I20-J25.9),arteriosclerotic heart disease?ICD-10 code:I25.1?,acute myocardial infarction?ICD-10 code:I21.0-I21.9?,cerebrovascular disease?ICD-10 Code:I60-I69.9?.The generalized additive model?GAM?,which controlled for temperature,humidity and time variables,was used to explore the correlation between atmospheric pollutants and the daily deaths of the circulatory diseases.To avoid collinearity and co-curvature,this study used a single pollutant model and identified the pollutant and daily deaths as linear relationships with reference to most existing studies.ERR10 is used as a risk indicator,namely the excess risk caused by each increment of 10concentration units of pollutants.Both the single day and cumulative hysteresis effects were analyzed using distributed nonlinear lag model?DLNM?.DLNM can construct a two-dimensional cross-basis function consisting of an exposure-response function and lag-response function,which enables us to predict the relationship between the exposure and the risk within a specific lag time period and their potential effect thresholds.Considering some scholars have suggested the relationships between air pollution and deaths as nonlinear,the exposure-response function of DLNM was defined as a natural spline function with a degree of freedom of 3 in these analyses in order to enhance the flexibility of the model.If the spline function?ie,the exposure response curve?tends is relatively straight,the exposure-response relationship can be considered as linear;If the spline function is obviously not linear,the exposure-response relationship is more likely to be nonlinear.First we explored the associations between air pollution and various kind of circulatory diseases deaths.Then we analyze the influences of extreme temperatures and seasons on these associations,in which Z-tests were used to detect the potential interactions.For the effects of potential factors on the exposure-response relationship,this study analyzed and compared the exposure-response curves of different population,seasons,lag days,age groups and genders.In order to further explore the influences of the various factors on the exposure-response relationship,this study analyzed the exposure-response curves of different circulatory diseases deaths under different seasons,lag days,by different ages and genders,respectively.Effect threshold were also explored.All statistics were two-sided,with P<0.05 as statistically significant.Results:During 2014-2017,daily deaths of all types of circulatory diseases in Shenyang showed an increasing trend year by year.Except for O3,the concentration of 5 other air pollutants except decreased year by year;there was no obvious trend of meteorological factors during the years.The six types of pollutants were significantly correlated with each other,among which PM2.5,PM10,NO2,SO2 and CO were positively correlated with each other,and O3 was negatively correlated with the other5 kind of pollutants.O3 is the most suspicious risk factor for most circulatory deaths.For most pollutants,women are more sensitive than men.In cerebrovascular diseases,the lethal effect of O3 is more pronounced than in other circulatory diseases and men are more susceptible than women.Only female ASHD has a positive correlation with PM2.5,SO2 and PM10.Different seasons and temperatures interact with exposure-response relationships.For seasonal analyses,the interactions were similar in death of 3 types of diseases.The common point is that most lethal effects of the pollutants were weakned in summer and winter but the lethal effects of O3 were enhanced in winter,and there were obvious gender differences.Significant seasonal differences were found in the strengths of the associations between O3 and deaths,and the ERRs were usually larger in winter,suggesting that the effects of O3 are affected by the seasons.In addition,in the seasonal analysis the fatal effects of PM2.5,PM10,SO2 decreased in summer and winter,suggesting that the fatal effects of these pollutants may also be affected by different seasons.The analysis of interactions of extreme temperature indicated that the cold days may strengthen but the hot days may weaken the lethal effect of air pollution,and the most affected pollutant was the O3.The most susceptible population to extreme temperature is the female cerebrovascular population.Generally the cumulative RR of O3 and CO maintained an increasing trend.Except for O3,the exposure-response relationship between most pollutants and deaths has no obvious linear trend.Some curves also have obvious effect thresholds,some of which were lower than the current ambient air quality standards.Lag period,season and age can significantly affect the trend of exposure-response curve:the heterogeneity of exposure response in different seasons is large,and most of the pollutants in winter have no effect threshold,suggesting that in winter the population circulatory diseases were more sensitive to concentration pollutants.The increasing trend of cumulative risk of deaths is more obvious during the shorter lag period,and the response curve slows down or even decreases with the increase of the lag time.Compared with the lower age group and higher age groups,the middle age group deaths were more sensitive to short-term exposure to pollutants.Conclusions:?1?There are significant positive associations between short-term air pollution exposure and cardiovascular,cerebrovascular and total circulatory deaths in Shenyang,and women are generally more vulnerable to air pollution;?2?We found interactions between extreme temperature/season and the exposure-response relationship of air pollution and deaths,and the interaction effects also have obvious gender differences.Winter and cold may strengthen O3's effects on men circulatory deaths,while summer or hot days may weaken their effects;?3?Not all The exposure-response relationship between short-term exposure to air pollution and circulatory disease deaths tended to be linear,and some pollutants have effect thresholds;seasons,lag time,age and gender are the factors than can affect the exposure-response relationship. |
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