An Analysis On The Association Of PM_2.5,Chemical Constituents And Residential Green Space On Blood Lipids In An Essential Hypertensive Population

Background:A large number of epidemiological investigations have confirmed the health damage caused by PM_2.5（fine particulate matter with aerodynamic diameter≤2.5μm）.Residential green space has been considered to have a beneficial effect on blood lipids,which may be due to its role in reducing the levels of air pollution.However,there are limited studies on the association of exposure to PM_2.5,chemical constituents and residential green space on lipid metabolism disorders among the hypertensive population,particularly in China.In this study,we analyzed the association of exposure to PM_2.5,chemical constituents and residential green space on blood lipids in an essential hypertensive population.Then we investigated the association between exposure to the mixtures(PM_2.5and chemical constituents)and blood lipids.Additionally,we explored whether residential green space could have an effect on blood lipids by reducing the levels of PM_2.5and chemical constituents.In other words,whether PM_2.5and chemical constituents were the mediating factor in the association between exposure to residential green space and blood lipids.In order to deepen the understanding on the association of exposure to PM_2.5,chemical constituents and residential green space on blood lipids.This study would also provide scientific evidences for reducing air pollution and planning residential green space.Objectives:（1）To evaluate the association between exposure to PM_2.5and chemical constituents and blood lipids in an essential hypertensive population,and find the main constituents.（2）To assess the association between exposure to residential green space and blood lipids in an essential hypertensive population,and to explore whether PM_2.5and chemical constituents are the mediating factor in this association.Methods:（1）Study subjects:37,530 participants with essential hypertension were included in the"Cardiovascular Disease Risk Factors Monitoring and Standardized Management of Hypertension"project from May 2010 to December 2011.（2）Exposure assessment:firstly,we derived grid concentrations of PM_2.5and chemical constituents from the V4.CH.02 product developed by the Dalhousie University Atmospheric Composition Analysis Group（DUACAG）,including PM_2.5,black carbon（BC）,nitrate（NO₃^-）,ammonium（NH₄⁺）,sulfate(SO₄^2-),organic matter（OM）,and mineral dust（DUST）.Secondly,monthly mean atmospheric temperature data was derived from the weather dataset at the spatial resolution of 0.1°namely the China Meteorological Forcing Dataset（CMFD）.Finally,the NDVI（Normalized Difference Vegetation Index）,an objective indicator,was used to assess the level of residential green space.（3）Statistical analysis:the generalized additive mixture model（GAMM）was applied to assess the association of single-exposure to PM_2.5,chemical constituents,residential green space on blood lipids.The weighted quantile sum（WQS）model was used to analyze the association between exposure to the mixtures(PM_2.5and chemical constituents)and blood lipids.In addition,the"mediation"package was used to explore whether PM_2.5and chemical constituents were the mediating factor in the association between exposure to residential green space and blood lipids.Finally,subgroup analysis was conducted according to demographic characteristics,daily life behaviors and environmental factors.Results:（1）We found the exposure to PM_2.5and chemical constituents were positively associated with total cholesterol（TC）,triglyceride（TG）,hypercholesterolemia,hypertriglyceridemia,and dyslipidemia.Compared with short-term exposure to PM_2.5and chemical constituents,long-term exposure to which had a stronger effect on blood lipids.For example,the odds ratio（OR）for dyslipidemia was 1.133[95%confidence interval（CI）:1.065,1.205]on long-term exposure to PM_2.5,however,the OR for dyslipidemia was 0.995（95%CI:0.971,1.020）on short-term exposure to PM_2.5.（2）In the results of WQS model showed that long-term exposure to the mixtures(PM_2.5and chemical constituents)was positively associated with TC,TG,hypercholesterolemia,and dyslipidemia,but not associated with hypertriglyceridemia.The estimated weight of the DUST,OM,and NO₃^-had the highest relative contribution among the association.During short-term exposure,no significant association between exposure to the mixtures(PM_2.5and chemical constituents)and blood lipids was observed.（3）The exposure to residential green space was negatively associated with TC,TG,hypercholesterolemia,hypertriglyceridemia,and dyslipidemia.Compared with long-term exposure to residential green space,short-term exposure to which had a stronger effect on blood lipids.For each 0.1 increase in NDVI_long-term,TC decreased by0.440%（95%CI:-0.722,-0.157）.And the OR for hypercholesterolemia and dyslipidemia were 0.921（95%CI:0.884 0.960）and 0.950（95%CI:0.920,0.980）,respectively.Then,for each 0.1 increase in NDVI_short-term,TC and TG decreased by0.917%（95%CI:-1.250,-0.583）and 1.121%（95%CI:-1.854,-0.382）,respectively.And the OR for hypercholesterolemia,hypertriglyceridemia,and dyslipidemia were0.870（95%CI.0.828,0.915）,0.949（95%CI:0.908,0.992）,and 0.915（95%CI:0.880,0.950）,respectively.（4）The exposure to PM_2.5and chemical constituents was negatively associated with NDVI.PM_2.5and chemical constituents were the mediating factor in the association between exposure to residential green space and blood lipids.The mediation analysis clarified that the PM_2.5and chemical constituents could explained-5.02%-26.33%of the association between exposure to residential green space and blood lipids.For example,23.92%of the negative association between with long-term exposure to residential green space and dyslipidemia was related to PM_2.5.Only5.81%of the negative association between short-term exposure to residential green space and dyslipidemia was related to PM_2.5.（5）The results of the subgroup analysis showed that the association of exposure to PM_2.5and chemical constituents with blood lipids was more significant among participants who were female,overweight and obese.The beneficial effect of residential green space on blood lipids was observed in participants living in the North.The association between exposure to residential green space and blood lipids was strengthened by physical activity.Conclusion:（1）The exposure to PM_2.5and chemical constituents may increase the risk of dyslipidemia in this essential hypertensive population,especially in female,overweight and obese individuals.Moreover,DUST,OM,and NO₃^-may be the main constituents affecting blood lipids.（2）The exposure to residential green space may reduce the risk of dyslipidemia in this essential hypertensive population,especially participants living in the North and doing daily physical activity.（3）Residential green space may promote the beneficial effects on blood lipids by reducing the levels of PM_2.5and chemical constituents.