Effect Modifications Of Greenness On The Risk Of Lung Cancer Mortality Associated With Air Pollution In A Small Area

BackgroundWith the dual pressures of lung cancer as the leading cancer in China and the serious health risk caused by air pollution,studies exploring the impacts of long-term exposure to air pollutants on lung cancer mortality,especially evaluating the potential mitigating effects of greenness on this impact,are relatively scarce,especially in China.ObjectivesTo explore the separate associations of long-term exposure to air pollutants or greenness with lung cancer mortality in a small geographic area,and then to examine the potential effect modifications of greenness on lung cancer mortality risk associated with air pollutants.MethodsIn this study,we collected lung cancer incidence and death cases,air pollutants data,vegetation indices,and baseline information:demographic information,permanent address codes,population density,spatial GDP,road density,and walking index from 2014 to 2019 in Pingyi County,Shandong Province.We applied two-level Cox proportional risk regression models to calculate risk ratio(HR)and adjusted risk ratio for long-term exposure to air pollutants(PM2.5,PM10,NO2,CO,SO2,O3)or greenness(NDVI,EVI,and SAVI)and lung cancer mortality,respectively.Further,we used a stratified approach to assess the modifying effects of greenness(NDVI)on lung cancer mortality related with air pollutants,with Q-tests to identify statistically significant.Results(1)From 2014 to 2019,a total of 4465 cases of lung cancer were reported in Pingyi,including 2967 deaths from lung cancer.The 6-year mean exposure measures P50(P25,P75)of PM2.5,PM10,NO2,O3,SO2 and CO were 68.95μg/m3(67.45μg/m3,70.43μg/m3),112.30μg/m3(111.52μg/m3,113.66μg/m3),38.67pg/m3(36.78μg/m3,39.27μg/m3),108.73μg/m3(107.89μg/m3,110.07μg/m3),35.86μg/m3(35.13μg/m3,36.37μg/m3)and 1.10 mg/m3(1.06 mg/m3,1.13 mg/m3),respectively.There were significant positive correlations among the air pollutants except for no correlation between O3 and PM10;and significant negative correlations between O3 and the other five air pollutants.During the same period,the mean exposure measures P20(P25,P75)of NDVI,EVI and SAVI were 0.44(0.33,0.51),0.48(0.35,0.57),and 0.33(0.24,0.38),respectively,and there were significant positive correlations among the three indexes.(2)The results of the two-level Cox proportional risk regression model showed that air pollutants or greenness exposures were associated with the mortality risk from lung cancer.Among the three outcomes of all-cause mortality,tumor mortality and lung cancer mortality from the lung cancer patients,PM2.5,PM 10,NO2.SO2,and CO all contributed to the hazard effect,and NO2 had the strongest effect.In the fully adjusted model for lung cancer mortality,the HR(95 Cl%)corresponding to PM2.5,PM10,NO2,SO2,and CO were 1.344(95%Cl:1.295 to 1.395),1.304(95%Cl:1.263 to 1.346),2.078(95%CI:1.756 to 2.460),2.078(95%CI:1.756 to 2.460),1.229(95%Cl:1.199 to 1.26),and 1.023(95%CI:1.019 to 1.026),respectively.However,greenness were protective effects on all three mortality outcomes for lung cancer.After grouping NDVI,EVI,and SAVI in three quartiles(Tertilel,Tertile2,and Tertile3),respectively,fully adjusted models indicated that NDVI,EVI,and SAVI present the strongest protective effects on the lung cancer mortality at the Tertile3 level,corresponding to HR(95%CI)of 0.832(95%Cl.0.755 to 0.917),0.754(95%CI:0.686 to 0.830)and 0.820(95%Cl:0.742 to 0.907),respectively.(3)By grouping NDVI in three quartiles,we further examined the differences in the effects of air pollutants on the risks from lung cancer mortality at different NDVI levels.In the all-cause and tumor mortality from the lung cancer patients,we observed a significant difference in the HR related to NO2 in NDVI-T2 versus NDVI-T3(P<0.0167).In the outcome of lung cancer mortality,HR associated with both NO2 and CO were significantly different in NDVI-T2 versus NDVI-T3,with NO2-related HR of 2.931(95%CI:2.265 to 3.793)and 1.302(95%CI:0.923 to 1.834)in NDVI-T2 versus NDVI-T3,respectively;COrelated HR were 1.027(95%CI:1.021-1.032)and 1.016(95%CI:1.009-1.022)in NDVI-T2 versus NDVI-T3,respectively.Conclusions(1)PM2.5,PM10,NO2,SO2 and CO long-term exposure are all risk factors for lung cancer mortality,and greenness is a protective factor for lung cancer mortality.(2)Greenness significantly alliviated the risk of NO2-related all-cause mortality,tumor mortality,and lung cancer mortality from the lung cancer patients,as well as its could also mitigate the risk of CO-related mortality from lung cancer.