The Effects Of Particulate Matter On Mortality And Clinicopathological Features Of Esophageal Cancer

BackgroundThe International Agency for Research on Cancer(IARC)Working Group classified outdoor air pollution and particulate matter in outdoor air pollution as carcinogenic to humans(Group 1).Some indexes were defined to indicate the level of outdoor air pollution,of which the NO2,SO2,PM10 are widely used in China.PM10 refers to the particulate matter with aerodynamic diameters of less than 10μm.It can remain suspended in the atmosphere and is a mixture of extremely small particles and liquid droplets adsorbed organic chemicals,acids and metals that vary in size,composition,and origin.The long-term effects of air pollution on lung cancer have been consistently documented worldwide.However,the effects of air pollution,especially PM10 on other cancers appear to be less clear.Esophageal cancer is one of the most commonly diagnosed cancers in China.Interestingly,there exist striking geographical variations in the incidence and mortality rates of esophageal cancer,which implies that environmental factors might play a major role in cancer development.However,the effects of air pollution on esophageal cancer appear to be less clear.What is more,to our knowledge,no prior studies ever exist estimating the association between PM10 and mortality as well as clinicopathological features of esophageal cancer.Because of the high prevalence of both esophageal cancer and air pollution in China,it is necessary to understand whether air pollution has adverse effects on esophageal cancer.ObjectiveThe objective of the study was to estimate the association of air pollution,including PM10,SO2 and NO2 on the mortality rates of esophageal cancer in Shandong Provence,China,and the effect of PM10 on the clinicopathological features of esophageal squamous cell carcinoma of the patients in Qilu Hospital,Shandong,China.MethodsEcologic analyses were made to examine the associations between air pollution and esophageal cancer mortality.The city-level mean concentrations of PM10,SO2,NO2 were plotted against the age-standardized mortality rates of esophageal cancer in 2015,respectively.Scatter plots were made and correlation analyses were then processed.Multiple linear regression analyses of esophageal cancer mortality rates were run with the combination of mean concentrations of PM10,SO2,NO2 and city-level smoking rates.Smoking was taken into consideration because it was a risk factor that increased esophageal cancer mortality.To further estimate the effect of atmospheric PM10 on clinicopathological features of ESCC,we compared detailed medical information between different pollution level groups.1,255 eligible patients were divided into two groups.We introduced the most relevant confounder,cigarette-smoking status,as an adjustment to minimize the bias.Clinicopathological features of both groups,including demographics(gender,age at diagnosis),clinical and pathological characteristics(tumor location,primary tumor invasion,regional lymph nodes metastasis,histological grade,stage,lymph-vascular invasion and tumor size)were compared.ResultsIn the ecologic cross-sectional study,correlation analysis section,PM10(p=0.046)and NO2(p=0.03)both had significant linear correlations with esophageal cancer mortality rates.After introducing smoking as a risk factor in models of multiple linear regression analysis,PM10 was still an independent risk factor that increased esophageal cancer mortality rates.This study further compared clinicopathological features of 1,255 eligible esophageal squamous cell carcinoma patients by dividing them into different pollution level groups.There was statistically significant difference in gender distributions(p=0.02)between groups after subgroup analysis.There were more female patients in the high PM10 level group than the low PM10 level group.It suggested that females were more sensitive to higher PM10 level pollution.The features that manifested the degree of malignancy of esophageal cancer,including primary tumor(T stage),regional lymph nodes(N stage),histological grade,stage,lymph-vascular invasion and tumor size demonstrated no statistically significant difference between groups.ConclusionsOur research showed positive associations between air pollution and esophageal cancer,there also existed some limitations and bias.Air pollution is certainly not the only reason that increases the risk of esophageal cancer among people.It might only contribute slightly when compared with tobacco smoking and other risk factors.However,our study will provide to be an alarm for the government agencies and policy makers that air pollution might be a reason for the ever-increasing cancer burden in China.Controlling air pollution might be a practical way to prevent cancer.