Short-term Effects Of Indoor Air Pollution On Respiratory System Among Undergraduates In Gansu Rural Areas

Objectives 1.To understand the fuel types,heating mode,and indoor and outdoor air pollution of the Gansu rural areas in winter;2.To explore the influencing factors of respiratory health of college students during winter vacation;3.To deeply analyze the effects of short-term exposure to indoor air pollution（IAP）of the Gansu rural areas in winter on respiratory health and related biomarkers of college students.Methods The freshmen of Lanzhou university from Gansu rural areas were recruited from November 2018 to March 2019.The winter vacation was exposure time and the study consisted three phases,including before winter vacation（before exposure）,during winter vacation（during exposure）and after winter vacation（after exposure）.We conducted the questionnaire,physical examination,and sample collection for all subjects on the last day of each phase.Through screening,84 participants finished the completed questionnaire for three times,among which 70 participants completed lung function and urine biomarker data for three times,who were all came from different villages.We obtained not only the basic information,energy use,lifestyle and so on during winter vacation,but also surveyed the respiratory symptoms in three stages through questionnaires.The IAP exposure index was calculated according to the indoor energy use characteristics of heating mode,cooking fuels,and the information like room ventilation frequency and cooking frequency,and so on in the questionnaire.The outdoor air pollution data of before and after winter vacation in Yuzhong Campus of Lanzhou University were obtained from the National Urban Air Quality Real-time release platform,China.And a chemical transport model（WRF-Chem V3.9）was used to simulate the outdoor air pollutant levels of every participant’s study area during winter vacation,including particulate matter with aerodynamic diameter≤10μm(PM₁₀),nitrogen dioxide（NO₂）and sulfur dioxide（SO₂）.The lung function indicators included forced vital capacity（FVC）,forced expiratory volume in the first second（FEV1）,peak expiratory flow（PEF）,and ratio of forced vital capacity in the first second and forced expiratory volume（FEV1/FVC）.The urine biomarkers included leukotriene E4（LTE4）,8-hydroxydeoxyguanosine（8-OHdG）,8-epi-prostaglandin F2 alpha（8-epi-PGF2?）and malondialdehyde（MDA）.Statistical analysis methods were performed using repeated measure variance analysis,linear mixed effect model and so on,comprehensively analyzing the short-term effects of IAP exposure on respiratory health and related biomarker of college students from Gansu rural areas.Results1.The subjects lived in towns/villages where coal was widely used for heating（85.70%）.The main heating fuel was coal and/or biomass（82.10%）,76.20%of the subjects in the living room using coal stove for heating,and 69.00%of the subjects in the bedroom using coal stove and/or Kang for heating.Besides,the subjects with coal and biomass for cooking were 52.40%and 13.10%,respectively.2.Through comparative analysis,we found that IAP exposure index was significantly higher during winter vacation than before and after winter vacation（P<0.05）.However,the concentrations of outdoor air pollutants during winter vacation were lower than before and after winter vacation.Basically,the concentrations of PM₁₀,SO₂ and NO₂ during winter vacation were lower than before and after the winter vacation.3.Logistic regression results showed that IAP exposure（OR=1.396,95%CI:1.073,1.816）and outdoor NO₂（OR=1.125,95%CI:1.027,1.233）were positively correlated with the occurrence of respiratory symptoms.4.Three lung health indexes comparison found the FEV1/FVC was significantly lower during winter vacation than after winter vacation（P<0.05）.However,the LTE4was significantly higher after winter vacation than before/during winter vacation and the 8-epi-PGF2?was significantly higher during winter vacation than before winter vacation（P<0.05）.The difference was not statistically significant for the other indicators in the three stages.5.The correlation analysis results of outdoor air pollutants and health indicators provided that LTE4 was negatively associated with SO₂（r=﹣0.14,P<0.05）.MDA was negatively related with PM₁₀（r=﹣0.20,P<0.05）.8-epi-PGF2?was negatively correlated with NO₂（r=﹣0.18,P<0.05）and SO₂（r=﹣0.19,P<0.05）.6.After controlling the basic information,each 1 unit increase in the IAP exposure index was significantly correlated with a 34.27%decrease in FEV1/FVC.What’s more,each 1 increment in the IAP exposure index was significantly associated with an 86.98%increase in 8-epi-PGF2?,after controlling the basic information and outdoor air pollutants.However,after controlling the basic information and outdoor air pollutants,there was no significant change for the other indicators.Conclusions1.The IAP caused by using coal,biomass and so on in winter of subject’s home may be serious.2.Short-term exposure to IAP and outdoor NO₂ in winter of Gansu rural areas may be risk factors for inducing respiratory symptoms of subjects.3.Short-term exposure to IAP in rural winter may lead to a decrease in lung ventilation function by oxidative stress in subjects,which suggests that the IAP exposure to college students in Gansu rural countryside may affect their respiratory system health.