中国3城市大气NO2短期暴露对医院每日门诊人次的影响

Impact of short-term exposure to ambient nitrogen dioxide on daily outpatient visits in 3 cities of China

【目的】探讨我国大气二氧化氮(NO2)短期暴露对医院门诊人次的影响。【方法】在北京、上海、广州3座一线城市,收集所选5家医院的每日门诊量数据,研究时间为2013—2015年,病因诊断与分类参照《国际疾病分类标准》第10版进行编码(A00-R99)。匹配距离各个医院最近的环境空气质量国控点监测站的每日平均空气污染数据,采用每日城市平均气象因素(温度、湿度)。利用时间序列分析方法的广义相加模型(GAM),调整时间趋势、星期几效应、节假日效应、气象因素后,研究大气NO2暴露对医院每日门诊人次的影响;采用随机效应模型进行meta分析;分析污染物的滞后效应、双污染物混杂以及潜在的季节效应。【结果】每日平均门诊数3949人次,5家医院的每日空气平均NO2暴露水平为55.3μg/m^3。滞后分析结果显示当天NO2暴露对每日门诊的影响最大,NO2浓度每上升10μg/m^3,每日门诊人次升高0.85%(95%CI:0.51%~1.19%)。在控制细颗粒物、臭氧、二氧化硫和一氧化碳之后,NO2对门诊人次的影响保持稳健。NO2的效应在冷季高于暖季,其暴露-反应曲线呈近似线性。【结论】我国主要城市NO2短期暴露可显著增加医院每日门诊的就诊风险,提示应采取有效措施进一步降低NO2空气污染水平。

[Objective]To explore associations between short-term exposure to ambient nitrogen dioxide(NO2)and hospital outpatient visits.[Methods]Daily outpatient visit data were obtained from 5 hospitals in Beijing,Shanghai,and Guangzhou,the three major cities in China.The study period was from 2013 to 2015.The causes of disease were determined in accordance to the International Classification of Disease 10th version,with the codes A00-R99.Daily air pollution data were from the nearest state-controlled environmental monitoring stations.City-level environmental factors were acquired,including temperature and relative humidity.A time-series generalized additive model(GAM)was adopted to explore the effect of daily NO2 exposure on hospital outpatient visits,after controlling the time trends,day of week(DOW),holiday,and environmental factors.Then a random-effect meta-analysis was used to pool the results across cities.We also explored the lag structure,two-pollutant models,and potential seasonal effect.[Results]During the study period,the average daily outpatient visits were 3949.The average NO2 exposure level was 55.3μg/m^3.The lag analysis showed that NO2 exposure had the greatest effect on outpatient visits every day.For a 10μg/m^3 increase in NO2,outpatient visits remarkably increased by 0.85%(95%CI:0.51%-1.19%).The associations of NO2 remained robust after controlling co-pollutants,including fine particulate matter,ozone,sulfur dioxide and carbon monoxide.The effects of NO2 were more in cool seasons,and the exposure-response curves between NO2 and outpatient visits were nearly linear.[Conclusion]Short-term exposure to NO2 increases the risk of hospital outpatient visits in major cities,suggesting a need to further lower exposure levels of NO2 in China.