Mills I C, Atkinson R W, Kang S, Walton H, Anderson H R
Public Health England, Centre for Radiation, Chemical and Environmental Hazards, Oxfordshire, UK.
Population Health Research Institute and MRC-PHE Centre for Environment and Health, St George's, University of London, London, UK.
BMJ Open. 2015 May 11;5(5):e006946. doi: 10.1136/bmjopen-2014-006946.
Short-term exposure to NO₂ has been associated with adverse health effects and there is increasing concern that NO₂ is causally related to health effects, not merely a marker of traffic-generated pollution. No comprehensive meta-analysis of the time-series evidence on NO₂ has been published since 2007.
To quantitatively assess the evidence from epidemiological time-series studies published worldwide to determine whether and to what extent short-term exposure to NO₂ is associated with increased numbers of daily deaths and hospital admissions.
We conducted a quantitative systematic review of 204 time-series studies of NO₂ and daily mortality and hospital admissions for several diagnoses and ages, which were indexed in three bibliographic databases up to May 2011. We calculated random-effects estimates by different geographic regions and globally, and also tested for heterogeneity and small study bias.
Sufficient estimates for meta-analysis were available for 43 cause-specific and age-specific combinations of mortality or hospital admissions (25 for 24 h NO₂ and 18 of the same combinations for 1 h measures). For the all-age group, a 10 µg/m(3) increase in 24 h NO₂ was associated with increases in all-cause, cardiovascular and respiratory mortality (0.71% (95% CI 0.43% to 1.00%), 0.88% (0.63% to 1.13%) and 1.09% (0.75% to 1.42%), respectively), and with hospital admissions for respiratory (0.57% (0.33% to 0.82%)) and cardiovascular (0.66% (0.32% to 1.01%)) diseases. Evidence of heterogeneity between geographical region-specific estimates was identified in more than half of the combinations analysed.
Our review provides clear evidence of health effects associated with short-term exposure to NO₂ although further work is required to understand reasons for the regional heterogeneity observed. The growing literature, incorporating large multicentre studies and new evidence from less well-studied regions of the world, supports further quantitative review to assess the independence of NO₂ health effects from other air pollutants.
短期接触二氧化氮已被证明与不良健康影响有关，人们越来越担心二氧化氮与健康影响存在因果关系，而不仅仅是交通产生污染的一个指标。自2007年以来，尚未发表关于二氧化氮时间序列证据的全面荟萃分析。
定量评估全球发表的流行病学时间序列研究的证据，以确定短期接触二氧化氮是否以及在何种程度上与每日死亡人数和住院人数增加有关。
我们对204项关于二氧化氮与每日死亡率及多种诊断和年龄段住院人数的时间序列研究进行了定量系统评价，这些研究在截至2011年5月的三个文献数据库中被索引。我们按不同地理区域和全球范围计算了随机效应估计值，并检验了异质性和小研究偏差。
有足够的估计值可用于43种特定病因和特定年龄组合的死亡率或住院人数的荟萃分析（24小时二氧化氮的有25种，1小时测量的相同组合有18种）。对于全年龄组，24小时二氧化氮浓度每增加10μg/m³，全因、心血管和呼吸系统死亡率分别增加（0.71%（95%可信区间0.43%至1.00%）、0.88%（0.63%至1.13%）和1.09%（0.75%至1.42%）），呼吸系统（0.57%（0.33%至0.82%））和心血管疾病（0.66%（0.32%至1.01%））的住院人数也增加。在分析的组合中，超过一半发现了特定地理区域估计值之间存在异质性的证据。
我们的综述提供了明确证据，表明短期接触二氧化氮与健康影响有关，尽管需要进一步开展工作以了解所观察到的区域异质性的原因。越来越多的文献，包括大型多中心研究和来自世界上研究较少地区的新证据，支持进一步进行定量综述，以评估二氧化氮对健康的影响相对于其他空气污染物的独立性。
