Department of Toxicology, Gradient, Cambridge, Massachusetts 02138, USA.
Crit Rev Toxicol. 2009;39(9):719-42. doi: 10.3109/10408440903283641.
The effects of 0.1 to 0.6 ppm nitrogen dioxide (NO2) on airway hyper-responsiveness (AHR) to airway challenges in asthmatics have been evaluated in several controlled exposure studies. The authors conducted meta-analyses and meta-regressions of these studies using several effect measures for AHR: a change (in NO2 versus air) in (1) the provocative dose of a challenge agent necessary to cause a specified change in lung function (PD), (2) the change in FEV1 after an airway challenge, and (3) the fraction of subjects with increased AHR. Although several effect estimates from the meta-analyses are statistically significant, they are all so small that they are not likely to be clinically relevant. More importantly, there are no exposure-response associations for any effect estimates based on linear meta-regressions or analyses of effect estimates for exposure groups (0.1 to <0.2 ppm, 0.2 to <0.3 ppm, etc.). This is also generally the case for analyses stratified by airway challenge (specific/nonspecific), exposure method (mouthpiece/whole chamber), and activity during exposure (rest/exercise). The results of these analyses indicate that, to the extent the effects observed are associated with NO2 exposure, they are sufficiently small such that they do not provide evidence that NO2 has a significant adverse effect on AHR at concentrations up to 0.6 ppm.
已有几项对照暴露研究评估了 0.1 至 0.6ppm 二氧化氮（NO2）对哮喘患者气道高反应性（AHR）的影响。作者使用 AHR 的几种效应度量对这些研究进行了荟萃分析和荟萃回归：（1）引起特定肺功能变化的刺激剂量变化（在 NO2 与空气之间）；（2）气道挑战后 FEV1 的变化；（3）AHR 增加的受试者比例。尽管荟萃分析中的几个效应估计在统计学上具有显著性，但它们都非常小，不太可能具有临床相关性。更重要的是，基于线性荟萃回归或暴露组效应估计分析（0.1 至 <0.2ppm、0.2 至 <0.3ppm 等），对于任何效应估计都没有暴露反应关系。对于按气道挑战（特异性/非特异性）、暴露方法（口件/整个腔室）和暴露期间活动（休息/运动）分层的分析，情况也是如此。这些分析的结果表明，在观察到的影响与 NO2 暴露相关的程度上，它们非常小，因此不能证明 NO2 在高达 0.6ppm 的浓度下对 AHR 有显著的不良影响。
