Exposure to ambient airborne particulate matter is a major risk factor for mortality and morbidity, associated with asthma, lung cancer, heart disease, myocardial infarction, and stroke, and more recently type 2 diabetes, dementia and loss of cognitive function. Less is understood about differential effects of particulate matter from different sources. Underground railways are used by millions of people on a daily basis in many cities. Poor air exchange with the outside environment means that underground railways often have an unusually high concentration of airborne particulate matter, while a high degree of railway-associated mechanical activity produces particulate matter which is physicochemically highly distinct from ambient particulate matter. The implications of this for the health of exposed commuters and employees is unclear. A literature search found 27 publications directly assessing the potential health effects of underground particulate matter, including in vivo exposure studies, in vitro toxicology studies, and studies of particulate matter which might be similar to that found in underground railways. The methodology, findings, and conclusions of these studies were reviewed in depth, along with further publications directly relevant to the initial search results. In vitro studies suggest that underground particulate matter may be more toxic than exposure to ambient/urban particulate matter, especially in terms of endpoints related to reactive oxygen species generation and oxidative stress. This appears to be predominantly a result of the metal-rich nature of underground particulate matter, which is suggestive of increased health risks. However, while there are measureable effects on a variety of endpoints following exposure in vivo, there is a lack of evidence for these effects being clinically significant as may be implied by the in vitro evidence. There is little direct evidence that underground railway particulate matter exposure is more harmful than ambient particulate matter exposure. This may be due to disparities between in vivo exposures and in vitro models, and differences in exposure doses, as well as statistical under powering of in vivo studies of chronic exposure. Future research should focus on outcomes of chronic in vivo exposure, as well as further work to understand mechanisms and potential biomarkers of exposure.

中文翻译：

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地下铁路系统中颗粒物空气污染对健康的影响–对证据的严格审查

暴露于环境中的空气传播颗粒物是导致死亡和发病的主要危险因素，与哮喘，肺癌，心脏病，心肌梗塞和中风有关，最近与2型糖尿病，痴呆和认知功能下降有关。人们对来自不同来源的颗粒物的不同影响了解得很少。许多城市每天都有数百万人使用地下铁路。与外部环境的空气交换差意味着地下铁路通常具有异常高的空气中颗粒物浓度，而与铁路相关的高度机械活动产生的颗粒物在物理化学上与周围的颗粒物高度不同。这对于裸露的通勤者和员工健康的影响尚不清楚。文献检索发现27家出版物直接评估了地下颗粒物的潜在健康影响，包括体内暴露研究，体外毒理学研究以及与地下铁路中发现的颗粒物研究相似的研究。这些研究的方法，发现和结论均进行了深入的审查，并进一步发表了与最初搜索结果直接相关的出版物。体外研究表明，地下颗粒物可能比暴露于环境/城市颗粒物更具毒性，特别是在与活性氧生成和氧化应激有关的终点方面。这似乎主要归因于地下颗粒物的富金属性质，这提示增加了健康风险。然而，尽管体内暴露后对多种终点均有可测量的作用，但缺乏证据表明这些作用具有临床意义，如体外证据可能暗示的那样。几乎没有直接证据表明地下铁路颗粒物的暴露比周围颗粒物的危害更大。这可能是由于体内暴露与体外模型之间的差异，暴露剂量的差异以及在慢性暴露的体内研究的支持下进行的统计所致。未来的研究应集中于慢性体内暴露的结果，以及进一步的工作以了解暴露的机制和潜在的生物标志物。缺乏证据表明这些作用具有临床意义，如体外证据可能暗示的那样。几乎没有直接证据表明地下铁路颗粒物的暴露比周围颗粒物的危害更大。这可能是由于体内暴露与体外模型之间的差异，暴露剂量的差异以及在慢性暴露的体内研究的支持下进行的统计所致。未来的研究应集中于慢性体内暴露的结果，以及进一步的工作以了解暴露的机制和潜在的生物标志物。缺乏证据表明这些作用具有临床意义，如体外证据可能暗示的那样。几乎没有直接证据表明地下铁路颗粒物的暴露比周围颗粒物的危害更大。这可能是由于体内暴露与体外模型之间的差异，暴露剂量的差异以及在慢性暴露的体内研究的支持下进行的统计所致。未来的研究应集中于慢性体内暴露的结果，以及进一步的工作以了解暴露的机制和潜在的生物标志物。和暴露剂量的差异，以及在慢性暴露的体内研究的支持下进行统计。未来的研究应集中于慢性体内暴露的结果，以及进一步的工作以了解暴露的机制和潜在的生物标志物。和暴露剂量的差异，以及在慢性暴露的体内研究的支持下进行统计。未来的研究应集中于慢性体内暴露的结果，以及进一步的工作以了解暴露的机制和潜在的生物标志物。