Abstract：
Urbanization has numerous benefits to human society, but some aspects of urban environments, such as air pollution, can negatively affect human health. Two major air pollutants, particulate matter (PM) and polycyclic aromatic hydrocarbons (PAH), have been classified as carcinogens by the International Agency for Research on Cancer. Here, we answer two questions: (1) What are the carcinogenic effects of PM and PAH exposure? (2) How does carcinogenic risk vary across geographical regions? We performed a comprehensive literature search of peer-reviewed published studies examining the link between air pollution and human cancer rates. Focusing on studies published since 2014 when the last IARC monograph on air pollution was published, we converted the extracted data into relative risks and performed subgroup analyses. Exposure to PM2.5 (per 10 μg/m3) resulted in an 8.5% increase in cancer incidence when all cancer types were combined, and risk for individual cancer types (i.e. lung cancer and adenocarcinoma) was also elevated. PM2.5 was also associated with 2.5% higher mortality due to cancer when all types of cancer were combined, and for individual cancer types (i.e., lung and breast cancer). Exposure to PM2.5 and PM10 posed the greatest risk to lung cancer incidence and mortality in Europe (PM2.5 RR 2.15; PM10 RR 1.26); the risk in Asia and the Americas was also elevated. Exposure to PAH and benzo[a]pyrene significantly increased the pooled risk of cancer incidence (10.8% and 8.0% respectively) at the highest percentile of exposure concentration. Our meta-analyses of studies over the past decade shows that urban air pollution in the form of PM2.5, PM10, and PAH all elevate the incidence and mortality of cancer. We discuss the possible mechanisms of carcinogenesis of PM and PAH. These results support World Health Organization\'s conclusion that air pollution poses among the greatest health risks to humans living in cities.
摘要：
城市化对人类社会有许多好处,但是城市环境的某些方面，比如空气污染，会对人类健康产生负面影响。两种主要的空气污染物，颗粒物（PM）和多环芳烃（PAH），已被国际癌症研究机构列为致癌物。这里,我们回答了两个问题:(1)PM和PAH暴露的致癌效应是什么?(2)致癌风险在不同地理区域之间的差异如何?我们对同行评审的已发表研究进行了全面的文献检索,这些研究研究了空气污染和人类癌症发病率之间的联系。专注于自2014年IARC关于空气污染的最新专著出版以来发表的研究，我们将提取的数据转换为相对风险,并进行亚组分析.当所有癌症类型结合时，暴露于PM2.5（每10μg/m3）导致癌症发病率增加8.5％，个别癌症类型（即肺癌和腺癌）的风险也升高。当所有类型的癌症合并时，PM2.5还与癌症导致的死亡率增加2.5％相关。和个别癌症类型(即，肺癌和乳腺癌)。在欧洲，暴露于PM2.5和PM10对肺癌发病率和死亡率的风险最大（PM2.5RR2.15；PM10RR1.26）；亚洲和美洲的风险也有所增加。暴露于PAH和苯并[a]芘在暴露浓度的最高百分位数下显着增加了癌症发病率的合并风险（分别为10.8％和8.0％）。我们对过去十年的研究进行的荟萃分析表明，PM2.5，PM10和PAH等形式的城市空气污染都会提高癌症的发病率和死亡率。我们讨论了PM和PAH致癌的可能机制。这些结果支持世界卫生组织的结论，即空气污染对生活在城市中的人类构成最大的健康风险。
