According to the World Health Organization, both indoor and urban air pollution are responsible for the deaths of around 3.5 million people annually. During the last few decades, the interest in understanding the composition and health consequences of the complex mixture of polluted air has steadily increased. Today, after decades of detailed research, it is well-recognized that polluted air is a complex mixture containing not only gases (CO, NO_x, and SO₂) and volatile organic compounds but also suspended particles such as particulate matter (PM). PM comprises particles with sizes in the range of 30 to 2.5 μm (PM₃₀, PM₁₀, and PM_2.5) and ultrafine particles (UFPs) (less than 0.1 μm, including nanoparticles). All these constituents have different chemical compositions, origins and health consequences. It has been observed that the concentration of PM and UFPs is high in urban areas with moderate traffic and increases in heavy traffic areas. There is evidence that inhaling PM derived from fossil fuel combustion is associated with a wide variety of harmful effects on human health, which are not solely associated with the respiratory system. There is accumulating evidence that the brains of urban inhabitants contain high concentrations of nanoparticles derived from combustion and there is both epidemiological and experimental evidence that this is correlated with the appearance of neurodegenerative human diseases. Neurological disorders, such as Alzheimer's and Parkinson's disease, multiple sclerosis, and cerebrovascular accidents, are among the main debilitating disorders of our time and their epidemiology can be classified as a public health emergency. Therefore, it is crucial to understand the pathophysiology and molecular mechanisms related to PM exposure, specifically to UFPs, present as pollutants in air, as well as their correlation with the development of neurodegenerative diseases. Furthermore, PM can enhance the transmission of airborne diseases and trigger inflammatory and immune responses, increasing the risk of health complications and mortality. Therefore, understanding the different levels of this issue is important to create and promote preventive actions by both the government and civilians to construct a strategic plan to treat and cope with the current and future epidemic of these types of disorders on a global scale.

中文翻译：

---

城市空气污染中的颗粒物和超细颗粒物及其对神经系统的影响

据世界卫生组织称，室内和城市空气污染每年导致约 350 万人死亡。在过去的几十年里，人们对了解污染空气复杂混合物的成分和健康后果的兴趣稳步增长。今天，经过几十年的详细研究，人们公认，受污染的空气是一种复杂的混合物，不仅包含气体（CO、NO _x和 SO ₂）和挥发性有机化合物，还包含颗粒物 (PM) 等悬浮颗粒。PM 包含尺寸范围为 30 至 2.5 μm 的颗粒（PM ₃₀、PM ₁₀和 PM _2.5) 和超细颗粒 (UFP)（小于 0.1 μm，包括纳米颗粒）。所有这些成分都有不同的化学成分、来源和健康后果。据观察，PM 和 UFP 的浓度在交通适中的城市地区较高，在交通繁忙的地区有所增加。有证据表明，吸入化石燃料燃烧产生的 PM 会对人类健康产生多种有害影响，而这些有害影响不仅仅与呼吸系统有关。越来越多的证据表明，城市居民的大脑含有高浓度的燃烧产生的纳米颗粒，并且流行病学和实验证据表明这与人类神经退行性疾病的出现有关。神经系统疾病，例如阿尔茨海默氏症和帕金森氏症 s 病、多发性硬化症和脑血管意外是我们这个时代主要的衰弱性疾病，它们的流行病学可归类为突发公共卫生事件。因此，了解与 PM 暴露相关的病理生理学和分子机制，特别是作为空气污染物存在的 UFP，以及它们与神经退行性疾病发展的相关性至关重要。此外，PM 可以增强空气传播疾病的传播并引发炎症和免疫反应，增加健康并发症和死亡率的风险。所以，