细颗粒物（PM2.5）对健康的影响

The danger of PM2.5 lies in its physical ability to bypass the body’s natural defenses. Larger particles (like PM10) are often trapped in the nose and upper respiratory tract and can be cleared by coughing or sneezing. However, PM2.5 particles are small enough to travel past these defenses, reaching the bronchioles and alveoli—the tiny air sacs in the lungs where gas exchange occurs. Once in the alveoli, they can cause localized inflammation and oxidative stress, impairing lung function and exacerbating conditions like asthma and chronic obstructive pulmonary disease (COPD).

此外，即使是最小的颗粒也能穿过肺泡毛细血管屏障，进入血液。循环中的颗粒物会引发全身炎症和氧化应激。这是PM2.5与心血管疾病之间的关键关联机制。炎症会促进动脉粥样硬化（动脉硬化和狭窄），增加血栓风险，并导致高血压。PM2.5的化学成分，包括重金属、硫酸盐、硝酸盐和有机化合物，也增加了其毒性。长期暴露于PM2.5被认为是全球过早死亡的主要环境风险因素，并且还与儿童神经发育问题和成人神经退行性疾病有关。