加拿大University of Toronto研究人员分析11,000人的心脏CT扫描，并将住址与Ontario政府过去10年的空气监测资料连结，发现即使在许多已开发国家相对较低的城市空气污染水准下，长期暴露仍与心脏损害相关。Kate Hanneman指出，研究组的平均污染微粒暴露量远低于当地空气品质标准，但仍可侦测到冠状动脉粥样硬化讯号，显示心血管危害可能不存在明确安全阈值。

研究显示，冠状动脉疾病与PM2.5及二氧化氮暴露有显著相关。PM2.5直径为2.5微米，约比人类头发小30倍，来源包括车辆废气、工业排放与日益增加的野火。长期PM2.5暴露增加15%时，冠状动脉有害钙质堆积增加11%，斑块形成增加13%，阻塞性疾病增加23%；此效应在女性中强于男性。

研究为观察性设计，不能证明因果关系，但Sonya Babu-Narayan表示结果符合空气污染长期伤害心脏的既有知识，并支持更严格限制。WHO估计全球每年有420万例死亡与室外空气污染相关，其中心血管死亡约占一半；空气污染也与慢性阻塞性肺病、失智症、肺癌和呼吸道感染相关。研究并指出，因化石燃料燃烧同时推动空气污染与温室气体排放，改善空气品质政策可同时有益心血管健康与地球。

Researchers at the University of Toronto analysed CT heart scans from 11,000 people and linked their home addresses to Ontario government air-monitoring data from the previous 10 years, finding that long-term exposure to urban air pollution was associated with heart damage even at the relatively low levels common in many developed countries. Kate Hanneman noted that the study group’s average exposure to polluting particles was well below local air quality standards, yet a measurable coronary atherosclerosis signal was still detectable, suggesting there may be no clear safe threshold for cardiovascular harm.

The study found significant associations between coronary artery disease and exposure to PM2.5 and nitrogen dioxide. PM2.5 has a diameter of 2.5 microns, about 30 times smaller than a human hair, and comes from vehicle exhaust, industrial emissions, and increasingly wildfires. A 15 per cent increase in long-term PM2.5 exposure was linked to an 11 per cent rise in harmful coronary artery calcium build-up, a 13 per cent rise in plaque formation, and a 23 per cent rise in obstructive disease; the effect was stronger in women than in men.

The research was observational and cannot prove causation, but Sonya Babu-Narayan said the findings match existing knowledge that air pollution can damage the heart over time and support stricter limits. The WHO estimates that 4.2mn deaths a year globally are linked to outdoor air pollution, with cardiovascular deaths accounting for about half; pollution also contributes to chronic obstructive pulmonary disease, dementia, lung cancer, and respiratory infections. The study also noted that because fossil fuel combustion drives both air pollution and greenhouse gas emissions, air-quality policies can benefit cardiovascular health and the planet simultaneously. (Key numbers: 420)