Ambient Ultrafine Particulate Air Pollution and Incidence of Cardiovascular Diseases

Fine particulate matter (PM2.5) pollution is causally linked to cardiovascular diseases (CVDs), but the long-term effects of potentially more toxic ultrafine particles (UFP) are unclear. We evaluated the associations between long-term exposure to UFP concentrations and the incidence of overall and cause-specific CVDs in 453,692 middle-aged and older UK Biobank participants living >100 m from major roads, followed from 2006–2010 baseline to 2023. A Cox proportional hazard model was applied to estimate the hazard ratio (HR) and 95% confidence interval per interquartile range increment in UFP concentrations. Long-term exposure to ambient UFP was associated with a 3% higher incidence risk of overall CVD (95% CI: 1–4%). Significant positive associations were observed for several specific CVDs, including chronic rheumatic heart diseases, hypertension, ischemic heart diseases, conduction disorders, heart failure, and cerebrovascular diseases (HRs: 1.03–1.09), while others showed no association. These associations were generally robust to adjustment of other air pollutants including PM2.5. The exposure–response relationship curves were generally linear without thresholds. This large prospective study suggests that UFP is an independent, modifiable CVD risk factor, distinct from PM2.5, relevant even for populations distant from major emission sources. This highlights the need to consider UFP in air quality management and public health strategies.