Ambient Ultrafine Particulate Air Pollution and Incidence of Cardiovascular Diseases

Fine particulate matter (PM_2.5) 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 PM_2.5. 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 PM_2.5, relevant even for populations distant from major emission sources. This highlights the need to consider UFP in air quality management and public health strategies.