Long-term Exposure to Ultrafine Particles and Incidence of Cardiovascular and Cerebrovascular Disease

Abstract

Background/Aim: Multiple lines of research have indicated that exposure to ambient air pollution (mostly measured as particulate matter less than 2.5 µm in size [PM2.5]) plays a significant role in morbidity and mortality. However, there is growing evidence that exposure to ultrafine particles (UFP – particles smaller than 100nm) may play an under-explored role in the aetiology of several illnesses, including cardiovascular disease. Methods: We studied the association between long-term exposure to UFP (predicted via land use regression) and incident cardiovascular disease using Cox proportional hazard models in a longitudinal study of 40,011 Dutch residents. Hazard ratios (HR) for UFP were compared to HRs for more routinely monitored air pollutants including PM10, PM2.5 and NO2. Results: Long-term UFP exposure was associated with an increased risk for all incident cardiovascular disease (HR: 1.18 per 10,000 particles/cm3, 95% CI: 1.03:1.34), myocardial infarction (HR: 1.34, 95% CI: 1.00:1.79), and heart failure (HR: 1.76, 95% CI 1.17:2.66). Similar findings were observed for NO2 and coarse PM (PM between 10 and 2.5 µm) but not for PM2.5. Elevated (albeit non-statistically significant) HRs for UFP exposure were also observed for cerebrovascular diseases. Two-pollutant models (UFP + NO2 and UFP + PMcoarse) identified that the elevated risk estimate remained for UFP, while results for PMcoarse and NO2 typically attenuated towards the null. Conclusions: These findings strengthen the evidence that UFP exposure plays an important role in cardiovascular health and that risks of ambient air pollution may have been underestimated based on conventional air pollution metrics such as PM2.5.