Abstract P247: Multi-pollutant Mixtures and Digital Vascular Function in the Framingham Heart Study

Background: Studies of ambient air pollution and microvascular function have shown conflicting results. Aim: We investigated whether the association between fine particle mass with diameter ≤2.5μm (PM 2.5 ) and microvascular function varies according to air pollution characteristics. Methods: We assessed baseline pulse amplitude and the ratio of fingertip pulse wave amplitude pre- and post- brachial artery occlusion (PAT ratio) in 1,365 participants of the Framingham Offspring and Third Generation Cohorts. We used K-means clustering to categorize mixtures of air pollutants into 5 distinct clusters of days with similar multi-pollutant profiles using elemental data and gases. We assessed the interaction between preceding day PM 2.5 and cluster adjusting for season, meteorology and covariates. Results: We observed differences in associations between PM 2.5 and baseline pulse amplitude by cluster (P=0.02 for interaction). On days with either low overall PM 2.5 levels but dominated by road and traffic dust and a high proportion of ultrafine particles (cluster 1) or high contributions of oil and wood combustion (cluster 5), higher PM 2.5 was associated with higher baseline pulse amplitude (see Figure). In contrast, on days with either a strong contribution of crustal materials, a mixture of fine and ultrafine particles, or agglomerated particles from regional sources (cluster 2, 3, and 4 respectively), PM 2.5 was not significantly associated with baseline pulse amplitude. We observed similar, non-significant associations between PM 2.5 and PAT ratio across the air pollution mixture clusters (P=0.14 for interaction). Conclusions: Air pollution mixtures with contributions from heating oil and wood combustion or traffic and road dust, both having high proportions of ultra-fine particles, were associated with altered microvascular tone. Our findings suggest that specific mixtures of particulate pollution may have distinct vascular consequences and support further studies of air pollution clusters to inform public policy. .