Objectives Environmental factors such as air-pollution has been postulated to synergise with traditional risk factors in determining cardiovascular risk. We assessed the relationship of particulate matter exposure [personal black carbon (BC) exposure and PM_2.5] with autonomic function and functional measures of vascular risk in an urban megacity.

Methods 65 adult non-smokers with metabolic syndrome underwent continuous assessment of personal level BC using microaetholometers during a 5-day period. Regional PM_2.5 were collected at 3 urban sites and averaged. Autonomic function, arterial compliance and digital arterial endothelial function was measured in the final 24 hours. HRV measures included both frequency and time domain measures. The relationship between various BC and PM_2.5 lag-structures (1/3/5 day lags and moving averages) and outcomes were assessed.

Results Mean personal BC was 4.78 μg/m³ while mean ambient PM_2.5 was 63.3 μg/m³. An increase of 1 μg/m³ in BC 1-day prior was associated with an increase of 24-h heart rate of 42.2% [95% CI, 3.2% to 81.2%]. On adjustment of covariates, 1-day lag BC was negatively associated with HF power, rMSSD, and R-R interval. Ambient PM_2.5 exposure showed a different pattern with 5-day and 3-day moving averages being significantly associated with lower HF and TP on multivariate analysis. There was no relationship between arterial PWV, augmentation index and digital endothelial function and any of the exposure measures.

Conclusions Changes in BC levels and PM_2.5 are associated with alterations in autonomic function, albeit with different temporal relationships suggesting that compositional differences may differentially impact autonomic function. Our findings have implications for the association between anthropogenic sources of air-pollution and cardiovascular events.