Association between traffic emissions mixed with resuspended dust and heart rate variability among healthy adults in Delhi

Abstract

Aerosol emissions from vehicles have been linked to changes in heart rate variability (HRV) parameters of the susceptible population in developed countries. In the present study, the effects of vehicular emission and resuspended road dust on HRV parameters in healthy adults (18–43 years of age) were assessed at Delhi, India, a metro city where the world’s largest youth population 356 million of age group 10–24 years resides as per census report of 2011. The study presents personal exposure concentration of fine particulate matter (PM1 and PM2.5) at a road site in Delhi and its link with the changes in HRV parameters. The mixed effect model treated particulate matter (PM) mass concentration, age of participants, body mass index, and climatic parameters (ambient temperature and relative humidity) as independent variables and HRV parameters as dependent variables. The observed data showed that per inter quartile range (IQR) increase in PM1 resulted in a considerable decrease in the HRV indices: percentage of successive NN-intervals that differ from each other by greater than 50 ms (pNN50) [− 26.6% (− 40.52, − 1.29)], root mean square of differences between successive NN-intervals (r-MSSD) [− 9.8% (− 17.53, 1.32)] and high-frequency power (HF) [− 15.6% (− 27.61, 2.89)], and considerable increase in low frequency (LF) by HF ratio [24.0% (0.95, 45.39)]. Greater changes were seen in most of the HRV parameters for PM2.5 as compared to PM1, probably due to the presence of fine dust along with vehicle emissions which aggravate the effect. The change in HRV parameters is considered as a powerful and independent predictor of changes in cardiac autonomic nervous system. The trend observed in the present study was in congruence with that observed in previous studies except for LF, and the reductions in HRV indices were well within the range when compared with literature. But still the impact on HRV was significant which raises a concern for the healthy population which forms a large portion of the society. Also, in light of the limited evidence on the effect of PM1 on cardiac health, the present study summarized that PM1 has a significant impact on HRV too which is of concern due to its high contribution to total PM.