Associations between personal exposure to metals in fine particulate matter and autonomic nervous system dysfunction among healthy adults

The impact of airborne particulate matter and its metal components on autonomic nervous system (ANS) dysfunction in healthy subjects remains unclear. The aim of this study was to examine the effects of personal exposure to airborne particulate matter on the ANS in young, healthy adults. This longitudinal study recruited 82 adults aged 20 to 35 years from districts A and B. District A had lower ambient PM_2.5 levels than district B. Personal exposure to fine particulate matter and metals in PM_2.5 was collected every two months. The heart rate variability (HRV) indices of each participant were measured three times. The relationship among the PM_2.5 concentration, metals in PM_2.5 and HRV level was investigated by a generalized estimating equation with an autoregression of order 1. The average age of the participants was 26.4 ± 3.6 years in district A and 21.9 ± 1.5 years in district B (p < 0.001). After adjusting for covariables, significant changes in Log₁₀ standard deviation of normal to normal (SDNN) intervals and Log₁₀ square root of the mean of the sum of the squares of differences (r-MSSDs) were related to unit changes in Log₁₀ iron in PM_2.5 (β = –0.033, 95% CI = –0.060 to –0.0056, p < 0.05 and β = –0.041, 95% CI = –0.075 to –0.0076, p < 0.05, respectively). The Log₁₀ SDNN levels were significantly positively related to Log₁₀ gallium in PM_2.5 (β = 0.054, 95% CI = 0.0064 to 0.10, p < 0.05). Exposure to heavy metals in airborne particulate matter was associated with ANS dysfunction.