Heart rate variability in adolescents exposed to ultrafine particles downwind of a major trade bridge in Buffalo, New York

Ultrafine particles (UFP) have become a large health concern due to their high number to mass ratio and potentially increased toxicity. These particles have been shown to penetrate into the lower segments of the lungs causing pulmonary inflammation and particle overload from decreased alveolar macrophage-mediated clearance. Adolescents may be at more at risk for exacerbated health effects as a result of sensitivity to alveolar damage from chronic exposures to elevated levels of UFP. Heart rate variability (HRV) has become a common marker for assessing changes in cardiac autonomic activity.; This study was performed to measure HRV from UFP exposures in adolescent subjects residing within the lower west side of Buffalo, NY downwind of the Peace Bridge connecting Ft Erie, OT to Buffalo, NY, a known source for heavy diesel truck traffic. Eight subjects, ages 13 to 17 years, were monitored for several hours each using the LifeShirtRTM system to collect continuous ambulatory ECG, respiratory, and accelerometry (i.e., motion) measurements. During the monitoring period, the subjects asked to sit indoors and outdoors at rest for 30 minutes to determine the effects of outdoor versus indoor particle concentrations. Particle number and size distributions were recorded indoors and outdoors using high time resolution samplers measuring particle sizes from 5.6-560 nm. UFP number concentrations outdoors ranged from 12,000 to 151,000 particles per cubic centimeter among the subjects homes. Indoor particle concentrations were low, as sources such as cooking were controlled during the study to prevent increased UFP generation.; This is the first study to monitor continuous ambulatory ECG, respiratory rates, and accelerometry in the field for PM exposure assessment. Across all subjects, there was an average R-R interval decrease of 43 ms with no clear trend of decreased HRV (e.g., standard deviation of normal-to-normal intervals or SDNN) from indoors to outdoors. Accelerometry values for each subject were consistently low during the specified controlled indoor and outdoor monitoring times as expected. Values were 2.0 on a scale of 0-5 (e.g. 0=laying down, 5=running). Accelerometer data may provide a preliminary assessment for examining motion and postural changes resulting in elevated heart rates in versus changes in cardiopulmonary activity from PM exposure resulting in elevated heart rates. Respiratory rates across all subjects were within normal ranges of 18-23 breaths per minute. Overall, when exposed to higher concentrations of UFP from moving indoor to outdoors, a clear trend was not found between elevated UFP exposures and decreased HRV between the adolescent subjects.