A controlled trial of acute effects of human exposure to traffic particles on pulmonary oxidative stress and heart rate variability

Robert J. Laumbach, Howard M. Kipen, Susan Ko, Kathie Kelly-McNeil, Clarimel Cepeda, Ashley Pettit, Pamela Ohman-Strickland, Lin Zhang, Junfeng Zhang, Jicheng Gong, Manoj Veleeparambil, Andrew J. Gow

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BACKGROUND: For many individuals, daily commuting activities on roadways account for a substantial proportion of total exposure, as well as peak-level exposures, to traffic-related air pollutants (TRAPS) including ultrafine particles, but the health impacts of these exposures are not well-understood. We sought to determine if exposure to TRAPs particles during commuting causes acute oxidative stress in the respiratory tract or changes in heart rate variability (HRV), a measure of autonomic activity.

METHODS: We conducted a randomized, cross-over trial in which twenty-one young adults took two 1.5-hr rides in a passenger vehicle in morning rush-hour traffic. The subjects wore a powered-air-purifying respirator, and were blinded to high-efficiency particulate air (HEPA) filtration during one of the rides. At time points before and after the rides, we measured HRV and markers of oxidative stress in exhaled breath condensate (EBC) including nitrite, the sum of nitrite and nitrate, malondialdehyde, and 8-isoprostane. We used mixed linear models to evaluate the effect of exposure on EBC and HRV outcomes, adjusting for pre-exposure response levels. We used linear models to examine the effects of particle concentrations on EBC outcomes at post-exposure time points.

RESULTS: Mean EBC nitrite and the sum of nitrite and nitrate were increased from baseline at immediately post-exposure comparing unfiltered to filtered rides (2.11 μM vs 1.70 μM, p = 0.02 and 19.1 μM vs 10.0 μM, p = 0.02, respectively). Mean EBC malondialdehyde (MDA) concentrations were about 10% greater following the unfiltered vs. filtered exposures, although this result was not statistically significant. We found no significant associations between exposure to traffic particles and HRV outcomes at any of the time points. At immediately post-exposure, an interquartile range increase in particle number concentration was associated with statistically significant increases in nitrite (99.4%, 95% CI 32.1% to 166.7%) and nitrite + nitrate (75.7%, 95% CI 21.5% to 130.0%).

CONCLUSIONS: Increases in markers of oxidative stress in EBC may represent early biological responses to widespread exposures to TRAPs particles that affect passengers in vehicles on heavily trafficked roadways.

Original languageEnglish
Article number45
Pages (from-to)45
Number of pages1
JournalParticle and Fibre Toxicology
Issue number1
Publication statusPublished - 2014
Externally publishedYes


ASJC Scopus subject areas

  • Medicine(all)

Cite this

Laumbach, R. J., Kipen, H. M., Ko, S., Kelly-McNeil, K., Cepeda, C., Pettit, A., Ohman-Strickland, P., Zhang, L., Zhang, J., Gong, J., Veleeparambil, M., & Gow, A. J. (2014). A controlled trial of acute effects of human exposure to traffic particles on pulmonary oxidative stress and heart rate variability. Particle and Fibre Toxicology, 11(1), 45. [45]. https://doi.org/10.1186/s12989-014-0045-5