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

Abstract

BackgroundFor 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.MethodsWe 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.ResultsMean 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%).ConclusionsIncreases 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.

Toward point-of-care management of chronic respiratory conditions: Electrochemical sensing of nitrite content in exhaled breath condensate using reduced graphene oxide

“…Sample preparation EBC samples collected for a previous study 53 were utilized. The details of the sample collection procedure have been previously described, but briefly, 1-2 mL of EBC was collected during 20 min of tidal breathing from each of seven adult subjects using an EcoScreen device (Jaeger, Wurzburg, Germany), which condensed the exhaled breath at − 20°C.…”

“…All surfaces were triple-rinsed with nitrite-free water prior to contacting the EBC, and the samples were frozen at − 80°C for later analysis. In the previous study, nitrite concentrations were measured using selective catalytic reduction and chemiluminescence detection (NOA 280i, GE Analytics, Boulder, CO, USA) 53 . All solutions were prepared with distilled water.…”

“…The results obtained provide insight into the response expected for clinical samples. Nitrite levels in EBC have been reported in the μM range 7,53 . We used both cyclic voltammetry (CV) and square wave voltammetry (SWV) to measure the redox current resulting from spiking buffer solutions with various concentrations of nitrite into the EBC sample.…”

Understanding Air Pollution and Cardiovascular Diseases: Is It Preventable?

“…However, the authors noted that these study were not double blinded, and so the findings may be biased by subjects’ awareness of whether they were wearing a respirator or not. Another study reported that markers of oxidative stress (nitrite and nitrite + nitrate) in exhaled breath condensate were increased immediately after 1.5-h car rides during which subjects breathed unfiltered vehicle cabin air, but not after rides during which subjects breathed HEPA-filtered air via a powered air purifying respirator [41]. Unfortunately, under most daily life scenarios, wearing face masks is not a long-term practical strategy; however, it may be useful for short periods during extreme exposures (e.g., high-risk individuals during travel to polluted regions, occupational exposures, activities near hot spots such as roadways).…”

Mitochondrial toxicity of tobacco smoke and air pollution

“…The extended duration and heavy breathing associated with manual labor of certain occupations (e.g. transportation, landscaping, construction) as well as the increased exposure to household air pollution among women, children and the elderly in low- and middle-income countries (who spend more time indoors than male adults) results in a greater burden of exposure and subsequent greater pulmonary disease in these sub-populations 14, 63–65, 229, 234 . The increasing prevalence of acute respiratory diseases has also been linked to climate change and alterations in ground level ozone pollution distribution 228, 229 .…”