August 6 | 2019

Acute Blood Pressure and Cardiovascular Effects of Near-Roadway Exposures with and without N95-Respirators. 

Morishita M, Wang L, Speth K, Zhou N, Bard RL, Li F, Brook JR, Rajagopalan S, Brook RD.

Am J Hypertens. 2019 Jul 27. pii: hpz113. [Epub ahead of print] DOI: 10.1093/ajh/hpz113



The risk for cardiovascular events increases within hours of near-roadway exposures. We aimed to determine the traffic-related air pollutants (TRAP) and biological mechanisms involved and if reducing particulate matter<2.5 µm (PM2.5) inhalation is protective.


Fifty healthy-adults underwent multiple 2-hour near-roadway exposures (Tuesdays-Fridays) in Ann Arbor during 2 separate weeks (randomized to wear an N95-respirator during one week). Monday both weeks, participants rested 2-hours in an exam room (once wearing an N95-respirator). Brachial blood pressure, aortic hemodynamics and heart rate variability were repeatedly-measured during exposures. Endothelial function (reactive hyperemia index [RHI]) was measured post-exposures (Thursdays). Black carbon (BC), total particle count (PC), PM2.5, noise and temperature were measured throughout exposures.


PM2.5 (9.3±7.7 µg/m3), BC (1.3±0.6 µg/m3), PC (8375±4930 particles/cm3) and noise (69.2±4.2 dB) were higher (p-values<0.01) and aortic hemodynamic parameters trended worse while near-roadway (p-values<0.15 versus exam room). Other outcomes were unchanged. Aortic hemodynamics trended towards improvements with N95-respirator usage while near-roadway (p-values<0.15 versus no-use), whereas other outcomes remained unaffected. Higher near-roadway PC and BC exposures were associated with increases in aortic augmentation pressures (p-values<0.05) and trends toward lower RHI (p-values<0.2). N95-respirator usage did not mitigate these adverse responses (non-significant pollutant-respirator interactions). Near-roadway outdoor-temperature and noise were also associated with cardiovascular changes.


Exposure to real-world combustion-derived particulates in TRAP, even at relatively-low concentrations, acutely worsened aortic hemodynamics. Our mixed findings regarding the health benefits of wearing N95-respirators support that further studies are needed to validate if they adequately-protect against TRAP given their growing worldwide usage.