• Michael T Young, Karen Jansen, Kristen E Cosselman, Timothy R Gould, James A Stewart, Timothy Larson, Coralynn Sack, Sverre Vedal, Adam A Szpiro, and Joel D Kaufman.
• Department of Environmental and Occupational Sciences, University of Washington, Seattle, Washington (M.T.Y., K.J., K.E.C., S.V.).
• Ann. Intern. Med. 2023 Dec 1; 176 (12): 158615941586-1594.

BackgroundAmbient air pollution, including traffic-related air pollution (TRAP), increases cardiovascular disease risk, possibly through vascular alterations. Limited information exists about in-vehicle TRAP exposure and vascular changes.ObjectiveTo determine via particle filtration the effect of on-roadway TRAP exposure on blood pressure and retinal vasculature.DesignRandomized crossover trial. (ClinicalTrials.gov: NCT05454930).SettingIn-vehicle scripted commutes driven through traffic in Seattle, Washington, during 2014 to 2016.ParticipantsNormotensive persons aged 22 to 45 years (n = 16).InterventionOn 2 days, on-road air was entrained into the vehicle. On another day, the vehicle was equipped with high-efficiency particulate air (HEPA) filtration. Participants were blinded to the exposure and were randomly assigned to the sequence.MeasurementsFourteen 3-minute periods of blood pressure were recorded before, during, and up to 24 hours after a drive. Image-based central retinal arteriolar equivalents (CRAEs) were measured before and after. Brachial artery diameter and gene expression were also measured and will be reported separately.ResultsMean age was 29.7 years, predrive systolic blood pressure was 122.7 mm Hg, predrive diastolic blood pressure was 70.8 mm Hg, and drive duration was 122.3 minutes (IQR, 4 minutes). Filtration reduced particle count by 86%. Among persons with complete data (n = 13), at 1 hour, mean diastolic blood pressure, adjusted for predrive levels, order, and carryover, was 4.7 mm Hg higher (95% CI, 0.9 to 8.4 mm Hg) for unfiltered drives compared with filtered drives, and mean adjusted systolic blood pressure was 4.5 mm Hg higher (CI, -1.2 to 10.2 mm Hg). At 24 hours, adjusted mean diastolic blood pressure (unfiltered) was 3.8 mm Hg higher (CI, 0.02 to 7.5 mm Hg) and adjusted mean systolic blood pressure was 1.1 mm Hg higher (CI, -4.6 to 6.8 mm Hg). Adjusted mean CRAE (unfiltered) was 2.7 μm wider (CI, -1.5 to 6.8 μm).LimitationsImprecise estimates due to small sample size; seasonal imbalance by exposure order.ConclusionFiltration of TRAP may mitigate its adverse effects on blood pressure rapidly and at 24 hours. Validation is required in larger samples and different settings.Primary Funding SourceU.S. Environmental Protection Agency and National Institutes of Health.

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