Blood Pressure Effect of Traffic-Related Air Pollution : A Crossover Trial of In-Vehicle Filtration
Michael T Young1, Karen Jansen1, Kristen E Cosselman1
1Department of Environmental and Occupational Sciences, University of Washington, Seattle, Washington (M.T.Y., K.J., K.E.C., S.V.).
Background:
Ambient 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.
Objective:
To determine via particle filtration the effect of on-roadway TRAP exposure on blood pressure and retinal vasculature.
Design:
Randomized crossover trial. (ClinicalTrials.gov: NCT05454930).
Setting:
In-vehicle scripted commutes driven through traffic in Seattle, Washington, during 2014 to 2016.
Participants:
Normotensive persons aged 22 to 45 years (n = 16).
Intervention:
On 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.
Measurements:
Fourteen 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.
Results:
Mean 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).
Limitations:
Imprecise estimates due to small sample size; seasonal imbalance by exposure order.
Conclusion:
Filtration 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 Source:
U.S. Environmental Protection Agency and National Institutes of Health.
