Recent research has suggested that not only does bumper-to-bumper traffic come at the cost of wasted fuel and environmental pollution, it also results in spikes in blood pressure.
Air pollution from traffic can cause a significant rise in blood pressure that can last up to 24 hours, according to the study from the University of Washington. The researchers said the spike is comparable to the effect of a high-sodium diet and can contribute to cardiovascular problems.
Long-term exposure to vehicle exhaust has been widely linked with respiratory problems such as asthma, especially in children, reports The Guardian.
“Traffic air pollution increases blood pressure within an hour of being in traffic and it stays elevated a day later,” said author Joel Kaufman, a physician and professor of environmental and occupational health sciences at the University of Washington.
For the study – published in Annals of Modern Medicine – 16 healthy people aged 22 to 45 underwent three separate drives as passengers through Seattle rush hour.
Two drives were “unfiltered”, meaning the road air was allowed to enter the car, as is the case for many drivers on the road today.
On the third drive, a Hepa (high efficiency particulate absorbing) filter was installed in the car, with participants unaware which drive had filtration. The researchers measured the blood pressure of the passengers before, during and after the two-hour drive.
Breathing unfiltered air resulted in blood pressure increase of more than 4.5mm Hg (millimetres of mercury) compared with filtered air.
Most of the pollution came from tailpipe exhaust or the fossil fuel combustion, as well as brake and tire wear. The filters were most effective in reducing ultrafine particles (86% decrease), black carbon, which is mostly from diesel (86%), and PM2.5 (60%), while gasses like carbon dioxide and nitrogen oxide were unaffected.
“The clue here is that these tiniest particles are probably what’s responsible for blood pressure difference,” Kaufman said.
Improving traffic and reducing driving with fossil fuel vehicles are among the societal solutions that he sees as effective.
On an individual level, avoiding these exposures by spending less time in traffic is the best possible action. If that’s not possible, closing windows, getting a car filter, and putting air on the recirculation setting can also help, or wearing an effective respirator mask can also offer protection, especially on public transport.
“If you live in an area that has heavy traffic-related air pollution, you want to keep your windows closed and have air filtration capability in your home,” he said.
Study details
Blood Pressure Effect of Traffic-Related Air Pollution: A Crossover Trial of In-Vehicle Filtration
Michael Young, Karen Jansen, Kristen Cosselman, et al.
Published in Annals of Modern Medicine on 28 November 2023
Abstract
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.
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 two 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 three-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.
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