Nov. 30, 2023 – Breathing unfiltered air while commuting during rush hour can harm your health just as much as eating a high-sodium diet, new research suggests, pointing to yet another everyday danger of exposure to air pollution.
In a study, University of Washington researchers drove people through rush-hour traffic in Seattle, exposing them on some days to unfiltered air and during other trips to air that entered the vehicle through an enhanced air filter. Their blood pressure was monitored during the drives and for 24 hours afterward.
The average starting blood pressure of the people in the study was 123/71 mm Hg. Blood pressure rose rapidly by an average of more than 4 mm Hg, peaking about an hour into the drive and remaining high for 24 hours. The increase was similar to the effects of eating a diet high in salt, according to a summary of the study published by the University of Washington.
“The body has a complex set of systems to try to keep blood pressure to your brain the same all the time. It’s a very complex, tightly regulated system, and it appears that somewhere, in one of those mechanisms, traffic-related air pollution interferes with blood pressure," researcher Joel Kaufman, MD, MPH, a doctor and professor of environmental and occupational health sciences, said in a statement.
The findings were detailed in a paper titled “Blood Pressure Effect of Traffic-Related Air Pollution: A Crossover Trial of In-Vehicle Filtration,” published this week in the journal Annals of Internal Medicine. Sixteen people took part in the study, which was done from 2014 to 2016. Each person rode in a vehicle on three separate days and did not know whether it was equipped with high-efficiency particulate air (HEPA) filtration. The people in the study were 22 to 45 years old.
The impact of long-term exposure to traffic-related air pollution has already been linked to numerous other health problems, including issues with the heart and blood vessels, asthma, and lung cancer, as well as to a higher risk of early death.
“We know that modest increases in blood pressure like this, on a population level, are associated with a significant increase in cardiovascular disease,” Kaufman said. “There is a growing understanding that air pollution contributes to heart problems. The idea that roadway air pollution at relatively low levels can affect blood pressure this much is an important piece of the puzzle we’re trying to solve.”
The researchers noted that the size of pollution particles filtered during their experiment is noteworthy. Ultrafine particles, which are less than 100 nanometers and too small to be seen, are not regulated.
"Ultrafine particles are the pollutant that were most effectively filtered in our experiment – in other words, where the levels are most dramatically high on the road and low in the filtered environment,” Kaufman said. “So, the hint is that ultrafines may be especially important [for blood pressure]. To actually prove that requires further research, but this study provides a very strong clue as to what’s going on.”
The study results suggest that filtration could protect people from the harmful impact on blood pressure from traffic-related air pollution, but a larger study would be needed to validate their findings, the authors wrote.
