Car passengers’ blood pressure significantly increased by unfiltered rush-hour air

Exposure to traffic-related air pollution has long been linked to a variety of health issues such as cardiovascular diseases and lung cancer, as well as respiratory diseases such as bronchitis and respiratory tract infections.

Now, researchers from the University of Washington, exploring the health risks that vehicle passengers face while travelling in heavy traffic, have noticed a significant increase in blood pressure when passengers are exposed to unfiltered air in high traffic scenarios such as rush-hour.

The increase in blood pressure was noted both while in the car and for up to 24 hours afterwards.

Joel Kaufman, a UW physician and professor of environmental and occupational health sciences who led the study: ‘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.’

The research team drove healthy participants between the ages of 22 and 45 through rush-hour traffic in Seattle while monitoring their blood pressure.

On two of the drives, unfiltered road air was allowed to enter the car, mirroring how many of us drive. On the third, the car was equipped with high-quality HEPA filters that blocked out 86% of particulate pollution.

Breathing unfiltered air resulted in net blood pressure increases of more than 4.50 mm Hg (millimeters of mercury) when compared to drives with filtered air. The increase occurred rapidly, peaking about an hour into the drive and maintaining a high level for at least 24 hours.

Kaufman said: ‘We know that modest increases in blood pressure like this, on a population level, are associated with a significant increase in cardiovascular disease. 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.’

Interestingly, the levels of PM2.5 measured in the unfiltered cars was relative low – equivalent to an AQI of 36 but there were high concentrations of ultrafine particles.

‘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.’