Let’s give thanks to those people who take part in clinical studies and, always to some extent, suffer in the name of science.

You could probably fill a city with volunteers who were deprived of sleep or made to eat lard for a month.

There were those participants famously ordered to unleash the sadist within, and forever be shamed by their gross moral failure.

There was a boredom study, where some participants gave themselves electric shocks to escape the tedium.

What about getting stalled in traffic?

By comparison, sucking on a little traffic exhaust for a couple of days isn’t so bad, right? Well, it’s not great.

Traffic-related air pollution (TRAP) is made up up of ultrafine particles. These include black carbon; oxides of nitrogen; carbon monoxide (CO); carbon dioxide (CO2); and other particulate matter. In observational studies, TRAP exposure has been recognised as a risk factor for cardiovascular disease and other health effects.

A new study finds that it nudges your blood pressure upward while you’re sitting at the wheel.

The cough-cough study

This was a small study. Just 16 volunteers, ages 22 to 45, were enlisted by the University of Washington. They were, one at a time, driven through traffic in Seattle, Washington, for three days.

On two of those days, “on-road air was entrained into the vehicle”. That is, ambient traffic exhaust was drawn into the car which was equipped with a “sham” or pretend filter.

On the third day, the vehicle was equipped with high efficiency particulate air (HEPA) filtration.

Blood pressure was monitored up to 24 hours before, during and after these drives. Inhalation of traffic-related air pollution while in a car with unfiltered air was associated with a 4.5mm Hg increase in blood pressure.

This change in blood pressure “occurred rapidly, peaked within 60 minutes of exposure, and persisted over 24 hours”.

According to Medical News Today, the blood pressure increase is on par with other cardiovascular risk factors such as lack of exercise or excessive salt intake.

On the upside: the effects of air pollution on blood pressure “may be reduced with effective cabin air filtration”.

The study was published this week in Annals of Internal Medicine.

Other research

A 2015 study found that long-term exposure to air pollution can cause damage to brain structures and impair cognitive function in middle-aged and older adults.

A 2018 study linked exposure to residential air pollution during foetal life with brain abnormalities that may contribute to impaired cognitive function in school-age children.

As The New Daily reported last year, living less than 50 metres from a major road has been linked to a significantly higher incidence of dementia and Parkinson’s disease.

The implication is that chronic exposure to traffic pollution increases your risk of these neurological diseases, a theory supported by previous research.