Heavy air pollution can have immediate effects on the heart and blood vessels, but a simple facemask may offer some protection, new research suggests.

In one study, researchers found that when young men were exposed to air polluted with diesel exhaust, their arteries temporarily stiffened.

Meanwhile, a second study showed that healthy adults had higher blood pressure and a less healthy heart-rate pattern when they walked through the streets of Beijing without a facemask.

The good news, the study found, was that the cardiovascular effects were diminished when volunteers donned a facemask like those worn by construction workers to keep from breathing dust.

"Our message from this is that the use of a facemask in heavily polluted cities ... has the potential to improve patients' cardiovascular risk, especially in high-risk populations," said lead researcher Dr. Jeremy P. Langrish, of the University of Edinburgh in the UK.

However, he told Reuters Health, it's too soon to make specific recommendations to people who are especially vulnerable to the acute cardiovascular effects of air pollution. That includes the elderly and those who have other risk factors for heart attack, like high blood pressure or diabetes.

Both studies, published in the journal Particle and Fibre Toxicology, included healthy young volunteers. In the first, researchers led by Magnus Lundback, of University Hospital Umea, in Sweden, had 12 men pedal stationary bikes for one hour on two occasions — once in filtered air, and once in air contaminated with diesel exhaust.

Using non-invasive tests, the researchers found that the polluted air caused the men's wrist arteries to stiffen during exercise.

In the other study, Langrish and his colleagues had 15 healthy volunteers walk the streets of Beijing for two hours on two separate days. On one day, they wore a facemask.

The researchers found that when participants wore the facemask, their average blood pressure was several points lower. They also had better heart rate variability — the ability of the heart to speed up or slow down in response to demands.

Langrish said he and his colleagues are looking to confirm the findings in a larger trial of patients at elevated risk of heart attack.

A caveat is that the masks used in this study were designed for occupational use. Before the study, Langrish and his colleagues tested a number of masks — including several marketed to bicyclists and pedestrians — and found that the occupational mask was more effective at filtering out fine particles.