Just as in real estate, it seems a key component to success in exercise may come down to three little words: location, location, location.

British researchers took two groups of older adults, ages 60 and up, on a two-hour walk in two areas of London to assess the impact air pollution had on their lung function. Some strolled along Oxford Street, a busy commercial area with a lot of vehicle traffic, and others through the leafy and traffic-free Hyde Park.

As might be expected, those who walked around Hyde Park got the bigger boosts, including better lung function and less arterial stiffness up to 26 hours after their exercise. The Oxford Street walkers had none of these benefits. And participants who had chronic obstructive pulmonary disease reported coughing up more phlegm, wheezing more and having an extended shortness of breath.

For many people, including the elderly or those with a chronic disease, the only exercise they can do is to walk, and physicians often recommend they get out more and do so. But the study showed that air pollution on city streets can wipe out these beneficial health effects.

Gasoline- and diesel-powered vehicles are prime generators of outdoor air pollution, which causes an estimated 4.5 million deaths a year worldwide and has been linked to cardiovascular diseases, respiratory diseases and lung cancer.

We’re a long way from replacing all gas-powered vehicles with those using electricity or other energy sources, but the researchers said the study findings should push policy makers to make reducing exposure to air pollution a high priority … because many people simply can’t tolerate the levels that exist now.