It perhaps comes as no surprise that people walking in the park fared better.
"However, telling joggers to avoid polluted streets is not a solution to the problem".
Physical measurements were taken before and after the walks to show the effects of the exercise on cardiovascular health, including measurements of lung volume exhaled, blood pressure, and the degree to which the blood vessels could expand.
"When you walk, your airways open up. and your blood vessels dilate, or open up. and these effects can last for a few days". He also said the impacts are likely to apply to other age groups, but further studies are needed on that.
Over-60s should avoid Oxford Street if they want to go for a healthy walk, the researchers said.
Rudy Sinharay, M.B.B.S., from Imperial College London, and colleagues recruited 40 healthy volunteers, 40 individuals with chronic obstructive pulmonary disease (COPD), and 39 with ischemic heart disease, age 60 years and older, to a randomized, crossover study.
Furthermore, they discovered walking in Hyde Park reduced arterial stiffness by more than 24 percent for both healthy and coronary heart disease patients. Even though London is not one of the world's most notoriously polluted cities, there is a lot of diesel pollution in downtown streets such as Oxford Street, and there is much less in nearby Hyde Park, with its trees, bushes and grassy spaces.
"In all participants, irrespective of their disease status, walking in Hyde Park led to an increase in lung function", the researchers wrote in the Lancet medical journal. The researchers found that levels of pollution - including fine particulate matter, black carbon and nitrogen dioxide - were significantly higher on Oxford Street compared to the park.
The authors say more research is needed to confirm this finding.
Chung said traffic pollution might also affect younger people doing their shopping in the heart of a city.
"The exercise is good for you but the higher the pollution levels, the less helpful it is. We're talking about pollution you get on an ordinary day walking up and down the high street", Chung said.
"Our model indicates that in London, health benefits of active travel always outweigh the risk from pollution", lead author of the research Marko Tainio said when it was published in 2016. These beneficial responses were attenuated after walking on Oxford Street. "We agree that this is good advice for recreational walking for people who can make that choice", he added.
"We need to reduce pollution so that everyone can enjoy the benefits of physical activity in any urban environment", he added. "It's important to that people continue to exercise".
Professor Stephen Holgate, special adviser on air quality to the Royal College of Physicians in the United Kingdom, believes that "we can be quite confident from this (new) study that it is the pollution that is the factor responsible for changes in lung function".
Interestingly, the study found that the volunteers with heart disease who were being treated with medication were less negatively affected by the pollution.
Tainio highlighted that encouraging people to exercise could in turn reduce pollution levels.
With support from the network of cities, he will set up a trial million-pound street-by-street air monitoring system to analyse pollution in over 1,000 hotspots including in schools, hospitals, construction sites and busy roads. "For example, the planned removal of buses and taxis from Oxford Street should help to achieve this", he said.