Air pollution is responsible for around 5.5 million premature deaths worldwide each year.
"Combined with evidence from other recent studies, our findings underscore that we can't really tolerate the levels of air pollution that we now find on our busy streets", coauthor Fan Chung said in a statement.
"If people can not find a green place or a park to exercise, I think they probably should exercise indoors", Chung said.
Pregnant women exposed to air pollution from road traffic are more likely to give birth to babies that are underweight or smaller than they should be, a study conducted in the United Kingdom warns. Average day and night-time road traffic noise levels were also estimated.
They found higher levels of these air pollutants, particularly PM2.5, were associated with two per cent to six per cent increased odds of low birth weight and one per cent to three per cent increased odds of being small for gestational age.
Other scientists said the study was important evidence of the harms of air pollution, although they would not advise people to stop walking in the city streets, because the benefits for healthy people were reduced but not completely lost. "That should allow everyone to be able to enjoy the health benefits of physical activity in any urban environment".
Transient subjection to traffic exhaust in built up locations like New York City's Broadway or Chicago's Michigan Avenue can annul the positive outcomes of a two hour walk which would have benefitted the heart and lungs of these people.
"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.
Two-thirds of the volunteers had been diagnosed with either heart disease or chronic obstructive pulmonary disease (COPD), while the others were healthy (no pre-existing heart or lung condition).More news: Former Dem rep fired by Morgan Stanley denies harassment allegations
The team measured how much pollution the volunteers breathed in and measured heart and lung function. Data analysis was carried out at the MRC-PHE Centre for Environment and Health at Imperial College London and Kings College London, and the Rutgers School of Public Health in New Jersey.
Volunteers who took a walk in Hyde Park experienced a decrease in the stiffness of their arteries, a benefit normally seen after exercise. Air pollution exposure has been linked to increases in hospital admissions and deaths from cardiovascular diseases, respiratory diseases and lung cancer.
However, people who walked around the park benefited from increased blood flow and their arteries became less stiff by 24% in some cases, and the Oxford Streetwalkers were with just a 4.6% improvement for healthy participants.
The researchers also note that stress from the increased noise and activity of Oxford Street may have had an effect on the study's results.
They also claimed that while the study only involved two relatively short walks, the findings suggest that repeated exposures to air pollution would not be beneficial to respiratory and cardiovascular systems.
"For many people, such as the elderly or those with chronic disease, the only exercise they very often can do is to walk", Chung said.
"Combined with evidence from other recent studies, our findings underscore that we can't really tolerate the levels of air pollution that we now find on our busy streets", said Fan Chung, professor of respiratory medicine and head of experimental studies medicine at Imperial College's National Heart and Lung Institute.
Now, a British study has gone a long way towards answering that question.