Living in a city with high levels of air pollution can wreak havoc on a person’s health. Air pollution in China has led to the proliferation of lung cancer diagnoses. And higher air pollution levels have been linked to increased stroke and premature birth rates. Despite the risks, should pollution keep anyone from getting outside and staying physically active?

Researchers from the University of Cambridge recently conducted a study examining the risks associated with air pollution and whether they outweigh the potential benefits of outdoor physical activity. Not only do activities like casual cycling and walking benefit us in spite of air pollution risks, they found, but they can also reduce harmful emissions from cars.

"Our model indicates that in London health benefits of active travel always outweigh the risk from pollution,” said Dr. Marko Tainio from the MRC Epidemiology Unit at the University of Cambridge, in a statement. “Even in Delhi, one of the most polluted cities in the world — with pollution levels 10 times those in London — people would need to cycle over five hours per week before the pollution risks outweigh the health benefits.”

Tainio and his colleagues used information from international studies to compare air pollution in different areas around the world to the risks and benefits of different levels of intensity and duration of active travel. Active travel, such as walking and cycling, is seen as great way to bolster our daily physical activity, but concerns have been raised over pollution.

Among cities in the World Health Organization’s Ambient Air Pollution Database, only 1 percent are home to pollution levels high enough that the risks outweigh any healthy benefits of physical activity after a half hour of cycling each day. The research team also pointed out that more people on bicycles would lead to fewer vehicle emissions.

"We should remember, though, that a small minority of workers in the most polluted cities, such as bike messengers, may be exposed to levels of air pollution high enough to cancel out the health benefits of physical activity," Tainio added.

Evidence has shown that air pollution leads to as many as 40,000 deaths each year in the United Kingdom. As bad as air pollution levels are currently, experts fear the future will be much worse. Researchers from Harvard’s engineering and applied sciences school recently announced that they expect air pollution levels to skyrocket by 2050.

"Whilst this research demonstrates the benefits of physical activity in spite of air quality, it is not an argument for inaction in combating pollution,” explained senior author Dr. James Woodcock. ”It provides further support for investment in infrastructure to get people out of their cars and onto their feet or their bikes, which can itself reduce pollution levels at the same time as supporting physical activity."

Although there is no denying the harmful effects air pollution can have on our health, there is hope if we start to remedy the situation. Researchers from the University of Southern California examined more than 4,600 children between the ages of 5 and 18 from 1993 to 2012. During this period, certain areas of California experienced a 47 percent decline in ambient air pollution. That coincided with a 32 percent reduction in bronchitis symptoms among 10-year-olds with asthma. Children without asthma were also 21 percent less likely to experience respiratory issues.

Source: Tainio M, et al. Can Air Pollution Negate the Health Benefits of Cycling and Walking? Preventative Medicine. 2016.