Exercise benefits ‘outweigh’ pollution risk, research finds

Research by the University of Cambridge claims that health risks from air pollution do not outweigh benefits from outdoor exercise.

Health benefits from walking and cycling in major cities like London outweigh the risks from air pollution, according to new research.

The study, published in the journal Preventive Medicine, is the first to model the risks and benefits of walking and cycling, across a range of air pollution concentrations in locations around the world.

Londoners can benefit from cycling despite air pollution

Londoners can benefit from cycling despite air pollution

Research was led by both the Centre for Diet and Activity Research (CEDAR), a partnership between the Universities of Cambridge and East Anglia, and the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge.

This new research aims to disprove concerns about air pollution and its potential health risks when taking ‘active travel’, such as walking and cycling, in polluted urban environments, the authors claim. Researchers also added that the findings in turn reinforce the support for cycling and active travel in cities, which can help reduce vehicle emissions.

Previous studies

Previous studies conducted across Europe, USA and other regions have also shown that the health benefits of exercise in polluted environments are greater than the risks. However, unlike the latest research, these studies were conducted in areas of relatively low pollution and therefore there is uncertainty when applying the results to more polluted cities.

Leading the new study was Dr Marko Tainio from the MRC Epidemiology Unit at the University of Cambridge, who commented: “Our model indicates that in London health benefits of active travel always outweigh the risk from pollution.”

“Even in Delhi, one of the most polluted cities in the world — with pollution levels ten times those in London — people would need to cycle over five hours per week before the pollution risks outweigh the health benefits” – Dr Marko Tainio, University of Cambridge

Additionally, the study found that only 1% of cities in the World Health Organization’s Ambient Air Pollution Database had pollution levels so high that risks from air pollution could overcome health benefits when cycling for half an hour every day.

However, Dr Tainio said: “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.”

Senior author Dr James Woodcock, from CEDAR added: “Whilst this research demonstrates the benefits of physical activity in spite of air quality, it is not an argument for inaction in combatting pollution.”

Instead, Dr Woodcock said it should provide “further support for investment in infrastructure”, getting people walking or cycling instead of driving, which promotes both health and reduced pollution.


The study assessed long-term average levels of cycling and walking from 0 up to 16 hours per day and air pollution exposure was estimated through the changes of fine particulate matter (PM2.5) concentrations ranging from 5 to 200 μg/m3.

For the global average urban background of PM2.5 concentration at 22 μg/m3, the benefits of physical activity outweighed the risk of air pollution, even under extreme levels of active travel, the researchers claimed.

By increasing pollution levels to areas with PM2.5 concentrations of 100 μg/m3, risks would outweigh the benefits after 1hr 30min of cycling per day or more than 10 hours of walking per day.

Overall, the research claimed that the benefits of active travel outweighed the risks from air pollution in all cases but the most extreme pollution concentrations.


Data was compiled using computer simulations to compare the risks and benefits of different levels of active travel, including its intensity and duration, and also, the air pollution in different locations globally, using information from international epidemiological studies and meta-analyses.

Limitations of the study include the lack of information on impacts of short-term episodes of increased air pollution and excluding information on the previous disease history of individuals.

Air pollution is one of the leading environmental risk factors for health and a recent report by the Royal Colleges of Physicians and of Paediatrics and Child Health suggested it may contribute to around 40,000 early deaths a year in the UK.

CEDAR, based in the MRC Epidemiology Unit is funded through the UK Clinical Research Collaboration and works to shape public health practice and policy. The work was also supported by the project Physical Activity through Sustainable Transportation Approaches, funded by the European Union.

Related Links

Can air pollution negate the health benefits of cycling and walking? – Report


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