The benefits of walking and cycling outweigh the negative effects on health of air pollution, even in places with high levels of air pollution such as New Delhi - one of the most polluted cities in the world, according to a new study.
This new evidence strengthens the case for supporting cycling even in polluted cities - an effort that in turn can help reduce vehicle emissions, researchers said.
"Our model indicates that in London health benefits of active travel always outweigh the risk from pollution," said Marko Tainio from University of Cambridge in the UK.
"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," said Tainio.
Regular physical activity reduces the risk of diseases such as diabetes, heart disease, and several cancers.
One way for people to increase their levels of physical activity is through 'active travel' - for example walking and cycling; however, concern has been raised about the potential risk due to air pollution while walking and cycling in urban environments, researchers said.
Air pollution is one of the leading environmental risk factors for people's health. One of the main sources of air pollution in cities is transport and a shift from cars, motorbikes and buses to active travel would help to reduce emissions, researchers said.
However, people who walk or cycle in such environments will inhale more pollution, which could be detrimental to their health.
Researchers from CEDAR, a partnership between the Universities of Cambridge and East Anglia, and the Medical Research Council used computer simulations to compare the risks and benefits for different levels of intensity and duration of active travel and of air pollution in different locations around the world, using information from international epidemiological studies and meta-analyses.
The study is the first to model the risks and benefits of walking and cycling across a range of air pollution concentrations around the world, researchers said.
Using this data, they calculated that in practical terms, air pollution risks will not negate the health benefits of active travel in the vast majority of urban areas worldwide.
Only 1 per cent of cities in the World Health Organisation's Ambient Air Pollution Database had pollution levels high enough that the risks of air pollution could start to overcome the benefits of physical activity after half an hour of cycling every day, researchers said.
The findings were published in the journal Preventive Medicine.
The OECD report further said a reduction in crop yields
as a result of "dirty air" will weigh on most countries' economies.
Exceptions will include Brazil, Russia and some Latin American countries where agricultural land is set to be less affected, meaning improved export competitiveness and thus economic gains.
The report further said for most air pollutants, emissions are projected to increase in the coming decades.
"Rising emissions reflect the underlying baseline assumptions on economic growth: with increasing GDP and energy demand, especially in fast growing economies such as India and China, emissions of air pollutants rise, albeit at a slower pace than GDP," it said.
The number of premature deaths is unequally distributed across the world. The highest number of deaths takes place in non-OECD economies and particularly in China and India.
As per the OECD report, welfare costs from premature deaths are by 2060 projected to more than double in OECD countries, going from USD 1.4 trillion in 2015 to USD 3.4-3.5 trillion in 2060.
Nevertheless, larger costs are estimated for non-OECD economies, where they amount to almost USD 1.7 trillion in 2015 and are projected to increase roughly ten-fold to reach USD 15-22 trillion in 2060.
"That is due to the high and rising number of premature deaths in China and India, as well as the projected increase in income in these countries, which leads to higher values associated with each premature death," OECD said.
