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Active travel is always healthier than the car

by on 2017/06/29

Compared to the belching fumes and loud noises we are bombarded with when walking beside a busy street, the environment within a car seems quite peaceful. This sense of security leads many people to believe that being in the car protects them from air pollution and particulates. Parents might think this is especially the case for small children, with their lower stature and delicate developing bodies. But is it better for your kids’ health if they walk or cycle, even if exposed to urban air pollution, or take the car.

What did the media say?

The headline was “Air pollution more harmful to children in cars than outside, warns top scientist” and Guardian journalist Damian Carrington refers to a number of experiments and invited comment from scientific experts, a practice we very much recommend at Research the Headlines. This well supported article argues that extensive research shows that in fact the air within cars is more polluted, and therefore more harmful to health, than the air outside, even on the same route. This means active travel is the better choice.

The impetus of Carrington’s article was an opinion piece in the same newspaper on the same day by Chief Scientific Adviser to the UK Government, David King: “Smoking in cars is banned. But children still inhale toxic fumes in backseats”. On the one hand King is pointing out the government’s inconsistency: we are quick to protect children with regulations for their health against cigarette smoke, but then the most pervasive and daily of dangers – air pollution – is ignored. He notes that parents don’t realise there are high levels of air pollution in cars and their kids would be healthier by walking or cycling. King specifically cites an article published last year by an international team led by the University of Cambridge.

What did the researchers do?

These researchers asked, at what level of pollution is it no longer healthier to walk or cycle? Most studies finding a benefit for active travel have been conducted in high income countries such as Europe, which have relatively low levels air pollution. Maybe in very polluted cities, active travel is not healthier than driving.

The study by Tainio and colleagues, published in Preventative Medicine, was not an experiment nor was it particularly on children.  It involved a statistical analysis of the relationship between background levels of pollution in urban settings and the long-term health impacts of regular physical activity due to active travel – cycling or walking the commute. The researchers looked at two important decision points for health: 1) when there is no further health benefit from doing more active travel, and 2) when there is more harm from pollution than benefits from activity.

To estimate a realistic range of pollution levels, the researchers drew on a worldwide database of air pollution in 1622 cities across the globe. Looking at that list, I found that for the UK, Greater London and Sheffield have the worst pollution and Aberdeen the least. To place that in context, the pollution in Delhi, India, is more than 10-fold higher than the highest pollution levels in the UK.

The researchers analysis demonstrated that the long-term health benefits of walking and cycling outweigh the harmful effects of being exposed to air pollution during that activity by a long-shot. For example, given the level of air pollution found in the average city, one can cycle for 7 hours or walk for 16 hours per day before reaching the point where no further benefits are possible. This is compounded when assuming that time spent cycling replaced time driving a car; the health benefits always exceeded the health risks except in the most extremely polluted cities.

The bottom line

Given the levels of pollution found in the vast majority of cities in the world, including the UK, it is always healthier to walk or cycle for your transportation. Skip the car in the morning and get yourself and the kids out by bike and foot!

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