city cycling cuts air pollution

A study of the public cycle sharing scheme in Barcelona (called Bicing) reveals that the overall effects on health are positive, and there are significant reductions in general air pollution especially carbon emissions. The results could be applicable to London, where a bike sharing scheme has been up and running since 2010 and has attracted millions of hires.

Bike sharing schemes in cities are meant to benefit our health by reducing traffic congestion. In fact, London was a little late to this particular party. Barcelona launched its scheme in 2007, the same year as Paris, Seville and a year later than Lyon and Stockholm. The idea has spread to China with Hangzhou starting a cycle sharing scheme in 2008 and Guangzhou last year.

The proliferation of cycle schemes will provide a lot of data on how increasing the popularity of cycling may impact on urban air quality and also on citizens' health. Contemplating cycling in the city, you may wonder whether you are more at risk of lung or heart disease from exposure to particulate matter, from diesel exhaust and other pollution sources, or whether the impact on your fitness and heart health will outweigh these risks. This new study, undertaken by researchers in Barcelona, with colleagues in Madrid, Poland, and Finland, provide some answers.

Direct outcomes on health from increased urban cycling are hard to measure. Instead, the researchers used a new computer model that can integrate data from scientific studies and local measurements. Around 11% of the population of Barcelona (just over 182,000 people) uses the bike share scheme, with most journeys done for commuting to work or school. Here are the main findings:

  • Air pollution. Exposure to particulate matter (PM2.5s and finer particles) which has strong associations with all cause mortality, was assessed. Each year, there were an extra 0.13 cyclist deaths from exposure to air pollution. It would take many years before the number of deaths from exposure to air pollution was significant. Remember that London's poor air quality is said to cause 4,300 deaths per year, to put the risk from cycling into context.
  • Mortality from road traffic accidents. The roads are dangerous - most cyclists would acknowledge that. The Barcelona study found that there were an estimated 0.03 extra cyclist deaths from bike sharing - maybe far fewer than you might have feared.
  • Physical activity. This was where the main benefit in cycling lies. An extra 12 lives a year would be saved by bike sharing. The reason is that obesity and inactivity are such major causes of serious health problems and mortality.
  • Carbon dioxide emissions. Emissions of 9,000 tonnes of carbon dioxide pollution a year are averted by cycle sharing, presumably because if people are on a bike, they cannot be driving a pollution-emitting vehicle.

Of course, many questions remain. How does the cycling scheme effect asthma symptoms for example? What about the impact of more cycling on other emissions - especially PMs and nitrogen oxides? Carbon dioxide itself does not have a direct impact on health - it is more of a long term problem in the form of climate change. Urban areas like London need to restrict dirty vehicles, as well as encouraging cycling. Are these results from Barcelona applicable to other cities? And how do these results from a computer model compare with other ways of measuring the health impact of public transport? But let's hope people are encouraged by this news of how urban cycling can, overall, benefit health - because more cycling will also improve the air quality in our cities with further positive impact upon health. But, of course, it can only be a small part of an overall transport policy that puts public health at the top of the agenda.

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