Good News: Biking In Beijing Helps More Than Hurts

 Air Pollution, China public health, Exercise  Add comments
Aug 042010
 
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Here’s a very common expat question: is riding a bike in a city helping or harming your health? Fortunately, someone researched this exact question and now we can breathe with some relief, as the verdict is in: biking is beneficial.

The article was just published in Environmental Health Perspectives journal and is an essential read for those bikers out there, or the many fence-sitters a bit scared of Beijing’s streets and air. The paper, from a Netherlands group, reviewed all the current literature and data from multiple cities around the world and came up with some very encouraging figures:

For the individuals who shift from car to bicycle, we estimated that beneficial effects of increased physical activity are substantially larger (3 – 14 months gained) than the potential mortality effect of increased inhaled air pollution doses (0.8 – 40 days lost) and the increase in traffic accidents (5 – 9 days lost). Societal benefits are even larger due to a modest reduction in air pollution and greenhouse gas emissions and traffic accidents.

Conclusions: On average, the estimated health benefits of cycling were substantially larger than the risks relative to car driving for individuals shifting mode of transport.

The article has many good points, for example by noting that car drivers actually breathe in dirtier air than bikers, but bikers inhale more deeply. From the article:

Overall, air pollution exposures experienced by car drivers were modestly higher than those experienced by cyclists, with mean ratios of 1.16 for PM2.5, 1.01 for ultrafine particles and 1.65 for elemental carbon or soot. However, increased physical activity results in higher minute ventilation in cyclists than car drivers, with estimates from two Dutch studies reporting that the minute ventilation of cyclists was 2.3 times (van Wijnen et al. 1995) and 2.1 times (Zuurbier et al. 2009) higher than that of car drivers. Therefore, inhaled doses of fine particles and to a lesser extent elemental carbon may be higher in cyclists.

You can also read a news report about this article from Bloomberg: City Cycling Seems to Have More Upsides Than Down.

Biking To Work: Get All The Exercise You Need!

I think this is a very encouraging article, as it may sway some of you to bike more in Beijing as a form of exercise. Those few minutes each way on your commute can add up enough to give you the recommended heart-healthy exercise levels. Here are more details why:

In several physical activity studies, metabolic equivalent (MET) is used as an indicator of physical activity and the minimum goal should be in the range of 500 to 1000 MET·min·week. Leisure cycling or cycling to work (speed 15 km·hr) has a MET value of 4 and is characterized as a moderate activity. Hence, a person shifting from car to bike for a daily short distance of 7.5 km would meet the minimum recommendation (7.5 km / 15 km·hr = 30 minutes) for physical activity in 5 days (4 MET x 30 minutes x 5 days = 600 MET·min·week).




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 Posted by at 12:47 am
  • Kevin

    This data is totally inapplicable to Beijing. You said it's based on an average PM2.5 concentration of 1.01 – the average over the last 25 hours in Beijing is 35.7 (source: http://twitter.com/beijingair ). The rate of traffic accidents will also be a lot worse in China than in Holland, which is known for its road safety.

    • http://www.myhealthbeijing.com Dr Richard Saint Cyr

      Sorry, Kevin, I don't see a reference to a 1.01 concentration of PM2.5 in the article. The article mentions a ratio of car/bike ultrafine pollution of 1.01: that's a ratio and not an absolute value. It's from Table 1, a collection of multiple studies from London, the UK, Amsterdam and other cities.

      And all of the study is a meta-review of multiple studies from cities all over the world, not just a Netherlands city. And the estimates are extrapolations. So the basic results are still valid here.

      But of course, the air quality here is likely worse than the Netherlands, as is the traffic, so the benefit/risk would likely be a bit less than the 9 times estimated here. Perhaps some researcher can take this study's methods and plug in the numbers for Beijing…

      • Kevin

        Oops, you're absolutely right – I didn't read it correctly and commented without understanding. Sorry!

  • http://intensedebate.com/people/myhealthbeijing Dr Richard Saint Cyr

    Meiguanxi. It actually helped me to clarify the post for others. The nice thing is that this makes the data more relevant to all cities, including Beijing

  • http://www.myhealthbeijing.com Dr Richard Saint Cyr

    Here's more from the paper which describes a bit of the issues in extrapolating their data to developing countries:

    In summary, it is unlikely that the conclusion of substantially larger benefits from cycling than risks is strongly affected by the assumptions made in the scenario, including the use of data from the Netherlands. Because concentration–response functions are mostly based on studies in Europe and North America, they may not apply in developing countries. For air pollution, there are no studies on long-term mortality effects in developing countries. The generally higher ambient air pollution concentrations could lead to higher losses in life-years comparing cycling and car driving. Traffic accident statistics for the Netherlands are probably not transferable to developing countries. For physical activity, there is evidence from a Chinese study (Matthews et al. 2007, http://aje.oxfordjournals.org/cgi/content/short/1… with very similar benefits. Hence, very large differences in concentration–response functions for air pollution and traffic accidents from the functions we used would be necessary to tip the balance between benefits and risks.

   

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