Is cycling in the city doing more harm than good?

Host: Dr Andrew Rochford

Wednesday, June 17, 2009

Cycling has become increasingly popular over recent years. After walking, aerobics and swimming, cycling is the fourth most popular exercise in Australia. And it's not just a weekend thing, more and more of us are choosing to ride to work.

There's no doubt that riding a bike is great for our health. But, what about if we are cycling near traffic? Could we be putting our health at risk by riding in the city where there is air pollution present?

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The main pollutants in large cities are ozone, particles, nitrogen dioxide, carbon monoxide and sulphur dioxide.

With the help of the NSW Institute of Sport, Dr Andrew Rochford teamed up with elite cyclists Skye-Lee Armstrong and Alex Carver, plus senior physiologist Dr Nathan Townsend to test one of the main pollutants, carbon monoxide (CO).

Carbon monoxide is an odourless, colourless gas. It forms when the carbon in fuels does not completely burn. Vehicle exhaust contributes most carbon monoxide emissions. Carbon monoxide enters the bloodstream through the lungs and binds to haemoglobin, the substance in blood that carries oxygen to cells. Carbon monoxide reduces the amount of oxygen reaching the body's organs and tissues.

The team of four rode for approximately 27km straight into Sydney's peak-hour traffic with the aim to test whether carbon monoxide (CO) levels increase in a person after riding along a typical traffic route.

Dr Townsend took initial micro blood samples from Andrew, Skye-Lee and Alex to gauge their baseline CO level. Dr Townsend then took a second sample at the end of the bike ride to check whether the CO levels had increased.

We also tested Neil, a bike courier who rides on average 50-70km per day around the city to check how his CO levels fared.

Results
Andrew's CO level increased from 1.9 percent to 2.2 percent.
Sky-Lee's CO level increased from 2.1 percent to 2.4 percent.
Alex's CO level increased from 2.1 percent to 2.5 percent.

And what about the bike courier Neil? His base level was slightly higher than our other three samples at 2.7 percent.

The four levels of our test cyclists were all relatively low. While Andrew, Skye-Lee and Alex's CO levels increased slightly, physiologist Dr Townsend says this isn't a concern. "A high value is above 10 percent so even after the ride into the city during peak hour traffic these CO levels only increased a small amount," he said.

The same goes for our bike courier Neil. Nathan says "Even though Neil is out there all day, his CO levels still weren't really high."

Conclusion
For most cyclists, the benefits from regular exercise from bike riding far outweigh the risk from pollution. Cyclists should use bike paths where possible and avoid cycling directly behind motor vehicles. Studies have shown that at just 10m away from traffic, pollution levels drop by 90 percent.

And the good news is, even if the carbon monoxide levels do increase slightly after a ride, the elevated levels will only stay around for about five hours, but the health benefits of cycling will last for a lot longer!

User reviews

Cyclists, babies in prams and anyone walking slowly near heavy traffic is naturally exposed to the poisons. Are you all trying to say traffic is merely a sea breeze from the Pacific? I know of people who after years of cycling in the city now suffer illness that affects their nerves. It seems childish to hide your head in the bush like a rabbit and come up with explanations that try to evade the obvious. Wake up to the fact that for example Sydney has awful air quality along some main routes and people suffer from the traffic fumes even in their flats with windows open to the main streets. Combined with the particles of the dry bushland around, dust, the particles from the roads and tyres, the carbon monoxide bakes itself into particles that are a natural killer. The only solution is electric driven cars.

It seems the article's main point is valid, even though its journalistic merit is questionable - the more cyclists the better. Swap 1 car for a cycle at peak hour (most are one person) = less pollution, more road room, 1 more bike = one person getting exercise, everyone breathes better air, roads are safer. Certainly sounds good to me (a Brisbaner living in London). To the motorcyclist who wants to use cycle lanes - motorbikes are terrible polluters, they block cycle lanes (in London), they make cycling more dangerous than any car or bus. So no. Sometimes we still need cars in Oz but why not ride to work from 10km out? Sell the 2nd car and hire a car if you need an extra one. Get healthier for the benefit of you, your family, and society. Save a packet too! And to Rob in Sydney, think! Try not to strain anything! Millions are spent on education for drivers = 100s of deaths. Almost nothing is spent on education for cyclists and cyclists have barely caused a death.

More importantly is such a mundane question of any interest to anyone?

...would be to take the same measurements from someone who drove to work who was on the road in traffic for a similar time. This would give a better idea of whether cycling exposes you to 'worse' pollution than driving. Test the pedestrians while you're at it! I do agree though that the health benefits (and convenience, and time savings, and incidental environmental improvements) far outweigh the risks.

What a pity just when I anticipated that nine msn was onto a good story as a lead up to the tour de france, we get this commentary. Cycling 10m from cars is not advised as this leads to cars squeezing you into the kerb and also getting annoyed, take the lane be a vehicle like you legally are and take your kids cycling in parks so that they get the skills to cycle in traffic. NSW is the most lagging state in the country for bike infrastructure and it is all so dispersed and disjointed you are doing potential cyclists a disservice by encouraging them to ride in parks and paths. If only more academics had cycle training and rode to campus well such attitudes may change. His last sentence is well put though and good to read.

I ride downhill mountain bikes and belong to the mba (mountain bikes Australia) so I am a fellow bicycle rider, we also have to road bikes at home so its not uncommon for myself to be seen on the side of the road playing with the traffic on my road bike on the way home from TAFE. Anyways I think you are wrong because even if we walk, jog, run, swim or drive to work we are still in the same air pollution so why just pin point this subject to bike riders, if this is another attempt to get the bikes of the road and away from traffic then im sure there are other ways if you dont like us being there build some more bike lanes there isnt enough anyways and if you are seriously worried about the air pollution getting into the lungs of bike riders than write a letter to kevin. I love to ride so dont *** with it. k .

Thats good news. Other studies have shown air pollution is worse inside cars than outside where a cyclist rides, due to trapping and build up of pullutants. A cyclist behind a smelly diesel truck can often avoid the fumes by pulling over or riding away from the exhaust, but a car driver just has to suffer if they are caught behind.

I am a motorcycle rider really why don't i have lanes such as this?... i pay maib registration do cyclists? As a motorcyclist i believe i should have the bicycle lane as well i pay the fee's but yet i understand some cyclist register but mostly they do not. It is unacceptable that a motorcyclist can not access these lanes with a cyclist. We accept you as an equal and will look after you in rough time please accept us..

This segment proves a good point about the concentration of carbon monoxide in the bloodstream, but what do we usually associate poisonous fumes with? We usually associate them with the direct affects on lung tissue. The fumes need to pass through the lung tissue before they enter the bloodstream. This is where people are having major problems although the NSWIS is not addressing this. The study shown in this segment is a typical example of barely qualified representatives showing off their most sophisticated gear. And another point lies in the fact that the NSWIS cannot afford in any way to discourage cycling, from a sales perspective and from a support perspective. If the NSWIS did however expose the affects of pollution on lung tissue, there would be potential for the company to lose sales commissions and lose their involvement with various cycling associations. Australia is all about conspiracies relating to financial benefits.

How about the fact that cyclists just rule the roads and the footpaths and just follow their own rules. Hazard to pedestrian''s health more like it, because one of these days, a pedestrian will be killed one of these days if it hasn't happened already.

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