Mark Cavendish, Bradley Wiggins and the other hopefuls in tomorrow's Olympic road race have another thing to worry about - air pollution.
We wrote last week about one of the services that lets you know about the air quality in your local area, and a Roadcc reader has let us know that in Putney, which features twice on the road race route, both in and out of central London, levels of nitrogen dioxide are nine out of a possible 10.
Official government advice when the figures hit these heights is:
For the general population: "Anyone experiencing discomfort such as sore eyes, cough or sore throat should consider reducing activity, particularly outdoors."
For at risk individuals: "Adults and children with lung problems, and adults with heart problems, should reduce strenuous physical exertion, particularly outdoors, and particularly if they experience symptoms. People with asthma may find they need to use their reliever inhaler more often. Older people should also reduce physical exertion"
Now these are world class athletes, so they're probably not in the 'at risk' groups, to be fair, but it's an interesting comment on London's roads and air quality.
According to government information, nitrogen dioxide is pretty nasty stuff:
Nitrogen dioxide (NO2) is one of a group of gases called nitrogen oxides. Road transport is estimated to be responsible for about 50% of total emissions of nitrogen oxides, which means that nitrogen dioxide levels are highest close to busy roads and in large urban areas. Gas boilers in buildings are also a source of nitrogen oxides.
There is good evidence that nitrogen is harmful to health. The most common outcomes are respiratory symptoms such as shortness of breath and cough. Nitrogen dioxide inflames the lining of the lung and reduces immunity to lung infections such as bronchitis. Studies also suggest that the health effects are more pronounced in people with asthma compared to healthly individuals.
In recent years the average level of nitrogen dioxide within London has not fallen as quickly as predicted. This largely appears to be the result of diesel cars creating more nitrogen dioxide than was anticipated.
Nitrogen dioxide also reacts with hydrocarbons in the presence of sunlight to create ozone, and contributes to the formation of particles*.
*tiny bits of solids or liquids suspended in the air, that can settle in the airway and deep in the lungs and cause health problems.
After an unpromising start, having to be bribed by her parents to learn to ride without stabilisers, Sarah became rather keener on cycling in her university years, and was eventually persuaded to upgrade to proper road cycling by the prospect of a shiny red Italian bike, which she promptly destroyed by trapping a pair of knickers in the rear derailleur. Sarah writes about about cycling every weekend on road.cc.