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Cycling puts healthy Londoners on road to early heart disease

This is exactly what Toronto Hoof & Cycle warned about six years ago in Choking us to death: The Air Pollution Crisis and Its Effects on Bicycle Couriers.

The solution is not to move cyclists it's to decrease and eventually eliminate emissions.

There have been studies that show pollution levels "higher" inside cars than the ambient air quality outside but those studies took the outside measurements at a fixed point 50m-100m away from any road or vehicle. Cyclists ride directly in traffic not 50m to 100m away.

There are many reasons messengers are so at risk:
  1. Proximity - the closer you are to the source the greater the exposure
  2. Duration - the more time you spend in pollution, the greater the risk
  3. Rate of breathing - the higher your rate of breathing the more particulates you bring into your lungs and blood. (This is one of the main reason children are more at risk.
  4. Long term frequency - once you have damaged your lungs and heart they become more sensitive to the effects of pollution to the point that it can cause a heart attack even many days after exposure.
And factor in  that particulates from "clean" diesel engines are a known carcinogen.

The Sunday Times, August 22, 2005

Cyslists may be doing themselves more harm than good by pedalling to the office along congested roads, according to pioneering research by the British Heart Foundation.

Tests showed that after just one hour of cycling in traffic, the microscopic particles carried in diesel fumes caused significant damage to blood vessels, increasing the risk of heart disease.

Those cycling at high speeds in the hope of improving their fitness levels are doing themselves the most damage, by breathing in a higher volume of the polluted air.

The system of locating most cycle paths within bus lanes has the perverse effect of forcing cyclists to inhale the most dangerous air, spewed out by diesel-powered buses and taxis.

The number of diesel-engine cars in Britain grew from 1.6million to 5million between 1994 and last year.

The health warning will dismay the many commuters who have switched to bicycles to improve their fitness, to avoid high fuel prices or, in London, because they fear another terrorist attack on public transport.

Cycling is on the increase. In London it is up by 25per cent in the past year, according to cycling charity CTC, and Transport for London has reported an extra 50,000 bike journeys a week since the July 7 bombs.

There is no dispute in principle about the health benefits of cycling -- it improves the circulation, keeps weight down and boosts fitness -- yet the new research indicates they could be outweighed by the polluted conditions of a busy road.

"Cycling through congested traffic exposes the cyclist to high levels of air pollution, especially as the exercise of cycling increases breathing and the individual's exposure," said David Newby, British Heart Foundation senior lecturer in cardiology at Edinburgh University. "This is bad for the heart."

He had 15 healthy men cycle on exercise bikes for an hour while being exposed to levels of diluted diesel exhaust comparable to the air they would inhale cycling on a congested city road.

Six hours after exposure to the fumes, damage was detected to their blood vessels. They became less flexible and there was a reduction of a protein that breaks down blood clots in the heart. This is associated with the early stages of heart disease.

Diesel exhaust includes nanoparticles of carbon and a range of metals. The particles are so tiny that experts say that it is pointless for cyclists to wear masks, because the mesh cannot be fine enough to block them.

If cycle paths were located away from roads the health risks would be greatly reduced. At just 10m from traffic, pollution levels drop by 90 per cent.

"While they are exercising, cyclists breathe two to three times as much air as car drivers," Dr Newby said. "We need to locate cycle lanes away from major roads."

His research has been submitted to the journal Circulation.

The level of pollution inside a car is typically higher than that of the air on the road outside, because a proportion of the pollutants become trapped within the vehicle.

Next month, the British Committee on the Medical Effects of Air Pollutants, a government advisory body, will publish a report highlighting the risks of heart disease from traffic pollution.

Jon Ayres, professor of environmental and occupational medicine at Aberdeen University and chairman of the committee, says typical urban traffic pollution poses the same risk of heart disease as passive smoking.

"Exercising outside (in cities) will be a contributory cause of heart disease in healthy individuals," Professor Ayres said. He said it was a lesser factor than a person's blood pressure or cholesterol level but "of the same order as passive smoking".

A report by the British Medical Association, published in 2002, shows that passive smoking increases the risk of lung cancer by 20 to 30per cent and heart disease by 25 to 35per cent. Thirty people die from passive smoking a day, according to a recent study published in the British Medical Journal.

Research published in the New England Journal of Medicine in October last year found that people susceptible to heart disease are three times as likely to suffer a heart attack an hour after exposure to traffic pollution than on days when they were away from traffic.


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