Cycling in cities could do more damage than good to a rider’s heart due to dangerous pollutants in the air, a new study based on cycling in Dublin has found.
The Dublin study is not the first to suggest that air pollution in cities may pose a health risk to cyclists back in 2011 we reported on a study conducted by Proffessor John Grigg for Barts and The London School of Medicine which found that London cyclists inhaled 2.3 times more black carbon than pedestrians. That same year a study in Ottawa suggested that cyclists could experience short term heart irregularities in urban cyclists exposed to high levels of pollution.
The problem for cyclists is that when they exert themselves breathe more heavily than pedestrians, meaning their exposure to miniscule particles of polluting chemicals is increased.
The Scientists who have studied cyclists in Dublin say that these chemicals reduce the ability of the heart to respond to different rates of exertion (a similar finding to the 2011 Ottawa study).
They noted that: “These [findings] indicate that exercise while commuting has an influence on inhaled particulate matter, associated with acute declines in heart rate variability, especially in pedestrians and cyclists.”
As well as exhaust fumes, studies have shown that vehicle brakes and tyres also generate potentially dangerous particles, which can penetrate the lungs due to their tiny size and work their way into the bloodstream.
The Dublin study of 32 fit healthy cyclists was led by Marguerite Nyhan of Trinity College Dublin, who advised riders to choose relatively traffic-free routes for their health.
A spokesman for Sustrans, a charity that campaigns for cycling and walking, said: “Air pollution is a concern and Sustrans is calling on the government to ban unfiltered diesel vehicles from Britain’s cities. However, the benefits of cycling and walking far outweigh the health risks.”
Professor Ross Anderson of the government’s advisory committee on the medical effects of air pollutants told the Sunday Times (£): “While the health benefits of cycling are likely to be beneficial, the balancing of risks is problematic. Other epidemiological evidence suggests that traffic pollution has lasting health effects.”
While any exposure to pollution is unlikely to be a good thing it it worth noting that the studies from Dublin, London, and Ottawa were based on a small sample sizes - 32 in Dublin, 42 in Ottawa. it's also worth noting that accordint to a Danish study car occupants are most at risk of inhaling harmful traffic pollution being exposed to up to four times the levels of pollutants that cyclists are.
Currently the best advice for urban cyclists who want to reduce their exposure to harmful pollutants is to opt for quieter routes on less busy roads. One other suggestion resulting fromt he Ottawa study is that cyclists should keep at least 15 feet back from a car or lorry's exhaust pipe. The closer you get to the exhuast the finer the particulates of the most harmful pollutants - but as they get further from the exhaust they tend to clump together in to heavier particles which fall to the ground and are thus less likely to be breathed in.
As we reported last year, Glasgow is the most polluted city in the UK, and the fifth worst in the whole of Europe, a study has shown.
The report from the European Environment Agency (EEA) measured the toxic gas nitrogen dioxide, caused by exhaust fumes and industrial pollution.
Only ten cities, of which Glasgow was one, breached the limits for the harmful gas. Levels in Glasgow were 46.3 microgrammes per cubic metre, above the legal European limit of 40mg/m3.
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.