Cycling in heavy pollution could affect heart's ability to respond to different levels of exertion, say Dublin scientists
By Sarah Barth, December 29, 2013
Cyclists at traffic lights
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 Ottowa 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 Ottowa 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
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
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
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 Ottowa were based
on a small sample sizes - 32 in Dublin, 42 in Ottowa. 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 Ottowa 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 li
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
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.
kely to be breathed in.
I n 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
Nitrogen dioxide also reacts with hydrocarbons in the presence
of sunlight to create ozone, and contributes to the formation of
*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.