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Re: Newsflash! Cycling is now unhealthy!
Posted: 31 May 2010, 11:48am
by reohn2
EdinburghFixed wrote:I've always felt slightly suspicious about research showing that cyclists breathe in fewer particulates. Suppose I take three times as many breaths when riding back from work as I would do in the car - assuming parity of journey time particulates in the car would need to be at 3x higher concentration for the total exposure to even out. So in that respect this new study agrees with what would have been my working hypothesis.
It's less clear why cyclists would have greater exposure than pedestrians however, as they may be breathing at a third of the rate but it takes them 5x longer (or more) to get to their destination. The only explanation that would make sense is that concentrations on the pavement are vastly lower than in adjacent cycle lanes (!!).
Which means it depends on how long someone spends in "bad air" x breathing rate,cyclists tend to spend less time in "bad air" than either peds or motorists in city centre travel,as they move faster(generally).
Jack wrote:-
Rather than seeing this as mocking healthy cycling I think it provides more evidence for limiting motorised vehicles in urban areas until they can control the particulates they pump outIts
Clearly a case for restricting the use of cars in city centres as a way forward for a cleaner air initiative,which to my mind is a better way forward for everyones health,pollution is a killer,just take a look at a long term smoker.
Re: Newsflash! Cycling is now unhealthy!
Posted: 31 May 2010, 12:26pm
by Fatou
EdinburghFixed wrote:I've always felt slightly suspicious about research showing that cyclists breathe in fewer particulates. Suppose I take three times as many breaths when riding back from work as I would do in the car - assuming parity of journey time particulates in the car would need to be at 3x higher concentration for the total exposure to even out. So in that respect this new study agrees with what would have been my working hypothesis.
It's less clear why cyclists would have greater exposure than pedestrians however, as they may be breathing at a third of the rate but it takes them 5x longer (or more) to get to their destination. The only explanation that would make sense is that concentrations on the pavement are vastly lower than in adjacent cycle lanes (!!).
The article gives the units as millions of particles inhaled for every meter travelled, not every breathe inhaled
Re: Newsflash! Cycling is now unhealthy!
Posted: 31 May 2010, 3:53pm
by Les Reay
From The Guardian a couple of years back:
Half an hour of sniffing diesel fumes in a busy city street is enough to induce a "stress response" in the brain, according to scientists who measured volunteers.
The response continued to increase even after they had stopped breathing the fumes.
The researchers speculate in a study published today that the changes in the brain may trigger other well-established body responses to diesel fumes, such as oxygen deprivation in the heart.
"The changes that we see can be interpreted as a stress response," said Thomas Sandström at the University of Umeå in Sweden.
"For the first time ever, air pollution effects in the brain have been visualised, which is an effect previously unheard of."
The team cannot be sure what part of the diesel pollution causes this effect, but studies in rats have shown that minuscule soot particles can make their way directly to the brain via nerves in the nose.
Paul Borm, from Zuyd University in the Netherlands, who led the study, said: "We believe our findings are due to an effect of nanoparticles or 'soot' particles that are a major component of diesel exhaust.
"These may penetrate to the brain and affect brain function."
We are back to the situation that existed in the middle of the last century with smogs and smoky chimneys but this time we can't see it, so for most people, it's OK.
Re: Newsflash! Cycling is now unhealthy!
Posted: 1 Jun 2010, 8:58am
by EdinburghFixed
Fatou wrote:EdinburghFixed wrote:I've always felt slightly suspicious about research showing that cyclists breathe in fewer particulates. Suppose I take three times as many breaths when riding back from work as I would do in the car - assuming parity of journey time particulates in the car would need to be at 3x higher concentration for the total exposure to even out. So in that respect this new study agrees with what would have been my working hypothesis.
It's less clear why cyclists would have greater exposure than pedestrians however, as they may be breathing at a third of the rate but it takes them 5x longer (or more) to get to their destination. The only explanation that would make sense is that concentrations on the pavement are vastly lower than in adjacent cycle lanes (!!).
The article gives the units as millions of particles inhaled for every meter travelled, not every breathe inhaled
Imagine as a baseline, somebody walking along a mile of road. For me, this takes 20 minutes, give-or-take, on foot, and 3 minutes, give or take, by bike. A good assumption would be that exactly the same air is being breathed by each party, since on an average Edinburgh road you'll be 3-6 feet away from somebody on the pavement, and the wind / passage of vehicles should be causing enough churn to even up.
The only explanation that fits, then, is that I inhale as much air in 3 minutes cycling as in 20 minutes walking. But this seems like a huge increase - 6.5x as much air per minute!
The comparison with drivers isn't that controversial because at 30mph, they are exposed for less time (and take fewer breaths) even though the air inside the car may be of a lower quality.
Re: Newsflash! Cycling is now unhealthy!
Posted: 1 Jun 2010, 9:17am
by rootes
Cunobelin wrote:7_lives_left wrote:I believe you are all looking at this the wrong way. What the article is telling us is that we have to wear both helmet and facemask.
... I'll get my coat
..or combine the two - the "Breath Air" helmet:
hmmmnn hardly the friendly face of cycling is it! cool though
Re: Newsflash! Cycling is now unhealthy!
Posted: 1 Jun 2010, 1:20pm
by Goosey
"Journalists in
Telling Lies Shock!!"
Re: Newsflash! Cycling is now unhealthy!
Posted: 1 Jun 2010, 2:39pm
by mark a.
Ok, so I've had a read of the actual paper (as opposed to the Times rehash, which I've only skimmed), which can be found on Science Direct for those with access. The abstract reads:
Emerging evidence suggests that short episodes of high exposure to air pollution occur while commuting. These events can result in potentially adverse health effects. We present a quantification of the exposure of car passengers and cyclists to particulate matter (PM). We have simultaneously measured concentrations (PNC, PM2.5 and PM10) and ventilatory parameters (minute ventilation (VE), breathing frequency and tidal volume) in three Belgian locations (Brussels, Louvain-la-Neuve and Mol) for 55 persons (38 male and 17 female). Subjects were first driven by car and then cycled along identical routes in a pairwise design. Concentrations and lung deposition of PNC and PM mass were compared between biking trips and car trips.
Mean bicycle/car ratios for PNC and PM are close to 1 and rarely significant. The size and magnitude of the differences in concentrations depend on the location which confirms similar inconsistencies reported in literature. On the other hand, the results from this study demonstrate that bicycle/car differences for inhaled quantities and lung deposited dose are large and consistent across locations. These differences are caused by increased VE in cyclists which significantly increases their exposure to traffic exhaust. The VE while riding a bicycle is 4.3 times higher compared to car passengers. This aspect has been ignored or severely underestimated in previous studies. Integrated health risk evaluations of transport modes or cycling policies should therefore use exposure estimates rather than concentrations.
My understanding is that the main points are:
- There is massive variation in pollutant levels between cities and in time
- However, cyclists always have higher pollutant levels in this study
- The paper talks about lung deposition (i.e. how much pollutant stays in the lungs) as well as the amount breathed in
- Cyclists are exposed to more pollution anyway, made worse by the fact that they're breathing harder
Three differences influence
the exposure of cyclists to air pollution. The most important one is
a large increase in breathing frequency and tidal volume which
increases the total inhaled volume. Secondly, for the same inhaled
quantity, the amount of particles that remains in the respiratory
tract is higher while exercising because of increased deposition.
Finally, the time needed to complete the route is often (but not
always) longer for the cyclist. Nevertheless it is mainly the differences
in ventilation (and associated deposition) that matter.
- There is huge variation between previous studies as to whether pollution is higher in cars than for cyclists and pedestrians. This study reckons (funnily enough) reckons it's got the best estimate due to sample size and methodology
- Although the study shows that cyclists have higher pollution levels, it's not clear what the negative health effects are and whether they are outweighed by the health benefits of cycling.
It's not all doom and gloom, as the conclusion states:
The results presented in this paper should be seen as an
opportunity to improve cycling conditions. Given the fact that
people who choose to cycle contribute to better air quality, policies
and measures should first target the motorized traffic that is a cause
of air pollution and focus on reducing exposure (rather than
concentrations) to prevent unwanted health effects.
Re: Newsflash! Cycling is now unhealthy!
Posted: 2 Jun 2010, 7:31pm
by Nutsey
Whats worse? Cycling through car fumes, or swallowing a bee in the countryside? Both have their pitfalls!