Is pollution a problem in urban cycling?

Question

I usually ride a bicycle in Barcelona. I'm concerned about pollution and I take an anti-pollution mask. Of course, some people scream because they confuse me with Hannibal Lecter but currently that's not a problem.

I've heard a lot of opinions about this: "don't care because pollution it's not harmful", "that masks make no sense" and so on...

What do you know about cycling and pollution? What about masks, are they effective at blocking pollution?

Note: I think objective/documented answers are the most useful. Please, try to avoid "I think that...", "my opinion is..." answers.

Answer 1

Rank, Folke and Jespersen (2001), "Differences in cyclists and car drivers exposure to air pollution from traffic in the city of Copenhagen", The Science of The Total Environment, 279:131-136

teams of two cyclists and two car drivers in two cars were equipped with personal air samplers while driving for 4 hours on 2 different days in the morning traffic of Copenhagen. The air sample charcoal tubes were analysed for their benzene, toluene, ethylbenzene and xylene (BTEX) content and the air filters for particles (total dust). The concentrations of particles and BTEX in the cabin of the cars were 2–4 times greater than in the cyclists’ breathing zone, the greatest difference being for BTEX. Therefore, even after taking the increased respiration rate of cyclists into consideration, car drivers seem to be more exposed to airborne pollution than cyclists.

Answer 2

Exposure while cycling is generally no worse than being in a vehicle.
In fact can be better depending on the weather and the amount of solvents in the plastic of your car. You do experience more when cycling heavily - simply because you breath more - but general medical evidence is that the benefits of increased fitness greatly outweigh any problems.

The mask probably helps if you cycle behind buses (it will stop some pm10s but it does nothing for ozone or other chemical pollutants)

• Bicycle messengers: energy expenditure and exposure to air pollution
• Commuters’ Exposure to Particulate Matter Air Pollution Is Affected 
by Mode of Transport, Fuel Type, and Route

Answer 3

Ways to reduce your exposure include:

1. riding on bike paths and secondary streets
2. riding at off-peak times (when traffic is low)
3. riding when commercial traffic (e.g. diesel-consuming trucks) is lower
4. riding before the sun gets high or after it begins to go down: ozone is produced by sunlight and takes time to develop (see image below from Chapter 6)

Richard Turco's book provides an excellent overview of urban smog and pollution

Answer 4

This issue was highlighted on the BBC News website Cyclists are 'unaware of the risks from pollution' in an article aimed at raising awareness in cyclist of the short and long term effects of air pollution.

The article makes for a good read. A brief summary,

• Primarily pollution cause the cyclist’s airways to become inflamed and therefore narrow, trigger airway irritation, decrease the amount of oxygen that the blood can carry and reduce lung function.
• Pollution from being near or close behind diesel engines is of particular concern (small & ultra fine particles are inhaled deeper into the lungs).
• It can cause significant airway irritation and breathing difficulties for those with existing respiratory disease.
• Cyclists breathe more deeply during the physical exertion of cycling so may take in more particulates than car/bus users, but other studies suggest passengers in those cars/buses might actually be at a higher risk as they are sitting in an environment with limited ventilation
• Smarter cycling techniques can help (finding quieter roads, avoiding travelling behind or downwind of vehicle's exhaust fumes, etc)
• Cycling is a great way to get around cities and become fit. Cyclist should not be discouraged by concerns regarding air pollution but should be better informed.

Answer 5

I ride a bike almost everyday not in very clean city - Kharkov, UA. And had similar problem as you have. My decision was: breathe in by nose, breathe out by mouth. It's easier than doing this by nose only, and safer for lungs when breathe just by mouth. I'll explain: Mouth is not very good defended from a polluted air. But in nose we have small hairs that keep all the dust that comes through with the air. That's why we have to take out a lot of snots after any outdoor walk/ride in a polluted city. And it's ok.

So, let's conclude: 1. Don't cut a hair from nose; 2. Breathe in by nose, breathe out by mouth; 3. rinse out mouth and clean up nose after a ride.

Answer 6

I used a combination of a Respro Techno Anti-Pollution Mask and some Decathlon clear glasses like the ones Narcis Calvet suggests. I found that in the winter breathing out through the mask caused breath to leak out of the top of the mask and condense on the glasses, which was most annoying when standing still at the traffic lights.The pollution mask I found quite unpleasantly restrictive for breathing, and hot in summer sweaty too. I ended up using the mask on the most polluted part of my journey and then taking it off for the rest of the journey.

I honestly could not tell if the mask made much difference to my health, it definitely was dirty when the filters were changed so it did catch some of the particles. I think drivers did respect me more when I looked more like Hannibal Lecter, I was elevated from Scum Cyclist to Scary Scum cyclist.

I must say the glasses did make a difference, I eyes were less prickly when I came home at the end of the day.

Answer 7

Interestingly, there was a point where studies (too long ago for me to even begin to remember sources) suggested that cyclists were probably less affected by pollution because, as a consequence of the regular exercise they were taking, their lungs were more efficient and so needed less air (and hence pollutants) to get the same oxygen. This was perhaps somewhat mitigated by being outside rather than in a box with filtered air (and the filtering has got more efficient).

What this means in practical terms - if the studies were right - is that you don't need to be specifically concerned as a cyclist but that doesn't mean that air quality isn't an issue you should be concerned about as an inhabitant of or visitor to a city.

Answer 8

Along similar lines as @Murph suggests cyclists are often less affected than vehicle passengers because the air intakes on most cars are placed lower to the ground than most cyclists' noses (recumbent riders take note ...). Many of the nasties, particularly particulate matter, sink and aren't at the higher levels.

Personally I've always struggled to breath enough through a mask so you end up taking great gulps of air when you stop at junctions - and these are the places with recognisably higher levels of pollution!

Answer 9

Tainio et al, (Can air pollution negate the health benefits of cycling and walking?, Preventive Medicine, June 2016, Vol.87:233–236), produced a model for cycling (and walking) in polluted cities, using data of one particular type of pollution (fine particulate matter) from various global cities.

Using a measure of minutes per day spent cycling, they find that the health benefits of cycling have a "tipping point" (after which no further benefits are observed) and a "break even point", after which the harm due to pollution outweighs the benefits of the exercise. The authors claim that, in almost all urban environments, the benefits of cycling outweigh the harm. The most polluted city they looked at, Delhi, however, has a tipping point of 30 mins/day and a breakeven point of 45 mins/day, which must make it a pretty unpleasant place to cycle!

The conclusion seems to me to be that if the choice is between cycling and driving, you're better off cycling (for any reasonable distance, such as commuting), because you'll be healthier and causing less pollution yourself. Personally, I like to avoid heavily polluted areas of my city for aesthetic reasons and also because they tend to be busier and slower than the alternatives.

Answer 10

Seems like the conclusions from the reports posted for this question range from "it's not a concern" to "it will kill you." Here's my two cents on short-term effects:
I live in a fairly polluted city (22nd in the US this year, I believe) and my experience is that anything above what is considered "moderate" ozone levels (0.060 to 0.075 ppm, source links below) has a noticeable impact on my health if I ride/commute. My throat and lungs become irritated and I wake up in the night in coughing fits. However, everyone's threshold is different and what bothers one person may affect the next more or less so. I use the site Air Now which is a service of the EPA that provides email alerts on air quality on a daily basis for cities around the US. Very useful for those who are stateside, and I would imagine that there are similar services in most countries. Assuming it bothers you at all, find a comparable service in your country (see the last link in this answer), find out what your threshold is and keep riding to a minimum on days when the air is particularly bad.

The following link has a good explanation on what ozone is and why it's bad in the lower atmosphere:
Air Info Now

And for those that are stateside, check these out:
Air now
Air Now

For international air quality reports, check the link below:
Local Air Quality Conditions (Air Now)

Answer 11

I live in NYC, and I ride every day from Astoria to Flat Iron. While I can't cite scientific research about how bad it can be for you, I'll say this: if I get caught in truck or bus traffic, the smoke almost always stops my spin immediately. I'm breathing heavier than normal, the smoke chokes me, and I lose all the momentum I've built up. There's just no breathing through that.

Cars aren't as much of a problem since I'm above the exhaust and cutting through it faster than it's rising.

It's a pretty big problem, and a lot of other riders have made shared Google Maps to avoid certain streets at certain times to avoid the exhaust fumes from the big guys. Just search for whatever city you're looking at and "Bike Routes" in Google Maps-- you'll usually find an annotated route with "rush hour rides" to avoid.

Answer 12

This is obvious, but do trust your own senses. In Witney, Oxfordshire (a lovely Cotswolds town in the UK) there's a short section of road (Bridge Street) where something about the layout of the road, traffic density, buildings, etc. seems to cause pollution to hang in the air. You can feel it just walking along that stretch of road.

If you find yourself repeatedly assaulted by fumes during a particular section of your route choose a new route that avoids the problem stretch.

Answer 13

In your case I'd use glasses for eye protection: shades for sunny days and transparent ones for cloudy ones. I work in Girona, a colleague went to the ophthalmologist on his bike and he quickly guessed he had gone there in a bike due to the pollution particles on his contact lenses. I guess if you don't use contact lenses this ends up directly on your eyes.

I use cheap glasses from Decathlon which are very affordable and have interchangeable lenses. I mostly use them for cross-country mountain bike or road cycling. They also help prevent things getting in your eyes in bad weather.