In many cases, the benefits of sports outweigh the risks of overexposure to pollutants.
Cycling and walking are two active modes of transport beneficial to health as they increase the body’s physical activity. But active transport also increases the amount of inhaled polluted air, which could have a negative impact on health.
So can we pedal safely in the city?
In 99% of cities, the benefit of sports is higher than the risk associated with pollution
An international team of researchers assessed the benefit/risk ratio of active transport in a polluted environment (2). The researchers modeled the effects of cycling and walking in different polluted environments and measured a duration from which there were no more health benefits. The effects on all-cause mortality were tested.
The study found that only 1% of the world’s cities have a level of pollution such that outdoor physical activities are detrimental to health: the health benefits of walking or cycling exceeded the risks associated with inhaling polluted air.
For Audrey de Nazelle, of Imperial College London, “The good news is that all over the world, in 99% of cities, it is safe to bike up to two hours a day.” According to Marko Tainio, who conducted this research, “even in Delhi, one of the most polluted cities in the world with pollution levels ten times those in London” people should spend more than five hours a week cycling so the risks of pollution prevail over health benefits.”
It is still better to avoid the proximity of cars
A study of the Harvard School of Public Health (3) somewhat nuances this idea: by sharing the road with cars, a cyclist increases by more than 30% his exposure to air pollutants than if he pedals on a bicycle path separated from the road .
In the city, pollution emissions related to road traffic are responsible for a significant part of air pollution. Among the air pollutants are: fine particulate matter (PM 10 and PM 2.5, PM = particulate matter), nitrogen dioxide NO2, carbon monoxide (CO) and ozone (O3).
Researchers in Boston have measured the pollution along 5 of the city’s cycle routes, including bicycle lanes directly adjacent to the road, bicycle lanes separated from the road and roads shared by buses and bicycles. The researchers surveyed these routes by bicycle with a pollution measuring device. In particular, they have measured two known elements to increase cardiovascular risk and the risk of lung cancer: carbon black (black carbon) particles and nitrogen dioxide.
Carbon black particles are emitted by exhaust (including diesel engines) and represent a relevant tracer of road traffic pollution. Nitrogen dioxide is a toxic gas produced by combustion. It causes inflammation of the airways.
The results show pollutant concentrations are one-third higher on bicycle lanes adjacent to roads than on more distant cycle lanes. The air quality is particularly bad at the intersection where the cars stop and restart. Conclusion: if you have a choice, opt for the green routes.
And in the gym the air is also polluted
You want to get into the gym to avoid pollution? This may not be the best idea … The quality of the air in the gyms is influenced by the maintenance of the buildings, the building materials, the type of ventilation but also by the occupancy rate and the type of activities carried out.
In a recent study (4), researchers placed equipment to analyze air quality in gyms in Lisbon. Carla Ramos, author of the study, obtained permission from 11 gyms to dispose of the equipment to analyze the air quality in both the weight rooms and the small ancillary rooms. The devices have been programmed to analyze pollutants in the air in late afternoon and evening when attendance levels are higher. The researchers assessed the pollutants generally found in indoor air: carbon monoxide, carbon dioxide, ozone as well as airborne particulate matter (dust) and chemical products (including formaldehyde) released by carpets, cleaning products, furniture, paint.
Researchers found high levels of airborne particulate matter, formaldehyde, and carbon dioxide (CO2) in gyms. The concentrations of these pollutants exceeded the European standards generally accepted for indoor air quality. The levels of these pollutants were particularly high during aerobics classes, during the time when people are confined in small rooms, move a lot and breathe heavily.
High concentrations of particulate matter and chemicals, such as formaldehyde, in the air are the most worrying problem. “They can cause asthma and respiratory problems,” says Carla Ramos. “Carbon dioxide, even if it is not toxic, could also be a source of concern.” At high concentration, it can train physical fatigue and cognitive confusion, which is not desirable during an aerobics course, adds Carla Ramos.
(1) Chen H1, Goldberg MS, Villeneuve PJ. A systematic review of the relation between long-term exposure to ambient air pollution and chronic diseases. Rev Environ Health. 2008 Oct-Dec;23(4):243-97.
(2) Tainio M, de Nazelle AJ, Götschi T, Kahlmeier S, Rojas-Rueda D, Nieuwenhuijsen MJ, de Sá TH, Kelly P, Woodcock J. Can air pollution negate the health benefits of cycling and walking? Prev Med. 2016 May 3. pii: S0091-7435(16)00040-2. doi: 10.1016/j.ypmed.2016.02.002.
(3) The Boston Globe. Cyclists, don your gas masks. By Kevin Hartnett.
(4) C.A. Ramos, H.T. Wolterbeek, S.M. Almeida. Exposure to indoor air pollutants during physical activity in fitness centers. Building and Environment 82 ( décembre 2014) 349-360