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  • Writer's pictureSanjay Kashalkar

Air Quality, Athletes and the Hong Kong Marathon.

Like running 🏃🏻‍♂️🏃🏼‍♀️? Read this.

We look at how athletes are affected by air quality and our experience from the Hong Kong Marathon.

Air Quality and Athletes

There are 3 main reasons why athletes are at an increased risk from air pollution. source

  1. Increased ventilation. During training an athlete can consume 20 times more air than a normal person at rest.

  2. A greater portion is inhaled via the mouth bypassing the normal nasal filtering mechanisms.

  3. A higher intake velocity means the deeper parts of the respiratory tract are affected.

Here are some studies that have even collected empirical evidence of how athletes performance is affected by air pollution.

  • Ozone is particularily damaging. People achieved a lower aerobics score on days with high ozone, Cakmak

  • Football performance dramatically reduced due to high PM in German stadiums Lichter

  • Inhalation during exercise and rest Leandro

a traditional 30-min of moderate aerobic exercise session might induce inhalation of high levels of pollutants when performed at dirtiest cities.

Minute ventilation (or air intake per minute, typically 6 litres) was compared in cities categorised by WHO as clean (white bar) or dirty (black bar). Notice the dramatically high jump in inhaled PM in polluted cities.

Major cities in Europe may not face high PM levels however the levels of NO2 have been found far in access of WHO standards.

image source:

The Hong Kong Marathon

Every year over 70,000 athletes take part in the Hong Kong Marathon. The high humidity and difficult course, makes it one of the most challenging courses.

However, like most major cities around the world, Hong Kong is not immune to air pollution. The government listened to the voices of the athletes and people and took concrete measures.

Starting 2013, civic organisations started to monitor air quality during the Marathon and tried to investigate the “on track" air quality.

Image: Hong Kong Marathon, West Kowloon highway under heavy air pollution, 2006.

Source: Wikipedia. (CC BY-SA 3.0)

Real time "on-the-track" Air quality monitoring

Is it safe to run?

The City university of Hong Kong and the Hong Kong Environment Protection Department collaborated to release a real time Air Quality Index (AQI) for the Hong Kong Marathon.

This was the first such measurement with a completely new generation of monitoring devices specifically developed for the project. It was able to accurately measure the AQI 'on the track'.

This real time AQI data was released by the sponsor, Standard Chartered together with the current weather information along the race track.

The basic concept was that people could monitor the air quality in real time to determine whether to continue in their competition or not.

Sheng Ye, Research Scientist at Signify GmbH was a staff member for this project.

One of the critical segments of the race was the western harbour tunnel. Let's look at that as an example.

The undersea western harbour tunnel

Throughout the Hong Kong Marathon route, the "critical" path is the long-path undersea Western Harbour Tunnel. Tunnels are commonly recognised as an air pollutant "trap", especially the undersea ones. Many air pollutants as well as CO2 are heavier than air, and get trapped in tunnels and accumulate within.

The Hong Kong government closed the tunnel traffic ahead of time and used mechanic ventilation to significantly improve the in-tunnel air quality for participants.

Here is an image from our real time AQI measurements for the undersea tunnel. Clear reductions of several air pollutants can be observed during the fan-on period, while participants ran through the tunnel.


Sun, L.; Wong, K.C.; Wei, P.; Ye, S.; Huang, H.; Yang, F.; Westerdahl, D.; Louie, P.K.K.; Luk, C.W.Y.; Ning, Z. Development and Application of a Next Generation Air Sensor Network for the Hong Kong Marathon 2015 Air Quality Monitoring. Sensors 2016, 16, 211.


Athletes are a high risk group when it comes to air pollution. If you frequently run long distances in urban areas, it helps to keep an eye on the real ground level air pollution along your route and the ozone levels for the day. Predictions as offered by many weather apps are often not 'ground level accurate' so do keep that in mind if you rely only on them.

Finally, large sporting events like the olympics and city marathons are an opportunity for stakeholders to apply large scale measures to improve air quality for the entire community. For the long run :-)

The city of Beijing has demonstrated this is possible by reducing the pollution by 30% during the 2008 Olympic games. Let's see what Paris has in store for 2024.


Sheng Ye

Sanjay K.



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