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The Best Time to Exercise in a City with High Air Pollution

When it comes to exercise, the important thing is that you actually do it in order to avoid health complaints such as cardiovascular disease. Exercise can improve your fitness, your health and your mood. Even so, it can be difficult to exercise in a polluted city with unhealthy air.

Nobody wants to be breathing in pollution when they are doing their best to stay healthy so when is the best time to exercise in a city with high air pollution levels? We decided to find out.

A person exercises in a city or town with high air pollution levels.

The best time to exercise in a highly polluted city

When do you think would be the best time to exercise in a city with high pollution levels? If you are anything like us, you might think that the best time to exercise would be when the city streets are at their quietest; the dead of night when there are fewer vehicles on the roads. Fewer people means less emissions and particle pollution, right? That should mean that the best time to engage in physical activity is in the early hours of the morning but that isn’t the case!

By analysing several years’ worth of PM 2.5 data in Beijing it is possible to see that pollution levels actually spike at night with the highest pollution levels occurring between the hours of 10pm and 4am. The lowest pollution levels are found to be between midday and 6pm, a time when there are a lot of people and vehicles about, and when there is a lot of energy being used.

Roughly the same result was found to be true for citizens in Shenyang (midday-6pm), Chengdu (2pm-7pm) and Delhi (11am-7pm). Hyderabad, Mumbai and Kolkata also showed a similar result.

This may change depending on which polluted country you are in but the best time to exercise in a city with high pollution levels is in the early to mid-afternoon.

Why is the afternoon the best time to exercise in a highly polluted city?

PM2.5 is lowest in the afternoon but why is this the case? Most would think that PM2.5 would be at its highest during the day with so many cars on the roads. The answer is a mixture of a number of different variables.

Wind is stronger in the afternoon

Wind plays a large role in dispersing pollution. Interestingly, there tends to be only a light wind in the morning with most wind picking up in the afternoon. Although it is unwise to assume, it is highly likely that wind being more common in the afternoon contributes to this time of day being the best time to exercise in highly polluted areas.

The mixing heights are lower at night

Mixing heights refers to the height above a surface at which a pollutant can be dispersed as it mixes with the air. The mixing height tends to be higher during the day as a result of numerous meteorological factors including wind speed and direction, temperature, humidity, solar radiation, and rainfall.