Based on 2019 data I analyzed the concentration of Nitrogen Dioxide (NO2) and Particulate Matter (PM2.5), when available, as they are two of the most common pollutants in urban environments due to vehicle traffic and household heating.
In a recent study, scientists selected 140,072 adults and after following them for an average of 2 years, they found that physical activity, even in high PM2.5 levels, is an important high blood pressure (hypertension) prevention strategy as the markers remained stable.
This is a great piece of news. However, I prefer to avoid pollution in the first place and not playing the constant game of good and bad. In our lives, many other factors contribute to health issues, and by eliminating air pollution you make sure that the eternal battle of survivor leans towards your favor.
Let’s take some random locations from across England and see which day and time of the week is the best to exercise outdoors. All data are from the official monitoring network (AURN).
I randomly chose to analyze data from the London Marylebone Road (MY1), which is an urban traffic station.
Based on the NO2 data, from Tuesday to Friday I don’t recommend anyone to run near that area as the highest concentrations are registered those days especially between 07:00 to 21:00 throughout the year. Remember the annual safe mean according to WHO is set to 40 μg/m3. Weekends and late nights between 00:00 to 06:00 in the morning seem to be adequate to exercise as traffic seems to calm down a lot. January, February, March, and June are the worst months too.
Based on the particulate matter data with an aerodynamic diameter smaller than 2.5 microns (PM2.5) and according to WHO, which has set a safe annual mean to 10 μg/m3, athletes shouldn’t exercise at all, with the worst months January, February, March, April, and May. The PM2.5 pollution is a byproduct of a combination of the traffic but also the household heating systems (biomass, oil, wood, etc).
Once more, I randomly chose a site in York, more specifically the York Heworth Green (YK13), which is a road station. Unfortunately, this station has only a NO2 monitor and no PM2.5.
From the NO2 data, we can see that in comparison to London’s MY1 station, the air quality is much better with lower concentrations throughout the year. Weekends and late nights are the best moments to exercise, midday looks fine too. The best months for outdoor activities according to the NO2 data are during summer, July, and August. Keep in mind, sunlight radiation can turn NO2 gas into ground-level ozone (O3), but the station doesn’t measure O3.
I will admit that I chose Sheffield because I know some people there and I wanted to learn when is the best time for them to do activities outdoors. The air quality station is in Sheffield Barnsley Road (SHBR), and it is an urban traffic station.
Once more, we can see that weekends are the best time of the week to do activities as people don’t commute to work. August by far the best month of the year too. I did a bit further analysis of the data for Sheffield, and I combined some surface meteorological data (wind speed and wind direction) to figure out the origin of the pollutants. During winter, the wind speeds are higher than in summer, and the high concentrations of NO2 come from the west.
Household heating contributes a lot of PM2.5 pollution in the area during the winter months. People in Sheffield could have breathed a lot fewer particles if they had invested in zero-emission heating solutions. During summer, the pollutant is almost gone because wood burners are not active. A wood stove emits more harmful air particulates (PM2.5 & PM10) than a diesel truck. Midday seems to be the best time to work out if you want to avoid breathing fine particles that can reach your lungs, heart and even your brain.
Although in a recent study researchers believe that urban exercise counteracts a dangerous effect of air pollution, I would suggest avoiding exercising in busy roads and choosing a green park for your workouts. Air pollution is sneaky.
Would you like to read a similar analysis for your location in the future, then leave a comment below.