We exercise for many reasons, from the short-term hit of endorphins to the long-term promise of healthier aging. Can one of them be protection from higher mortality risks during periods of high pollution?
Given our increasing urbanization and continued reliance on fossil fuels, paired with global warming has been increasing levels of pollution in many parts of the world. We often think of big cities and smog alerts when it comes to pollution, but rural environments aren’t immune. Look at the dust blown up during Strade Bianche or Paris-Roubaix, and the same thing happens with winds blowing topsoil off of farm areas.
The challenge for cyclists and other outdoor athletes is that we breathe in a lot of air during exercise, from a resting ventilation of 5-10 L/min to 100+ L/min during heavy exercise. That creates a much higher pollution load our body has to deal with. Coupled with this is that we typically switch to primarily oral (mouth) breathing above about 35 L/min, reducing any filtration from our nasal passages. Furthermore, athletes breathe deeply during exercise, meaning that we likely draw the pollutants deeper into our lungs.
We know that exercise has a host of overall health benefits through pretty much every system in our body. At the same time, we’re often exercising in polluted environments. So one question becomes: “Can regular exercise protect us from sudden periods of high pollution?”
Click on the video below to find out more!
Reference
Wong CM et al. Does regular exercise protect against air pollution-related mortality? Preventative Medicine. 44(5):386-392, 2007.
Video Transcript
We know that even moderate levels of exercise can bring about many health benefits. Can one of them be reducing the risk for death during periods of heavy air pollution?
In today’s episode, we’ll explore a study tracking natural deaths in Hong Kong over 1 year, and see whether there was any relationship between pollution levels and death rates in those who never exercised and those who did moderate exercise.
Air pollution is becoming a serious issue in many regions of the world. Often we think of it as a big-city problem from traffic, heavy industry, and coal-fired electrical plants. However, geography can also contribute, such as mountain ranges that can trap airflow and cause regional spikes in pollution even if the source is from far away. Rural regions can also experience high levels of pollution from wind blowing up dust and soil. Certain pollutants like ozone can also spike during summer and heat waves, as it is a direct chemical reaction between sunlight, heat, and pollutants like nitrogen dioxides and volatile organic compounds. There’s now little doubt that moderate exercise can provide a whole host of health benefits. Can one of these benefits be reducing the risk of death during periods of high pollution?
This question was the focus for a study by a Hong Kong research group.
To do this, they took data from a large project that tracked over 24,000 cases of natural deaths – those not counting accidents such as car crashes – in Hong Kong during the 1998 calendar year, representing 78% of all natural deaths in those over the age of 30 that year. Through interviews with next of kin, their physical activity level was categorized as “exerciser” if they performed exercise at least once a month during the 10 years preceding death. This represented about 30% of the group. Information was also gathered on education level, socioeconomic status, smoking history, and health history. Pollution levels, temperature, and humidity were tracked for each day.
First off, what were the characteristic of regular exercisers? In general, they were more likely to be female, wealthier and better educated, smoked less, had better health in the months and years prior to death, and also lived longer. This matches much of the existing literature concerning exercise in different population studies around the world. How did exercise affect death rates during pollution spikes? Each group was split into those over 30 and over 65 years old. In the non-exercisers, death rates increased with increases in particulate matter and ozone in those over 30. In those over 65, death rates were higher with these two pollutants and also higher levels of nitrogen dioxide. In contrast, with the exercisers, increased death rates were seen only in those over 30 with increases in sulphur dioxide. These patterns were true even when the different groups were matched for socioeconomic status, smoking, and previous health history.
Studies like this adds to the overwhelming evidence for the benefits to an active lifestyle. It’s important to note the extremely low threshold for being an exerciser in this study, at only once a month. This really highlights that even a little can go a long way. While actual exercise or intensity was not tracked, the authors theorized from previous studies that it was mostly walking or low impact exercise like tai chi, again highlighting that we’re not talking about extreme levels of activity or intensity. But if you do live in a polluted environment, there are some things you can do to decrease the risk from pollution exposure while you’re actually exercising. You can avoid higher pollution by exercising during early morning or avoiding rush hour. You can also exercise in parks or away from major traffic, or exercise indoors if there is good ventilation. Finally, breathing through your nose rather than your mouth, and also wearing a mask, can help filter pollutants from the air before it reaches your lungs.
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