How to Reduce Risk from Air Pollution during Physical Activity

In summer, many take advantage of the warmer temperatures to be physically active outside. If you're one of them, you're probably already accustomed to applying sun lotion, wearing a hat and carrying sufficient water to protect yourself from the sun and heat, but do you know how you can reduce the risk from inhaling air pollutants?

While the best protection against air pollution-related health risks would be a drastic reduction of pollutants, for example through the adaptation of the World Health Organization’s Air Quality Guidelines globally, an international research team from Spain, France, Brazil, and Canada recently screened the existing scientific literature and summarized recommendations that anybody can apply on an individual level when engaging in physical activity while air pollution levels are elevated. These recommendations were grouped into strategies that can be leveraged before and after exercising, and those that are relevant while being physically active.

Recommendations before and after exercising

Monitoring air pollution levels

Data from air pollution and weather stations and satellites allow the prediction of air pollution concentrations for specific locations. Making use of air pollution forecasts is crucial for optimizing the timing and location of physical activity. Local government websites (Canada, USA, Spain, Catalunya) and apps provide reliable data on air pollution conditions. Air quality indices, such as the European Air Quality Index, are used to raise awareness of current pollution levels and the associated health risks. However, caution is needed when comparing indices between countries as they may be calculated using different pollutants and standards. Wearable air pollution sensors are also available, but their validation is still limited.

Face masks

The effectiveness of masks depends on the pollutant, type of filter, and proper mask usage. Well-fitted N95 or FFP2 face masks that are regularly replaced can reduce the inhaled dose of particulate matter pollutants, the tiny solid or liquid particles in the air. Just like during the COVID-19 pandemic, face masks are only effective if a good seal can be attained. Typically, one can assume that the mask is well-fitted when the facemask moves inside, towards the mouth, as when one inhales. While exercising with a face mask can be uncomfortable, particularly at higher intensities, it can also be useful to wear facemasks on the way to or from the physical activity location (for example, when competing) to keep total inspired air pollution volumes as low as possible.

Medication & supplements

Individuals with pre-existing conditions are recommended to continue their medication intake as prescribed. Some studies indicate that supplements of beta-carotene, vitamin E and vitamin C once per week could potentially reduce the negative effects of ozone on lung function; however, more research is needed to confirm these findings.

Exposure reduction by time and distance

Avoiding physical activity in the early morning and late evenings, as well as vehicle rush-hour periods, can make a difference in the air pollution concentrations you are exposed to. “Air pollution” is a mixture of both particles and gases. Particles, for example from wildfires or vehicle engine emissions, settle closer to the ground late at night. In the morning hours, these ground level particle concentrations are often reduced as the sun rises. Ozone, a gaseous pollutant, is produced in the presence of sunlight, which is why its concentrations tend to peak in the afternoons. Finally, morning and evening rush-hour periods have been shown to affect gaseous and particulate pollutants in urban areas, when vehicle traffic into and out of metropolitan areas result in traffic congestions in densely populated areas, where air pollutants can get stuck. 

Recommendations while exercising

Exercise intensity and duration

At higher physical activity intensities, increased breathing rates result in a greater dose of air pollutants being inhaled. Once inspired, pollutants can travel down the airways into the lungs, and even get absorbed into the bloodstream, from where they can theoretically harm any organ. In contrast to what was expected, cyclists participating in a study reported higher levels of breathlessness when biking at lower intensities when compared to a higher intensity over 30 minutes while breathing diesel exhaust. The exact mechanisms are unclear and further research is needed to better understand the impact of high- versus low-intensity physical activity while breathing increased concentrations of air pollutants. However, when air quality is poor, it is recommended to reduce the duration of the exercise bout with the aim to reduce the inhaled dose of air pollutants, while still gaining the benefits from physical activity. 

Indoor exercise

Moving exercise indoors can be an alternative when outdoor air pollution concentrations are high, particularly when indoor facilities include air filtration systems such as high-efficiency particulate absorbing (HEPA) filters. However, building-specific room ventilation practices (like frequency and duration of opening the windows) and sources of indoor pollutants such as cleaning products, ice-resurfacing machines in ice rinks, and chemicals in swimming pools need to be considered.

Exposure reduction by distance

Within urban areas, pollution exposure can vary significantly, and even small changes in location can lead to significant reductions in air pollution exposure. Smaller streets, parks, or routes along rivers, lakes or the sea should be chosen over routes along busy traffic arteries or construction sites. Individuals with mobility impairment, such as wheelchair athletes or individuals using walkers or canes, may face challenges in accessing green or blue spaces, an issue concern that needs attention.