Does air quality affect running?

This article discusses the effect of pollutants when one runs in poor air quality. We discuss the various pollutant species that have adverse effects on one’s health.

Does air quality affect running?

Yes, poor air quality affects running. Depending upon the pace, running is medium to high intensity cardio exercise. Therefore, the body’s oxygen requirement during running increases.

Running itself is good for health. The WHO suggests that one should exercise for at least half an hour per day in order to reduce their risks for respiratory and cardiovascular diseases, which include serious afflictions such as heart attacks.

When one is running, their respiratory activity increases. This includes processes such as breathing rate, blood oxygen exchange rate, heartbeat per minute.

However, under poor air quality, when the concentration of air pollutants is high, the body becomes more vulnerable to the adverse effects of these pollutants. This, in turn adversely affects the running of an individual.

Over the previous decades, the air quality has deteriorated steadily, and is more pronounced in urban areas. This is mainly due to human activities that this degradation in air quality has been seen.

Which pollutants are responsible for affecting running

There are many pollutants that are responsible for the adverse effects on a person while running. Some of these include:

  • Carbon monoxide (CO)
  • Particulate matter (PM)
  • Oxides such as nitrous oxides (NOx) and sulphur dioxide (SO2)
  • Ozone (O3)

We will see how each pollutant species affects running.

Carbon monoxide (CO)

Carbon monoxide is a serious air pollutant, and in higher concentrations, it can prove to be lethal. It is a colorless, odourless gas, therefore it is hard to detect its presence.

Carbon monoxide is formed from incomplete combustion of fossil fuels and wood. It is also formed from smoking cigarettes.

Carbon monoxide forms a strong bond with haemoglobin, the compound present in red blood cells (RBCs), which is responsible for transportation of oxygen from the lungs to the tissues, and carbon dioxide from the tissues back to the lungs.

Thus, carbon monoxide causes reduced supply of oxygen to various tissues of the body. This causes issues such as rapid breathing, fatigue, dizziness, and so on.

While running, the breathing rate is 10-20 times higher than that for low intensity exercises such as walking. 

So, to run under elevated concentrations of carbon monoxide in the ambient air can increase susceptibility to more serious issues such as asthma, hypoxia, anoxia, ischemia, and even death.

Furthermore, CO has been found in studies to have a negative connection with blood pressure, meaning that exposure to CO causes runners’ blood pressure to drop. This could have implications to cardiovascular health in the long run.

Particulate matter (PM)

Ever since the onset of industrialisation, the rate of particulate matter in the ambient air has been rising steadily. In some places, it has even reached levels where it can have serious implications to health.

Particulate matter refers to particles, either solid or liquid, that are mixed and suspended in the air. They are a major part of air pollutants, and have a variety of natural and anthropogenic sources. They usually range between 2.5 to 10 microns (PM10 and PM2.5).

Particulate matter is a major contributor to both long term and short term illnesses. There are many well-documented studies that have shown progression of illnesses with an increase in the concentration of PM.

PM in the range of 2.5-10 microns are termed as inhalable particulate matter. These get entrapped by  the cilia that are present in the inner linings of the throat.

However, they contain particles of various chemical composition that can act as irritants and can cause exacerbations, especially in people that suffer from allergic asthma.

PM2.5 is of a major concern, as it can easily enter the lower respiratory tract, therefore causing more serious cardiac and respiratory issues.

Studies have shown that for every 5-6 g/m3 rise in PM2.5, there is a considerable increase in risk of cardiovascular disease, ranging from 0.5 to 1.5 percent. 

They also discovered a 69 percent increase in cardiovascular mortality following acute particle air pollution exposure. Surprisingly, acute PM2.5 exposure was linked to a greater probability of mortality from cardiovascular illness than from respiratory disease.

PM2.5 is a matter of concern, especially for people living in developing countries, where the ambient air quality for PM2.5 concentration is 10 times higher than the U.S. National Ambient Air Quality Standards.


Oxides refer to chemical species that contain oxygen atoms or ions in variable numbers. These are generated by natural processes as well, but they are more prevalent as anthropogenic pollutants.

Some of the well known oxides are nitrous oxides (NOx) species, which are composed of nitrogen and oxygen atoms in varying numbers. 

Amongst them, nitrogen dioxide (NO2) is a more prevalent species, which has been extensively studied and has been linked to several diseases that pertain to the cardiovascular system, as well as the respiratory system.

The other well-known pollutant that falls under the same category is sulphur dioxide, or simply SO2, that is a pungent gas which mainly acts as an irritant, and is linked with certain cardiovascular issues.

Both of these pollutants are mainly emitted from vehicular exhausts, with sulphur dioxide being in a relatively higher concentration for diesel-engine vehicles.

They are also emitted from industrial gases, thermal power plants, brick kilns, and combustion of solid fuels.

NOx species are deep lung irritants. They can cause inflammation of the inner linings of the windpipe, and trigger oversecretion of mucous. 

These conditions cause difficulty to breathe, wheezing, coughing, and can trigger asthma attacks in people that are susceptible to it.

SO2 has a characteristic pungent odor. This in turn acts as an irritant, and can cause irritation in the nose and throat, watering of the eyes, running nose, and so on. Therefore, it makes it harder to breathe while a person is running.


Ozone is a highly reactive gaseous molecule which is naturally present in the upper layers of the atmosphere, where it absorbs the sun’s damaging ultraviolet radiation. 

When present in the lower levels of the atmosphere, however, it acts as a pollutant, and can have serious adverse effects on human health, which also includes afflictions related to the cardiovascular and respiratory systems.

Ozone is formed as a secondary pollutant when chemical species such as polycyclic aromatic hydrocarbons (PAHs) and NOx species are emitted from vehicular exhausts and react with each other. 

This process gets sped up under certain conditions, such as warm weather, and bright sunlight. Therefore, ozone formation in the near surface level is more pronounced on clear sunny days.

Ozone acts as an irritant, due to its pungent odor. It can cause wheezing, irritation in the nose and throat, runny nose, watery eyes, difficulty in breathing, and can also trigger asthma attacks in people who are susceptible to it.

Ozone also affects the heart, as it can cause heart palpitations. This can cause pain in the chest, which can make it even harder to run.

What conditions makes it unsafe to run

There are certain conditions under which air quality gets degraded. As a result, running in such cases would cause more harm than the benefits of running. These conditions include:

  • Weather
  • Traffic conditions
  • Time of the day

Let us discuss these conditions in more detail.


Weather plays an important role in air quality. It regulates the air quality on days when there’s high pollution load, or can worsen it on other days.

In warm seasons, there is better mixing of air. However, warm conditions are also favourable for release of pollen, which are PM that are released from flowering plants. These pollen act as irritants in the upper respiratory tract.

In cold weather, the mixing height gets low. Furthermore, the condition can get favourable for the formation of an inversion layer, in which temperature stops decreasing with elevation and instead becomes warmer.

This causes the pollutants to get trapped near the surface level, and if the sources of pollution persist, they can cause the air quality to reach dangerous levels.

Traffic conditions

Most of the pollutants that we have discussed earlier, which have shown to adversely affect running, are generated from traffic.

In large cities, the chances of traffic congestion are high. Also, the air quality has been shown to worsen around the peak traffic hours. 

Moreover, certain pollutants that originated from vehicular exhausts react together to give rise to other pollutants like ozone and other NOx species.

Time of the day

Time of the day also plays an important role in the regulation of air quality. For example, in the nights when the temperature near the surface gets lower, there is a higher chance for the formation of an inversion layer.

This can cause the pollutants that were generated during the day to be trapped in the near surface air. This prevents the dissipation of pollutants from the area.

In the early morning, there is no traffic. Furthermore, reactions which give rise to ozonee have also not taken place, since the air has not been exposed to the required amount of light.

Hence, it would be better to go for runs in the early morning than in the afternoon, evening, or night, as the air quality will be relatively better in the morning, thereby reducing the risk of being harmed while running.

Other FAQs about Air Quality that you may be interested in.

Why does the air feel heavy in my house?

Can poor air quality affect pregnancy?

Can poor Air Quality cause Allergies?


Running is an important exercise that helps to maintain our cardiovascular as well as our respiratory health. However, running in poor air quality will cause more harm than it will do any good.

Certain conditions, such as weather, time of the day, and traffic conditions are factors that affect the air quality. Hence one should keep this in mind when they are deciding to go for a run.


When is it safe to run?

It would be safer to run in early mornings, rather than going for a run in the evening. In the mornings, there is none to a low extent of human activities. 

Due to this, pollutants such as PM, CO, SO2, NOx, are at low concentrations. Furthermore, since there hasn’t been enough time for daylight, ozone production wouldn’t be occurring as well.

Can running on a treadmill indoors be safe?

It might be unsafe to run indoors on a treadmill, as there are chances of indoor air pollution, from indoor sources, as well as outdoor pollution infiltrating through cracks and windows.

However, you can still run indoors on a treadmill by using an air purifier. Air purifiers with HEPA (High-Efficiency Particulate Air) filters are best suited for indoor purposes. The presence of an activated charcoal filter and a UV light further increases the efficiency of the filters.


  • MARR, LINSEY C.; ELY, MATTHEW R.  (2010). Effect of Air Pollution on Marathon Running Performance. Medicine & Science in Sports & Exercise, 42(3), 585–591.         doi:10.1249/mss.0b013e3181b84a85
  • Lee BJ, Kim B, Lee K. Air pollution exposure and cardiovascular disease. Toxicol Res. 2014;30(2):71-75. doi:10.5487/TR.2014.30.2.071