Exercising, Smoke, and Hazardous AQI

by Coach Anne Linton

I have had a few people reach out to ask me about the safety of exercising during this unprecedented fire crisis on the West Coast. In Bend, OR right now, the Air Quality Index (AQI) (has dropped from 500, which the Environmental Protection Agency (EPA) labels as  “hazardous” to around 300, or “Very Unhealthy” making the area one of the most polluted in the world.   Regardless,  going outside at these high levels of smoke-filled air is dangerous and you should definitely not exercise outside. If you have to be outside for work or other essential activities, at minimum, wear an N95 mask and minimize your time outdoors as much as possible.

Indoor exercise can be dangerous as well if particulate levels in your home remain high. Experts say that 20-50% of the particulate matter from poor air quality can get into your house. This will depend on your home. Things that make that number greater or lower depend on how tight your house construction is, the humidity level, your HVAC system, if you have an air filter and then finally if there are other toxins in your house, whether it be from cooking or other toxic materials like plastics. Indoor air quality can be measured with various devices such as a Foobot. The EPA has information here Indoor Air Quality.

Knowing about the EPA’s AQI ratings can help inform your decisions on when and where you can exercise.  The AQI is calculated from five major air pollutants: ozone, particle pollution (including PM2.5), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Generally, when the AQI is above 100 (going from moderate to unhealthy for sensitive groups), it’s wise to avoid intense exercise outside. Once the AQI goes up to the red and purple range (over 200–unhealthy and very unhealthy), it’s best to stay inside. In Bend, we’ve had multiple days in a row in the hazardous (maroon) range with AQI above 300. The longer you expose yourself to pollution, both daily and long-term, the greater risk to your health. See the chart below for a break-down of AQI.

Air Quality Index Basics from Airnow.gov

In addition to our forests, structures, cars, tires, plastics and other materials that produce toxins are currently burning in the fires, and the wildfire smoke you inhale will contain these pollutants and toxins. Out of all the pollutants in wildfire smoke, fine particulate matter (PM2.5) is the most dangerous to human health. These microscopic particles can infiltrate your eyes and respiratory system, even while indoors and in addition to causing minor symptoms such as burning eyes, they can also aggravate chronic heart and lung diseases. If you experience a headache, cough, sore throat, or runny nose, try to reduce your exposure as those are signs your exposure is adversely affecting you.

How does poor air quality, in particular smoke cause damage? Smoke and particulate matter cause an inflammatory reaction to the organs most exposed to it so primarily the respiratory system and the eyes. Breathing in such particulates can cause damage directly to the lung tissue and the heart and brain after it enters the blood stream via the lungs. This can result in oxidative stress which can cause many problems in your entire body at the cellular level. In addition, poor AQI can cause autonomic system imbalances by triggering irritant receptors in the lungs that then provide feedback to the brain which can cause a fight or flight response throughout the body. This can directly affect the autonomic control center of the heart which can lead to irregular heart beats (arrythmias). Overall, inhaling smoke and particulates can result in a cascade of events throughout the body leading to serious medical issues such as heart attacks, stroke and other vascular problems both immediately and in the long-term. All of this is why you should avoid high intensity exercise during times of poor air quality as heavy breathing or rapid breathing will bring more particulate matter into your lungs increasing your chances of these consequences as a result.

Understanding the effects of wildfire smoke exposure on human health is complicated and there still isn’t a lot of research. The composition of wildfire smoke varies, but during wildfire events, PM2.5 (2.5 microns, for reference a single hair is 70 microns) has been associated with exacerbations of asthma, chronic obstructive pulmonary disease and respiratory Emergency Department visits and hospitalizations.  A recent 2020 study from Canada examining the impact from PM2.5 wildfire smoke on health, found that hundreds to potentially thousands of premature deaths per year were attributable to wildfire smoke, as well as many non-fatal cardiorespiratory health outcomes. Wildfire smoke presents a risk to both communities in close proximity to wildfires as well as those farther away due to long-range air transport of pollutants. However, more premature deaths resulted from chronic over acute exposure, so make sure to limit your time outdoors as much as possible when the air quality is poor.

But what does it mean to limit your exposure if you’re not sensitive? Is it safe to be doing HIIT training inside with the house sealed and the AC running? Will a few days of exercising outside and inhaling smoke really cause that much damage?  In polluted areas, studies have concluded that you won’t negate the cardiovascular benefits of exercise in the “unhealthy” zone defined by the EPA until you’ve spent 10 hours walking or 5 hours biking outside. However, if you’re breathing hard, you’re going to hit that dividing line much earlier so . Short periods of activity might be OK in the moderate to unhealthy zone in polluted areas if you’re taking regular breaks inside in clean air, but what about exercising in wildfire smoke?

Here are my recommendations:

1.    If you have asthma, or underlying heart disease be extra cautious of exercising where you increase your respirations or get your heart rate up. Do not do any exercise unless you have been cleared by your health provider to do so.

2.    When the AQI is greater than 100-150, limit your exercise outside. If you have to do any exertion outside due to job/work/other, wearing an N-95 mask with an expiratory valve is best (these will not protect others from you if you have COVID). When it is over 300 stay indoors as much as possible and if you have to be outside wear a mask (N-95 is best, you can find diy instructions to simulate this online).

3.    If you are going to exercise inside remember it is estimated that 20-50% of toxins get into your house, so I recommend the following:

o   Keep your Heart Rate low–as a general rule I suggest not going out of your endurance zone ( Zone 2 up to 75-80% max heart rate). Please note that due to the poor air quality your HR may be higher than normal, so pay attention to that and DON’T BREATHE HARD. Remember, every time you breathe hard or deeply you are taking all the air down into your lower lungs. If there is small particulate matter (PM 2.5 or less) they end up going deep into your lungs causing an inflammatory reaction and getting into your blood stream.

o   If you have any symptoms of headache, cough, burning eyes that is your body telling you you are being exposed. If this is the case I suggest keeping your heart rate even lower, in your recovery zone ( less than 65% max HR). Just move but don’t do anything hard (an easy spin, yoga, or light stretching or strength training) and if any of the symptoms worsen then STOP exercising.

4.    Drink extra water. During wildfire events dry air is often a contributor so you may get dehydrated more easily. Drinking water will help flush toxins out of your system and keep your mucous membranes moist to help you fight off any of the inflammatory processes related to inhaling smoke.

5.    Meditate. Meditation has been shown to calm the nervous system so it can help to mitigate some of the effects of toxic smoke at the level of the nervous system. I think of meditation as a significant part of my training for health and well-being. Given this and the COVID pandemic now is a great time to practice meditation. Even 5-10 minutes a day can be helpful.

6.    Since wildfire smoke causes oxidative stress, avoid any foods or activities that increase that stress or stress in general, i.e. high intensity exercise of any type. Limit your use of alcohol and fried foods. Try to get good sleep and decrease other stresses you have control over.

7.    Increase your intake of antioxidant-rich foods like green leafy vegetables (broccoli, sprouts), berries, dark cherry juice, fish oil and other antioxidants. Moderate intake of C, D and E Vitamins is ok but don’t overdo it, as there have been studies looking at smokers who took large doses of these Vitamins and had adverse consequences.

8.    If you have sinus or allergy issues you can do a nasal wash with saline or neti pot daily to help decrease your risk for infection.

On a personal note I have had sinus surgery, so I am extra cautious. I won’t ride or do strenuous activity outside unless the AQI is under 75.

This will pass, but most of all let’s send our positive energy to those directly affected by the fires. There have been close to 500,000 Oregonians on evacuation notice with at least 40,000 who have been evacuated from their homes in Oregon (even more including California and Washington), not to mention an unknown number of lives and homes lost. So, in thinking about these folks, losing a few days of training is nothing compared to losing your home or even worse your entire town like Detroit, Blue River, Talent or Phoenix all small towns in Oregon destroyed by the fires.

And don’t forget that exercising your pets in wildfire smoke can be harmful to their health as well, especially those with heart or lung disease, puppies, and older animals.

Additional resources:

British Columbia Center for Disease Control

EPA and Wildfire Smoke

Wild Health Pocast on Air Health

Associations between respiratory health and ozone and fine particulate matter during a wildfire event

Wildfire Smoke and Human Health

Should You Stop Exercising During Wildfire Season?

Can air pollution negate the health benefits of cycling and walking?

Health impact analysis of PM2.5 from wildfire smoke in Canada (2013–2015, 2017–2018)

Meditation Apps:


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As with any of our blog posts or other information, this is meant to be informative only and does not constitute medical advice. Please reach out to your healthcare provider if you have any questions or concerns.