RBR reader Gary F. asks, “With all of the smoky days this summer and the air quality index running around 150 or so, do you curtail or modify your workout schedule to avoid the smoke?”
Gary, this is an excellent question because smoke and also ozone levels are international problems. There are multiple pollutants in the air. The general Air Quality Index (AQI) devised by the Environmental Protection Agency (EPA) aggregates the pollutants into one numerical index. Smoke and ozone are two key pollutants that affect lung function and therefore exercise. Smoke can come from a local fire or a fire a thousand miles away and the effects are different. Smoke can also affect an area occasionally or for weeks and the effects are also different. Ozone is generated locally.
When you inhale a large volume of smoke you are inhaling microscopic particles, which can inflame the lungs. Microscopic particles 2.5 microns in size — known as PM2.5 — are the greatest health hazard. They can penetrate the lungs and cross into the bloodstream. (The width of a human hair is about 70 microns). Those particles also can migrate from the lungs to affect your and blood vessels. Some research indicates smoke from wildfire may be more of a problem than regular air pollution.
Some people are more at risk:
- A person with heart or lung disease, such as heart failure, angina, ischemic heart disease, chronic obstructive pulmonary disease, emphysema or asthma.
- An older adult, who is more likely to have heart or lung disease than younger people.
- Children, including teenagers, because their respiratory systems are still developing, they breathe more air (and air pollution) per pound of body weight than adults, they’re more likely to be active outdoors, and they’re more likely to have asthma.
- A person with diabetes, who is more likely to have underlying cardiovascular disease.
- A pregnant woman, because there could be potential health effects for both the woman and the developing fetus.
High concentrations of smoke can trigger a range of symptoms.
- Anyone may experience burning eyes, a runny nose, cough, phlegm, wheezing and difficulty breathing.
- If someone has heart or lung disease, smoke may make the symptoms worse.
- People with heart disease might experience chest pain, palpitations, shortness of breath, or fatigue.
- People with lung disease may not be able to breathe as deeply or as vigorously as usual, and may experience symptoms such as coughing, phlegm, chest discomfort, wheezing and shortness of breath.
Researchers studied the long-term effects of smoke by studying firefighters who are exposed to smoke on multiple occasions. One study published in Wildfire Today focused on wildfire fighters who breath smoky air for days at a time and “concluded that firefighters’ exposure to smoke can increase the risk of mortality from lung cancer, ischemic heart disease, and cardiovascular disease.” Another study examined the effects on firefighters’ pulmonary function of one-time severe exposure to smoke six weeks after exposure and then 18 months later and found “firemen may develop lung disease related to their occupational exposure.”
Researchers in Colorado compared the effects of smoke from nearby or distant fires and found long-range smoke may be more toxic and since one of its characteristics is that its smoky smell disappears, it is less obvious. “’This is really the big issue,’ said Dr. Anthony Gerber, a researcher on lung disease at National Jewish Health in Denver, Co. ‘It used to be that we had a few days of high ozone or high particulates. Now we have weeks on end of smoke. You start to change the equation from short-term effects to long-term, potential increases for lung disease, cardiovascular disease.’” (Colorado Sun)
In one study people 30 healthy men exercised in normal air and then exercised breathing in diesel exhaust, a pollutant somewhat similar to wildfire smoke. They developed fleeting changes in how efficiently their blood vessels dilated and contracted as blood flowed through them. This study looked at the immediate effects of one-time exposure.
What’s the limit on exercising?
The AQI numerically ranks levels of pollution and describes the air quality. A range index value of 101 – 150 and means “unhealthy for sensitive groups.
“’This is probably the highest alert at which it is advisable for most people to exercise outside’, says Matthew Strickland, an associate professor of health sciences at the University of Nevada, Reno, who has studied links between wildfire smoke and emergency room visits.
“’My opinion is that it is reasonable to exercise on ‘unhealthy for sensitive groups’ days,’ he says, if you are not among those sensitive groups — such as people with asthma, the elderly and children — and ‘if you do not experience acute symptoms,’ he says. ‘But I would avoid exercising outside on days classified as ‘very unhealthy’” — purple — or ‘hazardous’ — maroon.’” (New York Times)
James Crooks concurs, “I would caution anyone against outdoor exercise when the A.Q.I. is ‘unhealthy’ or higher.” Crooks is a clinical assistant professor at the Colorado School of Public Health and associate professor of biostatistics at National Jewish Health hospital in Denver.
How to exercise
Here are ways to exercise if the AQI is above 100:
- Pollution levels change throughout the day so check the AQI before heading out the door. The website AirNow.gov gives real time data by zip code and the primary pollutants that have the highest AQI. In general air quality is worse later in the day.
- Before exercising asthmatics may need to increase their medication.
- If you have the occasional bad pollution day then take the day off. You’ve spent months building you fitness and you won’t lose it if you’re off the bike a few days.
- Change the length of your workout to limit exposure. Go for a 90-minute ride before breakfast instead of a three-hour mid-day endurance ride.
- Exercise inside with the doors and windows closed. This may help depending on the type of pollution and how airtight your house is. Here’s a column I wrote on 13 trainer workouts with maximum benefit.
- Change the type of workout. Here’s a column on Six strengthening exercises to prevent cramps and one on Why stretching may help you.
Riding hard is better
You probably assume low-intensity activities are better because you wouldn’t be breathing as deeply. Dr. Michael Koehle, the director of the Environmental Physiology Laboratory at the University of British Columbia, tested this in a study of 18 young male athletes. They pedaled stationary bicycles for 30 minutes on four different days. During two sessions, the subjects rode at an easy pace while wearing masks. In one of the sessions they breathed normal air and in the second session breathed diesel fumes. They repeated the protocol pedaling hard, while again breathing normal air in the third session and then polluted air in the fourth session. The scientists found the riders’ lungs seemed to labor more when they pedaled lightly in the polluted air than when they hammered.
“Dr. Koehle says, “’If I had to choose between a short, 20- to 30-minute, more-intense bike ride or a longer, easier, three-hour ride, based on the science, I’d recommend the shorter, more-intense workout, just because it would lead to two-and-a-half hours less air-pollution exposure.’ “
Experiments haven’t shown how long one should exercise when the air is smoky. If the air quality is orange or better Dr. Koehle says, “’something in the range of 30 to 60 minutes’” spent exercising outside ‘seems reasonable.’ ” (New York Times)
“N95 masks are the type of face covering protection that I would recommend for somebody who is outside during the air pollution caused by wildfires,” says Marina Vance. N95 and KN95 masks are equally effective if worn correctly; however, cloth masks are useless. Vance recommends throwing an N95 or KN95 mask away after a few uses. Vance is an assistant professor in the department of mechanical engineering and in the environmental engineering program at the University of Colorado, Boulder. (Healthline from University of Colorado)
Ozone — a form of oxygen — pollution is different than smoke. Wildfire smoke in your city is the result of factors beyond local control. Wildfires and winds determine if it’s smoky. Ozone results from local factors.
To make ozone, you need volatile organic compounds (VOC) including hydrocarbons and also nitrogen oxide and sunlight. Ozone results when the hydrocarbons and nitrogen oxide from car and industry emissions mix in the summer heat and sunlight. The pollution increases throughout the day and the sun has more time to cook it so ozone is typically higher later in the day. High humidity makes things worse because the moisture in the air traps the ozone.
Car and industry pollutants are not the only causes of ozone. Research by the National Oceanic and Atmospheric Administration (NOAA) shows that VOCs from personal consumer products make up a large portion of the pollution causing air pollution in every major city in America. VOCs evaporate from consumer products like sunscreen, shampoo, hair gel, bug spray, perfume, etc. One study showed about 42% of human-caused volatile organic compounds in the atmosphere in Boulder, CO are from consumer products and transportation emissions make up nearly all the rest. Another study showed cities like New York have more consumers and public transit and fewer cars and industries so consumer products make up about 78% of the total of ozone-causing compounds.
People can affect the ozone levels. Waiting until evening to gas up your car helps as do your choices of consumer products. “Air experts have an almost-ironclad rule about human-made ingredients and ozone: If you can smell it, it’s likely bad.” (Colorado Sun)
Wildfire smoke in major U.S. cities also tends to increase ozone levels by about 10 to 20 percent.”
The people at risk and the symptoms are similar to those of smoke.
Studies indicate that 10% to 20% of people have an acute response to ozone with a change in lung function. Ozone also changes the lung function in the other 80% to 90% but not as dramatically and they might not even notice the effects on their lungs. Why some normally healthy people are affected more than others is still a mystery according to Dr. William Eschenbacher, an associate professor of medicine at Baylor College of Medicine in Houston. (Los Angeles Times)
Ozone frequently causes respiratory symptoms during exercise and affect how your lungs work. The effects are worse after combined exposure to ozone and diesel exhaust. “Further studies are needed to identify pollutant and/or time thresholds for performing safe outdoor exercise in cities.” (Frontiers in Public Health)
If ozone levels are bad you should adjust your exercise even if you don’t feel the effects. You may not notice the effects until you discover you can’t ride as far or fast. What can you do? In addition to the above six recommendations on exercise on smoky days:
- Exercise in the early morning and late evening when ozone levels are lower.
- Avoid congested roadways. Pollution levels decline significantly just a few hundreds meters from a busy roadway.
- Unlike exercising when it’s smoky, short harder rides aren’t recommended when ozone is bad.
Exercise is important for both physical and mental health. If the AQI is 101-150 you don’t get to be a couch potato — you still should exercise unless you are in one of the groups at higher risk. Just be prudent.
Experts have a simple rule of thumb: if you can’t see five miles then it’s too smoky to go out. Last evening I could barely see the hills that far away and I could smell smoke so I only went for a short mountain bike ride. The smoke didn’t noticeable affect my lungs but my eyes got red. Conditions are similar today so I’ll do an indoor core and general strength workout. The forecast is better tomorrow so we’ll probably go kayaking.
Coach John Hughes earned coaching certifications from USA Cycling and the National Strength and Conditioning Association. John’s cycling career includes course records in the Boston-Montreal-Boston 1200-km randonnée and the Furnace Creek 508, a Race Across AMerica (RAAM) qualifier. He has ridden solo RAAM twice and is a 5-time finisher of the 1200-km Paris-Brest-Paris. He has written nearly 30 eBooks and eArticles on cycling training and nutrition, available in RBR’s eBookstore at Coach John Hughes. Click to read John’s full bio.