The world is on fire. Seriously. Current climate conditions mean longer, hotter, and dryer seasons everywhere and more wildfires burning hotter, longer and traveling further. This is our reality now even if we make the most aggressive cuts to anthropogenic sources of climate change. And smoke spreads thousands of square miles.
Wildfire smoke invades the air every endurance athlete gulps down. And understanding basic air quality measures doesn’t mean having to sample the hazard to know the air is bad. In the US, the National Weather Service and Environmental Protection Agency publish daily, city level, air quality forecasts and current data. These include Air Quality Index (AQI), Carbon Monoxide (CO), Ozone (O3), Nitrogen Dioxide (NO2), Sulfur Dioxide (SO3), 10-micron Particulate (PM10), and 2.5-micron Particulate (PM2.5). While wildfire produces all of these, the three you want to pay the closest attention to are AQI, PM10, and PM2.5. I will briefly explain the measures, why they matter to you and how you can limit harm.
Air Quality Index (AQI)
AQI is a composite of all of the measures listed above and other airborne hazards. AQI is scored from 0-500. Any value above 100 is hazardous. Above 100, athletes with breathing considerations should limit outdoor activity. For healthy athletes without breathing considerations, AQI under 200 is ok for reasonably strenuous training outdoors for shorter durations. Above 200, even healthy athletes should dial it back to indoor, easier effort, and short duration. Above 300 means take a rest day. If that is not possible, relocate to somewhere where the air is cleaner. Because AQI is a composite, similar scores on back-to-back days may be due to different hazards.
Common N95 masks are designed to filter particles, not noxious gases. Depending on the current hazard level, wearing an N95 mask on a high AQI day may not significantly change the air you’re breathing.
Particulate Matter 10 & 2.5 Micron (PM10 & PM2.5)
Particulate matter is dust, ash, fibers, bacteria, pollen and other materials that are light enough to float in the air. The two size categories are based on whether the particle can pass into lung tissue. PM10 mostly accumulates on upper respiratory tissue. PM2.5 is capable of traveling much deeper. PM2.5 can cause congestion, inflammation, and permanent damage in the alveoli—the tiny air sacs exchanging gases with blood.
Your post-gravel-ride cough is probably due to PM10 and larger-sized dust kicked up by tires. On the other hand, the gasping due to liquid filled alveoli from pneumonia is very similar to PM2.5 damage. Particulate matter is reported in average micrograms of matter per cubic meter (µg/m3) for each category. Low-risk concentrations of PM10 are less than 150µg/m3 and PM2.5 are 35µg/m3 over a 24 hour period.
Why does it matter?
If it is not already clear, a large dose or an extended exposure to airborne hazards can damage an athlete’s lungs. Sometimes permanently. Sometimes fatally. A highly exerted athlete moves up to five times their normal volume of air for any given time period. This means a much higher dose of airborne hazards in a shorter period of time.
What can be done?
During wildfire season (Northern Hemisphere: April-September, Southern: September-May) regularly check your local air quality data and forecast. If the AQI or PM numbers are indicating hazard, consider modifying the prescribed activity for the day. If particulate matter is the main hazard, properly worn particulate masks (N90, N95, N99, etc) can reduce exposure. For high PM10 days, training indoors is a viable alternative. Note, this is not viable for PM2.5 because it is small enough to saturate indoor spaces. If AQI is high but PM numbers are okay, modify activities or seek training locations with cleaner air.
Degraded air, by wildfire or other sources, is, unfortunately, a fact of life now. Because athletes move so much more air through their lungs, it is even more important to weigh long-term damage to short-term training benefits. Monitoring air quality measurements and implementing safety measures can reduce risk factors and keep athlete lungs strong and functioning for decades to come.
Want the air to improve as you grow older? Here’s a useful infographic on personal choices with the highest impact on anthropogenic sources of climate change. Final note: I am not a doctor. Just an educated coach and athlete who lives in a place that burns A LOT. These suggestions are not medical advice. If you suspect a sensitivity to airborne hazards, consult a doctor before exposure to potentially life-threatening conditions.