Your gym workout may expose you to deadly, toxic air

Even before the coronavirus pandemic hit the U.S. last spring, I always encouraged you to avoid exercising inside grimy, stinky gyms. We knew they were bastions of potentially harmful microbes, including methicillin-resistant staphylococcus aureus (MRSA) and staphylococcus aureus (staph). And now, a new study from researchers with the University of Colorado recently found that they’re also full of harmful, toxic air 

But before I get into the details, let’s go over some other reasons why outdoor exercise is always the better option… 

Being in Nature benefits the body, mind, and spirit 

I often extol the many benefits of exercising outdoors in Nature. For one, walking and climbing over soft, natural terrain is gentler on your joints than pounding away on the pavement or treadmill. Plus, since natural terrain is uneven, it poses more of a challenge, allowing you to build muscle and work on your balance and coordination ( a key factor associated with longevity)Which is especially important for older people. 

Second, studies show spending time in green or blue spaces (near the water) offers many physical and psychological benefits. In fact, people who just spend more time in green spaces live longer and develop fewer diseases. And in a large, 2013 study, 20,000 smartphone users reported feeling “happiest” when they spent time along the coastline and in marine environments. 

Lastly, theresoothing, peaceful, and spiritual dimension, with all the sights, sounds, smells, and feelings you experience by spending time near a woodland, forest, or body of water. 

Now, let’s get back to the new study that found exercising inside a gym exposes you to harmful, toxic air… 

Toxic air at fitness centers 

Researchers set out to evaluate the air quality in the university’s indoor fitness center. They measured a range of airborne toxins in real time, before, during, and after student workouts.   

It turns out, they found that one sweaty, heavy-breathing body during exercise emits as many chemicals as five normal, sedentary people. Plus, athletes produce up to five times as many chemical emissions while working out, compared to when they are at rest. 

But here’s where the danger comes in… 

Those normal human emissionsincluding amino acids and acetonecan chemically combine with chlorine bleach cleaners and disinfectants to form airborne toxins. (Many indoor gym facilities frequently use chlorine bleach-based disinfectants to sanitize exercise equipment and other high-touch surfaces.) 

Well, at the University of Colorado’s gym, when the amino acid emissions combined with the chlorine bleach vapors, it formed a harmful chemical group called N-chloraldimines 

The researchers said they need to conduct more research about the effects of N-chloraldimines on humans. But they did admit that the chemicals behave in a similar way as highly toxic (and sometimes deadly) chloramine gas, which you get when you combine bleach and ammonia! 

Dr. Zachary Finewax, the study’s lead author, said in an interview, “Humans are large sources of indoor emissions…and chemicals in indoor air, whether from our bodies or cleaning products, don’t just disappear, they linger and travel around spaces like gyms, reacting with other chemicals.” 

I should also note that the researchers conducted this study long before everyone started to kick their sanitation routines into high gear due to the coronavirus pandemic. Therefore, I think we can safely assume that indoor gyms today use much more chlorine bleach-based disinfectants on a daily basis. 

But despite their new findings, the researchers still claimed that a modern indoor gym with low occupancy may still be “relatively” safe, especially if masks are used  


Sure, wearing masks while exercising may lower your exposure to these deadly, man-made toxins. (And to the coronavirus.) But you may suffer from hyperventilation, heart attack, or even lung infections from these chemical combinations instead! 

Get up, get out, and enjoy the sunshine 

In the end, I suggest that you skip the costly and inflexible indoor gym memberships (if you haven’t already due to coronavirus concerns) 

Instead, get moving outside in Nature for just 140 to 150 minutes total per week. It’s healthier all around, even after the coronavirus fizzles out. 

Plus, now that we’re into May, the weather outside can be delightful for some outdoor walks, hikes, swimming, and gardening. You can even try forest bathing! (Learn how to indulge in this “new” trend in the March 2020 issue of my monthly Insiders’ Cures newsletter [The simplest way to reduce stress, lower blood pressure, and ward off cancer—naturally”]. Not yet a subscriber? Click here now!) 


“Quantification and source characterization of volatile organic compounds from exercising and application of chlorinebased cleaning products in a university athletic center.” Indoor Air, 2020;