Scientists tested air quality in a busy gym. The results were shocking

They say you never really appreciate what you have until it’s gone, and millions of people experienced that in reference to their local gym this year. Most gyms have been forced to shut down operations due to the COVID-19 pandemic, and countless people have been forced to make do with what little exercise space/equipment they have at home. 

Even so, the findings of a new study just released by the University of Colorado at Boulder will likely make you think twice about returning to your local gym or fitness center once doors re-open.

Researchers at UCB tested the air quality at an on-campus gym for student-athletes during a busy day and discovered a “chemical cocktail” in the air. Suddenly those YouTube workout videos don’t sound so bad.

What’s the source of all this fitness-related air pollution? Study authors point to two main culprits: human emissions and cleaning chemicals. 

When an individual engages in a strenuous workout their body emits far more chemicals than someone at rest. In fact, researchers calculate that a single exercising person emits about as many chemicals from their body as five people at rest. These chemicals usually include amino acids released from sweat and acetone from breathing and panting heavily. 

Meanwhile, it’s common practice for fitness centers to use chlorine-based bleach cleaners to disinfect exercise equipment and machines. While these cleaning substances do a great job of killing bacteria and viruses, they also seep into the surrounding air. 

Eventually, researchers say, these two distinct types of chemicals (cleaning products & human emissions) mix together to fill gyms with a new cocktail of chemicals that visitors inevitably breathe in during their work out.

“Humans are a large source of indoor emissions,” says lead study author Zachary Finewax, CIRES research scientist, in a release. “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.”

The air readings that doled out these findings were taken long before the coronavirus pandemic forced gyms to close their doors. Back in 2018, the research team set up a series of air-quality monitors inside an on-campus student-athlete gym.

Those monitors kept tabs on air quality within the fitness center before, during, and after all student workouts. Those readings indicate that people emit three to five times more chemicals while working out in comparison to before or afterward.

“Using our state-of-the-art equipment, this was the first time indoor air analysis in a gym was done with this high level of sophistication. We were able to capture emissions in real time to see exactly how many chemicals the athletes were emitting, and at what rate,” explains study co-author Demetrios Pagonis, a postdoctoral researcher at CIRES.

An especially troubling variety of chemicals known as N-chloraldimines were recorded in the gym air. These chemicals appear to be a result of combining human emissions and cleaning products. 

In more real-world terms, imagine one gym-goer uses an exercise machine and then wipes it down with a disinfectant. When the next person to use that machine is already drenched in sweat, the cleaning product and sweat mix together and release into the surrounding air.

As far as the health implications of breathing in these chemical mixtures, researchers don’t have any clear answers yet. However, “chemically similar” mixtures of ammonia and bleach are already confirmed to be harmful to human health.

“Since people spend about 90 percent of our time indoors, it’s critical we understand how chemicals behave in the spaces we occupy,” notes corresponding study author Joost de Gouw, CIRES Fellow, professor of chemistry at CU Boulder.

So, does all of this mean gyms should be avoided altogether? Not necessarily. Study authors believe a not-so-crowded gym with strong ventilation should still be “relatively safe” for gym-goers. This is especially true if everyone is wearing a mask as well, which will probably be a requirement in many gyms for at least the foreseeable future. 

The full study can be found here, published in Indoor Air.