Gym air quality is impacted by reactions of sweat and bleach

Researchers at UC Boulder have investigated the air quality of gyms, specifically focusing on the impacts of high bodily emissions during workouts, which are intensified by chemical reactions with cleaners. The experts report that one exercising individual emits as many chemicals from their body as up to five sedentary people.

The study shows that human emissions, including amino acids from sweat or acetone from breath, react with bleach cleaners to form new airborne chemicals with unknown impacts to indoor air quality.

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

In 2018, the CU Boulder team set up equipment to sample air quality in a weight room in the Dal Ward Athletic Center, a campus facility for university student athletes. The instruments measured a range of airborne chemicals before, during, and after athletic workouts. 

The analysis revealed that the athletes’ bodies produced 3 to 5 times the emissions during a workout compared to when they were at rest.

“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,” said study co-author Demetrios Pagonis.

Many gym facilities use chlorine bleach-based products to sanitize equipment on a frequent basis. When the cleaning products combine with emissions from sweat, they create a new cocktail of chemicals.

The researchers found that chemicals called N-chloraldimines were produced in the gym air from the mixing of bleach products and amino acids. This means that chlorine from bleach cleaner sprayed onto equipment was reacting with the amino acids released from sweating bodies, explained the study authors.

Further research is needed to determine the specific impacts that these compounds may have on indoor air quality. Compounds that are chemically similar, which form from the reaction of ammonia mixing with bleach, are known 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,” said study co-author Professor Joost de Gouw. 

While all of the data was collected for this study prior to the COVID-19 pandemic, the experts say that a modern gym with low occupancy and good ventilation may still be relatively safe for a workout, especially if masks are used.

The study is published in the journal Indoor Air.

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By Chrissy Sexton, Earth.com Staff Writer