A study published by a team of University of Vienna researchers in the Journal of Environmental Science and Technology Air examines the air quality from five indoor climbing gyms in Vienna along with four from France, Spain and Switzerland.
Indoor rock climbing has exploded in popularity across Europe and the United States. Of these visitors, about 20% are regulars and spend several hours a day, multiple times a week in climbing halls.
The latest AusPlay survey results for January 2024 - December 2024 show that in Australia there are 95,378 participating in sport climbing also often referred to as bouldering.
The Austrian researchers found that specialised climbing shoes with their highly functionalised rubber soles worn by climbers release an array of toxic chemicals into the air, which is then inhaled into the lungs.
In indoor climbing halls, ‘handholds’ and ‘footholds’ are attached to specialised walls, allowing individuals to attempt to manoeuvre up and down and across the walls.
Joint author of the new study, environmental scientist Anya Sherman, said many climbers would be familiar with the black residue left on footholds on indoor climbing walls and advised “climbers wipe it off to get a better grip, and it gets kicked up into the air.”
Friction between the shoe soles and the footholds generates rubber particles which can be aerosolised and inhaled directly upon generation, due to the brushing of holds, or by climbers falling onto mats and resuspending rubber particles that had settled. Eventually, aerosol particles also settle elsewhere as dust.
The study team included environmental scientist Professor Thilo Hofmann who noted “the levels we measured are among the highest ever documented worldwide, comparable to multi-lane roads in mega-cities.”
These chemicals have been linked to lung inflammation, organ damage, respiratory illnesses and even some types of cancer.
Following their results, the research team are now calling for climbing wall gyms to ensure effective ventilation and for climbing shoe designers to change the materials used to help protect climbers and gym staff.
The Vienna University researchers note that the presence of leachable rubber-derived compounds (RDCs) in climbing hall dusts may pose a higher health risk than conventional low-toxicity dusts, thereby providing a compelling rationale for further investigations.
This study found that while RDC concentrations in a variety of rubber-based consumer products are generally low, climbing shoes contain significantly higher levels. This contrast underscores that while rubber is widely used, only highly engineered consumer products, such as climbing shoes and tires, contain a high additive content.
The observed variability in RDC concentrations in air across the five climbing wall halls tested for the study suggests that factors such as hall size, check-ins per hour, and ventilation may directly influence indoor air quality.
The research team concluded that studies assessing the relationship between variables such as ventilation rate and RDC levels would help prioritise interventions to reduce RDC levels in climbing wall centres.
Access the study in the Journal Environmental Science and Technology Air
Image top. Climbing wall montage; Image below. Schematic of a climbing hall, with photos of the four types of samples analysed in the study. Specialised climbing shoes are worn with highly functionalised rubber soles (1, shoe soles). Friction between these shoe soles and the footholds generates rubber particles (2, foothold powder). Those can be aerosolised and inhaled directly upon generation, due to the brushing of holds, or by climbers falling onto mats and resuspending rubber particles that had settled (3, aerosol particulate matter). Eventually, aerosol particles also settle elsewhere as dust (4, settled dust). Credit: ACS EST Air 2025
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