Are our rock-climbing shoes shedding plastics?

“I spent the first two years of my PhD research studying the environmental fate of chemicals that are added to tyres to prevent their degradation. These tyre additives include a rubber-stabilizing chemical called 6PPD, a breakdown product of which was linked in 2020 to salmon deaths. It is estimated that tyre-wear particles contribute roughly 50% of global microplastic emissions. My initial research documented how these compounds can be taken up by lettuce.
I’m an avid rock climber, and as I continued to think about pollutants in rubber tyres, I began to wonder about the tread on climbing shoes — which are made from a similar material to help climbers to grip the rock. A colleague and I decided to extract the chemicals from our shoes and see what was happening. So far, we have tested 30 pairs of climbing shoes and found similar chemicals to those pollutants in tyres — albeit at different ratios.
After making this discovery, I started wondering whether these chemicals were being inhaled at the climbing gym. As well as white particles of chalk, which is used to help climbers grip, floating in the air, you can see tiny black particles on the climbing wall’s handholds and footholds. In this image, from earlier this year, I’m taking air samples in the fourth climbing gym we tested — at the University of Vienna, where I still work as a PhD student in environmental geochemistry.
During peak hours of activity, I use a glass contraption, called a twin-stage impinger, that mimics human respiration by pumping air at 60 litres per minute through two chambers that represent the upper and lower respiratory tracts. My team samples the climbing-gym air for three hours to measure the total mass of particles that reach each chamber, and therefore are theoretically inhaled by a person during a climbing session. Further work will explore what those particles are doing to the body.”