The Invisible Footprint of Climbing Shoes: High Exposure to Rubber Additives in Indoor Facilities

There is growing concern about rubber-derived compounds
(RDCs),
predominantly originating from tire and road wear particles. Other
consumer products, including sports equipment, also contain RDCs,
and human exposure to these compounds is of particular interest due
to demonstrated toxicity to animal species. In this study, we investigated
RDCs intentionally incorporated into climbing shoes for enhanced performance.
We found high concentrations of 15 RDCs in shoe sole samples (Σ15 RDCs: 25–3405 μg/g), aerosol particulate matter
(Σ15 RDCs: 2.6–37 μg/g), and settled
dust (Σ15 RDCs: 1.5–55 μg/g) in indoor
climbing halls. The estimated daily intake via inhalation/ingestion
of Σ15 RDCs for climbers and employees in some of
these facilities ranged from 1.7 to 48 ng/kg/day, exceeding known
intake levels of RDCs from other sources. Abrasion powder resulting
from friction between climbing shoes and footholds is the likeliest
source of high concentrations of RDCs observed in aerosol particulate
matter and settled dust. These findings reveal a previously unknown
human exposure route of RDCs.