Inhalation of climbing shoe particles is highly relevant for the human exposure to rubber-derived chemicals in indoor facilities

There is increasing research focused on rubber-derived chemicals (RDCs), predominantly originating from tire and road wear particles. Other consumer products also contain RDCs, but the overall human exposure to these compounds is unknown. This study investigated climbing shoes as a potential contributor to human indoor exposure to RDCs, including potentially harmful substances such as benzothiazoles, p-phenylenediamines (PPDs), and PPD-quinones. The soles of climbing shoes contain high but variable concentrations of RDCs (mean 711 μg/g). In indoor climbing halls, abrasion particles from these shoes can be suspended in the air. Dust and air samples were collected in two climbing halls and particulate matter in the inhalable and respirable fractions were analyzed for 15 RDCs. Concentrations in dust (16 to 43 µg/g) and particulate matter (23 to 35 ng/m3) exceed those reported from other environments. For most RDCs, estimated daily intake via inhalation (EDIinh) for adults visiting or working in these facilities exceeds the EDI from other sources. This highlights the potential concerns with using large amounts of rubber additives in consumer products. RDCs profiles in shoe samples differed from those in dust and particulate matter, indicating that RDCs are chemically transformed in airborne rubber particles. This finding has broader implications as similar transformations are likely to occur in airborne tire wear particles.