Researchers at Maria Curie-Skłodowska University in Poland say the finest fractions release greater amounts of bioavailable contaminants.

They report these contaminants to have stronger toxicity to soil organisms, plants and aquatic bacteria, highlighting potential environmental and health concerns.

Recycling tyres into rubber granulate for artificial turf, playground surfaces or running tracks is an alternative to stockpiling or incineration, but the rubber contains PAH.

The research team say previous studies have detected high PAH levels in rubber surfaces, but few have integrated chemical measurements with biological toxicity testing across different particle sizes.

They conclude that recycled tyre rubber granulate - particularly fine particle fractions - can act as a sustained source of bioavailable PAHs and metals in environments where human contact is frequent.

Read more in Toxicity and polycyclic aromatic hydrocarbons bioavailability in recycled tire rubber granulate of varying particle sizes in Environmental and Biogeochemical Processes.