Toxic chemicals Linked to Common Playground, Athletic Surface Material
Recycled crumb rubber, widely used in playgrounds and on athletic fields, may be releasing harmful toxins into the environment, according to new research raising concerns about potential health risks.
A growing body of evidence suggests that materials designed to promote sustainability may inadvertently pose threats to both ecosystems and human health. New research indicates that crumb rubber, the ubiquitous black granules made from recycled tires found on playgrounds, sports fields, and running tracks, could be leaching toxic chemicals into the surrounding soil and water for years to come.
The composition of crumb rubber, analyzing three different particle sizes. Scientists discovered high levels of polycyclic aromatic hydrocarbons (pahs) within the material. These compounds, when inhaled, swallowed, or absorbed through the skin, can pose a variety of health risks, including complications during fetal progress, liver and reproductive damage, and, in some cases, are known carcinogens.
Experts have already begun recommending precautionary measures, such as washing hands after playing on crumb rubber surfaces, avoiding eating while on synthetic turf, and limiting exposure during periods of extreme heat.
To quantify the potential danger, the research team measured both the total amount of PAHs present in the recycled rubber and the bioavailable fraction – the portion that can dissolve in water and be absorbed by living organisms. “Our results show that recycled tyre rubber contains very high concentrations of PAHs, especially in the smallest particle sizes,” explained Patryk Oleszczuk, the study’s corresponding author, in a press release. “These fine particles are more reactive and release a greater share of toxic compounds into water and soil, increasing the risk to ecosystems and potentially to human health.”
The study found total PAH levels ranging from 49 to 108 milligrams per kilogram, with the smallest granules consistently exhibiting the highest concentrations of toxins. Alarmingly, the bioavailable portion of these chemicals was also most pronounced in the tiniest particles, exceeding levels typically found in many contaminated soils and sediments.
Researchers further tested the real-world impact of these findings by exposing soil-dwelling invertebrates, garden cress plants, and marine bacteria to both solid rubber granulate and water soaked with it. All organisms exhibited adverse effects, with the smallest granules significantly reducing survival rates, growth, and biological activity. “Chemical data alone do not tell the whole story,” Oleszczuk stated. “By combining chemical analysis with ecotoxicological tests, we where able to demonstrate that the compounds released from rubber granulate are not just present, but biologically active and harmful.”
The team also identified potentially toxic metals, such as zinc and copper, in water extracted from the rubber, with metal levels in some instances exceeding established drinking-water guidelines. This is particularly concerning given the direct contact many people – especially children – have with these surfaces.
The problem is likely to worsen over time, as sunlight, heat, and moisture can further break down the rubber, potentially releasing even more hazardous substances into the environment. “Our findings suggest that the environmental safety of tire derived rubber depends strongly on particle size,” Oleszczuk said. “Fine granulates pose a disproportionate risk and should be carefully regulated, particularly in public spaces like playgrounds and sports facilities.”
Though, the path to regulation remains uncertain. A significant debate continues among researchers and public health officials regarding whether typical exposure levels to crumb rubber pose a significant health risk. A 2024 federal multi-agency research initiative, for example, reported no significant differences in PAH exposure between individuals using synthetic turf fields with crumb rubber infill and those on natural grass fields.
The Polish scientists emphasize that tire recycling remains an critically important environmental objective,but caution that not all recycled materials are inherently safe. “This study highlights the need to rethink how recycled materials are evaluated and applied,” Oleszczuk said. “Sustainability should not come at the expense of environmental or human safety.”
To mitigate these risks, the researchers advocate for size-specific regulations on recycled rubber, coupled with long-term safety monitoring and the development of safer alternatives.
