Recreational microplastics as emerging pollutants: effects of crumb rubber leachate across ecosystems

Crumb rubber from recycled tires is widely applied in recreational surfaces, where it leaches complex mixtures of chemicals. While tire-wear particles have been linked to aquatic toxicity, impacts of recreational crumb-rubber leachates remain underexplored across ecosystems. We generated leachate under conditions designed to approximate runoff from synthetic turf after rainfall. Suspect screening via liquid chromatography-tandem mass spectrometry (LC-MS/MS) identified five putative plasticizers-diethyl phthalate (DEP), dimethyl phthalate (DMP), dioctyl phthalate (DOP), di (2-ethylhexyl) phthalate (DEHP), and dibutyl sebacate (DBS), with DEP also detected in control pond water, underscoring the ubiquity of phthalates in environmental baselines. In freshwater planaria, survivorship, regeneration length, and eyespot spacing were unaffected, but swimming speed after regeneration was reduced by ∼59%. Preconditioned planaria also reached final body lengths ∼15% greater than controls, suggesting altered growth despite intact regeneration. In earthworms, leachate exposure did not impair survival, stress tolerance, or soil displacement, but individuals gained ∼77% more mass than controls, a result consistent with possible hormesis, changes in food availability, or true tolerance without measurable cost. In marine assays, dinoflagellate populations declined by 41% (low dose) and 60% (high dose) compared to controls, with no difference between doses, indicating threshold-level toxicity. Together, these findings show that crumb-rubber leachate can suppress primary producers and impair freshwater invertebrate performance, while earthworms may experience either compensatory growth or no adverse effects. The detection of multiple phthalates and emerging plasticizers underscores the risks of treating recreational crumb rubber as environmentally benign. Our results support recent EU restrictions on intentionally added microplastics and highlight the need for comparable action to protect ecosystems and human health.