Release of Zinc and Polycyclic Aromatic Hydrocarbons From Tire Crumb Rubber and Toxicity of Leachate to Daphnia magna: Effects of Tire Source and Photoaging.

Tire crumb rubber (TCR) has been widely used in artificial turf fields, however, the potential environmental risk of TCR and the effect of sunlight exposure are scarcely studied. Here, we evaluated leachability of Zn and polycyclic aromatic hydrocarbons (PAHs) in four types of TCRs and acute toxicity of leachates to Daphnia magna. The results showed that all types of TCRs tested released Zn (0.20-1.3 μg/g) and PAHs (9.4-17 μg/g) but only two were lethal to D. magna (mortality 73%). Notably, ultraviolet (UV) irradiation induced TCR to generate acidic leachate (pH ~ 4.8), which contained 24- and 1.2-fold higher concentrations of Zn and PAHs and therefore was more toxic to D. magna than that in the absence of UV treatment. These findings demonstrate source-dependent toxicity of TCR and highlight the need to consider the effect of photoaging when evaluating the environmental risks of TCR.