RESUMEN
Considering the large amount of tires that reach the end of life every year, the aim of this study was the evaluation of both acute and chronic effects of end-of-life-tire (ELT)-derived rubber granules (ELT-dg) and powder (ELT-dp) on a freshwater trophic chain represented by the green alga Pseudokirchneriella subcapitata, the crustacean Daphnia magna and the teleost Danio rerio (zebrafish). Adverse effects were evaluated at the organism and population levels through the classical ecotoxicological tests. Acute tests on D. magna and D. rerio revealed a 50% effect concentration (EC50) > 100.0 mg/L for both ELT-dg and ELT-dp. Chronic exposures had a lowest observed effect concentration (LOEC) of 100.0 mg/L for both ELT-dg and ELT-dp on P. subcapitata grow rate and yield. LOEC decreased in the other model organisms, with a value of 9.8 mg/L for D. magna, referring to the number of living offspring, exposed to ELT-dg suspension. Similarly, in D. rerio, the main results highlighted a LOEC of 10.0 mg/L regarding the survival and juvenile weight parameters for ELT-dg and a LOEC of 10.0 mg/L concerning the survival and abnormal behavior in specimens exposed to ELT-dp. Tested materials exhibited a threshold of toxicity of 9.8 mg/L, probably a non-environmental concentration, although further investigations are needed to clarify the potential ecological impact of these emerging contaminants.
RESUMEN
pp'-Dichlorodiphenyl-dichloroethylene (pp'DDE), a metabolite of pp'-dichlorodiphenyl-trichloroethane poses a risk for many ecosystems in spite of the banning of the parent compound because of its persistence and bioaccumulability. Nevertheless, the knowledge of acute and chronic toxicity on aquatic organisms is still very poor. In the present study, Daphnia magna was exposed to varying concentrations of pp'DDE in water and through diet to determine both acute toxicity and potential for effects on reproduction and survivability. The 48 h IC50 was 5.08 µg L(-1) (3.76-7.01 µg L(-1)). As pp'DDE concentration in water was not stable and the amount assumed by food cannot be established with certainty, the results of chronic toxicity tests were expressed as the concentration in the organism which caused a negative effect. Grazing activity was affected with a pp'DDE concentration in the organism of 24 ng mg(-1) d.w., while the lowest observed effect concentration for fecundity reduction was 109 ng mg(-1) d.w.
