ABSTRACT
OBJECTIVES: Potential environmental risks caused by chemicals that could be released from a recycled plastic product were assessed using a screening risk assessment procedure for chemicals in recycled products. METHODS: Plastic slope protection blocks manufactured from recycled plastics were chosen as model recycled products. Ecological risks caused by four model chemicals -di-(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), cadmium (Cd), and lead (Pb)- were assessed. Two exposure models were built for soil below the block and a hypothetic stream receiving runoff water. Based on the predicted no-effect concentrations for the selected chemicals and exposure scenarios, the allowable leaching rates from and the allowable contents in the recycled plastic blocks were also derived. RESULTS: Environmental risks posed by slope protection blocks were much higher in the soil compartment than in the hypothetic stream. The allowable concentrations in leachate were 1.0x10(-4), 1.2x10(-5), 9.5x10(-3), and 5.3x10(-3) mg/L for DEHP, DINP, Cd, and Pb, respectively. The allowable contents in the recycled products were 5.2x10(-3), 6.0x10(-4), 5.0x10(-1), and 2.7x10(-1) mg/kg for DEHP, DINP, Cd, and Pb, respectively. CONCLUSIONS: A systematic ecological risk assessment approach for slope protection blocks would be useful for regulatory decisions for setting the allowable emission rates of chemical contaminants, although the method needs refinement.