2.4. Initial Ecological Risk Assessment
Quantitative environmental risk assessment based on predicted environmental concentrations (PECs)
and predicted no effect concentrations (PNECs) which proposed identification of the risk of detected
organic pollutants to aquatic environment [21, 22]. In order to obtain conservative PEC/PNEC ratio, the
detected maximum concentrations of organic polluantts were regarded as the PEC and the PNECs were
proposed based on the lowest E(L)C50 and application of an assessment factor of 1000 [23-25].
ECOSAR software provided acute aquatic toxicity values (EC50 or LC50) of algae, daphnia and fish
based on a structure activity relationship (SAR) for organic compounds [26]. The PEC higher than the
PNEC meaned that the PEC/PNEC ratio is greater than 1, indicating the given substance of concern while
the PEC/PNEC ratio is smaller than 1, suggesting no significant concern [23].