Ecological risk assessment of p-toluidine in freshwater, sediment, and soil media

Para-toluidine (p-toluidine) is a high production volume chemical, of which about 5,000 tons/year are imported into Korea as of the 2018 registration. This substance is mainly used as an intermediate in the manufacture of paints, azo dyes, and pigments. In this study, an ecological risk assessment of p-toluidine was performed to investigate the risk to the environment assuming the worst-case exposure scenario. Ecotoxicity data was collected from the literature and the predicted no effect concentration (PNEC) was derived. The predicted environmental concentration (PEC) was calculated using the SimpleBox Korea v2.0 model. Hazard quotient (HQ) was calculated based on PEC and PNEC. The concentration of p-toluidine was measured in soil samples from workplaces with a HQ exceeding 1 to verify the results of modeling. PNECs for surface water, sediment, and soil were 0.00022 mg/L, 0.0025 mg/kg (dw), and 0.00037 mg/kg (dw), respectively. Based on regional-scale PEC, the HQ of freshwater, sediment, and soil media were all less than 1, but the HQ exceeded 1 at some local sites. Based on the fact that the measured environmental concentration in soil samples around the workplace is below the limit of detection and that all waste is incinerated at the actual workplace, p-toluidine is not likely to pose a high risk to the environment in Korea.