Screening-level risk assessment of Di(2-ethylhexyl)phthalate for aquatic organisms using monitoring data in Japan

Screening-level ecological risk assessments of di(2-ethylhexyl)phthalate (DEHP) for aquatic organisms in Japan were conducted using estimated statistical values based on surface water and sediment monitoring data and effect threshold values based on a large aquatic toxicity database. An alternative method is proposed to handle monitoring data that contain nondetects including multiple detection limits and to determine the statistical values of DEHP concentrations in Japanese surface waters. The No-Observed-Effect-Concentration (NOEC(water)) of DEHP for aquatic life of 77 micro g/L was determined giving equal importance to both physical effects probably caused by undissolved DEHP and to the intrinsic toxicity potentially caused by DEHP. The NOEC(sediment) of 615,000 micro g/kg was determined by the Equilibrium Partitioning (EqP) theory, conservatively assuming a threshold effect level in the water column as the water solubility of 3 micro g/L. The potential risks of DEHP in Japanese water environments were characterized simply by comparing the margin of exposure (MOE) with a specified uncertainty multiplier (UM). The MOE is expressed as the ratio of NOEC(water) or NOEC(sediment) to the expected environmental concentrations such as the 95th percentiles of the estimated DEHP concentration distributions for surface water or sediment. The results of risk characterization show that all MOE values calculated using the statistical values of DEHP concentrations in Japanese surface waters and sediments are above 10, indicating minimal risk. Although the DEHP concentrations of some surface water samples showed MOE values of less than 10, considering environmental chemistry such as bioavailable fractions and the form of existence of DEHP in a water environment, we conclude that the current levels of DEHP are of little concern to aquatic life in the majority of Japanese surface waters and sediments.