The environmental fate of six existing chemicals in laboratory tests

In a project aimed at developing a test strategy for the assessment of the ecotoxicological hazard potential of existing chemicals in the terrestrial environment, the soil degradation and leaching of six substances (Anthracene, 2,4-Dichlorophenol (2,4-DP), 2,4-Dinitrotoluene (2,4-DNT), Tris(2-chloroethyl)-phosphate (TP), Tetrachloroethene (Per), Octachlorodibenzo-p-dioxin (OCDD)) was investigated. The chemicals were selected as examples, with different physico-chemical properties such as, water solubility or log P-OW values. The methods used were standardised laboratory tests, required by the BBA (German Federal Research Centre for Agriculture and Forestry) as part of the pesticide registration process. In the degradation tests, which were carried out with German standard soil (Lufa St. 2.2) at concentrations of 5 mg/kg (except OCDD: 0.05 mg/kg), the DT values varied substantially (DT50: 4 to 167 days; DT90: 45 to > > 100 days). Due to its volatility, the test for Tetrachloroethene had to be modified which resulted in DT values of less than 1 hour. OCDD, on the other hand, did not degrade during the 100-day test period (theoretical DT50 value: 13002 days). With the exception of Tris (2-chioroethyl)-phosphate, which was slightly mobile, none of the other chemicals showed any mobility in the leaching tests, which were carried out with three standard soils (LUFA 2.1, 2.2, 2.3). Based on the experience gained in this project, degradation and leaching tests are recommended to be used to test existing chemicals which are likely to be distributed in the terrestrial medium. For this purpose, standardised methods used in the testing of pesticides have to be modified in order to allow for the various properties (especially different exposure scenarios) of existing or other environmental chemicals. (C) 1997 Elsevier Science Ltd.