1945 and ca. 1975, excluding Lake TF featuring the main peak in ca. 1985. ΣDDX concentrations peaked between 30 and 380 µg•kg -1 (median 225 µg•kg -1 ). These are, in fact, comparable to 4 of the 5 Canadian lakes examined by , which experienced direct aerial spray input of DDT in the 1950s-1970s, with maxima between ca. 130 and ca. 575 µg•kg -1 . developed consensus-based sediment quality guidelines (SEQs) for 28 chemicals of concern in freshwater ecosystems. Among them were a threshold effect concentration (TEC) and a probable effect concentration (PEC; not to be mixed up with predicted environmental concentration) for each analyte of concern. The TEC is intended to identify concentrations below which detrimental effects on sediment-dwelling organisms are not expected. The PEC on the other hand should indicate concentrations above which harmful effects on such organisms are expected to occur frequently. In the cases of ΣDDD and ΣDDE, TECs were 4.88 and 3.16 µg•kg -1 , respectively, and PECs were 28 and 31.3 µg•kg -1 , respectively. The latter were generally exceeded during the mentioned period of highest concentrations, by 2 to as much as 10 times in the case of ΣDDD, and by almost 3 times in the case of ΣDDE. Thus, detrimental effects for benthic fauna during the period of usage were very likely. Concentrations near the surface of the lake sediment were mostly < 10 µg•kg - 1 . They were in the same range as other surface sediment samples from anthropogenically influenced lakes. Similar concentrations as those found in our study were also observed in Lake Victoria in Uganda (mean ΣDDX 4.24 µg•kg -1 ; , Chinese Lakes Taihu (ca. 3.7-13.6 µg•kg -1 ; and Songyang (0.4-18.4 µg•kg -1 ; . In contrast, concentrations of DDD and DDE of some lakes (AR, BL, OR, PL) were similar to those found in remote alpine lakes of Switzerland (<LOD-4.75 µg•kg -1 ; . Concentrations in these four lakes are well below the TECs, indicating no acute threat to epibenthic fauna. Nevertheless, sublethal and chronic effects might still occur .