Selection and application of trophic magnification factors for priority substances to normalize freshwater fish monitoring data under the European Water Framework Directive: a case study

Abstract

Background The European Water Framework Directive (WFD) requires the monitoring of biota—preferably fish—to check the compliance of tissue concentrations of priority substances (PS) against substance-specific environmental quality standards (EQSs). In monitoring programs, different fish species are covered, which often are secondary consumers with a trophic level (TL) of about 3. For harmonization, a normalization of monitoring data to a common trophic level is proposed, i.e., TL 4 (predatory fish) in freshwaters, so that data would be sufficiently protective. For normalization, the biomagnification properties of the chemicals can be considered by applying substance-specific trophic magnification factors (TMFs). Alternatively, TL-corrected biomagnification factors (BMFTLs) may be applied. Since it is impractical to derive site-specific TMFs or BMFTLs, often data from literature will be used for normalization. However, available literature values for TMFs and BMFTLs are quite varying. In the present study, the use of literature-derived TMFs and BMFTLs in data normalization is studied more closely. Results An extensive literature evaluation was conducted to identify appropriate TMFs for the WFD PS polybrominated diphenyl ethers (PBDE), hexachlorobenzene, perfluorooctane sulfonate (PFOS), dioxins and dioxin-like compounds (PCDD/F + dl-PCB), hexabromocyclododecane, and mercury. The TMFs eventually derived were applied to PS monitoring data sets of fish from different trophic levels (chub, bream, roach, and perch) from two German rivers. For comparison, PFOS and PBDE data were also normalized using literature-retrieved BMFTLs. Conclusions The evaluation illustrates that published TMFs and BMFTLs for WFD PS are quite variable and the selection of appropriate values for TL 4 normalization can be challenging. The normalized concentrations partly included large uncertainties when considering the range of selected TMFs, but indicated whether an EQS exceedance at TL 4 can be expected. Normalization of the fish monitoring data revealed that levels of substances accumulating in the food web (TMF or BMF > 1) can be underestimated when relying on fish with TL < 4 for EQS compliance assessment. The evaluation also revealed that TMF specifically derived for freshwater ecosystems in Europe would be advantageous. Field-derived BMFTLs seemed to be no appropriate alternative to TMFs, because they can vary even stronger than TMFs.

PFAS accumulation in indigenous and translocated aquatic organisms from Belgium, with translation to human and ecological health risk

“…The TMFs in the present study were compared to those of other studies on freshwater ecosystems, and were higher than those reported by Loi et al [54] for PFOS (TMF = 1.3) and lower than those for PFUnDA (TMF = 1.7), although the general trend of biomagnification was comparable to the present study. Furthermore, the TMF PFOS calculated in the present study is in line with other European studies on lake and river food chains as reported by Rüdel et al [64]. On the other hand, Lescord et al [53] reported a negative relation between accumulation and trophic level for PFOS, PFNA and PFUnDA in a foodweb from the high Arctic.…”

“…For eel and perch, respectively, 44% and 58% of sampling locations exceeded the EQS biota, hh , indicating potential health risks to the food web and to top predators (including humans) through fish consumption. In a German monitoring study, PFOS was above the EQS biota,hh in 33% of the locations in perch muscle [64,65]. However, the current EQS biota, hh is based on the previous EFSA tolerable daily intake (TDI) value for PFOS of 150 ng/kg body weight, which can be converted to 10.5 µg per day considering a 70 kg person [26,56].…”

“…It was, however, stated that when determining the risk for secondary poisoning it is more appropriate to use whole fish measurements instead of fillet [25]. An average conversion factor between both matrices of about 3 was determined for perch [64,65,81]. This would increase the exceedance in perch to 45% of all locations.…”

The Concentration and Biomagnification of Pcbs and Pbdes Across Four Trophic Levels in a Marine Food Web

“…This was unexpected, as CB180 is the highest chlorinated congener in this study. However, the TMF for CB180 in this study is higher than reported globally, where Rüdel et al, (2020) reported a range of 1.2 -4.6 in pelagic and benthopelagic food webs in Italy, Norway, Finland and Canada; reported a TMF of 1.06 from a food web composed of invertebrates and fish in Ulson Bay, Korea. The value for CB52 is also much higher than reported globally.…”

Food web on ice: a pragmatic approach to investigate the trophic magnification of chemicals of concern

“…This requires a numerical TMF value rather than an answer to the question, whether the TMF is above or below 1. A recent analysis illustrated challenges associated with the normalization approach which may result in an overestimation of TMF corrected biota concentrations [82].…”