Comprehensive screening of polar emerging organic contaminants including PFASs and evaluation of the trophic transfer behavior in a freshwater food web.

Bioaccumulation and trophic transfer of persistent legacy contaminants have been intensively characterized, but little is known on the contaminants of emerging concern (CECs) in freshwater food webs. Herein, we comprehensively screened CECs with a focus on polar substances and further evaluated their trophic transfer behavior in selected items from the food web of Lake Templin, Germany. Weselected one plankton, two mussel, and nine fish samples covering three trophic levels. With an effective multi-residue sample preparation method and high-resolution mass spectrometry-based target, suspect, and non-target screening, we characterized 477 targets and further screened unknown features in complex biota matrices. Of the 477 targets, 145 were detected and quantified in at least one species (0.02-3640 ng/g, dry weight). Additionally, the suspect and non-target analysis with experimental mass spectra libraries and in silico techniques (MetFrag and SIRIUS4/CSI:FingerID) enabled further identification of 27 unknown compounds with 19 confirmed by reference standards. Overall, the detected compounds belong to a diverse group of chemicals, including 71 pharmaceuticals, 27 metabolites, 26 pesticides, 16 per- and polyfluoroalkyl substances (PFASs), 4 plasticizers, 3 flame retardants, 11 other industrial chemicals and 14 others. Moreover, we determined the trophic magnification factor (TMF) of 34 polar CECs with >80% detection frequency, among which 6 PFASs including perfluorooctane sulfonic acid (PFOS), perfluorodecanoic acid (PFDA), perfluorohexane sulfonic acid (PFHxS), perfluorotridecanoic acid (PFTrA), perfluorotetradecanoic acid (PFTeA), and perfluoroundecanoic acid (PFUnA), exhibited biomagnification potential (TMF =1.8 - 4.2, p < 0.05), whereas 5 pharmaceuticals (phenazone, progesterone, venlafaxine, levamisole, and lidocaine) and 1 personal care product metabolite (galaxolidone) showed biodilution potential (TMF = 0.4 - 0.6, p < 0.05).

Comparison of Alternative Methods for Bioaccumulation Assessment: Scope and Limitations of In Vitro Depletion Assays with Rainbow Trout and Bioconcentration Tests in the Freshwater Amphipod Hyalella azteca.

Bioaccumulation assessment predominantly relies on the bioconcentration factor (BCF) as the sole decisive metric. The test guideline 305 by the Organisation for Economic Co-operation and Development (OECD) provides the standard procedure for deriving this in vivo fish BCF, which is not only expensive and labor-intensive, but also requires many animals. Accordingly, there is a great need for and interest in alternative methods that can help to reduce, replace, and refine vertebrate tests, as described in the 3R principles. Two alternative approaches have been developed: the bioconcentration test with the freshwater amphipod Hyalella azteca and the OECD test guideline 319 which provides a method to determine experimentally derived in vitro metabolism rates that can then be incorporated into in silico prediction models for rainbow trout BCF calculation. In the present study both alternative methods were applied to 5 substances of different physicochemical characteristics. The results were compared with literature values of fish in vivo BCFs and additional BCFs obtained with the alternative methods, if available. Potential differences between the results of the test methods are discussed utilizing information such as in vivo metabolism rates. The currently available data set suggests that these 2 alternative methods pose promising alternatives to predict bioaccumulation in fish, although defined applicability domains have yet to be determined. Environ Toxicol Chem 2020;39:1813-1825. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Biotransformation Changes Bioaccumulation and Toxicity of Diclofenac in Aquatic Organisms.

Biotransformation plays a crucial role in regulating the bioaccumulation potential and toxicity of organic compounds in organisms but is, in general, poorly understood for emerging contaminants. Here, we have used diclofenac as a model compound to study the impact of biotransformation on the bioaccumulation potential and toxicity in two keystone aquatic invertebrates: Gammarus pulex and Hyalella azteca. In both species, diclofenac was transformed into several oxidation products and conjugates, including two novel products, that is, diclofenac taurine conjugate (DCF-M403) and unexpected diclofenac methyl ester (DCF-M310.03). The ratios of biotransformation products to parent compound were 12-17 for DCF-M403 and 0.01-0.7 for DCF-M310.03 after 24 h exposure. Bioconcentration factors (BCFs) of diclofenac were 0.5 and 3.2 L kgww-1 in H. azteca and G. pulex, respectively, whereas BCFs of DCF-M310.03 was 164.5 and 104.7 L kgww-1, respectively, representing a 25- to 110-fold increase. Acute toxicity of DCF-M310.03 was also higher than the parent compound in both species, which correlated well with the increased bioconcentration potential. The LC50 of diclofenac in H. azteca was 216 mg L-1, while that of metabolite DCF-M310.03 was reduced to only 0.53 mg L-1, representing a 430-fold increase in acute toxicity compared to diclofenac. DCF-M403 is less toxic than its parent compound toward H. azteca, which may be linked to its slightly lower hydrophobicity. Furthermore, the transformation of diclofenac to its methyl ester derivative was explored in crude invertebrate extracts spiked with an S-adenosylmethionine cofactor, revealing possible catalysis by an S-adenosylmethionine-dependent carboxylic acid methyltransferase. Methylation of diclofenac was further detected in fish hepatocytes and human urine, indicating a broader relevance. Therefore, potentially methylated metabolites of polar contaminants should be considered for a comprehensive risk assessment in the future.

Bioconcentration studies with the freshwater amphipod Hyalella azteca: are the results predictive of bioconcentration in fish?

Bioconcentration factors (BCF) for regulatory purposes are usually determined by fish flow-through tests according to technical guidance document OECD 305. Fish bioconcentration studies are time consuming, expensive, and use many laboratory animals. The aim of this study was to investigate whether the freshwater amphipod Hyalella azteca can be used as an alternative test organism for bioconcentration studies. Fourteen substances of different hydrophobicity (log Kow 2.4-7.6) were tested under flow-through conditions to determine steady state and kinetic bioconcentration factors (BCFss and BCFk). The results were compared with fish BCF estimates for the same substances described in the literature to show the relationship between both values. Bioconcentration studies with the freshwater amphipod H. azteca resulted in BCF estimates which show a strong correlation with fish BCF values (r2 = 0.69). Hyalella BCF values can be assessed in accordance with the regulatory B criterion (BCF > 2000, i.e., REACH) and thereby enable the prediction of B or non-B classification in the standard fish test. Therefore, H. azteca has a high potential to be used as alternative test organism to fish for bioconcentration studies.