Bioanalytical Tools in Water Quality Assessment

The first edition of Bioanalytical Tools in Water Quality Assessment was released in 2012. The field has exploded since and the second edition updates and reviews the application of bioanalytical tools for water quality assessment including surveillance monitoring. The book focuses on applications to water quality assessment ranging from wastewater to drinking water, including recycled water, as well as treatment processes and advanced water treatment. Emerging applications for other environmental matrices are also included. Bioanalytical Tools in Water Quality Assessment, Second Edition, not only demonstrates applications but also fills in the background knowledge in toxicology/ecotoxicology needed to appreciate these applications. Each chapter summarises fundamental material in a targeted way so that information can be applied to better understand the use of bioanalytical tools in water quality assessment. The book can be used by lecturers teaching academic and professional courses and also by risk assessors, regulators, experts, consultants, researchers and managers working in the water sector. It can also be a reference manual for environmental engineers, analytical chemists and toxicologists. Detailed descriptions of dose-response assessment, data reporting, mixture modelling and quality assurance/quality control are complemented by a series of online resources and tools to apply some of the principles and data methods explained in this book. This supplementary information is available at www.ufz.de/bioanalytical-tools

Probabilistic approaches in the effect assessment of toxic chemicals: What are the benefits and limitations?

There is an ongoing discussion whether in the environmental risk assessment for chemicals the so called ‘deterministic' approach using point estimates of exposure and effect concentrations is still appropriate. Instead, the more detailed and scientifically sounder probabilistic methods that have been developed over the last years are widely recommended. Here, we present the results of a probabilistic effect assessment for the aquatic environment performed for the pesticide methyl parathion and compare them with the results obtained with the common deterministic approach as described in the EU Technical Guidance Document. Methyl parathion was chosen because a sufficient data set (acute toxicity data for about 70 species) was available. The assumptions underlying the probabilistic effect assessment are discussed in the light of the results obtained for methyl parathion. Two important assumptions made by many studies are: (i) a sufficient number of ecologically relevant toxicity data is available, (ii) the toxicity data follow a certain distribution such as log-normal. Considering the scarcity of data for many industrial chemicals, we conclude that these assumptions would not be fulfilled in many cases if the probabilistic assessment was applied to the majority of industrial chemicals. Therefore, despite the well-known limitations of the deterministic approach, it should not be replaced by probabilistic methods unless the assumptions of these methods are carefully checked in each individual case, which would significantly increase the effort for the assessment procedur

Toxic Mixtures in Time—The Sequence Makes the Poison

“The dose makes the poison”. This principle assumes that once a chemical is cleared out of the organism (toxicokinetic recovery), it no longer has any effect. However, it overlooks the other process of re-establishing homeostasis, toxicodynamic recovery, which can be fast or slow depending on the chemical. Therefore, when organisms are exposed to two toxicants in sequence, the toxicity can differ if their order is reversed. We test this hypothesis with the freshwater crustacean Gammarus pulex and four toxicants that act on different targets (diazinon, propiconazole, 4,6-dinitro-o-cresol, 4-nitrobenzyl chloride). We found clearly different toxicity when the exposure order of two toxicants was reversed, while maintaining the same dose. Slow toxicodynamic recovery caused carry-over toxicity in subsequent exposures, thereby resulting in a sequence effect–but only when toxicodynamic recovery was slow relative to the interval between exposures. This suggests that carry-over toxicity is a useful proxy for organism fitness and that risk assessment methods should be revised as they currently could underestimate risk. We provide the first evidence that carry-over toxicity occurs among chemicals acting on different targets and when exposure is several days apart. It is therefore not only the dose that makes the poison but also the exposure sequence

Molecular Mechanisms in Ecotoxicology: An Interplay between Environmental Chemistry and Biology

A close collaboration between environmental chemistry and biological sciences is required for a complete understanding of ecotoxicological effects. Bioavailability and uptake of pollutants cannot be regarded as isolated chemical or biological questions. Knowledge of the effective concentrations in the organism or at the target site(s) is essential to link the fate and effects of a chemical and is a prerequisite for quantitative investigation of the modes of toxic action. These modes of action need to be unraveled using whole-organism or in vitro systems in order to be able to develop specific biomarkers and biosensors that can be applied as early warning systems. Our mode-of-action-based approaches, in which chemical and biological analytical tools are combined, should improve the understanding of ecotoxicological effects and should be implemented in the future in risk assessment

Experimental exposure assessment of designed chemical mixtures in cell-based in vitro bioassays

Cell-based bioassays are useful tools for the effect assessment of complex mixtures, but so far exposure assessment has not been performed for mixtures of chemicals. In the present study, cytotoxicity and activation of oxidative stress response were measured for three designed chemical mixtures with up to twelve components. The measurements of biological responses were complemented by concentration measurements using solid-phase microextraction to derive the freely dissolved concentrations of the mixtures (Cfree,mix). The tested mixtures showed slightly higher cytotoxic effects than predicted by the concentration addition model. Nominal and freely dissolved effect concentrations of the mixtures were very similar (within a factor of 1.5), but nominal concentrations (Cnom) and Cfree of the individual mixture components were only similar for the hydrophilic chemicals (e.g., caffeine, coumarin, lamotrigine). For hydrophobic (e.g., fluoranthene) and acidic chemicals (e.g., diclofenac, naproxen) Cfree was up to 648 times lower than Cnom. Chemicals were dosed in equipotent nominal concentration ratios and therefore contributed equally to the detected effects. Hydrophilic chemicals with low potency dominated Cnom,mix (up to 95%) and Cfree,mix (up to 99%). Several mixture components (e.g., diclofenac, ibuprofen, naproxen and warfarin) showed increasing free fractions with increasing Cnom,mix and therefore also a concentration-dependent contribution to Cfree,mix. Based on the findings of this study, we concluded that Cnom,mix will be sufficient for evaluating the toxicity of mixtures that contain chemicals with diverse physicochemical properties at low concentration levels. In contrast, for risk assessment purposes and quantitative in vitro to in vivo extrapolations, Cfree,mix is a better parameter because the in vitro responses can be related to freely dissolved concentrations in human plasma

Uptake and release kinetics of 22 polar organic chemicals in the Chemcatcher passive sampler

The Chemcatcher passive sampler, which uses Empore™ disks as sampling phase, is frequently used to monitor polar organic chemicals in river water and effluents. Uptake kinetics need to be quantified to calculate time-weighted average concentrations from Chemcatcher field deployments. Information on release kinetics is needed if performance reference compounds (PRCs) are used to quantify the influence of environmental conditions on the uptake. In a series of uptake and elimination experiments, we used Empore™ SDB disks (poly(styrenedivinylbenzene) copolymer modified with sulfonic acid groups) as a sampling phase and 22 compounds with a logK ow (octanol-water partitioning coefficient) range from −2.6 to 3.8. Uptake experiments were conducted in river water or tap water and lasted up to 25days. Only 1 of 22 compounds (sulfamethoxazole) approached equilibrium in the uptake trials. Other compounds showed continuing non-linear uptake, even after 25days. All compounds could be released from SDB disks, and desorption was proportionally higher in disks loaded for shorter periods. Desorption showed two-phase characteristics, and desorption was proportionally higher for passively sorbed compounds compared to actively loaded compounds (active loading was performed by pulling spiked river water over SDB disks using vacuum). We hypothesise that the two-phase kinetics and better retention of actively loaded compounds—and compounds loaded for a longer period—may be caused by slow diffusion of chemicals within the polymer. As sorption and desorption did not show isotropic kinetics, it is not possible to develop robust PRCs for adsorbent material like SDB disk

Antimicrobial Transformation Products in the Aquatic Environment: Global Occurrence, Ecotoxicological Risks, and Potential of Antibiotic Resistance

The global spread of antimicrobial resistance (AMR) isconcerningfor the health of humans, animals, and the environment in a One Healthperspective. Assessments of AMR and associated environmental hazardsmostly focus on antimicrobial parent compounds, while largely overlookingtheir transformation products (TPs). This review lists antimicrobialTPs identified in surface water environments and examines their potentialfor AMR promotion, ecological risk, as well as human health and environmentalhazards using in silico models. Our review also summarizesthe key transformation compartments of TPs, related pathways for TPsreaching surface waters and methodologies for studying the fate ofTPs. The 56 antimicrobial TPs covered by the review were prioritizedvia scoring and ranking of various risk and hazard parameters. Mostdata on occurrences to date have been reported in Europe, while littleis known about antibiotic TPs in Africa, Central and South America,Asia, and Oceania. Occurrence data on antiviral TPs and other antibacterialTPs are even scarcer. We propose evaluation of structural similaritybetween parent compounds and TPs for TP risk assessment. We predicteda risk of AMR for 13 TPs, especially TPs of tetracyclines and macrolides.We estimated the ecotoxicological effect concentrations of TPs fromthe experimental effect data of the parent chemical for bacteria,algae and water fleas, scaled by potency differences predicted byquantitative structure-activity relationships (QSARs) for baselinetoxicity and a scaling factor for structural similarity. Inclusionof TPs in mixtures with their parent increased the ecological riskquotient over the threshold of one for 7 of the 24 antimicrobialsincluded in this analysis, while only one parent had a risk quotientabove one. Thirteen TPs, from which 6 were macrolide TPs, posed arisk to at least one of the three tested species. There were 12/21TPs identified that are likely to exhibit a similar or higher levelof mutagenicity/carcinogenicity, respectively, than their parent compound,with tetracycline TPs often showing increased mutagenicity. Most TPswith increased carcinogenicity belonged to sulfonamides. Most of theTPs were predicted to be mobile but not bioaccumulative, and 14 werepredicted to be persistent. The six highest-priority TPs originatedfrom the tetracycline antibiotic family and antivirals. This review,and in particular our ranking of antimicrobial TPs of concern, cansupport authorities in planning related intervention strategies andsource mitigation of antimicrobials toward a sustainable future