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Abstract
Background
In surface waters, using liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS), typically large numbers of chemical signals often with high peak intensity remain unidentified. These chemical signals may represent natural compounds released from plants, animals and microorganisms, which may contribute to the cumulative toxic risk. Thus, attempts were made to identify natural compounds in significant concentrations in surface waters by identifying overlapping LC-HRMS peaks between extracts of plants abundant in the catchment and river waters using a non-target screening (NTS) work flow.

Results
The result revealed the presence of several thousands of overlapping peaks between water—and plants from local vegetation. Taking this overlap as a basis, 12 SPMs from different compound classes were identified to occur in river waters with flavonoids as a dominant group. The concentrations of the identified compounds ranged from 0.02 to 5 µg/L with apiin, hyperoside and guanosine with highest concentrations. Most of the identified compounds exceeded the threshold for toxicological concern (TTC) (0.1 µg/L) for non-genotoxic and non-endocrine disrupting chemicals in drinking water often by more than one order of magnitude.

Conclusion
Our results revealed the contribution of chemicals eluted from the vegetation in the catchment to the chemical load in surface waters and help to reduce the number of unknowns among NTS high-intensity peaks detected in rivers. Since secondary plant metabolites (SPMs) are often produced for defence against other organisms and since concentrations ranges are clearly above TTC a contribution to toxic risks on aquatic organisms and impacts on drinking water safety cannot be excluded. This demands for including these compounds into monitoring and assessment of water quality.

One of the concerns often voiced by critics of the precautionary principle is that a widespread regulatory application of the principle will lead to a large number of false positives (i.e., over‐regulation of minor risks and regulation of nonexisting risks). The present article proposes a general definition of a regulatory false positive, and seeks to identify case studies that can be considered authentic regulatory false positives. Through a comprehensive review of the science policy literature for proclaimed false positives and interviews with authorities on regulation and the precautionary principle we identified 88 cases. Following a detailed analysis of these cases, we found that few of the cases mentioned in the literature can be considered to be authentic false positives. As a result, we have developed a number of different categories for these cases of "mistaken false positives," including: real risks, "The jury is still out," nonregulated proclaimed risks, "Too narrow a definition of risk," and risk‐risk tradeoffs. These categories are defined and examples are presented in order to illustrate their key characteristics. On the basis of our analysis, we were able to identify only four cases that could be defined as regulatory false positives in the light of today's knowledge and recognized uncertainty: the Southern Corn Leaf Blight, the Swine Flu, Saccharin, and Food Irradiation in relation to consumer health. We conclude that concerns about false positives do not represent a reasonable argument against future application of the precautionary principle.

One of the lay public's concerns about genetically modified (GM) organisms (GMO) and related emerging technologies is that not all the important risks are evaluated or even identified yet—and that ignorance of the unanticipated risks could lead to severe environmental or public health consequences. To some degree, even the scientists who participated in the analysis of the risks from GMOs (arguably the people most qualified to critique these analyses) share some of this concern. To formally explore the uncertainty in the risk assessment of a GM crop, we conducted detailed interviews of seven leading experts on GM oilseed crops to obtain qualitative and quantitative information on their understanding of the uncertainties associated with the risks to agriculture from GM oilseed crops (canola or rapeseed). The results of these elicitations revealed three issues of potential concern that are currently left outside the scope of risk assessments. These are (1) the potential loss of the agronomic and environmental benefits of glyphosate (a herbicide widely used in no‐till agriculture) due to the combined problems of glyphosate‐tolerant canola and wheat volunteer plants, (2) the growing problem of seed lot contamination, and (3) the potential market impacts. The elicitations also identified two areas where knowledge is insufficient. These are: the occurrence of hybridization between canola and wild relatives and the ability of the hybrids to perpetuate themselves in nature, and the fate of the herbicide‐tolerance genes in soil and their interaction with soil microfauna and ‐flora. The methodological contribution of this work is a formal approach to analyzing the uncertainty surrounding complex problems.

Abstract
Background
The European Water Framework Directive (WFD) has been implemented to achieve a good ecological status in European water bodies requiring macrophyte community assessment as one of the biological quality elements (BQEs). While in several lakes in Schleswig-Holstein (Germany) different BQEs improved within recent years, no recovery of macrophyte communities in some lakes could be achieved, despite the reduction of nutrient input and eutrophication. Due to the fact that no impairment of phytoplankton could be observed, toxic stress due to sediment contamination was hypothesized as a possible limiting factor of macrophyte community recovery.

Results
Sediment toxicity was investigated by performing an extensive chemical screening of sediment contamination and a risk assessment based on toxic unit (TU) summation, using equilibrium water concentrations and algal toxicity as surrogates for lacking data on macrophyte toxicity. Possible indirect risks via toxic pressure on grazer were assessed via TUs based on crustaceans. The study revealed algal TUs of more than one order of magnitude below chronic toxicity thresholds in lakes with high and good status of the macrophyte community and increasing concentrations and frequency of exceedance of toxicity thresholds for lakes with moderate-to-bad status. The antifouling biocides irgarol and diuron were identified as major risk drivers. In addition, PAHs and glyphosate could not be ruled out to contribute to toxic pressure on macrophytes. Despite exceedance of toxicity thresholds for crustaceans, no connection of the ecological status of the macrophyte communities with toxic risks to grazers could be observed.

Conclusions
Our study suggests that in a multiple pressure situation the toxic pressure created due to the contamination of sediments with antifouling biocides is one of the limiting factors for the recovery of macrophyte communities in impaired lakes of Schleswig-Holstein. This finding is in agreement with a Europe-wide survey on almost 47,000 sites suggesting that no good ecological status can be observed at sites with contamination exceeding toxicity thresholds. Similar to the survey, our study indicates additional stressors preventing the achievement of a good quality status of the lake ecosystems.

AbstractEnvironmental factors contribute to the risk for adverse health outcomes against a background of genetic predisposition. Among these factors, chemical exposures may substantially contribute to disease risk and adverse outcomes. In fact, epidemiological cohort studies have established associations between exposure against individual chemicals and adverse health effects. Yet, in daily life individuals are exposed to complex mixtures in varying compositions. To capture the totality of environmental exposures the concept of the exposome has been developed. Here, we undertake an overview of major exposome projects, which pioneered the field of exposomics and explored the links between chemical exposure and health outcomes using cohort studies. We seek to reflect their achievements with regard to (i) capturing a comprehensive picture of the environmental chemical exposome, (ii) aggregating internal exposures using chemical and bioanalytical means of detection, and (iii) identifying associations that provide novel options for risk assessment and intervention. Various complementary approaches can be distinguished in addressing relevant exposure routes and it emerges that individual exposure histories may not easily be grouped. The number of chemicals for which human exposure can be detected is substantial and highlights the reality of mixture exposures. Yet, to a large extent it depends on targeted chemical analysis with the specific challenges to capture all relevant exposure routes and assess the chemical concentrations occurring in humans. The currently used approaches imply prior knowledge or hypotheses about relevant exposures. Typically, the number of chemicals considered in exposome projects is counted in dozens—in contrast to the several thousands of chemicals for which occurrence have been reported in human serum and urine. Furthermore, health outcomes are often still compared to single chemicals only. Moreover, explicit consideration of mixture effects and the interrelations between different outcomes to support causal relationships and identify risk drivers in complex mixtures remain underdeveloped and call for specifically designed exposome-cohort studies.

Abstract
Background
A large number of chemicals are constantly introduced to surface water from anthropogenic and natural sources. So far, unlike anthropogenic pollutants, naturally occurring compounds are not included in environmental monitoring programs due to limited knowledge on their occurrence and effects in the environment. Since previous studies suggest that natural compounds might contribute to mixture risks in aquatic ecosystems and for drinking water production, there is a need to increase empirical evidence on the occurrence of these compounds in aquatic systems. To this end, we performed target screening on 160 toxic secondary plant metabolites (PSMs), prioritized in silico for their likelihood of occurrence, persistence, toxicity and mobility in river waters, using liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS). The samples were collected during rain events from three Danish rivers from an area covered by grassland, forest and agricultural crops.

Results
In total, 27 targets belonging to different compound classes such as alkaloids, coumarins and flavonoids were detected, among them 12 compounds, which have not been reported in surface waters before. The most prominent compound class was the group of alkaloids with 41% of the detected targets, many of them detected in more than 80% of the samples. Individual compound concentrations were up to several hundred ng/L with the neurotoxic alkaloid coniine from poison hemlock and the flavonoid daidzein reaching maximum concentrations of about 400 and 282 ng/L, respectively. In some samples, especially from Vejle river, the rise in concentration of target compounds were associated with increase in the rain intensity and elevated water table in the river.

Conclusions
The measured natural toxin concentrations are well within the range of those of synthetic environmental contaminants and need to be considered for the assessment of potential risks on aquatic organisms and drinking water production.

AbstractAcetylcholinesterase (AChE) inhibitors are an important class of neuroactive chemicals that are often detected in aquatic and terrestrial environments. The correct functionality of the AChE enzyme is linked to many important physiological processes such as locomotion and respiration. Consequently, it is necessary to develop new analytical strategies to identify harmful AChE inhibitors in the environment. It has been shown that mixture effects and oxidative stress may jeopardize the application of in vivo assays for the identification of AChE inhibitors in the environment. To confirm that in vivo AChE assays can be successfully applied when dealing with complex mixtures, an extract from river water impacted by non-treated wastewater was bio-tested using the acute toxicity fish embryo test (FET) and AChE inhibition assay with zebrafish. The zebrafish FET showed high sensitivity for the extract (LC10 = relative extraction factor 2.8) and we observed a significant inhibition of the AChE (40%, p < 0.01) after 4-day exposure. Furthermore, the extract was chromatographically fractionated into a total of 26 fractions to dilute the mixture effect and separate compounds according to their physico-chemical properties. As expected, non-specific acute effects (i.e., mortality) disappeared or evenly spread among the fractions, while AChE inhibition was still detected in five fractions. Chemical analysis did not detect any known AChE inhibitors in these active fractions. These results confirm that the AChE assay with Danio rerio can be applied for the detection of neuroactive effects induced in complex environmental samples, but also, they highlight the need to increase analytical and identification techniques for the detection of neurotoxic substances.

Abstract
Background
Substantial efforts have been made to monitor potentially hazardous anthropogenic contaminants in surface waters while for plant secondary metabolites (PSMs) almost no data on occurrence in the water cycle are available. These metabolites enter river waters through various pathways such as leaching, surface run-off and rain sewers or input of litter from vegetation and might add to the biological activity of the chemical mixture. To reduce this data gap, we conducted a LC–HRMS target screening in river waters from two different catchments for 150 plant metabolites which were selected from a larger database considering their expected abundance in the vegetation, their potential mobility, persistence and toxicity in the water cycle and commercial availability of standards.

Results
The screening revealed the presence of 12 out of 150 possibly toxic PSMs including coumarins (bergapten, scopoletin, fraxidin, esculetin and psoralen), a flavonoid (formononetin) and alkaloids (lycorine and narciclasine). The compounds narciclasine and lycorine were detected at concentrations up to 3ʵg/L while esculetin and fraxidin occurred at concentrations above 1ʵg/L. Nine compounds occurred at concentrations above 0.1ʵg/L, the Threshold for Toxicological Concern (TTC) for non-genotoxic and non-endocrine disrupting chemicals in drinking water.

Conclusions
Our study provides an overview of potentially biologically active PSMs in surface waters and recommends their consideration in monitoring and risk assessment of water resources. This is currently hampered by a lack of effect data including toxicity to aquatic organisms, endocrine disruption and genotoxicity and demands for involvement of these compounds in biotesting.