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Abstract
BackgroundGuanylurea is the main transformation product of the antidiabetic drug metformin, which is one of the most prescribed pharmaceuticals worldwide. Due to the high rate of microbial degradation of metformin in sewage treatment plants, guanylurea occurs in higher concentrations in surface waters than its parent compound and could therefore affect aquatic wildlife. In this context, data for fish are scarce up to now which made us investigate the health of brown trout (Salmo trutta f. fario) in response to guanylurea.MethodsIn two experiments, eggs plus developing larvae and juvenile brown trout were exposed to three different concentrations of guanylurea (10, 100 and 1,000 µg/L) and, as a negative control, filtered tap water without this compound. Low internal concentrations were determined. The investigated parameters were mortality, length, weight, condition factor, tissue integrity of the liver and kidney, levels of stress proteins and lipid peroxides, as well as behavioural and developmental endpoints. It was found that guanylurea did not significantly change any of these parameters in the tested concentration range.ResultsIn conclusion, these results do not give rise to concern that guanylurea could negatively affect the health or the development of brown trout under field conditions. Nevertheless, more studies focusing on further parameters and other species are highly needed for a more profound environmental risk assessment of guanylurea.
Highlights
For the environmental risk assessment of chemicals, the inclusion of transformation products and the investigation of their contribution to the risk posed by the parent compound are often challenging and increase the complexity of the evaluation process
The substance is generated in sewage treatment plants by the microbial degradation of the antidiabetic drug metformin (Scheurer et al, 2012; Tisler & Zwiener, 2018; Trautwein & Kümmerer, 2011) and is detected in surface waters at concentrations up to 28 μg/L (Scheurer et al, 2012); the maximum concentration of the parent compound is about a factor of 10 lower (Scheurer et al, 2012)
The analysis of the tissue of brown trout larvae revealed that guanylurea was solely quantifiable in the Larval brown trout Nominal water concentrations [μg/L] Measured water concentrations Internal concentration [ng/g] Mortality [%] Time to hatch Heart rate [bpm] Body weight [g] Body length [cm] Condition factor [g/cm3] Lipid peroxide level [cumene hydroperoxide (CHP)-equiv./mg wet weight]
Summary
For the environmental risk assessment of chemicals, the inclusion of transformation products and the investigation of their contribution to the risk posed by the parent compound are often challenging and increase the complexity of the evaluation process. Due to the high rate of microbial degradation of metformin in sewage treatment plants, guanylurea occurs in higher concentrations in surface waters than its parent compound and could affect aquatic wildlife. In this context, data for fish are scarce up to now which made us investigate the health of brown trout More studies focusing on further parameters and other species are highly needed for a more profound environmental risk assessment of guanylurea
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