Assessing the risks posed by mixtures of chemicals in freshwater environments: case study of Lake Geneva, Switzerland

Abstract

Aquatic organisms are typically exposed simultaneously to several organic compounds released from human activities like agriculture, industries, or simply from people living in cities. The ecological risk assessment of mixtures of such compounds has therefore to be addressed by scientists. The aims of this paper are (1) to describe the current mixture risk assessment procedures, (2) to apply such approach to a specific case study, Lake Geneva and the River Rhône in Switzerland, and (3) to discuss the outcomes of such an application. Two models, called concentration addition and independent action, are recognized to be robust enough to predict the mixture effect of substances on a given species. They are classically used also to assess the risk of mixtures for the ecosystem, but their use is often limited by the lack of available ecotoxicity data. Adopting a first level assessment, we describe the evolution of the mixture risk for several years of Lake Geneva, and for 2010 for the River Rhône. These first assessments allow identification of the most problematic substances demanding risk reduction measures. Furthermore, again for the two cases studies, we show that the risk levels associated with mixtures of compounds can rapidly exceed critical aquatic thresholds, and therefore, it is the sum of the substances that is problematic, which is more challenging in term of risk management. Further analysis of effects in compound mixtures as well as a better characterization of the overall ecological risk are necessary for the thousands substances co-occuring at very low concentrations.

Predicting the Toxicities of Ternary Mixtures of two Metals and Sodium Dodecyl Sulfate to Serratia marcescens (SerEW01) from Otamiri River Water

“…Naturally, aquatic organisms are exposed simultaneously to several organic and inorganic compounds resulting from human agricultural, industrial and domestic activities [37]. In this study, SDS modulated the toxicity of the heavy metals and vice versa, giving EC 50S higher (lower toxicities) than those of the individual heavy metals but lower than that of SDS, in all the ternary mixtures tested.…”

Conventional Risk Assessment of Environmental Contaminants

“…Even when more data are available, allowing the use of statistical extrapolation techniques, based on SSDs, the specificity of the mode of action of the substance should be a priority factor in calculating the ecological risk (Guérit et al, 2008). Several studies have documented the intuitive approach that the effect of whole mixtures will be higher than the effects of a single individual compound with different species and different classes of chemicals, in the laboratory, in mesocosms, and in the field (Gregorio and Chèvre, 2014). In addition, intraspecific and interspecific competition is rarely considered when extrapolating from lower to higher biological organization levels (Kattwinkel and Liess, 2014 and literature quoted therein).…”

How water quality standards for pesticides affect the classification of the chemical status of rivers

“…The proposal for new standards by DETEC is part of this dynamic. Since the early 2000s, several studies have focused on the impacts of mixtures of pesticide on environmental species (see e.g., Backhaus et al, 2003;Beyer et al, 2014;Gregorio & Chèvre, 2014;Laetz et al, 2009;Relyea, 2009;Rizzati, Briand, Guillou, & Gamet-Payrastre, L., 2016). These studies showed that pesticides can act in isolation, as currently accounted for in the evaluation of the chemical status (Wittmer, Junghans, et al, 2014b), but can also interact in dose additive or synergic ways.…”