Eco-epidemiology of aquatic ecosystems: Separating chemicals from multiple stressors

Prospective mixture risk assessment and management prioritizations for river catchments with diverse land uses

“…The goal of various environmental policies in human-dominated ecosystems is to achieve a nontoxic environment and sound biological integrity (European Commission). This status has not been reached in many freshwater and marine systems, based on evidence on the occurrence of a wide array of chemicals in surface waters ) and organisms' tissues (US Environmental Protection Agency 2009), with associated evidence for multiple contaminant risks (Malaj et al 2014), impacts in bioassays (Conley et al 2017), and reduced species biodiversity and abundance in various human-dominated systems (Sch€ afer et al 2016;Posthuma et al 2016). Achieving negligible exposures and nontoxic conditions is challenging given the multitude of chemicals associated with human sources such as agricultural practices, treated wastewater, and urban runoff.…”

“…Many of these mixture approaches evaluate mixture risks by a default approach via aggregation of the individual RQs for each chemical in the mixture, such as the hazard index (HI ¼ P RQ ¼ P [PEC/benchmark concentration]), although the expected mixture effects are also quantified via mixture toxic pressures for species assemblages, expressed as multisubstance potentially affected fraction (msPAF) of species (de Zwart and Posthuma 2005). In addition, various methods are available to retrospectively evaluate the ecological risks and impacts of mixtures on the landscape scale (Posthuma et al 2016). The latter approaches offer an a posteriori quantitative risk or impact ranking of sites and stressors of concern (including chemical mixtures).…”

An expanded conceptual framework for solution-focused management of chemical pollution in European waters

“…Depending on the quality and availability of existing data, gaps can be identified and used as a basis for development of a strategy for additional monitoring. The contamination of European water resources with a wide range of chemicals has been found to pose a significant risk to ecosystems [2–4]. Due to the large number of possible environmental contaminants, and the fact that they never occur as individual chemicals but always in more or less complex mixtures, the identification of potentially relevant chemicals and mixtures as well as their prioritisation for monitoring and abatement are key challenges for regulators and other stakeholders.…”

“…Current monitoring and the innovative approaches taken together can provide a clear spatio-temporal ranking across samples in terms of frequency and degree of exceedance of criteria (if available for measured chemicals), combined with exceedance of (independent) effect-related signals. When such data are further collated into (bio)monitoring data sets that expand large regions, similar rankings can also be obtained via diagnostic, eco-epidemiological methods which look into the occurrence or abundance of species in relation to multiple stress [4]. After the initial ranking, based on monitoring, modelling or eco-epidemiology, or both, the aforementioned tools can be used for in - depth confirmation of the priority ranking of compounds and effects via site assessment using effect-based diagnosis, non-target effect studies, higher tier EDA and biomarkers.…”

“…[1–4]. Challenges remain to causally link the occurrence of specific polluting chemicals and chemical mixtures to the quality status of waters, to identify major chemical stressors, to identify emission and transport pathways, and finally to define solutions for the abatement of pollution-related risks and impacts.…”