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In the environment, chemicals and other stressors do not occur in isolation. They are often present with an assortment of other chemical and non-chemical stressors. Understanding the potential effect these combined stressors may have on aquatic life is difficult to uncover. Equally difficult is to predict the places & times combined stressors may have an adverse effect in order to potentially reduce these occurrences. Retrospectively, comparing existing ecological assemblages present at a test location compared to reference conditions allows for a measure of ecological impact. Apportioning stressors to these impacts can be a challenge. Waterborne has experience in understanding and predicting environmental mixtures, their potential effects, and how the diverse combination of these factors can be combined in order to protect ecological health.

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Mixture Toxicity

From developing a conceptual framework for your mixture question to designing ecotoxicological studies to assess mixture effects, Waterborne has the expertise to help answer your mixture questions. While a mixture may impact aquatic life, often the toxicity is linked to a select few chemicals in the mixture. There are several scientific strategies (concentration-addition, potency factors, etc) that can be used to address the complex question of mixtures and the strategy used is heavily dependent on the question at hand. We ensure a scientifically sound data package when Waterborne’s ecotoxicological mixture expertise is paired with our spatial analysis and modelling capabilities.

When developing exposure strategies, laboratory studies conducted with complex mixtures must be thoughtfully designed. Waterborne scientists have practical experience evaluating difficult-to test mixtures and multi-component formulations with numerous analytes. Custom-tailored dosing methodologies can be developed to maximize solubility in aqueous matrices for exposure. Assessments can also be made using component-specific evaluations, from which toxicity profiles can be developed from information on identified components with known modes of action.

Environmental Mixtures

Chemicals present in environmental mixtures come from a variety of sources:

  • Point source discharges such as wastewater treatment plants, storm water, or industrial discharges
  • Non-point sources such as agriculture, livestock production, diffuse runoff from hard surfaces containing petroleum or metal products such as roadways and parking lots
  • Other stressors, such as sediment, can originate from new residential or commercial construction

Waterborne’s ability to apply our environmental modeling capabilities across multiple sectors makes us well-suited to take an active role in estimating environmental mixtures. In the US, over 30 potential stressors from 8 categories were estimated for over 1000 sites in Ohio, and paired with biological monitoring of fish and aquatic invertebrates (Kapo et al., 2014). In Europe, Waterborne is participating in the understanding of environmental mixtures with programs coordinated by organizations such as ECETOC and SETAC.

Multiple Stressor Assessment

Waterborne is part of a consortium of companies and institutes who are examining the relative impact of stress factors, including chemical mixtures, to river systems by developing and using statistical and eco-epidemiological methodologies.

Prospective risk assessments of chemicals may include the use of bioavailability models, Species Sensitivity Distributions and mixture-effect modeling to estimate the proportion of species potentially affected by chemical mixtures. To test such approaches, it is imperative that data-sets be obtained that contain a range of prospective risks from chemicals and other stressors which can be matched to documented biological impacts using a geographic information system.

Since species assemblages can be affected by factors other than chemicals, an eco-epidemiological analysis of chemical risks needs to take into account the myriad of potential factors that may affect biological community status. These factors include in-stream habitat quality, eco-region, river size, and water chemistry. Characteristics of biological assemblage (traits) may also be helpful in diagnosing potential causation of impacts.