Predictive Environmental Risk Assessment of Chemical Mixtures: A Conceptual Framework

Abstract

Environmental risks of chemicals are still often assessed substance-by-substance, neglecting mixture effects. This may result in risk underestimations, as the typical exposure is toward multicomponent chemical "cocktails". We use the two well established mixture toxicity concepts (Concentration Addition (CA) and Independent Action (IA)) for providing a tiered outline for environmental hazard and risk assessments of mixtures, focusing on general industrial chemicals and assuming that the "base set" of data (EC50s for algae, crustaceans, fish) is available. As mixture toxicities higher than predicted by CA are rare findings, we suggest applying CA as a precautious first tier, irrespective of the modes/mechanisms of action of the mixture components. In particular, we prove that summing up PEC/PNEC ratios might serve as a justifiable CA-approximation, in order to estimate in a first tier assessment whether there is a potential risk for an exposed ecosystem if only base-set data are available. This makes optimum use of existing single substance assessments as more demanding mixture investigations are requested only if there are first indications of an environmental risk. Finally we suggest to call for mode-of-action driven analyses only if error estimations indicate the possibility for substantial differences between CA- and IA-based assessments.

Occurrence and ecological hazard assessment of selected antibiotics in the surface waters in and around Lake Honghu, China

“…(2) and (3) finally, so that the results of MHQ MEC/PNEC values are the same as the values of MHQ STU at each site (Table 3). These results indicated the toxicity profiles of the mixture compounds are similar, or all these antibiotics have the similar action modes to algae in the mixture components (Backhaus and Faust, 2012), which also justified the validity of using the MRQ STU model in the present study. The results are similar with those of Liu et al (2015) and Yao et al (2017).…”

“…Furthermore, the ecological hazard of antibiotic mixtures was evaluated using two methods proposed by Backhaus and Faust (2012). This approach uses the MHQ model, which is expressed by two parameters (MHQ MEC/PNEC and MHQ STU ), and the calculation formulas are shown as follows (Eqs.…”

“…Therefore, only assessing the single antibiotic hazards through the HQ value may underestimate the ecological effects of antibiotics in the real environment (Backhaus and Faust, 2012;Yao et al, 2017). Hence, in this study, two models (MHQ MEC/PNEC and MHQ STU ) for evaluating the comprehensive hazard at each sampling site were introduced.…”

“…The specific aims of this study are: (1) to discuss the temporal-spatial distribution of the selected antibiotics in Lake Honghu areas; (2) to analyze the sources of the antibiotics based on the correlations between environment variables and antibiotic concentrations; and (3) to assess the ecologic hazard of the antibiotics to the aquatic organisms according to the calculated hazard quotients (HQs) and mixture hazard quotients (MHQs) (Backhaus and Faust, 2012;Yao et al, 2017).…”

Incorporating the joint toxicity of co‐applied pesticides into the ecological risk assessment process

“…Thus, despite the label of "pesticide synergy," the ecotoxicity of many formulations might be adequately predicted based on an approach using CA. Concentration addition has been commonly suggested for use when conducting ERA with mixtures, especially for first-tier assessments (Chevre et al 2006;Backhaus and Faust 2012;EFSA 2013) and will be the primary model in our framework.…”