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2.6. Towards effect-based methods in monitoring and assessment
Assessment under the WFD currently does not consider mixture effects. It is, therefore, possible that concentrations of priority substances could be slightly below their respective EQS, meeting good chemical status, while the actual combination of substances present could be harmful. For example, if all five PSII inhibitors from the priority substances list were detected, individual concentrations might be at good chemical status but the mixture could nevertheless cause adverse effects (Figure 2.6). Additionally, while the list of priority substances represents certain hazardous chemicals, there are other substances present in surface waters which could contribute to mixture effects.
Mixture effect considerations could thus be integrated into the existing assessment schemes following two approaches that could be anticipated:
Compound-based mixture prediction: EQS for mixtures of similar acting compounds could be established and potentially considered in chemical status assessment.
For example, an EQS for the sum of all six PSII-inhibitors could be defined as the sum of the single substance concentrations divided by the single substance EQS. If this sum exceeds “one”, than the EQS of priority PSII-inhibitors is exceeded.
Mixture effect detection using effect-based methods: Joint effects measured with a bioassay instead or in addition to single chemical compound concentrations might be considered as indicators for the ecological status assessment.
For example, instead of determining the concentrations of each PSII inhibitor in a water sample, the sample would be concentrated and tested in a dilution series using a bioassay (e.g. algae growth inhibition test). At the point where the toxicity ceases, the dilution factor would be compared with the test result of a defined reference compound (e.g. diuron).
Currently, several whole organism-based assays and some cell-based assays are ready for routine use in an effect-based monitoring. Readiness for use implies fulfilling requirements regarding standardization, robustness, reproducibility - for several modes of action, we lack specific bioassays, even though there are many techniques available to researchers. Within the WFD water quality assessment, selection of the relevant bioassay could be derived from the biological quality elements assessed in the water body. Organism-based bioassays therefore could support the link between chemical and ecological monitoring and assessment (figure 2.10).
Figure 2.10: Biological effect assessment could serve to close the gap between ecological and chemical assessments and gain causal relationships
The European Commission (Wernersson et al. 2015) gives a summary of available bioanalytical tools in the technical report on aquatic effect-based monitoring tools under the WFD. Their readiness for monitoring applications has been evaluated in several projects (e.g. Kienle et al. 2015). These tools can be applied and used in a modular manner depending and targeted on the desired level of evidence (figure 2.11).
Two applications of effect-based methods can be foreseen:
The monitoring of chemical impact on biological quality elements (BQEs):
For effect monitoring, a module comprising different organism-based bioassays representing the different BQEs would provide evidence for total chemical impact. It would also enable direct linkage of effect observations with ecological monitoring data (figure 2.9 A, figure 2.10). However, to detect chemicals with an impact that emerge over a longer time scale, such as endocrine disruptors or mutagenic and genotoxic compounds, additional bioassays, such as cell-based mutagenicity assays and estrogen receptor activation assays should also be implemented (figure 2.9 B).
Investigations of pollutants which cause effects:
When investigating chemicals which could be causing effects through specific modes of action (table 2.1) or on specific, stress-related endpoints, additional bioassays are available. The application of such in vitro detectors may also be used to protect specific uses of a water body, e.g. drinking water abstraction.
Figure 2.11: Modular approach for application of bioassays in monitoring
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POLAND
In the "COMMUNICATION FROM THE COMMISSION TO THE COUNCIL" on the effects on human health and on the environment arising from exposure to many different chemicals is reference to three different terms discribing that problem: combination effects, mixture effects or cocktail effects. We would propose to use "combination effects" term instead of " mixture effect". That term stress more the problem which is described in the report and ensures that the term "mixture" will not be understood as the one defined in art 3.2 of REACH regulation.
DE-NW:
figure 2.10 - Please consider the comment above regarding figure 2.1
For example, if all five PSII inhibitors from the priority substances list were detected, individual concentrations might be at good chemical status but the mixture could nevertheless cause adverse effects (Figure 2.6).
Comment Belgium (Wallonia): the link between this sentence and Figure 2.6 is not clear.
Compound-based mixture prediction: EQS for mixtures of similar acting compounds could be established and potentially considered in chemical status assessment. For example, an EQS for the sum of all six PSII-inhibitors could be defined as the sum of the single substance concentrations divided by the single substance EQS. If this sum exceeds “one”, than the EQS of priority PSII-inhibitors is exceeded.
Comment Belgium (Wallonia): this approach assumes that the effects are additive and not synergistic or antagonistic. This should be indicated and the fact that the second approach (Mixture effect detection using effect-based methods) should be preferred.
The European Commission (Wernersson et al. 2015) gives a summary of available bioanalytical tools in the technical report on aquatic effect-based monitoring tools under the WFD. Their readiness for monitoring applications has been evaluated in several projects (e.g. Kienle et al. 2015).
Comment Belgium (Wallonia): important works have been carried out since this one and should be mentioned and summarized:
Subgroup EBM (Effect Based Methods) Task-WFD working on Effect based monitoring in the water framework directive. Proposal for a holistic approach. Report in preparation. The Main Objective of the activity of the group was to examine and further document the possible implementation of effect-based methods (EBMs) for monitoring and assessment in the WFD context, alongside traditional chemical analysis, bearing in mind their possible application under the MSFD. It will build on all scientific evidence and practical knowledge available to-date, including the conclusions of the CMEP work (technical report) and the estrogen monitoring project. The activity presented in the terms of reference is in line with the Commission Communication on mixtures and with the objectives of the 7th Environment Action Programme.
Two applications of effect-based methods can be foreseen:
Comment Belgium (Wallonia): According to me (and others working in the field) at least two other applications of effect-based methods can be added:
To assess the efficiency of measures taken to reduce a pressure (e.g. wastewater discharge) on key organisms and or function of the ecosystem.
Effect based monitoring/tools (sections 2.4, 2.5, 2.6)
In our opinion EBM can be useful and recommended if some prerequisites are fulfilled, such as:
We think it makes no sense trying to replace 45 targeted chemical analyses with 30 EBM tests, while in case of any positive EBM indication the targeted analysis still has to be done to find out whether there is any exceedance of an EQS or not.
Considering the mixture effect, we understand clearly the additive effect of the similar mechanisms, but we think in this case an EBM EQS should be introduced instead of concentrations of individual compounds.
Furthermore there is a philosophical problem here: we created EQSs at far lower concentrations than any toxicology effect, and now we try to use toxicology-like methods to make an indication.
page 23 “compound –based mixture prediction : EQS are derived from PNECs - PNECs can a have assessment/uncertainty factors associated with them so the argument for this will lead to LOD/LOQ concerns.
P24 Two applications are suggested. For the first (monitoring of chemical impacts on BQEs), why not simply use the BQE response as an indicator of stress – which might include some chemical effects? BQEs would integrate the effects of mixtures of chemicals (and other stressors) just as much as EBMs.
P23, 1st Paragraph: Regarding five PSII inhibitors all meeting EQS but cumulatively potentially causing effects – this is not the only question, there is also uncertainty with respect to the individual chemical EQS themselves and the level of protection that the assessment factors provide, i.e. are they overly protective.
P23, compound-based mixture prediction: No mention in the section of dioxin, furan and PCB TEQs approach for carcinogenicity (and used as the basis for the WFD EQS). Perhaps discuss this somewhere within the section?
P23, mixture effect detection using effect-based methods (EBM) and following sections: The example given (algal growth inhibition assay) is basically “DTA” – direct toxicity assessment (see comment above).
Not only is this time consuming, there are many practical difficulties to regulators performing such assays – culturing organisms in the laboratory, lack of skills etc.
We see use of EBMs as primarily being a way of benchmarking “traditional” EQS, as was done for steroidal oestrogens against the EE2 EQS (as the most potent oestrogen), and perhaps being used in investigative monitoring, but not being used in wide scale operation and surveillance monitoring.
This would not be practical and we argue that especially the whole organism assays – i.e. those that do not explore a specific or narrow set of MoAs – would not be useful and would tell you very little about what class of chemical was responsible for observed effects.
We would also oppose any additional vertebrate (i.e. fish) testing to that already conducted for chemical authorisation type regulation without a very good and ethical justification for its conduct.
P24, 1st bullet: This sounds like duplication of what could be observed in the environment, i.e. ecological status, with the right ecology assessment tools. At worst it is duplication.
It would also miss those longer-term population impacts that field data would stand a chance of capturing (even if cell-based assays are included, which do not give you a definitive answer with respect to whole organism effects).