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2.5.         Examples combining chemical and biological monitoring

While modern effect-based methods have been proposed for mixture assessment, as a complement to chemical and ecological monitoring, precedent already exists in this respect. Such methods offer something similar to the “biological oxygen demand” (BOD) which measures an overall condition in the water while not specifying the cause. Despite this lack of specificity, BOD is widely used in water management to protect surface waters (EEC, 1991; EC, 2000).

Currently, there are few requirements to use effect-based information in regulatory assessment. An example where effect-based monitoring is used for assessment is the Marine Strategy Framework Directive (EC, 2008b). Different descriptors of good environmental status, such as “concentrations of contaminants at levels not giving rise to pollution effects”, are defined and the assessment allows the integration of data on biological effects (Lyons et al. 2017). The application of bioassays for measuring the occurrence of dioxins and PCBs in foodstuffs (EU 2012) demonstrates how effect-based assessment might operate in a regulatory framework. The value of such information is that it integrates the effect of mixtures of chemicals irrespective of whether the combined effects are additive or different from an expectation.

For example, the total potency of compounds with estrogenic activity in a water sample can be determined by measuring the activity of the estrogen receptor in laboratory in vitro assays. Ideally, the bioassay captures the total effect of all chemicals with estrogenic effect in a sample. Practically, difficulties exist, though the robustness of techniques has improved for some modes of action in recent years (e.g. Altenburger et al. 2018, Leusch et al. 2018, Kunz et al. 2017).

For regulatory monitoring, techniques need to be robust and reliable, to meet legal challenge and ensure that investments are based on sound evidence. A series of International Standards Organisation (ISO) standardized methods is available for the use of biological methods for the assessment of effluents on water quality[1]. The EU water directives transposed into national regulation allow Member States to set requirements appropriate for the country level e.g. the German “Abwasserverordnung” (AbwV, 1997) specifies standard methods for specified types of waste waters.

To demonstrate the application of biological effect tools in monitoring, case studies have been undertaken. In a pilot study by Escher et al. (2014) the efficacy of different waste water treatments was determined using the observable effects of enriched water samples in about 100 different miniaturized and mainly cell-based bioassays (figure 2.8). Results showed the presence of different chemicals at different levels of pollution with diverse modes of action.

Figure 2.8: Examples of organism and cell-based bioassays for water monitoring

In a case study performed within the European FP7 project SOLUTIONS, Neale and colleagues (2017) investigated the WWTP effluent, upstream, and downstream river water samples in Switzerland. They compared bioanalytical results from 13 bioassays with results from chemical analysis of 405 compounds (see figure 2.9A).

Figure 2.9: Example of a comparative analysis of chemicals and combined effects using component-based mixture predictions (taken from Neale et al. 2017)

A)

B)

They found that of the 10 detected herbicides known to inhibit the photosystem II (PSII), terbuthylazine and diuron could explain the majority of biological effects (figure 2.9 B). The authors also showed that the detected chemicals could explain between 45 and 108 % of the observed biological effects. In samples collected upstream of the WWTP, only a fraction of the total measured effect could be explained by the detected chemicals.

[1] https://www.iso.org/committee/52972/x/catalogue/