Evaluation of Bioassays and Wastewater Quality ... - Oekotoxzentrum

It is important to note that both test types, in vitro and in vivo bioassays, answer qualitatively
different questions. In vitro bioassays based on specific cellular mechanisms, often combined
with sample enrichment, enable a highly sensitive detection of certain chemical substance
classes such as estrogens or herbicides, which are also relevant as micropollutants. However,
interpretation of the results in an ecological context and extrapolation to potential consequences
for whole organisms is difficult.
On the other hand, integrative in vivo bioassays without the need for sample enrichment provide
conclusive information about biological and potentially ecological effects such as growth,
reproduction, and mortality. They integrate the effects of all substances in a wastewater sample
such as chemicals, nutrients etc., but, depending on the used assays they give none or only
limited information about the causative substance classes or relevant molecular processes.
Another important point is that, depending on the endpoints used in the assay, the sensitivity of
the frequently applied test systems is often too low for the evaluation of the contamination with
micropollutants. This may be due in part to the limited exposure time or the lower sensitivity of
the standard bioassay species when compared to native species, as well as to the lack of
sensitivity of the investigated endpoints.
Figure 1 and Table 1 provide an overview of the tests performed in this study. The appropriate
bioassays selection aimed to cover relevant modes of action, such as mutagenicity, genotoxicity,
endocrine disruption (e.g. androgen, estrogen, and glucocorticoid receptor activation, modulation
of steroidogenesis), and herbicidal effects. Integrative in vivo bioassays were chosen to detect
general toxicity of the wastewater to whole organisms from different trophic levels, as well as
effects based on more specific endpoints, such as vitellogenin induction and number of offspring.
Figure 1: Overview of test organisms and test systems used in the two pilot studies Regensdorf and
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