049 The application of toxicogenomics for (drinking) water quality assessment
Due to anthropogenic activities, freshwater systems worldwide are exposed to thousands of compounds.
In the European Union, for example, there are more than 100,000 registered chemicals (EINECS list), of
which 30,000-70,000 are in daily use (Schwarzenbach et. al., 2006). About 300 million tons of synthetic
compounds are used annually in industrial and consumer products, and partially find their way to
natural waters (Schwarzenbach et. al., 2006). Such contamination can become an increasing problem for
aquatic ecology and e.g. drinking water production (Houtman, 2010, Schriks et. al., 2010). Many of these
compounds (such as hormones) raise concern, especially when the effects on various physiological
endpoints are unknown. However, chemical analytical monitoring of all individual compounds would
be practically impossible. Moreover, for the majority of the compounds the effects on biota remain
unknown since toxicity data is often absent. Therefore, sensitive in vitro bioassays can be applied (e.g.
van der Linden et. al., 2008), which often focus on a specific physiological endpoint such as endocrine
disruption (e.g. CALUX bioassays) or mutagenicity (e.g. Ames II test). The advantage of bioassays is that
(i) they detect any unknown compound that triggers a specific biological effect and (ii) the effects of an
entire mixture of compounds present in a sample can be determined. However, a disadvantage of
applying these assays may be that they focus on a relatively narrow selection of physiological endpoints
and that the ecological/human relevance often remains unclear.