Screening and human health risk assessment of pharmaceuticals and their transformation products in Dutch surface waters and drinking water

Numerous studies describe the presence of pharmaceuticals in wastewater and surface water,
groundwater and sometimes even drinking water (Monteiro and Boxall, 2010). Current monitoring
efforts are focused on parent compounds, while transformation products are usually not included.
However, as Escher and Fenner (2011) have shown, transformation products can be relevant for
environmental risk assessment. After consumption or application, pharmaceuticals can be transformed
in various (environmental) compartments. With regards to the fate of pharmaceuticals, firstly, they can
be transformed within the consumer (i.e. human metabolism) by phase I (activation, e.g. oxidation) and
phase II (conjugation) transformations (Testa and Kramer, 2008). Secondly, various chemical and
biological processes can transform the pharmaceuticals and transformation products during wastewater
treatment (e.g. hydrolysis, oxidation, de-conjugation, photodegradation) (Kern et al., 2010). Thirdly, the
pharmaceuticals and products can be transformed in the environment by similar processes as those that
may occur in the wastewater treatment plant (Escher and Fenner, 2011). Finally, the pharmaceuticals can
be transformed when surface water or groundwater is treated to produce drinking water. Especially
oxidative techniques such as ozonation, UV/hydrogen peroxide treatment and chlorination will lead to
the formation of (oxidized) transformation products (Richardson et al., 2007). Consequently, depending
on the properties of the compounds, numerous products can be formed in consumers and the water
cycle (i.e. wastewater treatment, the environment and drinking water production).