This manuscript is part two of a two-part study aiming to provide a better understanding and application of environmental data not only for environmental aims but also to meet forensic objectives. In this paper pharmaceuticals were investigated as potential chemical indicators of water contamination with sewage. The monitoring program carried out in Wales revealed that some pharmaceuticals are particularly persistent and/or ubiquitous in contaminated river water and therefore might be considered as potential conservative or labile wastewater indicators. In particular, these include some anti-inflammatory/analgesics, antiepileptics, beta-blockers, some H2-receptor antagonists and antibacterial drugs.