Whilst looking for some equipment prices I stumbled across this article.
No wonder the Italians are so batty.
"In 2005, a group of researches from Italy analyzed water samples from the Po River in northern Italy for the presence of cocaine and its main urinary metabolite - benzoylecgonine (BE). They took samples each day for four different days and extracted cocaine and BE by solid-phase extraction followed by analysis on LC - MS/MS with electrospray ionization.
Though the concentrations of benzoylecgonine and cocaine in the river were small - 25 and 1.2 ng/L, it is equivalent to 4 kg of cocaine per day that flows down the river or 40,000 (!) doses per day based on a typical cocaine dose."