When people take drugs, they end up in the water, either unchanged or broken down into specific metabolites. Increasingly, water can be tested to gauge how much drug use is going on in an area, and a new study shows that the level of illegal drugs being used in a community can be tested in real time, and potentially applied to help police narcotic use.
MAIN, D. (2014): Real-time Wastewater Analysis shows what drugs are being used where. Popular Science URL [Accessed: 02.08.2018]