Contaminants of Emerging Concern (CECs) are a broad class of compounds that include pharmaceuticals and personal care products (PPCPs), synthetic hormones, illicit drugs, and additives. They can generally be defined as being unregulated, occurring at low concentrations in the environment (µg/L to ng/L). Because some of these CECs are specific to a particular activity, for example caffeine for human wastewater, CECs have some potential as tracers of water quality impacts such as bacterial or nutrient pollution. In addition, some CECs are removed by standard municipal wastewater treatment processes (i.e., caffeine, nicotine) while others persist and are present in the discharged water (i.e., sucralose). This behavior makes it possible to differentiate between wastewater that has been through a municipal wastewater treatment plant and wastewater that has not (i.e., via a broken sewer line or a poorly functioning septic tank).