Disposal practices for unwanted residential medications in the United States.

The occurrence of trace levels of prescription and over-the-counter pharmaceuticals in the environment began to receive concerted attention nearly two decades ago. The public's growing awareness and concern over the presence of these chemicals, especially in drinking water, has served to catalyze considerable discussion and debate regarding the best practices for disposal of unused or unwanted medications. In the United States, the first federal guidance for consumers was issued in 2007.