The two main sources of pharmaceuticals in the environment are excretion and disposal. Most people flush their unused medicines down the toilet or sink. Sewage treatment plants are not designed to treat all the substances contained in medications. Although wastewater treatment plants are currently equipped to remove chemicals, foreign materials, and microorganisms from the water prior to ejecting it into natural waters, such as streams and lakes, active drug compounds from humans are not eliminated from the water in the treatment process. Treatment systems permit up to 93% of highly concentrated active drug compounds to leave the treatment plant. Therefore, most of these chemicals pass through the wastewater treatment facility (or they are processed through septic systems) and accumulate in rivers, lakes, ground water, and aquatic organisms. Even drugs thrown in the trash can eventually leach into the landfill and wind up in our ground water.

Many studies in the last ten years have detected pharmaceutical compounds in treated wastewater effluent, rivers, lakes, and ground water. According to the USGS, over 80% of waterways tested in the United States show traces of common medications such as acetaminophen, hormones, blood pressure medicine, codeine, and antibiotics. Samples from 139 streams in 30 states were analyzed during 1999 and 2000 for 95 chemicals and 82 of the 95 chemicals were detected at least once. Generally, these chemicals were found at very low concentrations (in most cases, less than 1 part per billion). Mixtures of the chemicals were common; 75 percent of the streams had more than one, 50 percent had 7 or more, and 34 percent had 10 or more.

The continuous exposure to low levels of pharmaceuticals can harm aquatic communities. This presents a problem to the aquatic environment because pharmaceutical compounds are specifically designed to affect biological organisms. While environmental concentrations are below acutely toxic levels, the main concern is the chronic and/or synergistic effects of the “cocktail” of pharmaceuticals humans have created in the water. The specific scientific harm caused by discharge of highly concentrated active drug compounds into our nation’s waterways is not precisely known due to the unknown effect of pharmaceutical drugs on organisms not intended to consume the drug, and the constantly changing chemical mixture discharged from wastewater treatment plants. Although extensive scientific study and additional analysis is needed to better understand the impact presented by these chemicals, researchers have already observed endocrine disruption in fish in close proximity to wastewater treatment plants. Endocrine disruption is the most widespread and documented effect that pharmaceuticals have on aquatic organisms. Chronic exposure to endocrine disruptors, such as the compounds used in birth control, can feminize male fish and debilitate their capacity to reproduce. Also of concern is the development of antibiotic resistant bacteria populations. A number of studies have shown a decrease in antibiotic effectiveness due to its widespread presence in the environment.

Additionally, an Associated Press five-month investigation concluded a vast array of pharmaceuticals have been found in drinking water supplies of at least 41 million Americans. At current levels, pharmaceutical residues are unlikely to pose an immediate risk to human health, but the long-term consequences of individual chemicals, and combinations of chemicals, are unknown, especially as concentrations rise.

Public Safety
Proper disposal of unwanted medicines is also a public safety issue. Keeping medicines around the home can lead to possible poisoning from accidental ingestion, particularly among young children and pets, or illegal use or theft. When unused or expired prescription drugs sit in the medicine cabinet, they become too easily available and appealing to potential drug abusers, especially young adults and youth. According to a National Survey on Drug Use and Health, persons between the ages of 12 and 17 abuse prescription drugs more than cocaine, heroin, and methamphetamine combined and prescription drug abuse is second only to marijuana use. Michigan has one of the highest rates of teen prescription drug abuse in the nation. A study by The White House Office of National Drug Control Policy found that an astounding 12% of teens in Michigan use prescription drugs recreationally, much higher than the 7% national average.

Additionally, medications left unattended can have tragic consequences. Among people aged 35–54 years, unintentional poisoning surpassed motor-vehicle crashes as the leading cause of unintentional injury death in 2005. Among the deaths attributed to drugs, the most common drug categories are cocaine, heroin, and a type of prescription drug called opioid painkillers such as oxycodone (Oxycotin) and hydrocodone (Vicodin). Furthermore, each year in the United States, more than 71,000 children aged 18 and younger are seen in emergency rooms for unintentional overdoses of prescription and over-the-counter drugs.

Properly getting rid of unused medicines reduces the risk that prescriptions will be mishandled and end up on the street.