Antibiotics transformed the world of medicine, but decades of widespread use have come at a high cost for the environment. Antibiotics wash into the general water supply from agriculture, medicine cabinet purges and wastewater treatment plants ill-suited for dealing with them. Since their discovery, millions of metric tons of antibiotics have been produced, used, and disposed of, and many of these drugs end up in the water system.
A nationwide study by the U.S. Geological Survey in 2000 found that 80 percent of the rivers and streams tested had detectable levels of pharmaceuticals like antibiotics and antidepressants.
The meat industry is notorious for over-prescribing antibiotics to livestock. In many cases, daily servings of antibiotics are used to achieve more rapid growth rates, and a good portion of the two trillion pounds of animal manure produced in livestock production sites in the USA is tainted with growth hormones and antibiotics. Because only a small amount of this manure is properly disposed of, trace amounts of antibiotics often leach into the groundwater supply or get swept into rivers and streams after rainstorms. In many cases, these levels are high enough to pose a risk.