Water pollution by pharmaceuticals

Other Names:
Water pollution by excreted drugs
Low level doping of water supplies

Pharmaceutical drugs given to people and to domestic animals – including antibiotics, hormones, strong pain killers, tranquilisers and chemotherapy chemicals – are present in surface water, in groundwater and in drinking water at the tap. As reported in 2016, nearly half of Americans used at least one prescription drug in the past 30 days. Nearly 22 percent used three or more during that timeframe and more than 10 percent used five or more. What is not metabolised is excreted in urine or faeces (in general between 30 - 90 percent of any medicine taken is excreted) where it enters the wastewater stream (and most water treatment plants are not equipped to remove drugs from the water supply).  Medications applied topically in the form of a cream or lotion are also problematic when the unabsorbed portion gets washed down the drain. Unused medications may be flushed down the toilet or drain by individuals and also by health care facilities, like nursing homes.  The manufacture of pharmaceuticals may lead to higher drug contamination levels downstream from the factories. Once in waterways, these unnatural chemicals pose not only a risk to human drinking water supplies but also cause harm to marine life.

In many populated areas of the world, between 30 to 60 drugs can be measured in a typical water sample. This is rarely done, however;  drugs are one of the few groups of chemicals in water that are not monitored. The official position of most administrations concerned with water pollution is that excreted drugs are not a problem because the concentrations found in the environment are usually below one part per billion (ppb). Notwithstanding, many drugs have been measured at environmental concentrations that individually exceed one part per billion (ppb); and several drugs measured together can also often exceed one ppb.





The first study that detected drugs in sewage took place at the Big Blue River sewage treatment plant in Kansas City in 1976. The problem was duly recorded in scientific literature and then ignored for 15 years. Another forgotten study conducted in Britain in the 1980s found more than 170 drugs in the River Lea in northeast London. The river water contained more than a tonne a year of drugs like aspirin and morphine derivatives, implying concentrations of up to one ppb.

A landfill used by the Jackson Naval Air Station in Florida, USA contaminated groundwater with a plume of chemicals that has been moving slowly underground for more than 20 years. The drugs pentobarbital (a barbiturate), meprobamate (a tranquiliser) and phensuximide (an anticonvulsant) are still measurable in that groundwater plume.

In 1992, water pollution monitoring in Germany detected clofibric acid, a drug used by many people in large quantities (1 to 2 grams per day) to reduce cholesterol levels in the blood. Clofibric acid is 2-(4)-chlorophenoxy-2-methyl propionic acid, a close chemical cousin of the popular weed killer 2,4-D. It has since been discovered that the entire North Sea contains measurable quantities of clofibric acid, with 50 to 100 tonnes entering the sea anew each year. The Danube River in Germany and the Po River in Italy also contain measurable quantities of clofibric acid. Of more immediate concern to humans is the finding that tap water in all parts of the city of Berlin contains clofibric acid at concentrations between 10 and 165 ppt. Also found are other drugs used to treat cholesterol such as phenazone, analgestics such as ibuprofen, antibiotics such as fluoroquinolone, and hormones such as oestrogen, as well as chemotherapy drugs for cancer treatment. The water supplies of other major cities had not then been tested, but the Swiss confirmed the presence of clofibric acid in Swiss lakes in 1998.

A study by the National Oceanic and Atmospheric Administration (NOAA) Fisheries’ Northwest Fisheries Science Center, reported in 2016, detected 81 chemical compounds in the water of Puget Sound, including the antidepressant Prozac and the diabetes medication metformin. The researchers then examined fish native to the Sound (juvenile Chinook salmon and Pacific staghorn sculpin) and detected 42 of the chemical compounds in their tissue, some at levels high enough to affect growth, reproduction and/or behavior. It’s unknown whether consuming fish contaminated with these drugs poses risks to humans and there may be additional risks because fish are exposed to complex chemical cocktails; mixtures may result in responses that occur at lower concentrations than single compounds alone.  Separate research has also linked exposure to the drug metformin to the occurrence of intersex fish, where male fish show evidence of feminization.  Metformin is one of the most common pharmaceuticals in wastewater (not only because it’s so commonly used but also because it is not metabolized by the human body and gets extracted unchanged).  While hormone-mimicking drugs such as birth control pills were previously blamed for intersex fish detected in Pennsylvania’s Susquehanna, Delaware and Ohio river basins, metformin is not a hormone-mimicking drug.  Researchers believe it may, however, be a “non-traditional endocrine-disrupting chemical.

Antidepressants are a group of drugs all-too-commonly found in water supplies. Researchers from the University of New England in Maine tested one antidepressant, Prozac, on fighting fish using concentrations similar to that found in waterways and found that after being exposed to the drug the fish became less bold.  Even after the fish were allowed to swim in clean water for one week, those exposed to Prozac still had lingering behavioral effects. Such changes, should they occur in the wild, could affect the fishes’ odds of survival significantly.

A 2014 report by UK-based environmental charity CHEM Trust noted that 613 pharmaceuticals have been found in the environment globally, but this is likely a vast underestimate, since analytical detection methods ar not available for most medications in use.  The report noted that 23 pharmaceuticals, including antidepressants, sedatives, antibiotics, painkillers and anti-cancer drugs, were detected in perch fish in Sweden.  Ethinylestradiol from birth control pills has been detected in Baltic Sea salmon. 

Over 60 percent of Americans are currently taking prescription drugs, and finding ways to properly dispose of expired or unwanted medications is a common problem.  Less than 2 percent of unwanted medications are returned to the pharmacies where they came from and roughly 35 percent of medications are simply flushed down the toilet.  Even more worrying, some chemicals still get into the water system when medications are used exactly as intended. Human bodies only metabolize a small fraction of the drugs they take in, meaning that a good portion of the active ingredients are excreted through urine and faeces or sweated out. This means that when you relieve yourself or take a shower, traces of the chemicals from your medication may wind up in the water system.

Related UN Sustainable Development Goals:
GOAL 3: Good Health and Well-beingGOAL 6: Clean Water and SanitationGOAL 12: Responsible Consumption and ProductionGOAL 15: Life on Land
Problem Type:
E: Emanations of other problems
Date of last update
23.03.2022 – 15:20 CET