Drug pollution, also called pharmaceutical pollution, happens when medicines and their broken-down parts enter water sources like groundwater, rivers, lakes, and oceans through wastewater. This type of pollution is mainly a form of water pollution.

A scientist from the Cary Institute of Ecosystem Studies in Millbrook, New York, said, "Pharmaceutical pollution is now found in waters around the world." Causes include old or worn-out systems, sewage overflows, and runoff from farms. Even when wastewater reaches treatment plants, these facilities are not designed to remove medicines from the water.

Sources and effects

Most of these drugs come from the body passing them out through urine. A smaller amount comes from old or unused medicines being flushed down the toilet, especially in hospitals where this happens more often than in homes. Some drug molecules are too small to be removed by regular water treatment plants. Upgrading these plants to use special water treatment methods that can remove these molecules can be costly. In the United States Great Lakes, drugs like antidepressants have been found in water. Researchers from the University of Buffalo discovered high levels of antidepressants in the brains of fish. Fish exposed to antidepressants show changes in behavior, such as less fear of danger, which can lower their chances of surviving attacks from predators.

Other sources of drug pollution include agricultural runoff, which happens when antibiotics used in livestock wash into water systems, and waste from pharmaceutical manufacturing. Drug pollution is linked to changes in the sex of fish and other water life. It is also thought to play a role in fish deaths, mass deaths of amphibians, and unusual physical changes in amphibians, along with other industrial pollution.

Pollution of water systems

In the early 1990s, scientists discovered that medicines were present in the environment. This led to more research, new rules, and public interest. During the same time, it was found that making one kilogram of an active medicine produced waste fifty to one hundred times larger than the medicine itself. This waste ended up in the environment. In the late 1990s, scientists found estrogens in wastewater. They concluded that this caused fish to develop female characteristics, which increased attention on medicines in the environment. Information about medicines in the environment dates back to the 1980s. Most medicines are designed to have small harmful effects for the people who take them. However, even small amounts of medicines can harm freshwater ecosystems.

In the United States, Spain, Germany, and the United Kingdom, over 101 different medicines were found in groundwater, surface water, drinking water, or tap water. Between 30 and 100 different medicines were found in similar waters in Thailand, Canada, Australia, India, China, South Korea, Japan, Sweden, Poland, Italy, the Netherlands, France, and Brazil.

In 2022, a major study on medicine pollution in rivers found that it threatens the health of people and the environment in more than a quarter of the studied areas. The study examined 1,052 sampling sites along 258 rivers in 104 countries, representing the pollution of water for 470 million people. It found that the most polluted areas were in low- to middle-income countries, where wastewater and waste management systems were poor and where medicines were made. The study also listed the most common medicines found in these areas.

• The release of oral contraceptives into freshwater ecosystems has caused fish and amphibians to develop female characteristics.
• Antipsychotics, which were created about seventy years ago, were not found in the environment until 2007. These medicines are used to treat conditions like depression, schizophrenia, autism, attention deficit hyperactivity disorder, and bipolar disorder. After being excreted by people through feces or urine, these medicines enter wastewater treatment plants, which do not remove them. These medicines have been found in drinking water, all types of water, and hospital sewage. Once in water, they may build up in the bodies of animals through the food chain.
• Psychiatric drugs, such as fluoxetine, sertraline, citalopram, chlorpromazine, and oxazepam, were found to change fish behavior and disrupt fish hormones. In invertebrates, these drugs caused problems with reproduction, hormone function, and behavior.
• Antineoplastic drugs, used in chemotherapy worldwide, pollute water and harm microorganisms in aquatic environments. These drugs are difficult to remove during wastewater treatment. Contaminated water with these drugs can harm aquatic life and human health. Chemotherapy drugs like cyclophosphamide, fluorouracil, doxorubicin, cisplatin, and mitomycin C were found to damage the DNA of aquatic organisms.
• Antibiotics are widely used to treat bacterial and fungal infections. Since they are only partially broken down in the body, unused antibiotics enter the environment. These medicines have been found in sludge, drinking water, wastewater, surface water, soil, groundwater, and sediments. Because they are hard to break down naturally, they remain in the environment for long periods. Scientists warn that antibiotics in the environment may lead to antibiotic-resistant bacteria, which could harm ecosystems and human health. Excess antibiotics in waterways worsen antibiotic resistance and could lead to more deaths. Antibiotics were also found to reduce the growth of algae, aquatic plants, and environmental bacteria.

Groundwater contamination by medicines, which are called contaminants of emerging concern (CEC) or emerging organic pollutants (EOP), has become a focus of study in environmental engineering, hydrology, and hydrogeochemistry since the late 1900s.

Medicines are suspected to cause long-term harm to aquatic ecosystems even at very low concentrations because they are chemically stable and active in the body. This makes them hard to break down in water, similar to other persistent pollutants. Continuous release of medicines into water systems raises concerns about their buildup in animals and their spread through the food chain. As groundwater systems become more vulnerable, organizations like the European Medicines Agency (EMA) have called for environmental risk assessments to protect these systems.

In the late 1900s, scientists studied how medicines move through groundwater and how they are broken down. Processes like biodegradation and chemical reactions with soil are important in determining how medicines behave in groundwater. Other factors, such as the movement of water and chemical interactions, also influence how medicines spread in groundwater.

A major goal in environmental protection is to create models that predict how medicines move through groundwater systems. These models help estimate the risks of contamination and guide efforts to reduce harm to the environment.

Prevention

Drug pollution is still a big problem worldwide because current methods are not working well enough. Most policies are focused on individual solutions, cost a lot of money, and only address problems after they happen. Biomarkers can be very useful for assessing the risks of medicines when making decisions about rules and regulations. They can show whether a non-target organism was exposed to a medicine and how harmful the medicine is to the organism if it was.

The main way to stop drug pollution is to burn unwanted medicines. Burning breaks down the active parts of the drugs, except in a few cases. The ash left after burning can be treated further before being sent to landfills, such as removing and recycling any heavy metals that might be present.

Many cities now have programs that offer collection points at places like drug stores, grocery stores, and police stations. People can bring their unused medicines to these locations for safe disposal instead of flushing them into waterways or throwing them in the trash, where they could become leachate.

Another part of preventing drug pollution involves environmental laws and rules. However, these laws face challenges like high costs for enforcement, corruption, and neglect. When enforcement is successful, it can also increase the costs of doing business. People continue to debate the advantages and disadvantages of these laws.

Manufacturing

In 2009, a serious example of drug pollution was discovered in India, where many drug companies are located. Not all drug manufacturing causes pollution. In areas where environmental rules are properly followed, factories clean their wastewater to a safe level. However, in some places, companies may avoid following rules if they can get away with it, such as by bribing inspectors or officials, or by shifting blame to others. This issue affects everyone because people in countries with strong rules are the main buyers of drugs made in places where rules are not properly followed, meaning others suffer the effects.