Cell inhibitors can cause significant harm to aquatic organisms. Image source: Physicist Organization Network
According to data from the World Health Organization, cancer is one of the most concerning global diseases. In 2020, approximately 10 million people died from cancer, and it is projected that by 2040, new cancer cases will increase to 29.5 million. As the global cancer incidence continues to rise, the use of cancer drugs in developed countries is also increasing at a rate of about 10% per year.
In a report on May 19th, the Physicist Organization Network pointed out that cancer drugs have made significant contributions to improving human health, but their environmental impact cannot be ignored. These drugs are widely present in the ecosystem, including in hospital wastewater, groundwater, and even drinking water, affecting the health of fish and potentially humans. Cancer drug contamination has become a globally significant issue that deserves attention.
"Lurking" in the ecosystem
Many cancer treatment drugs contain cell inhibitors.
According to the National Institutes of Health (NIH), cell inhibitors are substances that "slow down or stop the growth of cancer cells without killing them."
When cancer patients take these anticancer drugs, including cell inhibitors, some of the chemicals will eventually be metabolized and excreted from the patient's body. These waste products enter hospital or domestic sewage systems, and wastewater treatment plants cannot completely remove these chemicals, leading to some of them entering aquatic ecosystems and even drinking water supply systems.
A study published in the Journal of Hazardous Materials on April 5, 2023, by Alejandro González-Martínez and colleagues from the Water Research Institute at the University of Granada in Spain, found an increasing presence of these compounds in hospital wastewater, sewage treatment plant influent and effluent, river surface water and sediments, groundwater, and even drinking water.
Due to their harmful environmental impact, cell inhibitors are now classified as "emerging contaminants of concern" (CECs). With the increasing use of cancer drugs, the issue of drug metabolite pollution in the environment is becoming more pronounced.
The "killer" of aquatic organisms
While cell inhibitors are crucial for cancer treatment, they pose significant risks to all life, especially aquatic organisms.
These drugs continuously release into aquatic ecosystems, lowering the quality of surface water, endangering biodiversity, and disrupting ecosystem functions.
A paper published in the Journal of Hazardous Materials pointed out that anticancer drugs can affect algae, crustaceans, rotifers, and fish, among other aquatic organisms, and may lead to changes in soil and water microbial communities, altering ecosystem functions.
A recent report from the Quebec Center for Environmental Analysis (CEAEQ) in Canada revealed the potential risks that major cell inhibitors registered in Canada may pose to ecosystems, focusing on their toxicity and impacts on fish fry.
The CEAEQ report studied the effects of three phenoxamines, capecitabine, cyclophosphamide, and ifosfamide used in cancer treatment, as well as methotrexate used for non-Hodgkin's lymphoma, on fish health.
The researchers initially did not find significant negative effects of these drugs on fish mortality, hatching success, or heart rate. However, they later observed that cyclophosphamide had a significant impact on fish swim bladder inflation. If swim bladder inflation is impaired, fish cannot swim freely in water and are unlikely to survive.
However, the research team noted that further molecular analysis is needed to determine the exact cause-and-effect relationship between exposure to cell inhibitors and swim bladder inflation issues.
In a follow-up study published in April 2024, the research team found that cell inhibitors also affect the regulation of thyroid hormones in fish embryos. Disruption of thyroid hormone function may lead to developmental defects in fish, including swim bladder diseases.
Fish are not only an essential part of the aquatic food web but also an indicator of overall ecosystem health. Any disruption to their growth, development, and survival could have cascading and far-reaching effects on biodiversity.
Responsible drug use is essential
Researchers are also actively studying the risks of cell inhibitor contamination in drinking water for human health. It is evident that long-term consumption of water containing cyclophosphamide poses risks to children's health.
Can people mitigate the impact of these drugs on aquatic environments?
Researchers suggest that proper disposal of unused drugs is crucial. Investing in filtration technologies for cell inhibitor wastewater treatment is also indispensable. Lastly, governments must enact new regulations to provide strong support for these actions to reduce drug pollution. Cancer drugs are indispensable, but people must learn to use them responsibly.
Meanwhile, scientists must continue to research the environmental impacts of other commonly used drugs, understand their full effects, and develop targeted solutions.
González-Martínez and colleagues emphasize the need for a better understanding of the presence, persistence, and ecological impacts of anticancer drugs in wastewater and the natural environment to help design management strategies that protect aquatic microorganisms and mitigate potential ecological impacts.
