Certain molecules used to fight cancer could interfere with the proper functioning of an organ that fish need to survive, researchers from the National Institute of Scientific Research (INRS) have found.
Posted at 10:50 a.m.
Jean-Benoit Legault
The Canadian Press
The environmental impact of these anticancer molecules remains poorly understood at a time when the incidence of cancer is skyrocketing worldwide, leading to an estimated increase of 10% per year in the use of these drugs in developed countries.
“We’re most concerned about environmental contamination from metals or chemicals, but we don’t talk much about contamination from drugs,” said postdoctoral researcher Diana Castañeda-Cortés. And it’s not just cancer drugs, it’s all drugs. »
A report published in 2019 by the Center of Expertise in Environmental Analysis of Quebec warned that five cytostatic products – namely, molecules that are able to slow or stop the growth of cells, including cancer cells, without kill – seem particularly problematic when found in the environment.
These are tamoxifen, which is used to treat breast cancer; methotrexate, which fights non-Hodgkin lymphoma; capecitabine, against colorectal cancer; as well as cyclophosphamide and ifosfamide, which are used to treat several types of cancers.
INRS researchers conducted laboratory experiments during which they exposed fish for several days to the levels of contamination found in the environment.
They found that ifosfamide appeared to have a noticeable effect on the inflation of their swim bladders, an organ essential for maintaining buoyancy in the water. Without an inflated swim bladder, fish cannot swim freely in the water column and are unlikely to survive.
“We don’t know what the effects of longer exposure might be,” warned M.me Castañeda-Cortés. But we clearly see that something is happening and that we must continue to study the subject. »
However, scientists emphasize that further analysis is needed to confirm that exposure to cytostatics is specifically the cause of the swim bladder problem.
That being said, in another study published in 2024, the same researchers found that cytostatic chemicals also affected the regulation of thyroid hormones in fish embryos. A disruption in the function of these hormones could lead to developmental deficits in fish, including swim bladder disorder, they explain.
We currently do not know much about the impact on human health of these cytostatic molecules which contaminate drinking water. The researchers caution, however, that it is not far-fetched to consider a possible feedback loop that would see these molecules drive up cancer rates.
“We lack data and we do not want to be alarmist,” concluded M.me Castañeda-Cortés. But we really need to start paying more attention to how we dispose of these drugs. »
