Fundamental Science: Fish swimming in the pharmacy

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When was the last time you took any medication? For most Brazilians, the answer will be “a few hours ago”. When we ingest a medicine, the active principles are metabolized in our organism, resulting in modified or intact products that will be eliminated mainly through the urine. This, in turn, ends up in the domestic sewage, whose treatment methods are not very effective in eliminating pharmaceutical residues, a situation aggravated by pharmaceutical industry evictions, the use of veterinary drugs in animal husbandry and the inappropriate disposal of pharmaceuticals. . As a result, hundreds of these residues have been found in small concentrations in rivers and oceans, in the water we drink and even in remote environments such as Antarctica.

There are a number of classes of drugs that have a potential deleterious effect on the health of aquatic organisms, such as hormones, antidepressants, anxiolytics, anti-inflammatories and antibiotics. Some of these substances can degrade quickly in the environment, while others can persist for a long time, affecting aquatic animals. One of the first studies on the effect of these drugs on marine life was carried out in 2003 and still has repercussions today: male fish treated with ambient concentrations of fluoxetine, the active ingredient in the antidepressant Prozac, became more antisocial and aggressive, while females produced less eggs.

Since then, hundreds of studies have been carried out, with less than encouraging results for several drugs. One of the most detected drugs is the anti-inflammatory diclofenac, associated with a notable drop in the vulture population in India, and known to cause liver and kidney damage in trout. Another example is ivermectin, an antiparasitic widely used in animal husbandry, whose sale for human consumption grew by around 900% during the Covid-19 pandemic, despite its demonstrated ineffectiveness against the coronavirus. Ivermectin can persist for many months in ocean sediment, and laboratory studies suggest that even extremely low concentrations in the environment can decrease the population of small marine crustaceans and aquatic insects.

One of the most significant impacts of pharmaceutical pollution is contributing to the development of antimicrobial resistance. Microorganisms such as bacteria can undergo changes if exposed to antibiotics, becoming resistant to them, which reduces the effectiveness of antibiotic therapy, prolongs and worsens illnesses, in short, it is a global problem that has worsened in recent years. Current estimates attribute 1.27 million deaths to antimicrobial resistance in 2019. In recent years, dozens of antibiotics have been detected at levels above the tolerated level in the world’s rivers and oceans, including several regions of our country. In 2021, the World Economic Forum listed Brazil as one of the countries with the highest risk of transmitting antimicrobial resistance through water.

Another group of drugs that pose risks to the environment and human health are endocrine disruptors, substances that can alter the functioning of hormones in the body, pose risks to development, metabolism, growth, reproduction, in addition to predisposing to various diseases. Estrogenic pollution by oral contraceptives in rivers and lakes in several countries, for example, is associated with the feminization of male fish, altering their reproductive capacity.

There is a possibility that drug pollution could affect health and contribute to the population decline of several animal species, but a big question is understanding the magnitude of this problem in wildlife in every corner of the planet. Laboratory studies are capable of predicting the toxicity of a given drug for a given species, but in the environment the concentrations of these contaminants are dynamic, and they interact with other pollutants, such as pesticide residues.

In order to face this serious problem, we will need a lot of investment in science in the coming years, monitoring the amount of each residue in the Brazilian environment, understanding the risks they can bring to animals and human health, and finding effective ways of decontamination. On an individual level, we must avoid self-medication and correctly dispose of expired medicines, taking them to collection points in pharmacies or health centers.

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Rossana Soletti is a pharmacist and professor at the Federal University of Rio Grande do Sul.

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