In Mexico, the pollution of rivers, lakes, and reservoirs from wastewater discharges and everyday medications is growing silently. In response to this situation, the Environmental Network (Rema) of the National Polytechnic Institute (IPN) is working on a solution that is as powerful as it is simple: artificial wetlands capable of removing up to 100% of certain pharmaceutical contaminants.

The initiative is led by researcher Marcela Galar Martínez of the Department of Pharmacy at the National School of Biological Sciences (ENCB), where she directs the Aquatic Toxicology Laboratory.

For the past two decades, her line of research has centered on understanding how pollutants affect fish, invertebrates, and other aquatic organisms, and on developing practical ways to remediate affected water bodies. Today, this path has led her to coordinate a project that combines ecology, engineering, molecular biology, and behavioral toxicology, with both national and international collaborators, including the Interdisciplinary Professional Unit of Biotechnology (Upibi) at the IPN, the Autonomous University of the State of Morelos (UAEM), and the University of Curitiba in Brazil, working with Dr. Marcelo Pedrosa.

In 2004, when the study began, measuring the impact of pollutants on fish and other aquatic organisms and discussing oxidative stress and molecular toxicology in aquatic fauna was still emerging in Mexico; over time, the research team incorporated new methodologies such as biochemical studies, genetic analyses, biomarker observation, and more recently, behavioral bioassays, capable of measuring changes in fish behavior as an early indicator of toxicity.

These technical advances were not an end in themselves, but rather tools to address the three pillars of toxicology: prevention, treatment, and legislation. “First, we must identify which contaminants are present and what harm they cause. Then we must design eco-technologies that can remove them from the water and reduce their toxicity,” explained Marcela Galar.

That approach led to the development of previous projects at critical sites at the Madín and Villa Victoria dams, both in the State of Mexico, where her team assessed the presence of toxic compounds and tested techniques such as bioreactors and advanced oxidation systems.

It may seem harmless, but the medications we use every day—decongestants, pain relievers, and blood sugar-lowering drugs—generally end up in water bodies, not because of irresponsibility, but because the body inevitably eliminates them through urine and feces.

These compounds, known as emerging contaminants, are not always removed by wastewater treatment plants, and when they reach rivers and reservoirs, they have adverse effects on the fish and organisms that inhabit these ecosystems. Among the drugs the doctor’s team is studying are penicillin, metformin, and acetaminophen—common, everyday, and highly persistent contaminants.

WETLANDS CLEANED BY THE POWER OF NATURE

One of the project’s most promising contributions is the design of artificial wetlands based on science, not just aesthetics. Wetlands function as controlled marshes where plants, rhizome microorganisms, and associated bacteria work as a natural purification system.

“Plants can use these pollutants as a carbon source and reduce their concentration. These are nature-based solutions,” explained the Polytechnic scientist.

These wetlands may be surface-flow, subsurface, horizontal, and vertical; the challenge is to determine which plants to use, in what order to arrange them, and under what conditions, to achieve the most efficient removal—and this is where the collaborative work with Marcelo Pedrosa comes in, as he achieved surprising results in Brazil.

“Depending on how the plants are arranged within the wetland, up to 100% of certain pollutants can be removed,” noted Galar Martínez.

BRAZIL AS A LABORATORY

During a recent stay in Curitiba, Dr. Galar observed wetlands already operating at full scale. The Brazilian team is studying which genes in the plants enable them to metabolize, transform, or degrade toxic substances.

Inspired by this model, the Mexican project included a molecular biology phase to determine whether local plants or those proposed for the IPN wetlands possess these same key genes.

Meanwhile, three students from the ENCB’s Master’s Program in Sustainability and Environmental Innovation will travel to Brazil this semester to learn directly from these systems and determine the ideal arrangement of plants in Mexican wetlands.

TOXICITY TESTS AND SPECIES SELECTION

The project has been underway for a year, but progress has been significant. So far, plants with biotransformation potential have been selected, their genetic profiles evaluated, and toxicity tests conducted on test species such as zebrafish, common carp, plants like onions, and the lentil model, with the aim of observing different bioindicators.

The tests assessed the actual toxicity levels of the pollutants at environmentally relevant concentrations, which will allow for a rigorous measurement of how much toxicity is reduced after passing through the wetland. “We are not only seeking to reduce the concentration of the toxin, but to eliminate its actual toxicity,” she stated.

THE SOCIAL IMPACT

The project does not aim to remain on paper or in an academic laboratory. Its goal is for the final wetland design to be proposed to agencies such as the National Water Commission (Conagua), the Ministry of the Environment and Natural Resources (Semarnat), and water management agencies.

“The objective is to bring about change in our society. We want these wetlands to be incorporated into ecosystem restoration plans,” Galar noted.

One of the students on the team is already working on the final design of the wetland, which will be built based on the results obtained in Mexico and Brazil. Mexico faces urgent challenges related to water pollution; the Madín and Villa Victoria dams are examples of the scale of the problem nationwide. If the wetland project is officially implemented, it could become a national model for the cleanup and restoration of reservoirs contaminated by pharmaceuticals—one of the major environmental challenges of our time.