Although the world is advancing in environmental awareness, scientific studies reveal that invisible pollutants such as antibiotics, drugs, cosmetics, or industrial waste reach rivers, seas, and even drinking water. SERC Chile – UC researcher Ricardo Salazar-González is working on an innovative solution: solar radiation to eliminate these pollutants, in addition to proposing new regulations to measure and control them.

Unfortunately, plastic bottles, bags, and nets floating in rivers and seas have become part of the everyday landscape. Although environmental awareness has progressed, an invisible threat remains that is seldom discussed: emerging contaminants, which are compounds that silently seep into our waters.

These are residues such as pharmaceuticals, pesticides, microplastics, and other chemical compounds that, as Ricardo Salazar-González—researcher at the Solar Energy Research Center, SERC Chile, and director of the WATER² group—explains, "are contaminating water sources at an alarming rate. These substances are ignored in current monitoring and regulation systems and require meticulous attention due to their potential effects on the aquatic ecosystem and, consequently, on human health."

The UC academic also emphasizes that "all the products we consume or use daily contain chemical compounds that sooner or later end up in the water. They infiltrate, accumulate, and we do not measure them."

Indeed, during 2024, the Chilean salmon industry used 351.1 tons of antimicrobials, according to official data from SERNAPESCA. Of that total, more than 98% was administered during the seawater farming phase, representing a 10.8% increase compared to 2023, which exacerbates its potential environmental impact.

"We are talking about a high-concentration cocktail of antibiotics that we release into coastal ecosystems without having clarity on their long-term consequences," warns Salazar-González. "Not only are we promoting bacterial resistance, but we also lack mechanisms to track what happens next."

In light of this, Salazar-González emphasizes that "improving production practices is not enough. A robust regulatory framework is required, establishing clear limits, reduction goals, mandatory transparency and, above all, environmental surveillance. Today, in Chile, there is no systematic network or legal mandate to monitor antimicrobials or resistance genes in water bodies, whether continental or marine. Nor is there a requirement to evaluate their presence in sediments or native fauna."

Among these emerging pollutants are microplastics, which include residues from cosmetics, synthetic clothing fibers, and automotive industry waste, among many others. And as Salazar-González warns, "the problem is not only that they are everywhere, but that they persist. These particles act as vectors for chemical pollutants such as pesticides, pharmaceuticals, and heavy metals, as well as pathogenic microorganisms. They can even interfere with wastewater treatment processes, transporting antimicrobial resistance genes and challenging the effectiveness of our current technologies."

As part of the challenge of regulating these pollutants and measuring their impact on ecosystems, the research team led by Ricardo Salazar-González is working on a legislative proposal driven by SERC Chile, in conjunction with the Pontificia Universidad Católica de Chile, the Center for Public Policy (CPP), and the Water Law and Management Center (CDGA). The initiative seeks to create a National Antimicrobial Environmental Surveillance Network, articulated under the One Health approach.

This network would allow for the systematic monitoring of wastewater, rivers, intensive farming areas, and marine environments, providing environmental traceability for the first time to what currently flows unchecked. "Improving production practices is not enough. If we do not measure what we release into the environment, we will never be able to manage it. The science is there; now it is politics' turn," emphasizes Salazar-González.

Solar potential

According to research conducted by Salazar-González, along with other academics, electrochemical advanced oxidation processes (EAOP) offer hope. Through this technology and solar radiation, they have successfully eliminated emerging contaminants and disinfected contaminated water in real-world scenarios.

"Water can be decontaminated using solar photochemistry. This means we leverage the sun's UV radiation, which helps generate oxidant species and degrade the pollutants present in the water. Furthermore, solar energy can be used to power the water treatment system, making the process more efficient."

"In one of our latest works, we succeeded in eliminating emerging contaminants present in real water samples while simultaneously disinfecting the water. That is, it is 100% effective in degrading recalcitrant chemical compounds and pathogenic microorganisms," states Salazar-González.

Furthermore, solar photoreactors are low-cost and their size can be adapted to the required treatment volume. "And from an energy standpoint, it is possible to leverage photovoltaic solar energy to power the system with solar energy," says Salazar-González.