La Jornada: Compound used in plastics causes genetic damage in freshwater turtles

A compound used to give flexibility to plastics can damage the DNA of freshwater turtles and affect their growth, revealed a study carried out by researchers from the National Autonomous University of Mexico (UNAM).

In interview with The DayVíctor Hugo Reynoso Rosales, from the UNAM Institute of Biology, says that the first time he thought about this research was in 2015, when a video of a sea turtle with a straw in its nose went viral.

“The images, which reached millions of views, focused on microplastics; the use of straws and single-use bags was prohibited,” he recalls. So when one of his students told him about her interest in studying plastic waste, he saw the opportunity to return to the topic.

“We were clear that many turtles that eat microplastics die; but we did not know if they did so because of the plastics compacted in their stomach or because of the chemicals they release,” he points out.

For 14 weeks, the researchers studied 20 Mesoamerican tortoises (Trachemys charming), who received different doses of DEHP phthalate, a substance that is used to soften plastics such as PVC and is present in numerous everyday products.

They then analyzed blood samples to determine if the compound had damaged their genetic material. Additionally, they monitored their weight and shell length to assess whether their body growth was affected.

Laboratory analyzes showed that DEHP phthalate damages the turtles’ DNA and increases the presence of small structures called micronuclei, a sign that the cells suffered damage to their genetic material and were unable to completely repair it.

“Turtles have the ability to degrade plastic with their gastric acids. This means that all the chemicals that make up it pass almost freely through their digestive tract,” highlights Reynoso Rosales.

The study, published in the journal Aquatic Toxicologyis the first evidence of genetic damage caused by the phthalate compound DEHP in freshwater turtles. Until now, the effects of this compound had only been studied in fish and mammals.

The finding is relevant because this species, which lives from southern Mexico to Colombia, is consumed in some regions and is part of aquatic ecosystems where the presence of DEHP phthalate has been identified, such as the Atoyac River, which runs through several states. In these environments, contaminants can enter the food chain.

María Elena Calderón Segura, from the Institute of Atmospheric Sciences and Climate Change and who was in charge of the laboratory studies in this research, highlighted that what happens with turtles happens with other species in the environmental environment.

Every year, according to the United Nations (UN), between 400 and 600 million tons of plastic garbage are generated. Exposure to the Sun and high temperatures causes them to break and fragment into increasingly smaller particles. “Some of them we can even breathe without realizing it,” he says.

Furthermore, although many plastics end up in the sea, during their journey through soil, rivers and lakes, they release toxic chemical molecules or compounds, such as the phthalate DEHP, which can enter aquatic and terrestrial organisms.

“It has been found in muscle tissue of various fish, in whales,” says Calderón Segura. “The ecosystem is completely damaged, the presence of phthalates has already been recorded even in breast milk,” adds Reynoso Rosales.

Faced with the serious problem of plastic garbage disposal, researchers consider systematically measuring pollutants in the country’s water bodies. They highlighted the case of the Suchiate River, on the border of Mexico and Guatemala, at whose mouth with the sea plastics accumulate.

Looking to the future, experts consider it necessary to carry out more research on the presence of DEHP phthalate in bodies of water, seabirds that feed on fish, or in plants that could absorb them from aquifers.

Although the problem of plastics is global, Reynoso Rosales spoke out in favor of each country promoting a public policy to counteract it. It emphasizes that commitments should be made so that people take responsibility for the plastic waste they generate.

For Reynoso Rosales, the plastic problem is not limited to visible waste, but to the invisible pollutants that they release into the environment and that, through the food chain, can eventually reach the human body.