South American rivers harbor cancer-linked microplastics, studies show

It is well known that microplastics are collecting in the world’s oceans at an alarming rate, but research on the cancer-linked pollutant in rivers remains limited.

Now new evidence from two rivers in Latin America and the Caribbean shows that these tiny particles are present even in rural, downstream locations, highlighting the need to address their impacts on freshwater sources.

Microplastics—plastic particles less than five millimeters long—present a serious health risk to humans and wildlife, due to their toxic effects and ability to act as carriers of other pollutants, and have been linked to a rise in cancer cases.

According to research published in Science, up to 40 million tons of these plastic fragments are estimated to be emitted into the environment each year and this could double by 2040 if the problem is not addressed.

Latin American studies on microplastics represent less than 5% of the global output on this topic, while research on their presence in the region’s rivers is scarce.

This is despite Latin America being home to two of the 20 most plastic-polluted rivers on the planet—the Brazilian Amazon and the Magdalena River in Colombia.

Most existing Latin American studies focus on Brazil, Mexico and Chile, while in Argentina, the MappA project seeks to analyze more than 100 bodies of fresh water in 18 provinces of the country.

Cuba and Venezuela

In Cuba, new research published in Environmental Pollution examined microplastic pollution at sampling stations on two rivers: the Almendares, which runs through Havana, and the Baños del San Juan River, located in a rural area not far from the capital.

While the study found more microplastics in the urban river, the rural river did contain some plastic particles, showing that even areas without high concentrations of people experience this type of pollution.

The Venezuelan study, published in the Journal of Contaminant Hydrology, focused on Chichiriviche de la Costa, a small fishing village in the state of La Guaira, about 65 km from the country’s capital, Caracas. The research compared the levels of microplastics upstream and downstream of the Chichi River and in the bay where it flows, which is where the town is located.

The results showed that plastic pollution in river sediment was almost four times more downstream, showing that the village is a major source of pollution.

Interaction with organisms

José F. Grillo, co-author of the Venezuelan study, told SciDev.Net that it is essential to understand how microplastics behave in a “holistic” way, as well as analyze sources, sinks and their interaction with organisms, to “try to design interventions that can have an impact on this problem.”

Both studies identified clothing and textile fibers as the most common type of microplastic, deriving from synthetic fabrics such as polyester, which release tiny fibers during washing.

In areas with poor wastewater treatment, these fibers enter rivers and eventually end up in the ocean.

The findings of the Cuban team describe a high presence of polyethylene terephthalate, commonly used in bags and packaging, and polypropylene, used in food containers and ropes.

Jeny Larrea, co-author of the Cuban study and professor at the University of Havana, told SciDev.Net: “These are the plastics that are most used in the packaging of personal care products, cleaning products, nylon bags, which corresponds to what is reported in the literature.”

Both studies found that microplastic levels increased during the rainy season.

In Venezuela, the highest concentration of microplastics in Chichiriviche Bay was found near the mouth of the river, suggesting that the river acts as a direct channel of pollution from land to sea.

Microplastics also accumulate in river sediments. In Cuba, the data showed that plastic particles settle at the bottom of both rivers. The study found links between the presence of polypropylene and reduced activity of river microorganisms, indicating that these particles can disrupt natural processes such as the decomposition of organic matter.

These discoveries are an opportunity to advance a comprehensive analysis of microplastics as an environmental challenge that extends from land to sea, according to researchers.

However, there is a long way to go to better understand their impact on ecosystems and health.

Andreia Neves Fernandes, coordinator of the Laboratory of Environmental Processes and Emerging Pollutants at the Federal University of Rio Grande do Sul, told SciDev.Net there was a need to investigate “how organisms internalize plastic waste and examine the possible synergistic and antagonistic effects between microplastics, other environmental pollutants and organic matter.”

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