Brazilian study finds mussels can pass microplastics to humans
Mussels may serve as a gateway for microplastics into the human body, according to a study by the Federal University of the State of Rio de Janeiro (UNIRIO) published this week. These mollusks live on rocky seashores and are used in a variety of dishes in Brazilian cuisine.
Contamination occurs because these organisms, which are consumed by humans, feed by filtering water and cannot distinguish between microalgae, their natural food source, and microplastics, pollutants found in seas and rivers.
The UNIRIO study was published in the scientific journal Ocean and Coastal Research.
Although published in English, the journal is Brazilian and is edited by the Oceanographic Institute of the University of São Paulo (USP). The announcement was made in partnership with Agência Bori, a science journalism organization that promotes research and scientific studies.
Beach sampling
To reach their conclusions, the researchers collected brown mussels (Perna perna), a species widely used in cooking, at Praia Vermelha in Rio de Janeiro’s South Zone.
The shellfish were taken to a university laboratory, where researchers simulated environmental conditions.
To assess how the mussels filter water and ingest microalgae and microplastics, they were divided into three groups.
The groups were exposed to three different water solutions: one containing only microalgae, one containing only microplastics, and one containing a mixture of microalgae and microplastics.
After one hour, the team analyzed the water in the tanks and found that the mussels had consumed the materials indiscriminately, as explained to Agência Brasil by marine biologist and professor Raquel de Almeida Ferrando Neves, one of the study’s co-authors.
“We found that they cannot distinguish between natural particles and plastic particles,” she said.
In the tank containing the mixture, the mussels left behind about 48 percent of the microalgae and 52 percent of the plastic beads. For the researchers, the similarity between these rates demonstrates the species’ inability to distinguish between the two.
Microplastics
Microplastics are fragments of larger plastic materials that, under the effects of time and sunlight, break down into microscopic particles and end up in water, soil, and the air.
These particles can originate from marine debris such as packaging, bottles, tires, textiles, and painted surfaces. Paints, in particular, are a source of many of the chemical elements found in these fragments.
In late May, Agência Brasil reported that microplastics were detected in 93 percent of a sample of fish from the coast of Paraná state in southern Brazil.
Another Brazilian study even found microplastics in placentas and umbilical cords.
The World Health Organization acknowledges that the world is facing challenges related to microplastic pollution and calls for further research into the effects of these particles on human health.
Contaminants
Professor Raquel Neves, from UNIRIO’s Department of Ecology and Marine Resources, warns that microplastics may carry a wide range of contaminants on their surface.
“This poses a significant risk to human health because mussels are filter feeders, and filter-feeding organisms tend to accumulate chemical contaminants,” Neves explained.
The biologist, one of the winners of the 2023 edition of the For Women in Science Award - granted by the L’Oréal Group in partnership with the Brazilian Academy of Sciences and UNESCO - points out that the level of microplastics in the human body depends on diet.
“If a person consumes them only occasionally, the risk and exposure will be lower. We refer to this as a consumption risk analysis. If they consume them very frequently, they will be more exposed to that particular contaminant,” she noted.
Neves also pointed out that, unlike pathogenic microorganisms and gastrointestinal parasites, cooking food is not enough to reduce the health risks associated with microplastics.
In the case of biotoxins, microplastics, metals, and chemical contaminants, cooking does not reduce the levels of these substances in mussels.
Standardized behavior
The researcher believes that, although the mussels used in the experiment were collected from a specific location in Rio de Janeiro, the finding that they mistake microplastics for food applies to other regions as well.
“This species is found throughout the coast, so its behavior tends to be consistent across different locations. Feeding patterns and filtration rates do not usually vary geographically,” she says. “Instead, they are influenced primarily by food availability and, in this case, by the presence of plastic particles.”
Solutions
UNIRIO researchers argue that, to protect coastal communities and prevent cascading contamination, practical measures are needed to reduce pollution at its source, such as public policies to curb the dumping of waste into the sea and significantly restrict the use of single-use plastics.
The team also advocates for continuous scientific monitoring of mariculture areas, where marine organisms are cultivated, as a way to help ensure the long-term safety and sustainability of seafood production and consumption.
