Microplastics with a diameter of less than 5 millimeters (mm) and nanoplastics, which measure less than 0.001 mm, are accumulating along the Brazilian coastline, according to a series of studies carried out by different research groups from around the country over recent years. A recent FAPESP-funded investigation that compared samples from 40 countries found that the Santos estuary on the coast of São Paulo is one of the most contaminated places in the world when it comes to microplastics. The researchers analyzed oysters and mussels — two animals that filter water for food — with the aim of measuring the occurrence of this residue in the environment. An article published in the journal Science of the Total Environment in May revealed that an average of 12 to 16 plastic particles were detected per gram (g) of mollusk tissue, a large amount considering that the animals only weigh 5 g, on average.
Invisible to the naked eye, microplastics and nanoplastics are not only contaminating the waters off the Brazilian coast. They have also been detected in rivers, in the soil where food is grown, and in the air we breathe (see Pesquisa FAPESP issue nº 281). When involuntarily absorbed by living beings, they infiltrate the digestive system, lungs, bloodstream, and even the placenta of pregnant women. Scientists from all over the world are studying how widely these residues are dispersed in nature and the risks they pose to the environment and human and animal health.
The abundance of particles in the estuary of Santos, a city with high urban density that is home to the largest port in Brazil, came as no surprise. The coast of Santos receives water from rivers that cross several cities, as well as industrial effluents and residential sewage carried by underwater outfalls in the region.
The range of elements that generate microplastics is enormous, but the main item found in the Santos estuary was synthetic fiber composed of polyamides, elastanes, and polyester, possibly originating from textile factories, clothing manufacturers, and general wear during domestic clothes washing.
“The water used to wash these fabrics goes into the sewage, which is not treated and is dumped into the sea via underwater outfall,” explains Ítalo Braga de Castro, a marine biologist from the Sea Institute at the Federal University of São Paulo (IMar-UNIFESP) who led the study, carried out by master’s student Victor Vasques Ribeiro.
Microplastics can be divided into two groups. The first is the raw materials, which are already small at the time of manufacture, such as the millimetric pellets used to create other plastics and the microbeads used as exfoliants in cosmetics and toothpastes. The other group is secondary microplastics, which are the result of the degradation of larger plastics into microfragments. Among the latter, the origins are highly diverse. Bags, fabrics, bottles, cigarette butts, tires, and polystyrene are just some examples.
From Pará to Rio Grande do Sul
In one of the first nationwide studies on the presence of microplastics off the Brazilian coast, marine biologist Tommaso Giarrizzo, a visiting professor at the Institute of Marine Sciences at the Federal University of Ceará (Labomar-UFC), collected sand samples from 22 beaches between Pará in the North and Rio Grande do Sul in the South. He then quantified and characterized the microplastics found according to the materials from which they originated, as well as the human occupation profile of the locations where they were collected, based on proximity to urban centers, level of tourism, and distance to ports or industries in the petroleum production chain. The paper describing his findings is currently under review by Science of the Total Environment.
“We hope that our study will contribute to the creation of a protocol for identifying, analyzing, and monitoring the presence of microplastics along the country’s coastline,” says Giarrizzo, who has also studied the occurrence of plastic fragments in Amazonian rivers and coastal waters. In an article published in the scientific journal Marine Pollution Bulletin in October 2020, a group from the Federal University of Pará (UFPA), where Giarrizzo was a visiting professor, described finding microplastics in the stomach contents of longnose stingrays (Hypanus guttatus) caught in the region.
In 2020, Labomar-UFC mapped the 573 kilometers of Ceará’s coastline and found plastic particles along the entire route. The largest concentrations were identified on beaches in the state capital of Fortaleza. “Microplastic is light and very easily dispersed. Particles generated in one location circulate and soon reach others, even in deep waters. The effects on marine life are still being studied,” says Marcelo de Oliveira Soares, the Labomar-UFC biologist who led the study. “Microplastics, alongside global warming, are one of the causes of coral bleaching and death, but we still need to understand the role of each factor in this problem.”
Other studies have looked at the coast of Rio de Janeiro, specifically in Guanabara Bay. In a 2016 article in the journal Ocean & Coastal Management, scientists from the Institute of Geosciences at Fluminense Federal University (UFF) concluded that the level of this micropollutant in the water changes depending on the season. The authors reported that during the summer, microplastic concentrations on the beaches studied ranged from 12 to 1,300 particles per square meter (m2), while in the winter months, levels dropped to between 3 and 743 particles per m2. The explanation is that in the summer, which is the rainy season in Southeast Brazil, more plastic waste is carried into Guanabara Bay by the dozens of rivers and streams that flow into it.
Another investigation, carried out by scientists from the Institute of Marine Biology at the Federal University of Rio de Janeiro (UFRJ), showed that there are an average of five floating microplastic particles per cubic meter (m3) of water in the Guanabara Bay, while the sediment on the seafloor contains 26,000 particles per m2 in the areas studied. “The extremely high concentration of microplastics in the sediment of Guanabara Bay compared to most other areas studied around the world suggests a high risk of contamination for benthic organisms and demersal fish, which are likely ingesting microplastics,” conclude the authors of the 2019 article describing the study in Marine Pollution Bulletin. Benthic organisms and demersal fish live on or near the seabed.
“A third study by our group, conducted in the same bay, compared the high concentration of plastics with the density of organisms [of the same dimensions] present in the sediment, known as macrobenthos. We found more microplastics than polychaetes [a type of aquatic worm] and about the same number of crustaceans — both animals are important to the diets of fish and crabs,” highlights biologist Gisela Mandali de Figueiredo, who led the studies. “These crab and fish therefore face a major risk of ingesting microplastics when feeding, either because they confuse them with their prey or because they simply cannot avoid them due to their abundance in the sediment.”
Oceanologist Fabian Sá of the Department of Oceanography and Ecology at the Federal University of Espírito Santo (UFES) says one concern about plastic pollutants is their effect on the marine food chain. Zooplankton at the base of the pyramid ingest plastic nanoparticles, says Sá, and are then consumed by small fish and crustaceans. These in turn serve as food for larger marine animals and are also part of the human diet.
“Marine biodiversity is currently declining worldwide, but it is very difficult to determine how much of this loss is caused by microplastics and how much is the result of other pollutants or the combined effects of these different contaminants,” says the scientist, pointing out that several studies have highlighted biodiversity losses caused by plastic pollution. The zooplankton study was carried out as part of Jennifer Bernardino’s master’s degree, supervised by Sá.
In addition to causing problems for the digestive system when ingested, microplastics can cause poisoning. Soot, hydrocarbons, toxic metal particles, pesticides, and other pollutants adhere to plastic when they come into contact with it. As a result, the tiny fragments act as carriers of these pollutants.
Plastic particles also contain potentially harmful chemical elements in their composition when adsorbed, since most plastics are made of synthetic polymers produced from petroleum derivatives. They have different physical properties depending on their functions and applications, and therefore have different compositions of chemical inputs and additives that give them characteristics such as rigidity, malleability, flexibility, color, and resistance.
Leonardo Martins / Getty ImagesPlastic waste and debris in Guanabara Bay, Rio de JaneiroLeonardo Martins / Getty Images
One chemical substance used to provide rigidity and transparency is bisphenol A (BPA), considered potentially carcinogenic in certain circumstances and thus banned from being used to manufacture baby bottles in several countries, including Brazil. Another example is phthalate, an ingredient used to make the final product more malleable, but which is potentially harmful to health.
Experts warn that the impacts of microplastics and nanoplastics go beyond the physiological effects of ingesting the particles. Poisoning can occur even without direct consumption, as an effect of particulate leaching. Leaching is the process of a material being dissolved by water. “A plastic pellet that falls from a cargo ship into the sea will be releasing toxins within 24 hours,” warns marine biologist Caio Rodrigues Nobre, author of a 2015 article on the subject published in Marine Pollution Bulletin.
Nobre found that decomposing plastic pellets in the sea generate enough toxicity to impact the embryonic development of sea urchins (Lytechinus variegatus). “Some sea urchin larvae exposed to plastic pellets suffer growth delays, others do not grow properly, and many do not even become sea urchins,” reports the biologist, highlighting that during the study, he isolated the effect of the pellets from other factors that may affect the development of sea urchin embryos. According to Nobre, the toxic effects depend on the composition of each microplastic and are not identical in different marine organisms. Further studies on various elements of aquatic fauna are needed to better understand the problem.
During his PhD, funded by FAPESP, Nobre studied the effects of microplastics that adsorb triclosan — an antibacterial agent used in cosmetics and personal hygiene products — on Crassostrea oysters and swamp ghost crabs (Ucides chordatus), as described in articles published in Archives of Environmental Contamination and Toxicology in 2020 and Chemosphere in 2022. Adsorption is the process by which molecules or ions adhere to the surface of a material through chemical or physical interactions.
“For both species, the contaminating effects of microplastics exposed to triclosan were greater than the effects of regular microplastics. We also observed that the effects were significantly more harmful to the gills of the crabs than the oysters,” says the biologist, who is currently doing a postdoctorate at UNIFESP’s Sea Institute.
In another line of research, a team from the Institute of Science and Technology at São Paulo State University (UNESP) investigated microplastic contamination in flood control reservoirs in Greater São Paulo, used to capture and regulate the flow of rainwater in cities. In one reservoir located in the neighborhood of Aricanduva, the researchers detected 109,000 units of microplastic per kilogram (kg) of sediment collected from the waterbed. Fifty-three percent was tire waste. Rubber also generates microparticles that are harmful to the environment.
The level of microplastics in the Aricanduva reservoir was almost double the amount found in samples the group collected from a reservoir in Poá in 2020. In Poá, the contaminant concentration was 57,500 units per kg of sediment. “The denser the urbanization of a region, the more microplastics are generated there and the greater the environmental impact as a result,” says Rodrigo Moruzzi, a civil engineer who specializes in sanitation and led the study, published in the journal Environmental Pollution in December 2022. The population density of Poá, at 6,000 inhabitants per square kilometer (km2), is just under half the density of Aricanduva (12,800 inhabitants per km2).
The rainwater that picks up and carries microplastics in urban areas is discharged directly into rivers without passing through sewage treatment plants. These rivers lead to the sea, but they often supply treatment plants for the population’s drinking water. These plants, however, were not designed to deal with microplastics.
“There are no established procedures for removing the material or limits set on the amounts of microplastics allowed in drinking water,” points out Moruzzi. Even sewage treatment plants do not have specific protocols for removing microplastics from effluents. “The material is not the target of any established processes. It is eventually removed by technologies designed to retain other suspended pollutants,” he notes.
Moruzzi highlights a common point raised by scientists studying the occurrence of plastic particles in nature. “The only places without microplastics are the places we haven’t looked yet. As soon as you look, you find it.” Although we have known of the existence of microplastics since the 1970s, it is only in the last 15 years that scientific research began rigorously assessing the problem and attempting to understand the risks they pose to life.
Projects
1. Mussels (Perna perna) and oysters (Crassostrea brasiliana) as bioindicators of microplastic contamination in the Santos estuary (São Paulo) (nº 20/08960-7); Grant Mechanism Master’s (Msc) Fellowship; Supervisor Ítalo Braga de Castro (UNIFESP); Beneficiary Victor Vasques Ribeiro; Investment R$53,422.81.
2. Bivalve molluscs as contemporary and historical sentinels of microplastic contamination (nº 22/08669-6); Grant Mechanism Doctoral (PhD) Fellowship; Principal Investigator Ítalo Braga de Castro (UNIFESP); Beneficiary Victor Vasques Ribeiro; Investment R$249,082.56.
3. Assessment of the environmental risk of the interactions between microplastics, drugs, and antimicrobials: An ecotoxicological approach (nº 17/12193-9); Grant Mechanism Doctoral (PhD) Fellowship; Supervisor Camilo Dias Seabra Pereira (UNIFESP); Beneficiary Caio Rodrigues Nobre; Investment R$244,312.94.
Scientific articles
RIBEIRO, V. V. et al.Oysters and mussels as equivalent sentinels of microplastics and natural particles in coastal environments. Science of the Total Environment. vol. 874. may 2023.
PEGADO, T. et al. Ingestion of microplastics by Hypanus guttatus stingrays in the Western Atlantic Ocean (Brazilian Amazon Coast). Marine Pollution Bulletin. vol. 162. oct. 2020.
CARVALHO, D. G. & BAPTISTA NETO, J. A. Microplastic pollution of the beaches of Guanabara Bay, Southeast Brazil. Ocean & Coastal Management. vol. 128, pp. 10–17. aug. 2016.
ALVES, V. E. N. & FIGUEIREDO, G. M. Microplastic in the sediments of a highly eutrophic tropical estuary. Marine Pollution Bulletin. vol. 146, pp. 326–35. sept. 2019.
NOBRE, R. C. et al.Effects of microplastics associated with triclosan on the oyster Crassostrea brasiliana: An integrated biomarker approach. Archives of Environmental Contamination and Toxicology. vol. 79, pp. 101–10. apr. 11, 2020.
NOBRE, R. C. et al.Combined effects of polyethylene spiked with the antimicrobial triclosan on the swamp ghost crab (Ucides cordatus; Linnaeus, 1763). Chemosphere. vol. 304, pp. 135–69. oct. 2022.
GOEHLER, L. O. et al.Relevance of tyre wear particles to the total content of microplastics transported by runoff in a high-imperviousness and intense vehicle traffic urban area. Environmental Pollution. vol. 341. dec. 2022.
MORUZZI, R. et al. Stormwater detention reservoirs: An opportunity for monitoring and a potential site to prevent the spread of urban microplastics. Water. july 14, 2020.
Republish
