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The threat of microplastics

Tiny plastic fragments are everywhere and removing them poses a major challenge

Artistic representation of microplastics dissolved in water

Léo Ramos Chaves

From the Mariana Trench in the Pacific Ocean to the Alps, from the beaches of remote islands to the world’s largest metropolises, microplastics are everywhere, often completely unseen. Increasingly detailed analysis highlights the ubiquitous nature of this plastic debris—tiny spheres, fragments of film, or fibers up to five millimeters in length, which often can only be seen with a microscope. They have been found not only in the earth, sea, and freshwater bodies, but also in the air we breathe, tap water, bottled water, sea salt, honey, beer, seafood, and consequently, in human feces.

Research into microplastics is a relatively new field and has only gained momentum this century, most strongly in recent years. Although we have known of its presence in the oceans since the 1970s, it was not until 2004 that the term was incorporated into the scientific literature by British researcher Richard Thompson, a professor of marine biology at the University of Plymouth, UK. Most studies so far have examined the marine environment and biota, since so much microplastic ends up in the oceans via rivers, streams, and sewage.

“Microplastics have the potential to greatly alter the oceanic biota and ecosystem of our planet as a whole,” says physicist Paulo Artaxo, from the Institute of Physics at the University of São Paulo (USP) and a member of the FAPESP Program for Research into Global Climate Change. “The effects of this type of pollution are not yet fully understood or quantified. We need to do a lot more scientific research to characterize the material and study the extent of its distribution and concentration, its effects on ecosystems and living things, and how to remove them from the environment.”

A joint initiative by European and Brazilian institutions plans to invest €10.5 million into research on four major themes related to the source, distribution, and impact of microplastics on the marine environment. The call for proposals is the result of a partnership between the Brazilian National Council of State Research Funding Agencies (CONFAP) and the intergovernmental JPI Oceans platform created by the European Union (EU). Brazil is participating in the effort alongside 14 European nations. FAPESP expects to receive up to €600,000 for future research projects.

“The great challenges faced by the oceans cannot be solved by one single country,” says marine biologist Isabelle Schulz of JPI Oceans and the German Marine Research Consortium, noting that ocean waters connect all continents. “It is important to take an integrated approach to microplastic research and monitoring. This joint call will help improve the health and productivity of the seas and oceans and will teach us more about the impacts of human activities and climate change on these ecosystems,” says the German researcher. “The knowledge gained can be translated into public policy and useful products and services.”

Diverse impacts
The challenge of this type of research is that plastic comes in such a diverse range of types, formats, shapes, and sizes. As well as microscopic pieces, there are even fragments that are nanometric in scale (less than a thousandth of a millimeter), which are theoretically capable of entering the bloodstream and reaching organs such as the liver, kidneys, and brain. “We currently face great difficulty understanding the world of nanoparticles,” says Alexander Turra, a professor at the USP Oceanographic Institute. “We don’t have the technology needed to monitor these particles or to study their effects on ecosystems and biodiversity.”

Since 2012, Turra has been part of an independent international research group called GESAMP (Group of Experts on the Scientific Aspects of Marine Environmental Protection) that advises the United Nations (UN). Its focus is on the biggest challenges posed by plastics and microplastics. In March, the group released a report guiding countries on how to monitor and evaluate waste at sea, including microplastics.

A 2014 study led by Turra in Santos, on the coast of São Paulo State, found plastic pellets—small spheres used to produce plastic materials—buried up to 2 meters deep in beach sand, suggesting the problem is much larger than previous estimations that they were limited to the surface. In the same region, 75% of mussels were found to have ingested microplastics. Research based on laboratory experiments indicates that plastic particles can affect the growth, reproduction, development, and even survival of marine organisms.

Another study, conducted by the Austrian Environmental Agency and the Medical University of Vienna, revealed that stool samples from eight volunteers from various countries contained varying amounts of microplastic—despite the small sample size, the pilot study was the first of its kind and had significant international repercussions. “Plastics are pervasive in everyday life, and humans are exposed to plastics in numerous ways,” the study’s lead researcher Philipp Schwabl told the German news agency Deutsche Welle. “It is highly likely that during various steps of food processing or as a result of packaging, food is being contaminated with plastics.”

Infográfico Alexandre Affonso

Although they have already been detected in organisms at all levels of the food chain, there is still no evidence that the particles accumulate and biomagnify along the chain, Turra points out. Bioaccumulation is the process through which substances are assimilated and accumulated in the tissues of organisms, while biomagnification is a phenomenon related to the progressive accumulation of substances along the food chain. “Unlike other pollutants, where concentrations are higher in predators at the top of the food chain, this does not seem to happen with microplastics.” Particles assimilated by organisms appear to be excreted at one point or another.

This is what seems to have happened with the individuals who participated in the Austrian study and was also observed in sea anemones in a laboratory experiment carried out by researchers at the Carnegie Institution for Science in Stanford, California. Those that ingested microfiber plastic, offered with or without shrimp—their natural prey—all eliminated the particles. The problem is that due to climate change, many organisms are already under severe stress and therefore take longer to expel them. “The constant exposure of anemones to microplastics could be aggravated by the existence of other stressors, worsening the adverse effects,” suggests Brazilian oceanographer Manoela Romanó de Orte, one of the authors of the study.

According to the researcher, an estimated 90% of the microplastics found in coastal ecosystems are microfibers—most of which come from the washing of synthetic clothing. “Sixty percent of clothes are made from plastic fibers such as nylon, acrylic, and polyester. When we wash these clothes, thousands of fibers are released and many pass through the filters of washing machines and sewage treatment plants and end up in rivers and oceans,” says Orte, who works at the Global Ecology Department of the Carnegie Institution for Science.

@5gyres Plastic fragments in beach sand@5gyres

Chemical contamination
As well as the physical effects, such as potential obstruction of the digestive tract in smaller organisms, scientists are also concerned about the chemical effects of microparticles ingested or inhaled by humans and animals, which could function as vectors of microorganisms and contaminants such as persistent organic pollutants (POPs)—synthetic compounds resistant to natural degradation. There are two types of substances associated with these particles: those that exist in the plastic itself, commonly used to give it special properties, such as phthalates and bisphenol A, both of which are known endocrine disruptors capable of altering the hormonal system; and substances adsorbed by the microplastics, which may include heavy metals and POPs.

Phthalates are a type of plasticizer used to make PVC more flexible. According to Miguel Bahiense Neto, president of the Plastivida Socioenvironmental Institute of Plastics, they are only used in a small fraction of this type of polymer. Bisphenol A, meanwhile, is the raw material of polycarbonates. “These plastics are used to make long-life products such as electronics and construction materials,” says Bahiense.

According to chemist Cassiana Carolina Montagner, a researcher from the Environmental Chemistry Laboratory at the Chemistry Institute of the University of Campinas (UNICAMP), POPs are abundant in the environment and can accumulate in organisms. For over 10 years she has been studying so-called emerging contaminants—released into the environment through the use of drugs, pesticides, hormones, personal hygiene products—and found that concentrations of these substances in the rivers of São Paulo were at the same level as untreated sewage.

Now, with FAPESP funding, Montagner is studying microplastics and their ability to adsorb these contaminants in the urban water cycle—adsorption is the process by which molecules or ions are trapped on the surface of solid materials through chemical or physical interactions. Long before reaching the ocean, she notes, rivers receive sewage, they pass through treatment plants, and they are used for public water supply. “Especially in the South and Southeast, where urban density is very high, how effective are water and sewage treatment plants at removing these contaminants? How can we ensure that they are not allowing microplastics to reach the oceans and the general population? These are questions that the study aims to answer,” says the researcher.

A survey conducted two years ago by Orb Media, a Washington-based, nonprofit media organization, found that microplastics are present in tap water worldwide. Of the 159 samples collected on five continents and analyzed by researchers at the University of Minnesota, USA, 83% contained microplastics. Ten samples from the city of São Paulo were part of the study—nine of them were contaminated by plastic fibers. Last year, another study by the same organization examined bottled mineral water and reached similar conclusions.

The presence of microplastics in the air is also a cause for concern. At the USP School of Medicine, professor Thaís Mauad and researcher Luís Fernando Amato Lourenço, from the Experimental Air Pollution Laboratory, plan to evaluate the quantity of these fragments found in the air in São Paulo, to analyze their characteristics and their effects on human health. In a pilot study, they detected suspended plastic microfibers on Avenida Dr. Arnaldo, a major road in the west of the state capital. “Here in Brazil, we don’t yet have any idea of their concentration or chemical make-up, or what is attached to these airborne microplastics,” says Lourenço. New research will try to better understand these and other issues in the coming years.

1. Airborne microplastics: Detection in ambient air samples and lung tissue and the effects on cultured pulmonary epithelial cells (nº 19/02898-0); Grant Mechanism Research Grant – Sprint; Principal Investigator Thais Mauad (USP); Investment R$40,930.00.
2. Microplastics as vectors of emerging organic contaminants in Brazilian water systems (nº 18/21733-0); Grant Mechanism Regular Research Grant; Principal Investigator Cassiana Carolina Montagner Raimundo (UNICAMP); Investment R$155,494.47.

Scientific articles
TURRA, A. et al. Three-dimensional distribution of plastic pellets in sandy beaches: Shifting paradigms. Scientific Reports. Mar. 27, 2014
MONTAGNER, C. Microplásticos: Contaminantes de preocupação global no Antropoceno. Revista Virtual de Química. 2018.
DE ORTE, M. et al. Response of bleached and symbiotic sea anemones to plastic microfiber exposure. Environmental Pollution. Mar. 6, 2019.