Decomposed microplastics are more dangerous

A new study determines the effects of solar radiation and chemical pollution on plastic chips, and how this affects human cells contaminated with these microplastics.

The study was conducted by Vladimir Baulin from the Department of Chemical Engineering at the University of Rovira e Virgili (URV) in Tarragona in Catalonia, Spain, and Jean-Baptiste Fleury from the University of Saarland in Germany. For the study, a collection of pieces of plastic on La Pineda beach in Tarragona was taken as a reference.

The study authors found that plastic chips exposed to sunlight and chemicals are more harmful to human cells than when they were freshly made. Although it was known that contact with microplastics changes the functioning of human cells, until now the effect of aging of polymers on their properties has not been taken into account. The study concluded that decomposed pieces of plastic have a greater ability to damage cell membranes and that there is a direct relationship between this characteristic and their color.

We call microplastics those plastic particles ranging in size from one thousandth of a millimeter to half a centimeter, formed by polymers, usually synthesized from petroleum products. These are pollutants resulting from human activities and are present in almost all ecosystems of the world. Since their size and shape are very heterogeneous, there are always some that are able to penetrate inside the human body, among other things, through the food chain or through the air we breathe.

Previous studies conducted by Baulin have already shown that these particles, when in contact with cell membranes, have the ability to deform them. Specifically, the authors of this study found that microplastics stretch the membranes of human red blood cells and reduce their mechanical stability, changing their shape and ability to carry oxygen. Therefore, even at the cellular level there are indications that these fragments, once in the body, have a negative impact on human health. Unlike naturally occurring organic particles, microplastics are highly resistant to degradation and can accumulate in human tissue indefinitely.

Pieces of plastic on an island beach. (Photo: Susan White/USFWS)

In the new study, Balen and Fleury worked with pieces of plastic from La Pineda beach, collected directly from there by the Good Karma Association, to determine whether they caused the same damage to cell membranes as newly synthesized plastics. “These plastics are in the environment for many years, they are exposed to solar radiation, erosion, chemicals … and their properties do not necessarily have to be the same as when they left the factory or the polymers studied in the laboratory.” – explains Baulin.

Following a methodology based on microfluidics, which uses tiny droplets to determine the surface properties of materials, the team was able to link the level of plastic degradation to its level of oxidation. Consequently, the surface of microplastics that spent more time in the medium was more hydrophilic and wetted more easily. This is not an innocuous characteristic, especially when the particle comes into contact with a cell. Cell walls adhere more easily to the degraded polymer, resulting in more severe damage. “The results confirmed that the more hydrophilic the plastic particles, the stronger the adhesive interaction between the microplastic and the cell membrane,” they conclude. In addition, they also found that the most degraded plastics took on a more intense yellowish hue, indicating a relationship between the color of the particles and their ability to damage cells.

“We will continue to explore the impact of microplastics at the cellular level; We are already planning future studies to study how cell membranes behave when in contact with synthetic fibers,” predicts Baulin. The main source of fibers entering the sea is synthetic clothing, and they enter the sea through washing machines. Once there, some end up in the wild and enter the food chain, potentially ending up in humans.

The new study is titled “Aging influences mechanical interactions between microplastics and lipid bilayers.” And it was published in the academic journal The Journal of Chemical Physics. (Source: Rovira e Virgili University)