A new study says microplastics react with water. This is a problem for biology

Although plastic is usually neutral, its tiny particles have the potential to react with one of the most ubiquitous molecules in our environment and bodies.

One of the reasons that plastic has become so ubiquitous is that, in general, it is very chemically stable, meaning that it does not easily react with the materials around it. That is why this material is often used for food packaging and water bottles.

The same was thought to be true of microplastics—those tiny pieces of debris that detach from larger plastic bodies and, according to multiple studies, are distributed throughout nearly every ecosystem on Earth. But scientists at Columbia University and UC Berkeley have recently discovered that water can chemically activate the surfaces of microplastics, turning them into a potential hazard.

According to the findings of the paper published in Nature, this activity can lead to the spontaneous formation of chemicals that are able to change other molecules, such as those that are essential for living organisms. The authors note that this phenomenon occurs even under normal environmental conditions, without the need for sunlight or other factors that degrade plastic.

So how can microplastics be so reactive when larger plastics usually aren't? Scientists suggest that this has to do with more surface area available for these reactions to occur.

As pieces of plastic break down into smaller and smaller particles, the surface area increases dramatically, Wei Min, a professor of biomedical engineering and chemistry at Columbia University, said in a press release. "The microplastics then change the water that surrounds them, producing energetic, reactive radicals that likely contribute to the biological damage we see in animals and potentially in humans as a result of microplastic exposure."

Among these potentially dangerous chemical products—called reactive oxygen species—stand out a variety called hydroxyl radicals. They are particularly dangerous because they can steal electrons from proteins and lipids that make up cell membranes, disrupting their structure and function. "These are textbook examples of the kinds of molecules that can damage animal and human tissue," added Naixin Qian, a postdoctoral researcher in Min's lab who helped lead the research.

Our body has a defense against this type of damage. This is the biological function of buzzing molecules known as antioxidants. These neutralize reactive chemicals, but if the reactive compounds far outnumber the antioxidants, this line of defense can be lost.

This can turn into a scenario called oxidative stress and lead to cell damage. Previous research has previously identified oxidative stress among the cellular responses associated with exposure to microplastics, although the mechanisms responsible for this damage are not yet fully understood.

The extent to which microplastics have infiltrated our bodies remains an open debate, and some of the more exciting findings have been questioned. But if there is even a small amount of microplastic in our tissues, it can react with the water in our bodies.

Researchers were particularly concerned about the potential effects of blood, which is mostly water. If contact with this liquid can chemically activate the surfaces of microplastics, their presence inside the body could pose a greater risk beyond the pollutants they carry or release.

When researchers exposed red blood cells extracted from mice to different types of microplastics, the cells were deformed and ruptured—a phenomenon called hemolysis. These effects were greater for plastics that reacted more with water, indicating that this activity caused cell damage.

Research into the effects of microplastics has long focused on other chemicals leaching from particles or their physical effects, often assuming the plastic itself is chemically inert. Larger fragments are common, but these findings challenge the assumption that what is true of large-scale plastic is also true of the microscopic fragments into which it breaks down.

This story originally appeared on WIRED en Español and has been translated from Spanish.