Over the years, plastic waste in water breaks down into smaller and smaller pieces that are potentially more dangerous to organisms. Small animals could play a role in this process to a previously unimaginable extent, reports a research team from the China Ocean University in Qingdao in the specialized journal Nanotechnology of nature. Even a single rotifer can produce more than 350,000 plastic nanoparticles every day. In some bodies of water, tens of thousands of these transparent multicellular organisms, measuring only half a millimeter, live per liter of water.
Microplastics are particles up to five millimeters in size. Plastic particles that measure less than a micrometer are called nanoplastics. Many nanoparticles can be created from one piece of microplastic, which is why the shredding process is problematic, says Annika Jahnke, head of the department of ecological chemistry at the Helmholtz Center for Environmental Research in Leipzig. The smaller particles could be mistaken for food and eaten by significantly more marine life.
Compared to microplastics, nanoparticles also have a relatively larger surface area. “This would allow chemicals to be released from the particle or, conversely, absorbed more quickly,” says Jahnke. Plastic sometimes contains toxic additives that are supposed to make it softer, harder, flexible, colored or fire-resistant.
According to the specialist article, nanoplastics are therefore potentially more harmful to the environment and the health of people and other living beings than microplastics. “Recent studies show that very small particles can cross cell membranes and could therefore remain in the body longer than larger particles,” explains Jahnke. Researchers have already detected nanoplastics in people’s brains, blood, uterus and breast milk.
Other aquatic creatures also mistake plastic waste for food
Rotifers apparently mistake plastic for their natural food. Otherwise they crush and grind algae or organic residues with their chewing stomach. The research team led by Baoshan Xing of the Stockbridge School of Agriculture in Amherst, Massachusetts, placed the colorless, transparent animals with microplastic particles of different sizes in a container of water. The team looked at what was happening under the microscope: The rotifers mostly ingested particles of similar size to their algae-based food. A short time later, many nanoparticles accumulated in his digestive tract and were eventually expelled. Other aquatic inhabitants also confuse plastic waste with their traditional food. For Antarctic krill this was already described in a specialist journal in 2018.
However, rotifers are much more widespread. There are 2,000 known species worldwide, found in both sea and freshwater. They are mainly found in temperate and tropical areas of the world, where microplastic pollution is particularly high. The contribution of rotifers to the global production of nanoplastics is likely to be equally large. For China’s Poyang Lake, the country’s largest freshwater lake with an area of nearly 3,700 square kilometers, Xing’s team calculated that rotifers produce more than 13 quadrillion nanoparticles every day.
And the plastic problem is set to get worse, according to OECD forecasts: currently around 400 million tonnes of plastic are produced every year. Plastic production will double by 2050 and even triple by 2060. Currently only a tenth of plastic waste is recycled; the rest is burned, ends up in landfill or in the environment in an uncontrolled way. Micro- and nanoplastics come not only from decaying plastic waste, but also from tire abrasion, dust from the plastic industry, from washing machines when clothes made from synthetic fibers are found or from microbeads in cosmetics. To combat plastic pollution, international representatives are currently fighting for an agreement at the United Nations summit in Nairobi. Whether this should ban certain types of plastic or regulate the more than ten thousand chemicals contained in everyday plastic is part of the debate.