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 in ways never before imagined, reports a research team from China Ocean University in Qingdao in the journal Nature’s Nanotechnology. 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 just half a millimeter in size, 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. A piece of microplastic can produce huge amounts of nanoparticles, which is why the crushing process is problematic, says Annika Jahnke, head of the Department of Ecological Chemistry at the Helmholtz Center for Environmental Research in Leipzig. Smaller particles can be mistaken for food and consumed by significantly more marine life.
Compared to microplastics, nanoparticles also have a relatively larger surface area. This makes them more reactive, “so chemicals can be released from the particle more quickly,” says Jahnke. Plastics sometimes contain toxic additives that are supposed to make them softer, harder, more flexible, colored, or fire-resistant. Since nanoparticles can also collect toxins and pathogens from their environment like a sponge, organisms would also absorb more pollutants with them.
Nanoplastics are, therefore, potentially more harmful to the environment and the health of people and other living beings than microplastics, according to the specialized article. “Recent studies show that very small particles can pass through cell membranes and therefore remain in the body longer than larger particles,” explains Jahnke. Researchers have already detected nanoplastics in people’s brains, blood, uteruses 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 waste with their stomach to chew. 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 group observed what was happening under a microscope: the rotifers mainly ingested particles similar in size to their algal food. Shortly afterwards, many nanosized particles accumulated in his digestive tract, which were finally excreted. Other aquatic inhabitants also mistake plastic waste for their traditional foods. This has already been described for Antarctic krill in a specialized magazine in 2018.
However, rotifers are much more widespread. There are 2,000 known species worldwide, occurring in both sea and freshwater. They are mainly found in the temperate and tropical zones of the world – where microplastic pollution is particularly high. The contribution of rotifers to global nanoplastic production is likely to be correspondingly 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 of these nanoparticles every day.
And the plastic problem is expected to get worse, according to OECD forecasts: around 400 million tons of plastic are currently 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 landfills or in the environment without control. Micro and nanoplastics come not only from decomposing plastic waste, but also from tire abrasion, dust from the plastics industry, from washing machines when there are clothes made from synthetic fibers or from microbeads in cosmetics. To combat plastic pollution, international representatives are currently fighting for an agreement at a UN summit in Nairobi. Whether this should ban certain types of plastic or regulate the more than ten thousand chemicals contained in everyday plastics is part of the debate.