Micro- and nanoplastics are found everywhere: in soil, water and air. Previously, researchers have proposed many original options for removing these ubiquitous particles, but recently it turned out that an effective method of cleaning drinking water from them has been used by people since ancient times.

Experts in the field of biomedical engineering and microplastic studies from Guangzhou Medical University and Jinan University (both in China) talked about a long-known solution. Their experiments showed that boiling water with a high calcium content (also called hard) removed more than 80 percent of the microplastics in it.

For a study published in a journal Environmental Science and Technology LettersTap water samples of different hardness were taken in Guangzhou, China. They added three types of plastic particles (polystyrene, polyethylene and polypropylene) with sizes ranging from 0.1 to 150 micrometers. The samples were then boiled for five minutes, then cooled, and the content of plastic particles in the water was measured.

The fact is that when boiling in hard water saturated with minerals, insoluble calcium carbonate СaCO3 appears, simply put, scum. Researchers hypothesized that this might bind to plastic particles and co-settle with them.

This is what happened in the experiment. The cleaning effect was most pronounced in samples with increased hardness containing 300 milligrams of CaCO3 per liter. Boiling made it possible to remove up to 90 percent of plastic microparticles in water. In soft water (less than 60 milligrams of CaCO3 per liter), 25 percent of the added microplastics were removed by boiling.

Thus, researchers showed that the task of purifying drinking water from microplastics is solved not only with the help of expensive modern filtration systems, but also with such a simple and time-tested method as boiling, which also provides disinfection.

The scientists added that if lime deposits containing “encapsulated” plastic float to the surface, they can be removed by pouring water through a paper coffee filter.

The problem of widespread distribution of micro- and nanoplastics is causing increasing concern in the world due to the potential danger of these particles to human health. Because of their small size (five millimeters to one micrometer or less), they can enter the body through the mouth, nose and other open parts of the body.

At the same time, there is no consensus about them among scientists. Some argue that the accumulation of microplastics can lead to various pathologies, including plasticosis, in which scars form on internal organ tissues and digestion is impaired. At the same time, WHO had previously stated that they could not find convincing evidence about the harm of microplastics found in drinking water.