There is no convincing evidence that microplastic in drinking water is unhealthy, the WHO report says, a summary is available on a separate page. Most of the studies devoted to this issue do not meet the quality criteria developed for the analysis of microplastics, therefore their results should be treated with caution.
According to environmentalists, by 2017 around 8.3 billion tons of plastic were produced in the world and about 6.3 billion tons were thrown out. Plastic waste is gradually destroyed and disintegrated into microparticles (smaller than 0.5 millimeters) that pollute the water, including plumbing, soil and air. Plastic particles get into tap water from the ground (for example, they are washed away by rains), from poorly treated wastewater, together with industrial waste, from the air. It is believed that the potential danger can come not only from the particles themselves, but also from toxic contaminants and pathogens that can accumulate on them.
However, according to a new WHO report, the harm from microplastics entering the body has not yet been proven. Employees of the organization conducted a study of 52 publications devoted to this issue, and found that most of them are of poor quality. Only four of them, published in 2017 and 2018, met the necessary quality criteria: positive and negative control, sampling and processing methods, detection of the studied polymer.
The harm from plastic, chemical pollutants and pathogens that enter the body with it has not been proven. For example, the authors of a study in mice showed that animals fed microplastic water developed liver inflammation. However, the concentration of particles in drinking water, which was used in the experiments, was five times higher than in tap water. In another work, the same authors studied the harm of chemical pollutants that enter the body of mice with plastic, but again the concentration of microplastic fed to animals was 100 times higher than in tap water. At the same time, scientists used a mixture of organic substances, so they did not track the harm from each of them individually. According to the authors of the WHO report, such studies do not allow an unambiguous conclusion about the dangers of microplastics entering the body. However, biofilms formed on the surface of microplastics can indeed contain pathogenic bacteria, and plastic can serve as a vehicle for harmful microorganisms.
Studies ( 1 , 2 ) conducted by the European Food Safety Agency and the Food and Agriculture Organization of the United Nations showed that plastic particles larger than 150 micrometers probably do not stay in the body, but are immediately excreted in urine and feces, and smaller particles the body absorbs in small amounts (≤0.3 percent). More attention should be paid to nanoparticles with sizes less than 0.1 micrometers – up to seven percent of such particles are retained in the body. But it’s impossible to speak with confidence about the dangers of nanoplastics, since there is not enough data for this.
According to the report, it is quite possible to limit the ingress of microplastics into drinking water. To do this, you need to use less plastic, improve recycling programs for plastic waste, and thoroughly treat wastewater, which is the main source of contamination of drinking water with microplastics and other types of pollution. According to the WHO, 20 percent of wastewater is not subjected to even the second stage of treatment. While the most effective cleaning from microplastics occurs in the third stage of cleaning, for example, during ultrafiltration.
The authors of the report separately note that at the moment much more harm than microplastic is brought by pathogens and chemical pollution contained in drinking water. In 2016, 485 thousand people died from poisoning by water infected with pathogens in the world . According to 2017, about two billion people still drink water polluted by feces. Therefore, the priority now is not microplastics, but chemical and biological pollution.
However, the problem of microplastics in the coming years may become much more acute. Last year, researchers estimate that by 2030, 111 million tons of plastic waste will accumulate on the planet, which will have nowhere to go. China, which until recently was the largest importer of plastic, has banned the import of most of it into the country since 2018.