Microplastics in drinking water – how much are we really consuming?

Microplastics have become part of our daily diet. However, opinions as to how much of it we consume and from what sources it comes are sharply divided. The presence of plastics, ranging in size from a few millimeters to a few nanometers, has been confirmed, among others. In beer, wine, honey, salt, processed foods and even fresh fruits and vegetables. However, it is the information about the presence of microplastics in drinking water that has hit the public particularly hard and has been the subject of debate in many media outlets.

Adult water intake varies by gender, climate, diet and physical activity. The guidelines state that an adult (weighing about 60 kg) should consume about 2 liters of water daily. At the same time, we must remember that water can carry not only minerals or trace elements, but also micropollutants (substances of anthropogenic origin with concentrations in the range of nanograms and micrograms per liter of water sample). The researchers estimated that the average European’s daily exposure to microplastics could be 1,260 particles for tap water consumed and up to 9,800 particles for bottled water.

However, the presence of microplastics in drinking water depends on a number of factors, including. from the type and location of its intake, its environment, the local scale of urbanization and industry. But also on the test sampling methods themselves and their volumes, how the particles are identified, the detection limit or current weather conditions. As a result, data on the amount and type of plastic particles in drinking water are highly disparate. Is tap water a significant source of microplastics? And are conventional tap water treatment processes insufficient to protect our health from pervasive pollution?

Microplastics at the source – how many particles are in water resources?

In Europe, both surface water and groundwater are sources of resources for drinking. However, according to the European agency WISE – Freshwater, most of the water for consumption is taken from surface water, about 75 percent. comes from rivers and reservoirs, and 25 percent. from groundwater. Although each time the treatment technology is adapted to the original quality of the captured water so that it ultimately meets drinking standards, the origin of the water is of great importance, especially in the context of the presence of microplastic particles.

The fate of microplastics and their transport in aquatic environments is influenced by, among other things. density, particle shape and size, as well as links to flora and fauna. All these factors also interact with surface water characteristics, among others. With the speed of flows, seasonal variability, depth or bottom topography. Detected concentrations of microplastics in European surface waters typically ranged from 1 to 100 particles per cubic meter.

These are much lower values than those quoted in North America or Asia. The most common polymers were fragments and fibers of polyethylene and polypropylene. In addition, periodically higher concentrations were observed more often in standing reservoirs than in rivers. A study conducted in the Mazurian National Park found that 39 percent of the. all microplastic fibers detected in the river are less than 1 millimeter in diameter, and the particles can be carried by the wind even into water bodies that are not in contact with sewage (a significant source of microplastics in surface water).

An important store of microplastics in surface waters is bottom sediments. In European river sediments, concentrations ranged from 18 to 72,400. particles per kilogram of sample. Studies conducted in the German part of the Elbe River basin have shown that particle concentrations in sediments can be as high as 600,000. times higher than in the aqueous phase. With average concentrations ranging from 5 to 14 particles per cubic meter of water. Again, this analysis was dominated by microplastics in the form of fibers (46.5 percent), and to a lesser extent by fragments (22.9 percent) and granules (20.1 percent).

Although groundwater is more strongly protected from anthropogenic pollution than surface water, it too is affected by the presence of microplastics. The number of particles detected during the tests ranged from 0 to 44 in a liter of water. With more than 70 percent. particles detected were less than 200 micrometers in size, which is particularly worrisome given the higher migration and accumulation capabilities of smaller particles, known as nanoplastics, in our bodies. The abundance of microplastics in groundwater samples was influenced to varying degrees by human activity (land use) and population density. The number of particles was higher than the overall average mainly near areas used for agriculture and gas stations.

Are water treatment plants able to remove microplastics?

Studies show that water treatment plants fed by groundwater record much lower concentrations of microplastic particles than those fed by surface water. For example, the average number of particles at a German treatment plant fed by groundwater was 0.0007 particles per liter, while in the Czech Republic, where water is more often drawn from surface reservoirs and rivers, the number of particles ranged from 338 to 628 in the same amount of sample.

Conventional water treatment processes have the ability to remove at least some of the particles present. The literature reports that 70 percent. Microplastics are already retained at the filtration stage by the porous (sand) bed, and the final removal is 97 percent. In treated water after an activated carbon filtration process. About 93 percent. particles in the 125-250 micrometer size range, and 54 percent. in the range of 63-125 micrometers are removed by sand bed filtration. In the initial ozonation and sedimentation processes, the efficiency of microplastic removal is 81-88 percent.

Depending on the source, microplastic removal efficiencies in conventional water treatment processes range from 46 to 100 percent, with the lower range of efficiencies noted for smaller particles. Some researchers, however, report the risk of secondary microplastic contamination of the water as a result of the release of accumulated particles from the deposit or abrasion of plastic components present in tanks or pipelines. A summary of the effectiveness of conventional drinking water treatment processes is shown in Figure 1.

What is the scale of microplastic contamination in the tap water?

Currently, plastics are the main material used in water transportation. Although they are resistant to corrosion, fragmentation and abrasion of wires and buses can occur. An estimated 83 percent. samples of tap water flowing to consumers may contain microplastics. With their number varying from 0 to 930 particles per liter. Research conducted among others. in Belgium, Denmark, Italy, Norway and Germany showed that the number of particles in European tap water most often oscillates near the limit of quantification.

With that said, some researchers stress that this detectability may be affected by sample contamination during analysis and other contaminants falsely attributed to the microplastics group. Opinions are divided on how much the stage of transporting water with plastic materials affects its contamination with microplastics. The researchers stress that the particles found in tap water are not related to materials directly present in the networks.

The release of microplastics can also be seasonal. Analyses from Chinese cities show that the number of particles released increases in the warmer months (between April and July). This phenomenon may have to do with the effect of temperature on the increase in plastic degradation in the network, but it may also be due to the lower flows of the rivers (and therefore higher pollution) from which water is drawn into the network. This is particularly worrisome in the context of rising global temperatures caused by climate change. A comparison of the average number of microplastics in different matrices is shown in Figure 2.

Is bottled water a bad choice?

Microplastics in bottled waters can enter at all stages of production, so we are seeing an increased concentration of particles in this matrix. Studies show that particularly rapid growth occurs at the bottle cap stage. It is estimated that the number of particles can increase from 1 to as many as 317 particles per liter. The recent increase in interest in the topic of the presence of plastic particles in bottled water is primarily due to improvements in methods for determining microplastics.

Nearly 80 percent. particles found in plastic bottles are between 5 and 20 micrometers in size. Previously, detection of microplastics with such small diameters was impossible. Most of the particles identified in bottled water consist of polyester, as much as 84 percent. is polyethylene terephthalate (PET), which is the main plastic used in their production. With the development of modern analytical methods and improvements in sampling methods, the water environment is revealing new contaminants with still unknown impacts on humans and non-humans alike.

Nanoplastic in bottled water can make up from 50 to 90 percent. detected particles. A recent study alerts that the number of nanoplastics in a liter of bottled water could be as high as 240,000. The research, which appeared in the journal Science Advances November 17, 2023. have confirmed that nanoplastics interact with proteins found in the brain and may be responsible for changes linked to Parkinson’s disease and some types of dementia. Currently, Parkinson’s disease is called the fastest growing neurological disease in the world. And many data suggest that environmental factors may play a significant role in its development, although most have not been identified.

Micro- and nanoplastics are currently among the leading environmental pollutants. They are of great interest and concern for good reason, as they are a vector for many dangerous chemicals and antibiotic resistance genes. The ambitious goal of a 30 percent reduction. emissions of microplastics into the environment by 2030 can make a real contribution to reducing exposure of the water and land environment to particles, which is a benefit for protecting the health of future generations. We are not able to completely eliminate plastics from our daily lives, in many applications they are absolutely essential, but it is important to build a foundation for informed consumer choices. Tap water is still a much less significant source of microplastics than food (especially highly processed food) or the urban dust we breathe.

Dr.-Ing. Edyta Łaskawiec – water and wastewater technologist, assistant professor in the Department of Environmental Biotechnology at the Silesian University of Technology, science popularizer, author of an educational profile on Instagram platform: wastewater_based.doctor.