World Environment Day 2025: the invisible threat of plastic in drinking water
On World Environment Day 2025, a new concern takes centre stage: microplastic pollution in our drinking water. This is neither an isolated nor a recent phenomenon. As an article published in Current Opinion in Environmental Science & Health shows, reports of plastic particles in tap water have been appearing since 2017, with subsequent studies confirming their presence in both treatment systems and bottled water.
According to the same study, conducted by researchers Eerkes-Medrano, Leslie and Quinn, up to 9.24 particles per litre of tap water have been detected in countries such as the United States. In reusable PET bottles, concentrations reach an average of 4,889 particles per litre. The most worrying aspect is not the quantity, but the size: the vast majority are less than 5 microns in size, making them perfect candidates to cross human intestinal barriers and migrate to organs such as the liver or spleen.
Oceans get the limelight when it comes to plastic pollution. However, the problem has infiltrated one of the most intimate spaces of human life: drinking water
An independent analysis, reported in the article Microplastics in Drinking Water: Sources, Detection, Occurrence and Toxicity (Liu et al., 2024), further indicates that the type of polymer most frequently found in drinking water includes polyethylene, polypropylene, polyester and polyvinyl chloride. In many cases, these are fragments released from the water distribution systems themselves: pipes, valves or storage tanks, which are largely made of plastic materials.
According to the article, even the most advanced treatment plants are not able to completely remove these microparticles. In the Czech Republic, for example, already treated water had between 243 and 684 particles per litre. Conventional processes - coagulation, filtration and disinfection - are effective for pathogens and metals, but they are not designed to deal with such small particles.
The problem is not (only) in the oceans
For years, the environmental narrative around plastic has revolved around images of polluted beaches, islands of trash floating in the Pacific and seabirds with stomachs full of waste. But according to Singh et al.'s paper, published in Water Supply, microplastics are no longer just a marine problem: they are present in surface water, groundwater and even in so-called “clean” sources such as wells or bottled spring water.
Even the most advanced treatment plants are not able to completely remove these microparticles
Most surprisingly, they have also been detected in glass bottles, pointing to secondary sources of contamination: fibre-laden air, plastic utensils during bottling or even the clothing of operators in production plants. Singh and his colleagues warn that the problem is cross-cutting and requires a complete overhaul of the entire drinking water production chain, including storage, transport and marketing.
Going back to the study Microplastics in Drinking Water: Sources, Detection, Occurrence and Toxicity, (Liu et al., 2024), one of the least considered but potentially most relevant pathways for this contamination is atmospheric precipitation. Synthetic fibres may be suspended in the air and then deposited with rainfall in surface water sources. This would have direct implications for communities that collect rainwater for drinking, a vital resource in rural regions or developing countries.
What happens when plastic enters the body?
Questions about the effects on human health do not yet have conclusive answers. But the hypotheses are serious. According to the European study, a person consuming three litres of bottled water a day could be ingesting up to 15,000 plastic particles a day. While not all of them are able to penetrate into deep tissues, the smallest ones - especially those smaller than 1.5 microns - can. And once inside the body, they behave as double-edged agents: they are foreign bodies that can induce inflammation, and they also carry pollutants attached to their surface.
In animal models, it has been observed that microplastics can trigger oxidative stress, liver dysfunction and alterations in the immune system. In humans, although research is in its infancy, particles have already been detected in blood, faeces, placenta and even breast milk, according to reviews cited in the Indian article.
The risk is not only biological, but also psychological. The European article points to the existence of a possible ‘nocebo’ effect: the perception that one is consuming contaminated water can generate real adverse reactions in people, such as anxiety or gastrointestinal discomfort, even if the doses ingested are minimal.
The problem is compounded when the source of the water is considered. Water from rivers or reservoirs is more exposed to urban sources of pollution: sewage, surface runoff, industrial discharges. Groundwater sources appear to be more protected, but even they have shown the presence of microplastics in private wells, as documented by research in Ireland with concentrations of up to 6,500 particles per cubic metre.
And not all plastic that gets into the water comes from outside. PVC pipes, storage tanks, valves and filter membranes can also release fragments over time. The paradox is brutal: the very system that purifies and distributes water may be contributing to its contamination.
A silent crisis with a thirst for answers
A microplastic acts like a Trojan horse: heavy metals, pesticides, antibiotics and pathogenic microorganisms can be found attached to it
Exposure to microplastics through drinking water is only one of many possible routes. We also breathe them in, ingest them in food, touch them when handling everyday objects. But water has a symbolic and vital value that makes this situation an ethical and health priority.
Experts agree that more studies, better detection techniques and, above all, clear regulatory standards are needed. At present, there is no legal threshold for the presence of microplastics in water. Nor is there a consensus on how many are too many, or which type poses the greatest risk. And while the scientific debate rages, millions of people continue to drink without knowing what is in their glasses.
World Environment Day 2025 finds us at a silent crossroads. It is no longer enough to collect waste from beaches or ban bags in supermarkets. Plastic has infiltrated the most intimate cycle of life. And even if we don't see it, we carry it inside us.