Boiling Water: Can It Help Us Escape Microplastics?

In recent years, the issues of microplastics and nanoplastics have drawn increasing attention. These tiny plastic particles, invisible to the naked eye, are now known to be widespread not only in oceans and rivers but also in the tap water people drink every day. Global surveys have shown that more than eighty percent of tap water samples collected from fourteen countries contain plastic particles, most commonly polystyrene, polyethylene, and polypropylene. Once these particles enter the human body, they may accumulate in tissues and have been linked to long-term health concerns such as disturbances in gut microbial communities, insulin resistance, and metabolic disorders in the liver. Although the full health implications are still being investigated, it is becoming increasingly clear that microplastics represent a form of invisible pollution that can no longer be ignored.

（Courtesy of Yu Z et al. (2024) ）

Conventional drinking water treatment systems are capable of removing many suspended materials and chemical contaminants, yet they struggle to eliminate extremely small particles, particularly nanoplastics. More advanced filtration technologies do exist, but their high cost makes them difficult to implement on a global scale, especially in regions with limited resources. This raises an important question: is there a simple and practical method that ordinary households can use to reduce the amount of plastic particles consumed through drinking water?

A recent study offers an unexpectedly familiar answer—boiling water.

In water with relatively high hardness, meaning it contains larger amounts of dissolved calcium carbonate (CaCO3), boiling can remove a substantial proportion of plastic particles. When the concentration of calcium carbonate exceeds about 120 mg per liter, boiling the water can eliminate at least eighty percent of plastic particles ranging from 0.1 to 150 micrometers in size. The underlying reason lies in the chemical processes that occur during heating. As water approaches the boiling point, calcium carbonate begins to crystallize and form solid deposits commonly known as limescale. During this crystallization process, nano- and microplastics become attached to the newly formed crystals or become encapsulated within them. Once trapped inside these mineral structures, the plastic particles settle out of the water together with the precipitating minerals. In other words, the same mineral scale that often causes inconvenience in kettles and pipes can inadvertently help remove plastic particles from drinking water.

Experimental observations illustrate how strongly temperature influences this process. When water was gradually heated from 25°C to 90°C, only about thirty percent of plastic particles were removed. However, once the water reached the boiling point of 100°C, the removal efficiency rose sharply to approximately eighty-four percent. Microscopic imaging further revealed that calcium carbonate crystals begin forming directly on the surface of plastic particles before gradually enveloping them. These mineral structures appeared in several crystalline forms, including calcite, aragonite, and vaterite. Although the shapes and structures of these crystals differ, their ability to capture plastic particles appears broadly similar.

Water hardness also plays a major role in determining how effectively boiling can remove microplastics. In water containing around 180 mg per liter of calcium carbonate, more than eighty percent of plastic particles were removed after boiling. When the concentration increased to roughly 300 mg per liter, the removal efficiency rose to about ninety percent. Even in soft water, where calcium carbonate concentrations are below 60 mg per liter, boiling was still capable of eliminating roughly one quarter of plastic particles. The chemical properties of the plastic particles themselves can also influence the process. Plastics carrying negatively charged surfaces, such as unmodified particles or those containing carboxyl groups, tend to attract calcium ions more readily, allowing mineral crystals to nucleate and grow more easily on their surfaces. Positively charged plastics, such as those bearing amino groups, initially resist this interaction due to electrostatic repulsion. However, as temperature rises toward the boiling point, these charge effects weaken, and most types of plastic particles eventually become incorporated into the precipitating calcium carbonate crystals.

Researchers also attempted to estimate how boiling water might influence human exposure to microplastics on a global scale. By combining experimental removal efficiencies with reported concentrations of plastic particles in tap water from multiple regions, they estimated that individuals who regularly drink boiled water may ingest two to five times fewer microplastic particles per day compared with those who drink untreated tap water. A simple change in daily habit could therefore significantly reduce the amount of plastic entering the human body through drinking water. Nevertheless, the effectiveness of boiling depends on local water chemistry. In areas where water is extremely soft or where plastic contamination is unusually high, the reduction may be less pronounced.

Microplastic pollution is ultimately a global environmental challenge that spans the entire lifecycle of plastics—from production and consumption to waste management and recycling. Addressing the problem will require long-term changes at industrial and societal levels. Yet while large-scale solutions are being developed, everyday practices may still provide meaningful protection. Something as ordinary as boiling drinking water, a habit that has existed for centuries in many cultures, may unexpectedly serve as a modest yet effective defense against the growing presence of plastic particles in our environment.

Author: Shui Ye-You

Reference:

Yu Z et al. (2024). Drinking Boiled Tap Water Reduces Human Intake of Nanoplastics and Microplastics. Environmental Science & Technology Letters.

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