Better taste and smell and health reasons. Those are the two main reasons why people drink bottled water, according to a study from the Autonomous University of Barcelona. Spain is, in fact, the third European country that consumes the most bottled water (up to 107 liters per inhabitant). That clashes with one thing: that bottled water is not only much more expensive than tap waterbut now we know that it also has micro and nanoplastics in quantities much greater than estimated.
The original study. Some researchers from Columbia University analyzed three popular bottled water brands in the United States (whose names have not been revealed) in search of micro and nanoplastics. To do this, they used a new technique called Raman stimulated scattering microscopy based on probing samples with two simultaneous lasers tuned to resonate specific molecules.
Analyzing seven common plastics, the researchers developed an algorithm to interpret the results. According to Wei Min, co-inventor of the technique and co-author of the study in question, “it is one thing to detect and another to know what you are detecting.”
The findings. On average, this study found that one liter of bottled water contains 240,000 detectable plastic fragments, between ten and 100 times more than previous estimates. Specifically, the researchers state that they found between 110,000 and 370,000 plastic fragments in each liter, of which 90% were nanoplastics. In that sense, it is important to remember the difference between micro and nanoplastics:
- Microplastics: those whose size varies between 100 nanometers and five millimeters.
- Nanoplastics: those whose size is equal to or less than 100 nanometers.
The most common plastics. To no one’s surprise, one of the most common plastics was polypropylene terephthalate, better known as PET. It is the material that many bottles are made of. “It probably enters the water by breaking off pieces when the bottle is squeezed or exposed to heat,” say the researchers, who cite another study that suggests they can also break off when repeatedly opening and closing the cap.
Usual. And although the presence of PET is common, this plastic is surpassed by polyamide, a type of nylon that “probably comes from the plastic filters used to supposedly purify water before bottling it,” says Beizhan Yan, researcher of the study. Other common plastics the researchers found were polystyrene, polyvinyl chloride and polymethyl methacrylate.
And the rest? The technique used includes the seven most common plastics, but there are many other plastics. According to exposes Columbia University, “the seven types of plastic the researchers looked for only represented about 10% of all the nanoparticles they found in the samples; they have no idea what the rest are. If they are all nanoplastics, it could be tens of millions per liter.”
And what about those sold in Spain? That’s what he wanted to find out a study by the CSIC and the Barcelona Institute of Global Health. They have developed a technique to quantify particles between 0.7 and 20 micrometers, as well as the chemical additives released into the water and, for this study, they analyzed 280 samples of 20 commercial water brands. Only one of the brands did not contain microplastics, but all 280 samples contained plastic additives.
More specifically. The result is that, on average, one liter of water contains 359 nanograms of micro- and nanoplastics, an amount comparable to that obtained in the tap water found in a previous study made by the same group. “The main difference we found is the type of polymer: in tap water we found more polyethylene and polypropylene while in bottled water we detected mostly polypropylene terephthalate (PET), although also polyethylene,” said Cristina Villanueva, ISGlobal researcher and author of the study.
Lots of microplastic. Considering that we drink two liters of water a day, the authors estimate “an intake of 262 micrograms of plastic particles per year.” Regarding additives, 28 plastic additives have been detected, mostly stabilizers and plasticizers. According to the researchers, “our toxicity study showed that three types of plasticizers presented a greater risk to human health and, therefore, should be considered in risk analyzes for consumers.”
In that sense, other studies have discovered the presence of microplastics in atheromatous plaques in the arteries, which increases the risk of heart attack. From the American Diabetes Association they also ensure that some components found in bottles, such as BPA and the aforementioned microplastics, increase insulin resistance, thus reducing its effectiveness.
Images | Jonathan Chng in Unsplash
*An earlier version of this article was published in February 2024
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