In recent years, numerous studies have found traces of plastic in the most remote places in the world, including both polar circles. Concerns about this type of contamination have led to bans on plastic cutlery or glitter. This material contaminates not only entire objects that take centuries to decompose, but also the smaller particles released from them. Microplastics, fragments ranging from five millimeters to a millionth of a meter, fifty times thinner than a human hair, have been the focus of attention so far, but it is known that plastic can still be broken down into even smaller fractions, almost ad infinitum.
Nanoplastics, down to a billionth of a meter, are so small that they can penetrate all human tissues, travel through the bloodstream and reach the brain or placenta of pregnant women. Although there are concerns about its health effects, studies are still in their early stages and even knowledge of its occurrence is limited. This week, researchers at Columbia University publish an analysis in the journal PNAS examining whether nanoplastics are present in bottled water, what types, and in what quantities. Using a technique called stimulated Raman scattering microscopy, whose inventors include study co-author Wei Min, they found that, on average, about a quarter of a million of these plastic pieces could be found in each liter.
One of the most common components of these nanoplastics was PET (polyethylene terephthalate), the material commonly used to make plastic bottles. According to those responsible for the study, these particles can be released when the bottles are heated, when they are squeezed, or when the cap is opened and closed. However, polyamide was more common, a type of nylon that co-author Beizhan Yan said in a statement from Columbia University (US) likely comes from the plastic filters used before bottling water to supposedly purify it. The remaining most common materials are usually used in various industrial processes related to bottling.
“Methods have been developed to detect nanoparticles, but it was not known what they were studying,” explains Naixin Qian, co-author of the study. The new method allowed them to observe and individually count the amounts of nanoparticles from seven types of common plastics. However, this selection only represents 10% of the particles found. It is not known whether the residue is plastic or other types of particles. This shows how complicated it is to analyze such tiny elements and how much is still unknown about the composition of many of the things we consume.
A review of studies published in January by eBioMedicine notes that increasing evidence suggests that exposure to microplastics and nanoplastics can have negative effects on various human organs. However, the authors caution that the mechanisms by which these effects might occur, or whether long-term exposure to these particles increases the risk of disease, are unknown. Although the effects of some specific particles have been studied to assess their toxicity, in general there are many of them that – as this study shows – are abundant in commonly consumed products or in the environment and that have not been studied in detail. The authors of the work, led by Jorge Bernardino de la Serna from Imperial College London, state that future studies should examine exposure to micro- and nanoplastics, taking into account realistic concentrations, each individual's susceptibility to these substances or the dose required for one have a significant negative effect.
The authors of the study also want to use their technique to analyze tap water, in which microplastics were also found in significantly lower concentrations than in bottled water. In a world where nearly 400 million tons of plastic are produced each year and the material is used to make almost everything, there are countless opportunities for plastic nanoparticles to continue to be released and distributed into the environment or into living organisms to integrate. Determining the amount and composition of these particles more precisely is a step toward assessing the extent of the problem and its potential impact on health, and considering ways to reduce potential threats.
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