Plastic pollution continues to spread and new studies show the extent of the problem. Advances in analysis systems show, for example, the existence of microplastics and nanoplastics in packaged water in a proportion hitherto unknown, as indicated by a study led by experts from the Climate School of Columbia University (United States) whose results have been published (January 8) in the journal Proceedings of the National Academy of Science (PNAS)
"Using newly refined technology, researchers have entered a completely new plastic world: the little-known realm of nanoplastics, the generation of microplastics that have decomposed even further," highlights Columbia University in the presentation of the results of their equipment. "For the first time, they counted and identified these tiny particles in bottled water. They found that, on average, one liter contained about 240,000 detectable plastic fragments, between 10 and 100 times more than previous estimates, which were based mainly on larger sizes. ", details the prestigious American university.
Nanoplastics are so small that, unlike microplastics, they can pass through the intestines and lungs directly into the bloodstream and from there travel to organs such as the heart and brain, also in the placenta and fetus, explain the researchers. authors of the new study. The analysis system now presented will facilitate the discovery of nanoplastics where until now their presence could only be intuited, said study co-author Beizhan Yan, an environmental chemist at the Lamont-Doherty Earth Observatory at Columbia University.
Scientific and citizen attention to the possible presence of plastics in bottled water increased in 2018 with the publication of a study that indicated an average of 325 particles per liter; a figure that increased in subsequent studies.
Some experts developed methods to detect nanoparticles starting in 2018 but could not detail these types of materials, said the lead author of the new study, Naixin Qian, a graduate student in chemistry at Columbia University. Thus, global estimates of nanomass could be provided, but for the most part they could not count individual particles or identify which ones were plastics or other materials.
The new study uses a new application of the technique called stimulated Raman scattering (SRS) microscopy, which was co-invented by study co-author Wei Min, a biophysicist at Columbia University.
With this new technique, samples are probed with two simultaneous lasers that are tuned to resonate specific molecules. Focusing on seven common plastics, the researchers created a data-driven algorithm to interpret the results. “It's one thing to detect, but another to know what you're detecting,” Min said.
The researchers tested three popular brands of bottled water sold in the United States (they declined to name which ones), analyzing plastic particles down to just 100 nanometers in size. They detected between 110,000 and 370,000 particles in each liter, 90% of which were nanoplastics; the rest were microplastics. They also determined which of the seven specific plastics they were and plotted their shapes, qualities that could be valuable in biomedical research.
One of the most common was polyethylene terephthalate or PET. This wasn't surprising, since that's what many water bottles are made of. (It is also used for bottled soft drinks, sports drinks, and products like ketchup and mayonnaise.) It probably enters the water when chunks break off when the bottle is squeezed or exposed to heat. A recent study suggests that many particles enter the water when the lid is repeatedly opened or closed, and small particles are worn away.
The authors indicate that even filters created to retain nanoplastics are emitters of these compounds and point out what they describe as "a somewhat disturbing idea": the seven types of plastic sought in the new study represent only about 10% of all nanoparticles that they found in the samples and have no idea what the others are.
Researchers are now looking beyond bottled water. “There is a huge world of nanoplastics to study,” Min said. He noted that, by mass, nanoplastics comprise much less than microplastics, but “it is not the size that matters. "It's the numbers, because the smaller things are, the more easily they can enter us."
Among other things, the team plans to analyze tap water, which has also been shown to contain microplastics, although much less than bottled water. Beizhan Yan is running a project to study microplastics and nanoplastics that end up in wastewater when people wash clothes; according to his calculations so far coming from synthetic materials that make up many items. The study of the presence of nanoplastics in snow or ice from, for example, West Antarctica is also planned.
Additionally, the Columbia team is collaborating with environmental health experts to measure nanoplastics in various human tissues and examine their neurological and developmental effects. "It's not totally unexpected to find so much of this material," Qian said. "The idea is that the smaller things get, the more there is." The study was co-authored by Xin Gao and Xiaoqi Lang of Columbia's chemistry department; Huipeng Deng and Teodora María Bratu de Lamont-Doherty; Qixuan Chen of Columbia Mailman School of Public Health; and Phoebe Stapleton of Rutgers University.
