A new study has found that the average bottle of water contains nearly a quarter million fragments of “nanoplastics” — plastic particles so small they can potentially gum up the machinery of human cells.
The findings published Monday in the Proceedings of the National Academy of Sciences (PNAS) open a disturbing window into a largely unmapped corner of plastic pollution — a region marked by plastics the approximate size of viruses or vaccine particles.
“We know microplastics are always in the environment,” coauthor Beizhan Yan of Columbia University told The Hill. “They are high up in the alpine, and down in the Marianas Trench, and quite a lot in New York City water as well.”
But microplastics are comparatively large and easy to measure, he said — measurable in millionths of a meter, they can be viewed using technology such as a scanning electron microscope.
The team was concerned by nanoplastics, which are particles thousands of times smaller — measurable in billionths of a meter. These smaller sizes can translate to greater danger, Yan said, “because the smaller the particle size, they are easy to get into the human bodies and then cross different barriers.”
The tiny compounds, Yan added, “can cross into the blood, and then can cross the different barriers to get into the cells,” interfering with the organelles — cellular organs — “and causing them to malfunction.”
Both micro- and nanoplastics have been found to have a wide array of dangerous impacts on a staggering array of key systems in the human body, as a December article in The Lancet found.
That survey of recent research found that tiny plastics can interfere with the chemistry of the human body — causing impacts both on and from the communities of microbes in our gut that help us digest food.
Micro- and nanoplastics can lead to “oxidative stress, inflammation, immune dysfunction, altered biochemical and energy metabolism, impaired cell proliferation, disrupted microbial metabolic pathways, abnormal organ development, and carcinogenicity,” the Lancet authors wrote.
So if these possibly dangerous compounds are found in bottled water, is it safe to drink?
Knowing about the potential risks of nanoplastics is only half the puzzle: Scientists also need to know what plastic polymers people are actually ingesting, and in which quantities, to determine how dangerous exposure may be.
That’s where the PNAS study comes in. Using an innovative new method of laser imaging, the scientists were able to identify plastics of far smaller sizes than ever before, including several of potential concern.
By running water from three common brands through an extremely fine-grained filter, they were able to trap particles measurable on a scale of billionths of a meter — and then to identify them.
Those plastics, however, comprised just 10 percent of the total nanoparticles the scientists found. They also found as-yet-unidentified bits of microscopic clays, metals and the black carbon from fires — as well as plastics so degraded that the imaging technology couldn’t pick them up.
The mere presence of objects this size is potentially disruptive to the body, because even if they are chemically inert, they are small enough to get into and disrupt cells, rather like sand in an engine.
But the chemical structure of plastics makes them a particular worry, the scientists said.
Because plastics are so similar to the chemistry of living creatures — petrochemicals, after all, come from the ancient residues of long-dead organisms — they can mimic or disrupt key biological functions by imitating the structure of the chemical messengers that help drive a wide range of bodily functions.
The scientists found a wide array of plastics in the bottles, but five types predominated — starting with polyethylene terephthalate (PET).
Since PET makes up the structure of the bottles themselves, that finding came as little surprise. It also aroused little concern, since PET is thought to be generally safe, although PET compounds can contain the toxic catalyst antimony.
But the water in the bottles was also found to contain a wide array of potentially dangerous nanoplastics that aren’t found in the bottles themselves — pointing to unknown sources of environmental contamination.
The scientists identified compounds such as nylon, which breaks down into toxic monomers as it degrades; polystyrene (or Styrofoam, commonly found in foam containers), which can break down into the suspected carcinogen styrene; and polyvinyl chloride (PVC), which can contain harmful additives such as lead or phthalates, and which has been linked to disruptions in the nervous or endocrine systems.
In what the researchers called an ironic finding, they also found plastic compounds in the water that matched the primary material in reverse-osmosis filters — suggesting that the plastics had leached into the water by the very process of filtration, co-author Naixin Qian of Columbia University told The Hill.
But the more dangerous particles like PVC and polystyrene seemed to have entered the plastic bottles with the “source water” that filled them, Qian said.
One possibility for how these may have gotten into that water: According to the Environmental Protection Agency, plastics plants emit aerosolized plastic gases that can get into the environment — entering the air, and therefore rain and water.
Regardless of the source of the nanoplastics, however, the Columbia team was particularly concerned about the health risks they pose — especially to the very young and very old.
These particles are small enough to cross the blood-brain barrier, which means they may lead to neural degeneration, particularly in the aged, in whom the barrier is “looser,” Yan said.
Exposure to micro- and nanoplastics may lead to cell damage in the nervous system, leading to increased risk of nervous system disorders and changes in behavior — with nanoplastics being more damaging than microplastics.
Nanoplastics are also small enough to cross the placenta into the generally sheltered environment of the womb, with unknown effects on a developing fetus.
For example, nanoplastics can get inside the umbilical veins that pull blood and waste products back from an embryo, interfering with cell processes that help dispose of cellular debris. They can also cause significant damage to embryonic kidney and reproductive cells, as well as impairing the normal growth of the fetus’s heart.
The developing fetal nervous system is also highly susceptible to damage from environmental pollutants, and nanoplastics may make it harder for the cells in fetal brain tissues to stay alive.
Given that these plastics enter the body through drinking water — and therefore, the digestive system — that could be the site of the most immediate impacts. Scientists have found that PET interferes with key microbial communities in the human gut, encouraging the growth of harmful bacteria while suppressing beneficial ones.
And studies in mice have found that micro- and nanoplastics lead to cell death in the lining of the intestine and increase inflammation in the gut.
If nanoplastics are able to get from the digestive system into the blood stream, impacts could be much further reaching — beginning with heart disease.
There’s strong evidence that this can happen. A 2021 study found that when rats were fed water embedded with polystyrene, or Styrofoam, nanoparticles, those particles began to accumulate in their hearts — leading to the heart swelling with collagen, making it harder for it to beat and ultimately leading to untimely death among heart cells.
And tests in a petri dish found that nanoparticles could destroy human red blood cells, although they weren’t able to replicate these findings inside actual blood.
But troubling as these lab findings are, the risks of nanoplastics currently remain a matter of conjecture. While such particles can be very toxic to cells at high doses, it is far less clear what happens at the levels that ordinary people are actually exposed to.
That gap in our knowledge results from a gap in technology — without any reliable way to identify nanoparticles in the environment, scientists haven’t been able to accurately calculate how many of the particles to expose cells to in order to test the impacts of exposure.
The Columbia findings take a key step toward closing that gap.
As such, perhaps more significant than the findings themselves — which are alarming, but hard to put into context — was the way the Columbia University team discovered them: through a new method that the scientists say will allow them to identify specific nanoplastics in soils, the air and human tissue.
That method is called Raman scattering — a method co-developed by study co-author Wei Min that hits an unknown plastic particle with a laser beam and decodes the frequency of the light that bounces back to tell what plastic polymer is inside.
Compounds such as PVC, PET and polystyrene are all “made of different chemical bonds,” Min said. “Those different chemical bonds have different, essentially intrinsic energy. And we can use laser to interrogate that energy and detect the interaction between the laser and that part of the chemical bonds.”
That allows researchers to “distinguish different chemical bonds, and therefore different types of polymers,” Min added.
But Qian cautioned that the team still doesn’t have enough information to say, for example, how the nanoplastics levels found in bottles compare with levels in tap water around the nation. (The team expects to begin rolling out results for the nation’s supply of tap water within the next two years.)
Qian said that the baton is now passed to toxicologists to determine how the levels the team found in bottled water translate to actual health impacts.
“We only did the first step in terms of quantifying the exposure: how much [nanoplastics] there are in the bottle of water that we [are] actually exposed to every day,” Qian said.
“Once you have the precise exposure then you’ll be able to actually do more research on its consequences of the toxicity,” she said.
@The HILL