The bottled water you drink may contain hundreds of thousands of microscopic pieces of plastic, new research shows.
Microplastics—tiny bits of plastic that range in size from 1 nanometer to 5 millimeters in diameter—have been widely studied in recent years and have been found virtually everywhere on Earth, from the far reaches of the Arctic to the lining of human placentas.
One analysis estimated that Americans ingest more than 44,000 microplastic particles every year and inhale more than 46,000. But until recently, scientists couldn’t reliably measure even smaller particles, called nanoplastics.
Nanoplastics are less than 1 nanometer in size—a sheet of paper is about 100,000 nanometers thick, and a strand of DNA is 2.5 nanometers—and experts believe that if ingested, these bits of plastic can cross the blood-brain barrier, which protects the brain from toxins.
The new study, published in January in the Proceedings of the National Academy of Sciences, estimated a human may consume as many as 370,000 nanoplastic particles in one liter of bottled water.
“It’s sobering at the very least, if not very concerning,” Pankaj Pasricha, MD, MBBS, chair of the department of medicine at the Mayo Clinic, who was not involved with the new research, told Health.
Examining the Plastic in Bottled Water
For the new study, researchers tested three brands of bottled water sold in the United States, though the authors did not disclose which brands they included. They found that the water harbored an average of 240,000 pieces of plastic, 90% of which were nanoplastics.
The remaining 10% were microplastics, about a thousand times larger than nanoplastics.
A 2018 study first identified microplastics in 93% of samples taken from 11 types of bottled water sold in nine different countries. The average was more than 300 microplastic particles per liter. However, the new study found a plastic bottle of water may contain more than a thousand times as many nanoplastics.
“The concern with the nanoplastics in particular is that they have been found in human lungs and blood,” Phoebe Stapleton, PhD, an associate professor of pharmacology and toxicology at Rutgers University who co-authored the new study, told Health. “It means they are able to get through these traditional barriers. Now the questions are how long do they stay there, how do they get back out, and what are they doing when they are there?”
The team identified seven different plastic chemicals in their samples. Some chemicals, including polyethylene terephthalate (PET) and polyethylene (PE), were found in all three brands. The water packaging’s bottles and caps were made from these types of plastic, leading the authors to believe bits of the material shed into the water during packaging and transportation.
Other types, including polyvinyl chloride or vinyl (PVC), polyamide nylon (PA), polypropylene (PP), and polystyrene (PS), which is typically used in plastic foam, were likely introduced to the water before it was packaged since the packaging was not made from these materials.
“Because these nanoplastics are so small, they cannot get filtered out. They may have been in that source water,” said Stapleton, adding that nanoplastics may also have been introduced during the filtration process itself.
Because plastic is so ubiquitous in the environment, and plastic packaging is not the only way nanoplastics appear to get into food and water, the particles are virtually impossible to avoid completely, Pasricha said.
However, “it’s certainly possible that air or water filters could be designed to filter them out, and now that we know how to measure these particles, I am sure a lot of efforts towards that technology will happen,” he said.
Is Plastic Bad for Human Health?
At least 4,000 known chemicals are used to make plastic. Scientists don’t know how the vast majority may or may not impact human health.
Pasricha said he expects studies like this to be a call to action for the scientific community to better understand how different types of plastic impact human health.
“Scientists have speculated for a long time that these particles, whether inhaled or ingested, have the ability to do significant damage to the body,” he said. “It’s still not fully clear how they do that; they could do that because of their intrinsic toxicity, or they could be carriers of toxic materials even though they themselves are relatively inert.”
Bisphenol A (BPA), a chemical additive used in some plastics, has been found to be a reproductive and developmental toxin. For this reason, the Food and Drug Administration banned BPA in baby bottles and sippy cups in late 2012, but it’s still allowed in food and beverage packaging.
“Cells are able to take in plastics, especially nanoplastics, internalize, and bring them into the cells,” Stapleton told Health. “There has been some evidence of oxidative stress, changes to DNA and inflammation due to those particle-cell interactions.”
Oxidative stress occurs when there is an imbalance between free radicals and antioxidants, which neutralize free radicals. If not kept in check, free radicals react with other chemicals in the body and can damage fatty tissue, DNA, and proteins, leading to diseases such as diabetes and cancer.
Most research into plastic compounds’ effects on health has been conducted on animals, not humans. While some human studies have found phthalates, one of the most common chemicals used to make plastic, may cause more weight gain during pregnancy and increase a woman’s risk for gestational diabetes, these studies have not yet proven cause and effect.
Scientists are concerned that both phthalates and BPA are endocrine disruptors, meaning the chemicals interfere with hormones. This can particularly impact people who are assigned female at birth (AFAB). The Environmental Protection Agency recognizes DEHP, one of the most widely used phthalates, as a probable carcinogen, but its use hasn’t been restricted like BPA’s.
Most of the current evidence is circumstantial. Still, it isn’t a wide leap to assume ingesting plastic particles can have health impacts in the same way other particles, such as those found in air pollution, have been shown to harm human health, Pasricha said.
“These small particles are potentially of more concern to your health,” he said. “The smaller the particle, the more likely it can get into cells and penetrate the blood-brain barrier, and they are present in everyday sources like bottled water in quantities that appear to be even larger than microplastic particles.”
The Challenges of Studying Plastic
One reason for the lack of information about plastic’s health impacts is that scientists still know little about the material itself.
This was illustrated in a 2019 study examining eight common classes of plastics used in household items, including yogurt cups and sponges. Researchers found that six out of the eight contained toxic chemicals, but of the 1,400 total compounds the products contained, the team could only identify 260 of them.
“Plastic has the ability to absorb other things, too,” Stapleton said. “If it comes into contact with organic material or metals, it can release those compounds in the body as well.”
Although it’s still unclear exactly how plastics and the chemical additives used to make everyday plastic products may interfere with human health, one thing is certain: Humans are regularly ingesting plastic.
“We have now seen the extent of exposure, and it’s certainly cause for concern,” Pasricha said.