Research Demonstrates High Levels of Microscopic Plastic Pieces in Bottled Water

New research indicates that the bottled water you consume could be filled with hundreds of thousands of tiny bits of plastic, known as microplastics.

Microplastics - small fragments of plastic that range between 1 nanometer and 5 millimeters in diameter - have been extensively researched in recent years. They have been found practically everywhere on Earth, even in human placentas and in remote Arctic areas.

One estimation suggests that Americans consume over 44,000 microplastic particles every year, and inhale an additional 46,000. Until recently, however, scientists lacked a reliable method for measuring even smaller particles known as nanoplastics.

Nanoplastics are smaller than 1 nanometer - for comparison, a sheet of paper is roughly 100,000 nanometers thick, and a DNA strand is 2.5 nanometers. Experts warn that these tiny plastic particles may, once ingested, cross the blood-brain barrier that typically protects the brain from toxins.

A recent study, published in January in the Proceedings of the National Academy of Sciences, calculated that a single liter of bottled water could contain as many as 370,000 nanoplastic particles.

"It's sobering at the very least, if not very concerning," says Pankaj Pasricha, MD, MBBS, chair of the Mayo Clinic's Department of Medicine, who did not participate in the study.

The study's authors examined three bottled water brands sold in the United States, but did not reveal which brands these were. Their findings indicated that the water contained an average of 240,000 pieces of plastic, 90% of which were nanoplastics, and 10% larger microplastics.

An earlier study in 2018 identified microplastics in 93% of samples taken from 11 bottled water brands from nine countries, with over 300 microplastic particles found per liter on average. However, the newer study shows that a water bottle might contain more than a thousand times as many nanoplastics.

Phoebe Stapleton, PhD, Associate Professor of Pharmacology and Toxicology at Rutgers University and co-author of the study, expresses concerns about nanoplastics as these have been identified in human lungs and blood. This means they can cross traditional barriers. The questions now are how long they stay, how they exit the body, and their potential impacts once inside.

Seven different plastic chemicals were discovered in the samples. Certain chemicals like polyethylene terephthalate (PET) and polyethylene (PE) were found in all three water brands. The bottles and caps were made from these types of plastic, which led the research team to believe that small pieces of the material leaked into the water during packaging and transportation.

Other types, including polyvinyl chloride or vinyl (PVC), polyamide nylon (PA), polypropylene (PP), and polystyrene (PS), usually used in plastic foam, were likely present in the water before its packaging as the packaging materials did not contain these types.

Due to the tiny size of these nanoplastics, they cannot be filtered out. They could have been in the source water, adds Stapleton, and might also have been introduced during the filtration process

Given the omnipresence of plastic in the environment, and since nanoplastics can enter food and water through more than just plastic packaging, completely avoiding these particles seems virtually impossible, warns Pasricha. However, he believes it's possible to design water or air filters to remove them, a development that may now accelerate with the new capacities for measuring these particles.

There are at least 4,000 known chemicals used in the creation of plastic, and scientists are still unsure about how most of these impact human health.

Pasricha anticipates that studies like this will mobilize the scientific community to deeper understand the relationship between different types of plastic and human health.

He notes that scientists have long speculated that such particles could cause significant bodily damage when inhaled or ingested, although it's still uncertain whether their toxicity is inherent or if they carry other toxic substances, given that they themselves are relatively inert.

Bisphenol A (BPA), a chemical additive often found in plastics, has been identified as a reproductive and developmental toxin. Consequently, the Food and Drug Administration banned the use of BPA in baby bottles and sippy cups in 2012, although it is still allowed in other 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.”

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.