Drinking water from disposable plastic bottles may be passing hundreds of thousands of potentially harmful tiny plastic particles into our bodies, a new study finds.
Research published Monday in the Proceedings of the National Academy of Sciences found that a liter of water in a plastic bottle contained an average of about 240,000 detectable plastic fragments — 10 to 100 times more than previous estimates. A liter is a little more than 32 ounces, or one quart.
“The existence of microplastics [particles measuring 1 micrometer, or 0.001 millimeter, to 5 millimeters in length] and possibly even nanoplastics [less than 1 micrometer] has recently raised health concerns,” wrote Beizhan Yan, PhD, an environmental chemist at Columbia University’s Lamont-Doherty Earth Observatory in Pallisades, New York, and his coauthors.
For context, a human hair is about 70 micrometers across.
“In particular, nanoplastics are believed to be more toxic, since their smaller size renders them much more amenable, compared with microplastics, to enter the human body.”
While their true impact on human health is yet to be determined, micro- and nanoplastics are so small that they can pass through the protective tissues of the intestines and lungs and directly enter the bloodstream. From there, the fragments can travel to organs including the heart and brain. They can also cross through the placenta to the bodies of unborn babies.
A Potential Looming Public Health Threat
“Microplastics have been increasing in the environment for quite some time and now science is catching up to reveal the impact they are having on our health,” says Tracey J. Woodruff, PhD, MPH, director of the Program on Reproductive Health and the Environment at the University of California in San Francisco.
Woodruff led a team that looked at how microplastics in the environment adversely impact health for a 2023 California Senate committee report. Although significant clinical human trials have yet to be conducted on the topic, animal and lab studies suggest that microplastics may raise cancer risk and pose harm to the human digestive, reproductive, and respiratory systems, according to the report.
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Research also has linked micro- and nanoparticles to disrupting thyroid and endocrine function, obesity, and insulin resistance.
“Concerns about nanoplastics are warranted due to their ability to penetrate biological systems and carry various environmental pollutants,” says Dr. Yan. “It is important to note that the mere detection of nanoplastics in bottled water does not directly indicate immediate health risks. The impact depends on factors like toxicity, concentration, exposure duration, and the body’s response to these nanoparticles.”
He notes that further study is needed to assess the true health risk of these tiny plastic fragments, and that research then may be used to guide safety measures and regulations.
For those wanting to limit their exposure, Woodruff says that drinking tap water or water in glass bottles may be a safer alternative.
A New Microscopic Technique Identifies Tiniest Particles
For their investigation, Yan and collaborators chose three popular brands of bottled water sold in the United States; they declined to name which ones. Using a unique approach involving two simultaneous lasers that are tuned to make specific molecules resonate, the scientists identified 110,000 to 370,000 plastic particles in each liter. About 90 percent of these bits were nanoplastics, while the rest were microplastics.
“When we’re looking at environmental chemical exposures, early methods tend to underestimate amounts, so I’m not surprised that this more sensitive measure was able to identify more particles, especially since there is such widespread use of plastics in water bottles,” says Dr. Woodruff, who was not involved in the study.
One of the common types of plastic identified in the analysis was polyethylene terephthalate, or PET. This was not unexpected, since PET is used to make many water bottles as well as containers for sodas, sports drinks, and products like ketchup and mayonnaise.
Yan and his team, however, were surprised to find that PET was outnumbered by other plastic particles, including polyamide, a type of nylon. He pointed out that this type of plastic, ironically, probably comes from plastic filters used to supposedly purify the water before it is bottled.
“We had the impression that the majority of plastic particles inside bottled water would be PET particles of a few hundred nanometers in size,” says Yan. “This was incorrect. PET particles were found to be mostly in micron size, contributing only a limited portion of the particle population. There are many smaller particles other than PET that have greater particle numbers.”
In follow-up research, Yan and his colleagues intend to look at tap water, which also has been shown to contain microplastics, though far less than bottled water. Although tap water may not contain the amount of microplastics that slough off from bottles, Yan warns that we cannot surely say yet that tap water is safer, as it may contain higher levels of other pollutants, such as heavy metals and black carbon.
“This study illuminates the previously underestimated presence of nanoplastics in the water we consume,” says Yan. “Further research is essential to determine the extent of human exposure and to evaluate the environmental and health consequences of these nanoplastics.”