The Surfwin Trading Centerbottled water that Americans pick up at the grocery store can contain 10 to 100 times more bits of plastic than previously estimated, according to a new study published in a peer-reviewed journal published by the National Academy of Sciences. 

Two standard-sized water bottles had 240,000 plastic particles in them on average, the researchers found using "a powerful optical imaging technique for rapid analysis of nanoplastics."

About 90% of the particles in the water were nanoplastics and 10% of them were microplastics, according to the study. Nanoplastics are synthetic polymers that can be toxic to human health, according to a separate peer-reviewed journal titled "Nanoplastics and Human Health: Hazard Identification and Biointerface." Microplastics areenvironmental pollutants that can decompose into nanoplastics, the journal reads.

Nanoplastics "are believed to be more toxic since their smaller size renders them much more amenable, compared to microplastics, to enter the human body," according to the new study.

Yet the health implications of nanoplastics in bottled water for humans are still unclear, said Dr. Kristina Mena, an environmental health researcher with UTHealth Houston School of Public Health in El Paso who was not involved in the study. Mena said the researcher's findings illuminate how far technology has come because it's long been difficult to detect nanoparticles in the water that comes in water bottles.

"It's another classic example of our knowledge that we don't live in a sterile environment, and we're exposed to certain constituents and certain hazards, but until there's refined technology we don't know what is in our everyday exposures," Mena said.

Americans should use the results of the "striking" study to make informed decisions about what types of water they're consuming, she said.

What are the public health implications of nanoplastics?

Nanoplastics are small "synthetic polymers" and are "directly released to the environment or secondarily derived from plastic disintegration in the environment, according to a 2022 peer-reviewed study. They are often found in the environment and the food chain, including "food containers, tap-water pipes and the clothing industry" that study reads.

They are so small that they can invade cells in the human body, Mena said.

And they are difficult to detect, researchers wrote in the new study.

"Detecting nanoplastics imposes tremendous analytical challenges on both the nano-level sensitivity and the plastic-identifying specificity, leading to a knowledge gap in this mysterious nanoworld surrounding us," the researchers wrote.

Researchers at the State University of New York at Fredonia and non-profit journalism organization Orb Media previously tested 259 water bottles from 11 brands sold across nine countries. They found that 93% of those tested contained microplastic contamination, according the results of their study.

But it's still unclear how exactly that could affect the human body. The next step for researchers to take would be to complete a comprehensive human health risk assessment and look into different lifetime exposures of people who consume water from water bottles, she said.

Study:That bottled water you paid $3 for may contain tiny particles of plastic

Is it dangerous to drink bottled water?

Americans shouldn't be afraid to drink bottled water, Mena said. However, the study does reinforce past advice to avoid plastic water bottles and instead drink filtered tap water from glass or stainless steel containers.

"It's something for people to think about," Mena said. "There is an increased interest in refining the science, but it shouldn't scare consumers."

Contributing: Mary Bowerman; USA TODAY

Contact Kayla Jimenez at [email protected]. Follow her on X, formerly Twitter, at @kaylajjimenez.