Jan 10, 2024 - Science

Study: More tiny plastic particles in bottled water than previously thought

A plastic bottle with a drop of water falling from its lip.

Photo: Joel Saget/AFP via Getty Images

Bottled water contains more nanoplastic particles than previously thought, according to new research published in the Proceedings of the National Academy of Sciences on Monday.

Why it matters: The tiny plastic nanoparticles are a growing concern for human health and the environment because of their ubiquity, ability to pass through biological barriers in animals, including humans, and their potentially toxic effects on living organisms.

How it works: Nanoplastics are an extremely small subclass of microplastics, but because of their size, they are potentially more dangerous than larger fragments of plastics.

  • The tiny particles, imperceptible to the naked eye, have dimensions ranging from 1 nanometer to 1 micron. (For comparison, human hair is on average around 83 microns wide.)
  • They are so small that they have been observed penetrating living cells and interfering with the functions of organelles, like mitochondria and lysosomes, potentially contributing to metabolic and functional disorders.
  • Nanoplastics appear capable of moving up through the food chain and have been seen crossing the blood-brain barrier in fish, inducing brain damage.

Yes, but: Due to their size, researchers have found it difficult to study nanoplastics, as doing so requires extremely precise and strong instruments.

  • This has left major gaps in what we know about nanoplastics, such as how risky they are to human health and how they may function in nature.

By the numbers: In the new study, Columbia University researchers used a new laser-based microscopy technique paired with an algorithm that could identify specific types of plastic, and analyzed 25 liters of bottled water from three U.S. brands.

  • They found that on average, one liter of water, which is about two standard-size bottled waters, contained 240,000 particles of seven different types of plastic, about 90% of which were nanoplastics.
  • Their results were orders of magnitude more than the microplastic abundance reported in previous research on bottled water, likely because those studies considered only larger microplastics.
  • The remaining 10% of the observed plastic particles were larger microplastic fragments.

Yes, but: That wasn't the researcher's only unexpected result.

  • They had thought they would see in the samples a greater amount of particles of plastics used in the packaging material for the water, like the polyethylene terephthalate (PET) used to form the bottles and polyethylene (PE) in the caps.
  • While PET and PE were present in the samples, the most common polymer particles were plastics that aren't used in packaging, like polyamide (PA), polystyrene (PS) polypropylene (PP) and polyvinyl chloride (PVC),

Zoom in: They proposed that these particles were most likely introduced before or during water production.

  • They noted PP and PA are widely used for equipment or as coagulant aids in water treatment systems.
  • For example, PA is widely used as a reverse osmosis membrane in filtration systems.
  • PVC tubing is ubiquitously used to transport water, while PS is used in water purification systems.

Of note: Those results suggest that plastic bottles alone may not be the source of plastic pollution found in the analyzed drinking water.

  • It also suggests that any water fed through PA-containing reverse osmosis systems, water purification systems using styrofoam beads or PVC piping could contain such nanoparticles.

Zoom out: Plastics products are extremely strong. They break down, but most types do not decompose, biodegrade or compost, meaning they are often never fully broken down into their constituent elements unless incinerated.

The International Bottled Water Association (IBWA), which represents companies that produce and sell bottled water, said in a statement that additional research is needed to corroborate findings gained from the new microscopy method used in the study.

  • It also pointed to a 2022 World Health Organization report that concluded that though microplastics have been found in the environment and food, more research is needed to determine the health risks from microplastics exposure.

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