The presence of nanoplastics — the remnants of microplastics — has been measured and quantified in bottled water. Microplastics range in size from 5 mm down to 1 micrometer, while nanoplastics form particles below 1 micrometer.

Unlike microplastics, these previously unexamined plastic pollutants can enter the human bloodstream, organs and individual cells. Columbia University and Rutgers University researchers relied on a stimulated Raman scattering microscopy technique to determine that a liter of bottled water contained some 240,000 detectable plastic fragments, a quantity 10 to 100 times greater than previous estimates.

Analysis of three bottled water brands marketed in the U.S. documented 110,000 to 370,000 particles in each liter, 90% of which were nanoplastics; the rest were microplastics. As reported in Proceedings of the National Academy of Sciences, common plastics encountered included polyethylene terephthalate (PET), polyamide, polystyrene, polyvinyl chloride and polymethyl methacrylate.

The researchers theorize that some of the nanoplastics are released from the bottle package during transportation or storage, while others are derived from equipment components or coagulant aids deployed during water purification.