The widely repeated figure of 240,000 plastic particles per litre comes from a 2024 laboratory study of bottled water. Researchers estimated about that many identified plastic particles per litre on average in samples from three unnamed brands sold in the United States. It is not a count for every bottled-water product, and the experiment did not test whether drinking the water harms people.
What did the researchers count?
The team used laser-based microscopy and software that compared the signals from tiny particles with seven common types of plastic. Columbia University's account of the study reported counts ranging from roughly 110,000 to 370,000 identified plastic particles per litre across the tested brands. About 90% of the plastic particles counted were nanoplastics, smaller than one micrometre.
The microscope imaged many more nanoparticles than it could identify as one of those seven plastics. The targeted plastics accounted for about one in ten of all the nanoparticles imaged, according to the researchers' account. The remaining particles were not all shown to be plastic and should not be added to the identified-plastic count.
How widely does the result apply?
Three unnamed US brands are a narrow sample, not a survey of every brand, batch or country. The researchers used bottled water to demonstrate a way to detect very small particles. The study did not establish where the particles came from, directly compare bottled and tap water using the same test, or measure what happened to the particles in a person's body.
Counts from different studies also need care in comparison. The US Food and Drug Administration says methods for detecting and counting microplastics and nanoplastics are not yet standardized. Different methods may detect different kinds and sizes of particles.
What does the number say about health?
By itself, a particle count cannot establish a health effect or a safe or harmful dose. The US National Institutes of Health noted after the study that the potential health effects of these tiny plastic particles remained unproven and unknown. The FDA says current evidence has not demonstrated that the levels detected in water pose a human health risk.
That is not proof that the particles are harmless. A 2019 World Health Organization review, written before this imaging study, identified substantial gaps in evidence about microplastics in drinking water. Researchers still need comparable measurements and studies that can connect exposure with health outcomes.
The useful conclusion is narrower than the headline number may suggest: a newer method detected many small plastic particles in water from these three brands. This study did not determine an individual's health risk or establish which water source or filter is safer.
