Plastic is such a "pervasive" material that nearly every branded bottle of water tested in the largest investigation of its kind contained tiny particles of it.
Scientists who carried out the examination of more than 250 bottles from nine countries said their analysis found plastic "in bottle after bottle and brand after brand".
The tests, which were conducted at the State University of New York in Fredonia, found that there were typically 10 plastic particles per litre of bottled water. Each particle is larger than the width of a human hair.
The alarming findings came from research led by journalism organisation Orb Media, and was covered by the BBC.
There is no evidence that consuming such small particles of plastic has any ill health effects, but it comes at a time of heightened international concern of plastic pollution and the effect it is having on the environment.
Sherri Mason, a professor of chemistry at the university, told the BBC that the results were "not catastrophic", but said the numbers experts were seeing were "concerning".
She said: "We found [plastic] in bottle after bottle and brand after brand.
"It's not about pointing fingers at particular brands; it's really showing that this is everywhere, that plastic has become such a pervasive material in our society, and it's pervading water — all of these products that we consume at a very basic level."
The researchers recorded all their purchases on video to prove there was no contamination. A dye called Nile Red was then added to each bottled sample, as it sticks to pieces of plastic and makes them easily identifiable as particular types of polymer.
The process was praised by government consultants as being "well conducted" research. Just 17 of the 259 bottles of water sampled were found to have no evidence of plastic.
Companies contacted by the BBC insisted their products met the highest standards for safety and quality. The bottles were sourced from countries including Mexico, India, Germany and Brazil.
Around 480 billion plastic bottles were sold globally in 2016 — that's a million bottles per minute. Or 20,000 per second.
- Telegraph Group Ltd