Tests on major brands of bottled water have found that nearly all of them contained tiny particles of plastic.
In the largest investigation of its kind, 250 bottles bought in nine different countries were examined.
Research led by journalism organisation Orb Media discovered an average of 10 plastic particles per litre, each larger than the width of a human hair.
Companies whose brands were tested told the BBC that their bottling plants were operated to the highest standards.
The tests were conducted at the State University of New York in Fredonia.