Drinking from a plastic water bottle likely means ingesting microplastic particles, a new study claims, prompting fresh concerns — and calls for scientific research — on the possible health implications of widespread plastics pollution.

A study carried out on more than 250 water bottles sourced from 11 brands in nine different countries revealed that Microplastic contamination was nearly universal, found in more than 90% of the samples.

The study, by journalism organization Orb Media and researchers at the State University of New York at Fredonia, found an average of 10.4 microplastic particles about the width of a human hair per liter. That’s about twice the level of contamination discovered in the group’s earlier study on the ubiquitous plastic contamination in tap water across the globe, with the highest rate found in the U.S.