They found plastic in 93 percent of the bottles that included brands like Aquafina, Evian, San Pellegrino, Aqua, Dasani, Nestle Pure Life.
The tests, carried out at the State University of NY in Fredonia and co-ordinated by US-based journalism organisation Orb Media, found an average of 10 plastic particles per litre of water, each larger than a human hair.
For the study, researchers tested 259 individual bottles across 11 brands purchased from 19 locations in nine countries.
If your go-to water brand was listed as a main offender, trying a different brand for now is in your best interest, or better yet, consider investing in a glass bottle and refill it yourself to reduce waste altogether.
Prof Mason and her colleagues filtered their dyed samples and then counted every piece larger than 100 microns - roughly the diameter of a human hair. They were further analyzed using Fourier-Transform Infrared Spectrometry (FTIR) and identified as specific types of polymers.
If you included the smaller particles (6.5-100 μm), the average rose up to 325 microplastic particles per litre.
Around 480 billion plastic bottles were sold globally in 2016 - that's a million bottles per minute.
Although it's certainly possible that underwater critters consuming microplastics may be at risk of toxicity, once again, far more work is required to understand how risky, or not, such microplastic particles are.
Small quantities of plastic were found in them - believed to be from the air - but these were subtracted from the final results.
Joy Behar apologizes to Christians after Mike Pence's interview on "Hannity"
McCain was immediately interrupted and told her impression was "not actually true" by The View host Whoopi Goldberg. Behar said hearing voices is a "mental illness" before Sherri Shepard offered a limited defense of Pence.
Shock in Turkey after Basaran heiress, friends die in plane crash
Flight-tracking website FlightRadar24 writes the plane gained altitude and within minutes dropped drastically. Families of the victims arrived Monday in Shahr-e Kord, accompanied by Turkish diplomats, IRNA reported.
PARALYMPCIS/ Biggest winter Games yet kicks off in Pyeongchang
Even the 310,000 tickets could be sold out completely and the IPC is considering putting extra tickets on sale. Germany's Bach did not attend the Rio Paralympics in 2016 and was heavily criticized by some athletes.
The process was praised by government consultants as being "well conducted" research. Two of them commented on their own tests performed to screen for microplastics.
This is because although Nile Red dye can bind to substances other than plastic - such as fragments of shell or algae containing lipids - these would be unlikely to be present in bottled water.
"Based on what we know so far about the toxicity of microplastics - and our knowledge is very limited on that - I would say that there is little health concern, as far as we know", Martin Wagner, a toxicologist at the Norwegian University of Science and Technology, told Orb.
"We stand by the safety of our bottled water and remain committed to providing consumers with the highest quality products". It says the research "is not based on sound science".
A 2016 report from the European Food Safety Authority said the vast majority of consumed microplastic particles likely pass safely through the body.
It is not yet clear whether ingesting the plastics is harmful to human health, but the World Health Organisation on Thursday announced it would conduct a review into the potential risks.
In the meantime, Bruce Gordon, coordinator of the WHO's global work on water and sanitation, advised that there is no reason for alarm and that a much greater threat comes from the pollution of water supplies with sewage.