The bottled water industry is estimated to be worth nearly $200 billion a year, surpassing sugary sodas as the most popular beverage in many countries. But its perceived image of cleanliness and purity is being challenged by a global investigation that found the water tested is often contaminated with tiny particles of plastic.

"Our love affair with making single-use disposable plastics out of a material that lasts for literally centuries — that's a disconnect, and I think we need to rethink our relationship with that," says Prof. Sherri Mason, a microplastics researcher who carried out the laboratory work at the State University of New York (SUNY).

The research was conducted on behalf of Orb Media, a U.S-based non-profit journalism organization with which CBC News has partnered.

Mason's team tested 259 bottles of water purchased in nine countries (none were bought in Canada). Though many brands are sold internationally, the water source, manufacturing and bottling process for the same brand can differ by country.

The 11 brands tested include the world's dominant players — Nestle Pure Life, Aquafina, Dasani, Evian, San Pellegrino and Gerolsteiner — as well as major national brands across Asia, Africa, Europe and the Americas.

Researchers found 93 per cent of all bottles tested contained some sort of microplastic, including polypropylene, polystyrene, nylon and polyethylene terephthalate (PET).

10.4 particles/litre on average

Microplastics are the result of the breakdown of all the plastic waste that makes its way into landfills and oceans. They are also manufactured intentionally, as microbeads used in skin care products. Microbeads are now being phased out in Canada, after significant numbers began to appear in the Great Lakes and the tiny particles were found filling the stomachs of fish.

Anything smaller than five millimetres in size (5,000 microns) is considered microplastic.

Using the Red Nile test, researchers identified tiny particles believed to be microplastics in many bottles of water. (Orb Media)

Orb found on average there were 10.4 particles of plastic per litre that were 100 microns (0.10 mm) or bigger. This is double the level of microplastics in the tap water tested from more than a dozen countries across five continents, examined in a 2017 study by Orb that looked at similar-sized plastics.

Other, smaller particles were also discovered — 314 of them per litre, on average — which some of the experts consulted about the Orb study believe are plastics but cannot definitively identify.

The amount of particles varied from bottle to bottle: while some contained one, others contained thousands.

The purpose of the study was to establish the presence of the plastics in bottled water.

It's unclear what the effect of microplastics is on human health, and no previous work has established a maximum safe level of consumption. There are no rules or standards for allowable limits of microplastics in bottled water in Canada, the United States and Europe. Rules and standards for other countries from the study are not known.

Two brands — Nestle and Gerolsteiner — confirmed their own testing showed their water contained microplastics, albeit at much lower levels than what Orb Media is reporting.

Emerging science

Plastics are present nearly everywhere and can take hundreds of years to degrade, if at all. Many types only continue to break down into smaller and smaller particles, until they are not visible to the naked eye.

Plastics have also been known to act like a sponge, and can absorb and release chemicals that could be harmful if consumed by mammals and fish.

"It's not straightforward," said Prof. Max Liboiron of Memorial University in St John's.

"If you've ever had chili or spaghetti and you put it in Tupperware, and you can't scrub the orange colour out, that's a manifestation of how plastics absorb oily chemicals," says Liboiron, director of the Civic Laboratory for Environmental Action Research (CLEAR), which monitors plastic pollution.

The European Food Safety Authority suggests most microplastics will be excreted by the body. But the United Nations Food and Agriculture Organization has raised concerns about the possibility some particles could be small enough to pass into the bloodstream and organs.

It's not clear how the plastic is getting into the bottled water — whether it's the water source itself or the air or the manufacturing and bottling process.

"Even the simple act of opening the cap could cause plastic to be chipping off the cap," Mason said.

The science behind the test

The water tested was purchased in the U.S., Kenya, China, Brazil, India, Indonesia, Lebanon, Mexico and Thailand, and represented a range of brands across several continents. It was shipped to the specialized lab at SUNY in Fredonia, N.Y.

Scientists used Nile Red fluorescent tagging, an emerging method for the rapid identification of microplastics, as the dye binds to plastic. Scientists put the dyed water through a filter and then viewed samples under a microscope.

Prof. Sherri Mason carried out the laboratory work at the State University of New York (SUNY), on behalf of Orb Media. (Dave MacIntosh/CBC)

Mason's team was able to identify specific plastics over 100 microns (0.10 mm) in size but not smaller particles. According to experts contacted by CBC News, there is a chance the Nile Red dye is adhering to another unknown substance other than plastic.

Mason leaves open that possibility but leans strongly to the smaller particles being plastic.

The developer of the Nile Red method agrees.

Fluorescing particles that were too small to be analyzed should be called "probable microplastic," said Andrew Mayes, senior lecturer in chemistry at the University of East Anglia in the U.K.

Orb consulted several toxicologists and microplastics experts throughout the entire process who also reviewed the findings.

"This is pretty substantial," Mayes said. "I've looked in some detail at the finer points of the way the work was done, and I'm satisfied that it has been applied carefully and appropriately, in a way that I would have done it in my lab."

CBC News also asked multiple experts to review Orb's study; while similar questions came up with the Nile Red dye, they were convinced there was some level of microplastics in the water and further research was warranted.

Big brands respond

Nestle said in a response that it had tested six bottles of water from two of its brands — Nestle Pure Life and San Pellegrino — and found between two and 12 microplastics per litre, much lower than what Orb found in its study. The company suggested that Nile Red dye is known to "generate false positives."

Gerolsteiner also said its tests showed a "significantly lower quantity of microplastics per litre" in its products.

"We still cannot understand how the study reached the conclusions it did," the company said. "The research results do not correspond to the internal analyses that we conduct on a regular basis," the company said in a response.

Danone, the company behind Evian and Indonesian brand Aqua, told Orb it is "not in a position to comment as the testing methodology used is unclear. There is still limited data on the topic, and conclusions differ dramatically from one study to another."

Brazilian brand Minalba told Orb that it abides by all quality and security standards required by Brazilian legislation.

The American Beverage Association, which represents many of the biggest brands across North America, including Nestle, Evian, Dasani and Aquafina, told Orb that "the science on microplastics and microfibres is nascent and an emerging field…. We stand by the safety of our bottled water products and we are interested in contributing to serious scientific research that will ... help us all understand the scope, impact and appropriate next steps."

Brands Biserli and Wahaha did not respond to Orb's request for comment.

Plastics, plastics everywhere

Within three decades, there will be more plastics in the oceans than fish. They are having a profound effect on the environment. In the oceans, vast quantities float on the surface, trapping sea life and blocking the sun's rays from entering the waters.

Mason points out people can choose to not buy water in a plastic bottle, and to carry a refillable bottle instead. But for other products, there is no choice. The majority of products on grocery and retail store shelves are contained in plastic.

"It's portable, it's lightweight, it's convenient, it's cheap — that just makes it easy," Mason says. "It's so difficult to get people to care about things they can't see."