Advertisements for bottled water tend to play on themes of purity and healthy living. If sales figures are anything to go by, many of us seem to be buying into that. The global industry is worth €119 billion ($147 billion) a year.

But original research and reporting by the global journalism organization Orb Media, and shared with DW, muddies the association. 

The first of its kind on a global scale, the research tested bottled water from 11 brands bought at 19 locations in nine countries around the world for microplastics. The contaminant was identified in 93 percent of samples — in sometimes greatly varying quantities.

In a world where, according to forecasts by online statistics portal Statista, we will be drinking 391 billion liters of bottled water in 2017 — up from 288 billion liters in 2012 — the study begs the question: Is consuming such tiny plastic particles safe?

That's a tough question to answer. Despite the ubiquity of microplastics in the environment, toxicologists are still in the early stages of figuring out their potential threat to human health.

Read more: Germans slow to bin plastics habit

We don't yet know, says Rolf Halden, director of the Center for Environmental Health Engineering at Arizona State University, how many of these particles actually reach our bloodstream.

Many of these plastic particles will be too big to penetrate so deeply into our bodies. But if some were small enough to pass through the gut, "there would be concern about physical invasion of tissue and the chemical load associated with the plastics," Halden told DW.

Of mice and man

Describing microplastic as a "very challenging emerging contaminant," Heather Leslie, Environmental Chemistry and Toxicology expert at Vrije Universiteit Amsterdam, likens plastics and the chemicals in them to a bowl of spaghetti in which the noodles are the polymer chains, and chemical additives the sauce in between them.
"Depending on the recipe, you can have some chemicals in plastic that are toxic, and in fact a lot of 'substances of very high concern (SVHCs)' are associated with plastic products."

She's also concerned by what is known asparticle toxicity. 

"If tiny particles, including plastics, make their way to a tissue in your body, they can cause what's called oxidative stress, which can lead to chronic inflammation." That, in turn, is now understood to play a major role in the onset of a number of chronic diseases, Leslie explains.

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Albert Braeuning, a toxicogenomics expert at the German Institute for Risk Assessment (BfR), has been analyzing the effect of microplastic on mice. His team fed the animals huge doses of different sized pieces of microplastic for 28 days, and are now studying the effects of these particles on mouse tissues.

"As far as we have proceeded with the analysis of the samples, we have not seen anything adverse yet," he states.

Nonetheless, he stresses that further research is necessary to assess the "human situation."

Compiling a big body of evidence, Leslie says, will be a long process, just as it was with smoking and climate change. "It sometimes takes decades to figure it all out."

Mixed bag of results

The Orb study was supervised by Sherri Mason, a leading microplastics researcher at the State University of New York in Fredonia, who also managed a previous investigation by the organization into microplastics in tap water.
Her team injected each of the 250 bottles with Nile Red, a dye that adheres to oily materials — such as plastics — and filtered the water to 1.5 microns (0.0015 millimeters), which is smaller than a human red blood cell.

They found a per-liter global average of 10.4 particles in the 100-micron or 0.10-millimeter range. That is about the width of a human hair. 

Using a laser light technique to analyze these larger particles, the scientists were able to read their molecular signature and confirm they were indeed looking at plastics.

But they recorded a much higher number of even-smaller particles, which they also believe to be plastic.

Using specially designed software to count these particles, they revealed extreme variations between bottles — even those from the same source. While some showed low to zero readings, others revealed hundreds or even thousands of particles.

The highest number of microplastic particles the researchers recorded in a single liter was in excess of 10,000.

Their findings led them to conclude we could be drinking an average of 314 of these smaller particles per liter. Because they could not analyze them in the same way as the larger particles, the researchers cannot entirely rule out that other contaminants could be in the mix.

"As a scientist, I'd say yes there is a possibility. Is it highly probable? I don't think so," Mason told DW. "One of the questions would be: What else would you expect there to be in water? It's definitely not water, it's not minerals you might expect to be finding, because those don't absorb Nile Red."

Drinking the bottle with the water?

Researchers don't yet know where the contamination is coming from.

Among the plastics Mason did positively identify were nylon, polyethylene terephthalate (PET — typically used for plastic bottled drinks) and a 54-percent incidence of polypropylene, which is widely used to make bottle lids.

Microplastic even showed up in the samples they tested in glass bottles.

Read more: EU unveils plan to make all plastic packaging recyclable by 2030

Her findings align with the results of similar research conducted by Darena Schymanski of the Chemical and Veterinary Analytical Institute in Münsterland earlier in 2018. Using a different technique, she studied the prevalence of microplastic particles in bottled water in Germany.

"We found polyethylene terephthalate [PET] and polypropylene in the water," Schymanski told DW. "Those are the polymers that the bottles and the caps are made of."

An issue for the manufacturers

Andrew Mayes, senior chemistry lecturer at the University of East Anglia in the United Kingdom, who is familiar with techniques involvingNile Red and who reviewed Orb's findings, hopes they will advance the debate around the environmental impact of our packaging habits.

"Studies like this make people aware that while plastic is a wonder material, we need to use it and dispose of it with care and common sense," Mayes told DW. "I think it switches the onus onto the manufacturers.

In response to Orb's findings, Nestlé tested eight bottles from three locations. The results, the company said, did not show "microplastic particles beyond trace level."

A Nestlé spokesperson told DW they were "ready to collaborate with others to further develop the robustness and standardization of testing methods."

German bottled water producer Gerolsteiner said it has long "paid close attention" to microplastics and ensures its water is "regularly tested, both internally and by renowned laboratories."

"No traces of microplastics have been detected in our sources in the course of these tests," a Gerolsteiner representative said, adding that the findings were an opportunity to continue examining their processes.

In response to the Orb study, the World Health Organization (WHO) told DW it would "need to establish that microplastics occur in water at concentrations that would be harmful to human health" in order to adequately assess the risk. 

Stressing the importance of prioritizing known waterborne risks to health, the WHO said that as part of its ongoing assessment of water quality, it would review the "scarce available evidence" in this "emerging area of concern for consumers." 

But for toxicologists such as Halden, solving the microplastics problem runs deeper than method and process.

"The consumer has a role in communicating that they do not want to continue using materials we know to be sub-par based on today's standards of how things should be compatible with the environment and with human life."

"We are mass-producing yesterday's chemistry," he concluded.

*Clarification
Since publication PepsiCo has clarified that Epura is a proprietary brand of GEPP, which holds exclusive rights to PepsiCo products in Mexico.

Reporting in conjunction with Dan Morrison and Christopher Tyree of Orb Media. The full Orb Media report can be found atwww.orbmedia.org