Plastic pollution stories often focus on the sheer prevalence of the problem in the oceans, and that’s fair enough: Right now, there's about 17 Great Pyramids of Giza-worth of plastic in them, and it’s added to each year. A new report commissioned by journalism organization Orb Media, however, reminds us that plastic pollution isn’t a problem that we can avoid ourselves.

According to their analysis carried out in conjunction with the State University of New York in Fredonia, “93 percent of the bottled water tested showed some sign of microplastic contamination,” featuring polypropylene, nylon, and polyethylene terephthalate. This striking value was obtained by examining 259 bottles of water from 11 different brands, sold in nine different countries on five different continents.

Using an infrared microscope, the researchers found that, for particles around 0.1 millimeters in size, there’s roughly 10.4 per liter (2.3 gallons) of bottled water in various major brands. The report notes that this is “twice as much as within previous study on tap water.” This figure is just an average though, with some bottles containing very few and some containing magnitudes more.

The report also notes that far smaller particles were also identified using a dye that binds to plastic. Although present in far greater quantities – about 325 per liter – it isn’t clear that they are definitively plastic or not at this stage as their identity couldn’t be confirmed with the microscope.

Either way, “data suggests contamination is at least partially coming from the packaging and/or the bottling process itself,” the report explains. The brands affected include Nestle Pure Life, Dasani, Gerolsteiner, E-Pura, Evian, and Aquafina, to name just a few – again, with huge average microplastic variations across the board.

It's important to point out, however, that this isn't a peer-reviewed scientific study, but a report using scientific techniques. It is set to receive a technical review, but until then, it's worth keeping that in mind.

Although plastic pollution in general is decidedly grim, the specific risks of microplastic ingestion on human health are highly uncertain at present because the phenomenon remains under-researched. As odd as it may sound, we simply don’t definitively know what the dangers of long-term plastic ingestion on humans may be, which is why the caution around the ubiquity of microplastics is certainly nothing but sensible.

Fortunately, shortly after the publication of this latest report, the World Health Organization (WHO) announced that they are launching a review into the long-term risks of microplastics in drinking water.

Studies on marine ecosystems that are awash with microplastics are similarly unenlightened at present. They’re also trying to nail down the quantities of microplastics that are ingested, as well as comprehend what effects this will have on organisms’ health.

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 dangerous, or not, such microplastic particles are.

The full report is available to read here, with a visual breakdown available here.