The World Health Organization (WHO) will launch a review of the risks of drinking water from plastic bottles after a study found that 93% of bottles were found to contain microplastics.

Scientists based at the State University of New York were commissioned by non-profit journalism organisation Orb Media. Tests were carried out on more than 250 bottles from 11 leading companies which revealed “widespread contamination with plastic debris including polypropylene, nylon, and polyethylene terephthalate (PET)”.

Samples came from 19 locations in nine countries on five continents. Tests revealed a global average of 10.4 plastic particles per litre. They also showed a much greater number of even smaller particles that researchers said are also likely plastic. The global average for these particles was 314.6 per liter.

Polypropylene, used in bottle caps, made up 54% of those larger particles, nylon was 16% and PET was 6%. Some bottles had effectively zero plastic; one contained more than 10,000 particles per litre.

A WHO spokesperson told FoodBev that the organisation “would review the very scarce available evidence with the objective of identifying evidence gaps, and establishing a research agenda to inform a more thorough risk assessment”.

“For WHO to make an informed risk assessment, we would need to establish that microplastics occur in water at concentrations that would be harmful to human health.”

The bottled water industry has rallied to condemn the findings. The International Bottled Water Association said: “Microplastic particles are found everywhere – soil, air, and water. And, as the report states, currently there is no evidence that microplastics can cause harm to consumers.

It added: “Consumers can remain confident that bottled water products, like all food and beverages, are strictly regulated by the US Food and Drug Administration and, thus, are safe for consumption. The bottled water industry is committed to providing consumers with the safest and highest quality products.”

British Soft Drinks Association director general Gavin Partington said: “There is no evidence or scientific consensus worldwide about the potential impacts of microplastic particles on human health. 

“Our members have some of the most stringent quality standards in the industry, with all bottled water products produced using a multi-barrier approach. We stand by the safety of our bottled water and remain committed to providing consumers with the highest quality products.”

Figures released last year revealed that US consumers are drinking more bottled water than any other beverage, with sales up 10% in 2016. Global bottled water output is expected to soon hit 300 billion litres a year.