Bottled water contains 100 times more plastic nanoparticles than previously thought

The average litre of bottled water has nearly a quarter of a million pieces of microplastics and tiny, invisible nanoplastics, new research has found. 

These have been detected and categorised for the first time by a microscope using dual lasers.

Scientists had long figured there were lots of these microscopic plastic pieces, but until researchers at US universities Columbia and Rutgers did their calculations they never knew how many or what kind.

Looking at five samples each of three common bottled water brands, researchers found particle levels ranged from 110,000 to 400,000 per litre, averaging at around 240,000 according to a study in Monday’s Proceedings of the National Academy of Sciences.

Nanoplastics are particles that are less than a micron in size. There are 25,400 microns - also called micrometers because it is a millionth of a metre - in an inch. A human hair is about 83 microns wide.

Previous studies have looked at slightly bigger microplastics that range from the visible 5 millimetres, less than a quarter of an inch, to one micron. About 10 to 100 times more nanoplastics than microplastics were discovered in bottled water, the study found.

Much of the plastic seems to be coming from the bottle itself and the reverse osmosis membrane filter used to keep out other contaminants, said study lead author Naixin Qian, a Columbia physical chemist.

She wouldn’t reveal the three brands because researchers want more samples before they single out a brand and want to study more brands. Still, she said they were common and bought from US supermarket Walmart.

Researchers still can’t answer the big question: are nanoplastic pieces harmful to health?

“That’s currently under review. We don’t know if it’s dangerous or how dangerous,”