The study was published in the journal Proceedings of the National Academy of Sciences

The study used newly-developed laser technology that can find the smallest of fragments

The researchers found 240,000 tiny plastic particles in each litre of bottled water on average

About 90 percent of the fragments were nanoplastics, while the rest were microplastics

Researchers tested three popular brands of bottled water sold in the U.S.

As per researchers, the nanoplastics are believed to be more toxic than microplastics

Less than a micron in size, nanoplastics can pass through the intestines and lungs into the bloodstream and travel to organs including the heart and brain

They can be absorbed into human cells and tissue, and cross through the placenta to the bodies of unborn babies