India, Oct. 18 -- Plastics are supposed to be chemically inert. It's the reason they're used so frequently to package food, bottle water, and create children's toys: They're safe.

But something important happens when a large piece of plastic fragments into micro- and nanoparticles.

Its surface area increases dramatically relative to its volume. Vastly more of the material is now exposed to its surroundings.

A new study by researchers from Columbia University and the University of California, Berkeley, found that this newly created surface is not necessarily safe, and identified the chemical reasons why.

"As plastic fragments into smaller and smaller particles, its surface area increases enormously. Then microplastics change the water ...