Tampons are highly absorbent and are cheap. When they are submerged in contaminated water they absorb the chemicals and shine blue under ultra violet light.
One of the reasons for rivers becoming polluted is that the waste water form sinks, showers, washing machine which should flow in the sewers which are then treated at the sewage plant must have accidently mixed with the rainwater sewers.
Coauthor David Lerner, an environmental engineer at the University of Sheffield in England says, “A tampon is one of the few things you can buy that is not pretreated with optical brighteners.”
This makes it perfect to see brighteners from polluted water.
His team has tested 16 sewer outlets near campus and they found all of them polluted signaling the drains were misconnected.
They soaked the tampons in the sewers water for a day and then tested them under ultraviolet light.