Tampons can identify sewage pollution sources in rivers

Tampons may not be an obvious scientific tool, but engineers from the University of Sheffield in Britain have found in them a new utility - using them to identify the sources from where sewage is discharged into the river.

The natural, untreated cotton in tampons readily absorbs chemicals commonly used in toilet paper, laundry detergents and shampoos. These chemicals are also known as optical brighteners.

The study published in the Water and Environment Journal showed that when tampons are suspended in water contaminated by even very small amounts of detergents or sewage, they would pick up optical brighteners and glow under UV light.

"More than a million homes have their waste water incorrectly connected into the surface water network, which means their sewage is being discharged into a river, rather than going to a treatment plant," explained professor David Lerner who led the study.

Unfortunately, it is very difficult to detect where this is happening, as the discharge is intermittent, can not always be seen with the naked eye and existing tests are complex and expensive.

"The main difficulty with detecting sewage pollution by searching for optical brighteners is finding cotton that does not already contain these chemicals. That's why tampons, being explicitly untreated, provide such a neat solution," Lerner noted.

"Our new method may be unconventional - but it's cheap and it works," he pointed out.

The study used laboratory trials to determine how much detergent would need to be in the water to be picked up by the tampon test.

When a tampon was dipped for just five seconds into a solution containing 0.01ml of detergent per litre of water - over 300 times more dilute than would be expected in a surface water pipe - the optical brighteners could be identified immediately and continued to be visible for the next 30 days.

The technique was then trialled in the field by suspending tampons for three days in sixteen surface water outlets running into streams and rivers in Sheffield and then testing the tampons under UV light.

Nine of the tampons glowed, confirming the presence of optical brighteners - and therefore sewage pollution.