Tampons may act as a low-cost tool to detect where waste water from baths, washing machines, sinks and showers is polluting rivers and streams, UK researchers have found.
Engineers from the University of Sheffield in laboratory tests and field trials have shown that when tampons are suspended in water contaminated by even very small amounts of detergents or sewage, they will pick up optical brighteners and glow under ultra-violet (UV) light.
Optical brighteners - chemicals commonly used in toilet paper, laundry detergents and shampoos - are readily absorbed by the natural, untreated cotton in tampons.
These chemicals are used to enhance whites and brighten colours, and show up under UV light, a phenomenon often seen in glowing t-shirts under certain lighting in bars and clubs.
"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," said Professor David Lerner who led the study.
"Unfortunately, it's very difficult to detect where this is happening, as the discharge is intermittent, can't 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. Our new method may be unconventional - but it's cheap and it works," Lerner said.
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.
The team followed the pipe network back from four of the nine polluted outlets they'd identified, dipping a tampon in at each manhole to see where the sewage was entering the system.
They were able to successfully isolate the sections of each network where the sewage originated, narrowing down the households which would need to be inspected in more detail.
A visual inspection in one area immediately revealed a house where both a sink and soil stack were connected to the wrong sewer, researchers said.
