London, Oct 5 (IANS): You can now brush your teeth and take a bath with a clear conscience as researchers have found that the most common soaps, shampoos and detergents - also known as surfactants - pose a minimal risk to the environment.

The study showed that when the surfactants are used correctly and responsibly, and once they have been through a proper treatment plant, the risk to the surrounding environment is very low.

"The substances are made so that they degrade rapidly and thus do not pose a risk to the environment," said study co-author Hans Sanderson from the Aarhus University in Denmark.

For the purpose of promoting the sustainable use of surfactants, the researchers analysed their findings regarding the use, disposal, treatment and risk to the aquatic environment of the most important surfactant ingredients in North America. Although the studies are based in North America, they nevertheless apply on a global scale because they are more or less identical all over the world.

The result is a 100-page virtually encyclopaedic list, which sums up over 250 scientific studies spanning 40 to 50 years.

"It is the most comprehensive and definitive report to date regarding the environmental properties of detergent substances in soap products - in other words, personal care and cleaning products," Sanderson noted.

Surfactants have a special ability to dissolve fat while at the same time being water soluble. This is because they consist of components which have a hydrophilic head and a hydrophobic tail. The hydrophobic tails repel water but are fond of fat.

This means that the tails are the ones that dissolve the fat when we wash ourselves with soap. The surfactant's hydrophilic heads ensure that the fat is carried away in the rinse water.

The study was published in the scientific journal Critical Reviews in Environmental Science.