Medicinal drugs have been found in purified wastewater that is used for irrigation, and could therefore reach agricultural produce and even drinking water sources. As a result, experts say it is critical to develop systems to remove these materials, and also to expand testing for them.

Researchers at Tel-Aviv University successfully tested one experimental treatment system recently at the Gush Dan waste purification plant near Rishon Letzion.

At a conference at the Vulcani Institute in Beit Dagan two weeks ago, which was sponsored by the Water Authority and the Mekorot Water Company, several researchers reported having found traces of medications in treated wastewater meant for irrigation, and in groundwater as well, though in lower concentrations.

Thus far, however, no trace of drugs has been found in the water sources that supply drinking water.

At the Gush Dan plant, most of whose water is used for irrigation in the Negev, researchers from Hebrew University found a wide variety of medical materials, including some used in x-rays.

They discovered particularly high concentrations of carbamazepine, an anti-depressant that is also used to treat epileptics, and therefore postulated that this could be used as a marker to determine whether any drugs are seeping into drinking water.

What impact drug concentrations in the water might have on people's health remains unknown.

However, such concentrations have had a major impact on certain kinds of animals, including causing sex changes in fish in the Beit She'an Valley.

As a result, several experts at the conference said that treatment systems should be installed to break down drug concentrations even if the health impact is not yet clear.