Australian scientists fear that Canberra's sewage treatment plant could be filling the Murrumbidgee's fish with prescription drugs like Prozac.

Fish swimming below the Lower Molonglo Water Quality Control Centre could be high on a mixture of uppers and downers after American studies found fish from five US rivers were tainted with traces of medications and common chemicals, which are not removed by water purification.

Chemical contaminants in water expert Dr Stuart Khan said Canberra effluent was treated then released back in to the Murrumbidgee.

''[Canberra] would be an obvious place to look for high concentrations of pharmaceuticals in rivers and therefore potential concentrations accumulating to fish as reported in this study,'' Dr Khan said.

The common antihistamine diphenhydramine (Benadryl), an anticonvulsant and two antidepressants were among the seven types of pharmaceuticals found in the tissue and livers of fish from waterways in or near Chicago, Dallas, Philadelphia, Phoenix and Orlando.

In Australia, as in America, federal standards exist for treated waste-water, but they do not address pharmaceuticals or most personal care products, and little is known about the effects they have on the environment and wildlife.

Actew's Ross Knee said Canberra's water treatment plant did not specifically target pharmaceuticals.

''In Australia it's never been identified as an issue ... we tested our effluent for over 200 parameters recently and it included a lot of organics and pharmaceuticals, pesticides and herbicides, a lot were below detection limit but all were within the drinking guidelines.''

Dr Khan is urging a national water survey to investigate and resource poor quality waste water discharged into river environments.