However, drugs are one of the few groups of chemicals in water that are not monitored. The official position of most administrations concerned with water pollution is that excreted drugs are not a problem because the concentrations found in the environment are usually below one part per billion (ppb). Many drugs can be measured at environmental concentrations that individually exceed one part per billion (ppb). Several drugs measured together can also exceed one ppb. Some chemicals have potent effects on wildlife at concentrations far below one ppb.
No drug has ever been refused entry into the market based on estimated environmental concentrations, and no actual testing is conducted after a drug is marketed to see if the environmental concentration was estimated correctly. Controls on drugs have been the brief of health departments, which are concerned only with the effect of drugs on the humans to which they are administered.
Few effects of low level concentrations of pharmaceutical drugs in the environment are known. Many drugs are designed to modify hormone systems. Estradiol, the female sex hormone (and a common water pollutant), can alter the sex characteristics of certain fish at concentrations of 20 parts per trillion. The antibiotic streptomycin stops the growth of algae and some plants. Another obvious concern is disseminating antibiotics is their potential role in spreading antibiotic resistance. Ibuprofen prevents the growth of some bacteria. In marine environments many pharmaceuticals can kill crustaceans.
When a human or an animal is given a drug, anywhere from 50% to 90% of it is excreted unchanged. The remainder is excreted in the form of metabolites - chemicals produced as byproducts of the body's interaction with the drug. Researchers report that some of the metabolites are more lipophilic and more persistent than the original drugs from which they were derived. Because of the complexity of the chemistry involved in drug metabolism, and the interactions of the metabolites with the natural environment, researchers say is it practically impossible to estimate predicted environmental concentrations of any medical substances with available knowledge.
A landfill used by the Jackson Naval Air Station in Florida, USA contaminated groundwater with a plume of chemicals that has been moving slowly underground for more than 20 years. The drugs pentobarbital (a barbiturate), meprobamate (a tranquiliser) and phensuximide (an anticonvulsant) are still measurable in that groundwater plume.
In 1992, water pollution monitoring in Germany detected clofibric acid, a drug used by many people in large quantities (1 to 2 grams per day) to reduce cholesterol levels in the blood. Clofibric acid is 2-(4)-chlorophenoxy-2-methyl propionic acid, a close chemical cousin of the popular weed killer 2,4-D. It has since been discovered that the entire North Sea contains measurable quantities of clofibric acid -- an estimated 48 to 96 tonnes of clofibric acid with 50 to 100 tonnes entering the Sea anew each year. The Danube River in Germany and the Po River in Italy also contain measurable quantities of clofibric acid. Of more immediate concern to humans is the finding that tap water in all parts of the city of Berlin contains clofibric acid at concentrations between 10 and 165 ppt. Also found are other drugs used to treat cholesterol, such as phenazone, analgestics such as ibuprofen, antibiotics, such as fluoroquinolone, and hormones such as oestrogen, as well as chemotherapy drugs for cancer treatment. The water supplies of other major cities remain to be tested, but the Swiss confirmed the presence presence of clofibric acid in Swiss lakes in 1998.
2. Sewage sludge provides a major pathway by which drugs enter the environment. Until the drug problem is understood and controlled, it provides a solid scientific rationale for labelling sewage sludge a dangerous soil amendment, the use of which should be forbidden.