By Peter Montague
A new class of water pollutants has been discovered during the past six years.
Pharmaceutical drugs given to people and domestic animals, including antibiotics, hormones, strong pain killers, tranquillisers and chemotherapy chemicals given to cancer patients, are being measured in surface water, ground water and drinking water at the tap.
Large quantities of drugs are excreted by humans and domestic animals, and are distributed into the environment by flushing toilets, and by spreading manure and sewage sludge on to and into soil.
German scientists report that anywhere from 30 to 60 drugs can be measured in a typical water sample, if anyone takes the time to do the proper analyses.
The concentrations of some drugs in water are comparable to the low parts-per-billion levels at which pesticides are typically found.
To some people this is reassuring, but others are asking, "What is the long-term effect of drinking, day after day, a dilute cocktail of pesticides, antibiotics, pain killers, tranquillizers and chemotherapy agents?"
Of course, no one knows the answer. It is simply beyond the capabilities of science to sort out the many chemical interactions that could occur in such a complex chemical soup. The only solution to such a problem would be prevention.
The first study that detected drugs in sewage took place at the Big Blue River sewage treatment plant in Kansas City in 1976. The problem was duly recorded in scientific literature and then ignored for 15 years.
In 1992, researchers in Germany were looking for herbicides in water when they kept noticing a chemical they couldn't identify. It turned out to be clofibric acid (CA), a drug used by many people in large quantities (one to two grams per day) to reduce blood cholesterol levels.
Clofibric acid is 2-(4)-chlorophenoxy-2-methyl propionic acid, a close chemical cousin of the popular weedkiller 2,4-D. Based on that early discovery, the search for CA in the environment was stepped up.
Since 1992, researchers in Germany, Denmark and Sweden have been measuring CA and other drugs in rivers, lakes and the North Sea.
To everyone's surprise, it turns out that the entire North Sea contains measurable quantities of CA. Based on the volume of the sea (48.1 quadrillion litres) and the average concentration of CA, which is one to two parts per trillion, researchers estimate that the North Sea contains 43.5 to 87 tonnes of CA, with 45 to 90 more tonnes entering the sea each year.
The Danube River in Germany and the Po River in Italy also contain measurable quantities of CA.
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 parts per trillion. The water supplies of other major cities have not yet been tested.
As a result of this European work, a few US researchers are beginning to pay attention to drugs in the environment. Individual scientists within the US Food and Drug Administration (FDA) have been concerned about this problem for a decade, but so far the FDA has taken the official position that excreted drugs are not a problem because the concentrations found in the environment are usually below one part per billion.
Drugs are designed to have particular characteristics. For example, 30% of the drugs manufactured between 1992 and 1995 are lipophilic, meaning that they tend to dissolve in fat but not in water. This gives them the ability to pass through cell membranes and act inside cells.
Unfortunately, it also means that, once they are excreted into the environment, they enter food chains and concentrate as they move upward into larger predators.
Many drugs are also designed to be persistent, so that they can retain their chemical structure long enough to do their therapeutic work. Unfortunately, after they are excreted, such drugs also tend to persist in the environment.
A landfill used by the Jackson Naval Air Station in Florida contaminated ground water with a plume of chemicals that has been moving slowly underground for more than 20 years. The drugs pentobarbital (a barbiturate), meprobamate (a tranquillizer sold as Equanil and Miltown) and phensuximide (an anticonvulsant) are still measurable in that ground water plume.
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, Danish researchers say is it "practically impossible to estimate predicted environmental concentrations of any medical substances with available knowledge."
Yet US regulatory policy for new drugs depends entirely upon estimating concentrations that might result from excretion.
When a new drug is proposed for the market, the FDA requires the manufacturer to conduct a risk assessment that estimates the concentrations that will be found in the environment. If the risk assessment concludes that the concentration will be less than one part per billion, the drug is assumed to pose acceptable risks.
FDA has never turned down a proposed new drug 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.
German chemists have found that many drugs can be measured at environmental concentrations that exceed one part per billion. And of course several drugs measured together can exceed one part per billion.
Furthermore, there is ample evidence from research conducted during the past decade that some chemicals have potent effects on wildlife at concentrations far below this level. For example, 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, (one-fiftieth of one part per billion).
Another problem resulting from drugs in the environment is bacteria developing resistance to antibiotics.
The general problem of antibiotic-resistant bacteria has been recognized for more than a decade. Antibiotics are only useful to humans for so long as bacteria do not become resistant to their effects.
Hospital sewage systems discharge substantial quantities of antibiotics into the environment. Bacteria exposed to antibiotics in sewage sludge, or water, have an opportunity to develop resistance.
Stuart Levy, who directs the Center for Adaptation Genetics and Drug Resistance at Tufts University in Boston, says: "These antibiotics may be present at levels of consequence to bacteria — levels that could not only alter the ecology of the environment but also give rise to antibiotic resistance."
[Abridged from Rachel's Environment & Health Weekly. Like Green Left Weekly, Rachel's is a non-profit publication which distributes information without charge on the internet and depends on the generosity of readers to survive. If you are able to help keep this valuable resource in existence, send your contribution to Environmental Research Foundation, PO Box 5036, Annapolis, Maryland 21403-7036, USA. In the United States, donations to ERF are tax deductible.]