Drugs in the water supply
by David Bradley
Forget gender-bending estrogenics or human waste leeching into the aquifers. European research has turned up something that could be a far more insidious threat in our water supply - drugs.
Swiss chemist Hans-Rudolf Buser, known in the past for his work on dioxins,
was analysing lake water for pesticides when he and his team at the Federal
Research Station in Wadneswil picked up a spurious result. They were getting
a signal that indicated the presence of the herbicide mecoprop (used to kill
broad-leaved weeds in cereal crops) but the spectra were not quite right -
they actually looked more like those of the pesticide lindane but lindane
was not present. When the researchers looked more closely at the analyses
they found clofibric acid - a widely used cholesterol-lowering drug at
concentrations of some 1 to 100 nanograms per litre of water. The
concentration was correlated with population density of the region.
Clofibric acid is not produced in Switzerland, so the scientists ruled out an industrial source - spillage or effluent - immediately. They reached the only conclusion they could see as possible - that the drug had come from human waste - faeces and urine. Anything from half to almost all of a drug taken by a patient can pass through their body without being absorbed or metabolised and the original form of a drug can also be regenerated from excreted metabolites. The findings are reported in more detail in the March 21st issue of Science News. Buser notes that the amounts of this particular drug are very, very small so that they are unlikely to pose a health risk in the short term- they are present at millions of times less than the usual prescribed dose. The long-term effects or impact on the environment are not yet known.
Other scientists too are detecting the presence of pharmaceuticals. Thomas Heberer and Hans-Jürgen Stan of the Technical University of Berlin have also found clofibric acid and other lipid-regulating drugs such as phenazone and fenofibrate in groundwater below a German sewage treatment works. In addition, they have detected painkillers such as ibuprofen and diclofenac in the same place. This is perhaps more than a little worrying as the groundwater is used as a source of drinking water. They will be publishing their results in the Journal of Environmental Analytical Chemistry.
Thomas Ternes of the Institute for Water Research and Water Technology in Wiesbaden, has also found startling results: anticholestaemics, painkillers, antibiotics, beta-blockers, epilepsy drugs and contrast agents all present in sewage and rivers. Many of the compounds were detected only at parts per trillion but in small rivers where treated sewage water could form a large proportion of the volume, numerous pharmaceuticals were found in higher concentrations (up to 6 ppb). There are likely to be no short-term effects but who can say what effects continued exposure to even just tiny amounts of a chemotherapy agent, say, might have on healthy individuals?
Pharmaceuticals have not generally been considered as environmental pollutants - with the possible exception of the contraceptive pill, which has received much attention as one of the possible estrogenics allegedly giving rise to sexless fish, hermaphroditic Florida alligators, and falling human sperm quality. As such, the regulatory bodies concerned with the environment have concentrated almost entirely on industrial waste, pesticides, herbicides, and other agrochemicals and chlorinated organics
However, as analytical techniques have improved so has the detectability of even the tiniest traces of other compounds, such as the likes of clofibric acid, cancer chemotherapy agents, and numerous other pharmaceuticals. Although the amounts detected are very small, 4 ppb in the case of Buser's analysis of clofibric acid, their presence raises several issues: Are they a health risk to those drinking 'contaminated' water? What effect, if any are they having on the environment? And, in the light of emergence of new bacterial strains, how will the presence of antibiotic residues in water affect the development of resistance?
The problem of resistance would obviously depend on the concentrations of any antibiotics in a body of water. However, the levels of some can affect bacteria such as Escherichia coli at only the parts per trillion level. US researchers have found higher levels in effluent from hospitals while the levels of pharmaceuticals in water being reported in Europe are a thousand times higher than this limit.
Until July last year , the FDA in the US asked pharmaceutical manufacturers to estimate how likely it would be for a drug to enter the environment via the human waste route. The companies did not produce figures that warranted further investigations on most occasions (less than 1 ppb in their estimates) and the FDA has dropped the scheme from its approval process for new drugs.
The profile of individual drugs in terms of their effect on the environment might, however, be useful in prescribing. If there is an alternative with less potential environmental impact then why not use that in preference - providing it is suitable for a patient. It could add yet one more factor to the design and use of pharmaceuticals and without proof positive that the effects are worth worrying about legislative pressure will not be brought to bear and the manufacturers and doctors are unlikely to take note.
In March this year , a US National Research Committee announced that reclaimed waste water could be used to augment municipal drinking water supplies. The NRC, is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering and provides scientific advice under a congressional charter. The NRC report (Issues in Potable Reuse: The Viability of Augmenting Drinking-Water Supplies with Reclaimed Water) points out that waste water should only be used at times of most extreme needs and then only after major processing criteria have been met. The presence of industrial and agricultural chemicals would, of course, preclude a supply from being potable.
The NRC report, however, mentions likely contaminants, and whether they considered the presence of just small amounts of pharmaceuticals is not clear.
Much of the European detective work has been carried out over the last few years with results now being reported in full. It adds yet another factor to the list of concerns for environmental agencies to contend with. It is perhaps time pharmaceuticals were considered as potential pollutants alongside the likes of pesticides, herbicides, fertilisers and organics.
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