Pharmaceuticals working their way into nature put plants and animals in danger. Steve Farrar reports

Scientists are becoming concerned that pharmaceuticals may be slowly poisoning British wildlife.

A wide range of drugs - from toxic chemotherapy agents to nerve-affecting anti-epileptics - have been found throughout the environment in a series of surveys.

Although the detected concentrations are low, experts worry that this dilute cocktail of biologically active compounds might have long-term effects on plants and animals.

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The growing fears have prompted a surge of scientific interest in the potential threat.

Last month's Society of Environmental Toxicology and Chemistry annual meeting in Prague saw a five-fold increase in the number of papers addressing the issue compared with the previous year.

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The launch of a ?1.9 million three-year research programme involving 14 institutions to look into the environmental risk assessment of pharmaceuticals is expected to be announced by the European Commission soon. Both English Nature and the Environment Agency are monitoring the situation after preliminary studies.

Awareness of the potential impact of pharmaceuticals on wildlife has developed from work on endocrine disruptors, the so-called gender-bending chemicals.

In the course of this research, analytical techniques have been devised that have enabled scientists to test both wastewater and surface water for traces of drugs.

The results have been consistent - many different pharmaceuticals are finding their way from homes and hospitals, via the sewers, into the environment. A small proportion seeps from landfill refuse sites.

A study by the Institute for Inland Water Management and Waste Water Treatment in Lelystad, Holland, found residential areas produce a mix of pharmaceuticals distinct from those found in hospital areas. The team found that at least a dozen drugs regularly occur in lakes and rivers, including analgesics, anti-epileptics, beta-blockers, antibiotics, an anaesthetic and X-ray contrast media.

Marca Schrap, who led the work, said that the concentrations were low - ranging up to just over 100 nanograms per litre. But she noted: "Chronic effects cannot be ruled out - these pharmaceuticals are developed to produce biological effects."

The Environment Agency last year identified eight pharmaceuticals in British waterways.

John Sumpter, professor of biological sciences at Brunel University and a leading figure in the study of endocrine disruptors, said it seemed that many drugs were not being removed from waste water by modern sewage treatment processes. "We can find pretty much any pharmaceutical we want, particularly in the marine environment," he said.

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Among those of particular concern are anti-cancer compounds.

Andrew Johnson, an environmental microbiologist at the Natural Environment Research Council's Centre for Ecology and Hydrology, said: "They are the most toxic of all the drugs we use and it seems they pass through sewage treatment works undegraded." He said such pharmaceuticals may affect only one or two species in particular localities and may have been overlooked.

But Dr Johnson noted that the UK's relatively high human population and small river system might make any impact more pronounced. "We don't have enough evidence... to run around screaming but as responsible scientists, we should be giving it more attention than we are."

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It is thought there is little threat to humans as drinking water undergoes further treatment. The impact on animals is more problematic.

Tamsin Runnalls, a researcher in Professor Sumpter's laboratory, is looking at the effect of clofibric acid, a key ingredient in a lipid-lowering drug, on fathead minnows. She has found altered gene expression, lowered sperm counts and damaged embryos.

But whether this occurs in the environment is not known.

The first study to show a definite link between a pharmaceutical and a wildlife population crash was published in the journal Nature in January.

The recent catastrophic decline in vulture numbers in Southeast Asia was caused by the birds' consumption of cattle carcasses containing the painkiller diclofenac.

Lindsey Oaks, assistant professor of veterinary microbiology at Washington State University who led the research, said this was the result of acute poisoning rather than a chronic effect. But he noted: "It showed that these drugs are in the environment and in certain circumstances can have significant effects."

Professor Sumpter is planning to study the impact of diclofenac - found in UK waterways by the Environment Agency - in fish.

But even if it has no ill-effects in one species, other species may be suffering.

The effects of another veterinary medicine - the anti-parasite drug anthelmintic - is raising concerns at English Nature.

Alistair Burn, head of English Nature's freshwater group, said it might pose an indirect threat to horseshoe bats as the drug killed invertebrates living in dung from treated cattle, potentially depriving the bats of an important food source. "We are looking rather anxiously at what else the Environment Agency might turn up," he admitted.

David Macdonald, director of Oxford University's wildlife conservation research unit, said that in the absence of evidence, efforts to protect wildlife had to be directed at other priorities such as habitat loss or effects of pesticides.

But he noted that ecological damage was often the product of an interaction of many factors.

Professor Macdonald added: "It at least raises an eyebrow if not a warning flag that we should be prudent about complicated chemicals getting into the environment."

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steve.farrar@thes.co.uk