Agricultural gender crisis

Scientists plan to determine if steroids found in water are due to livestock.

Researchers are poised to discover whether steroid hormones excreted by livestock in the UK are reaching streams and rivers where they could be feminising male fish. This comes on the back of research in the US showing that intensive agriculture and aquaculture are sources of steroids capable of causing endocrine disruption in the aquatic environment.

There is a consensus that steroids in the aquatic environment are affecting fish, but it is not clear where they come from. Most research has focused on wastewater that contains human hormones, which might be causing feminisation of male fish and possibly even contributing to the steady decline in sperm count in men. However, a new study from the US highlights other ways in which steroids might be entering waterways. The significance of these sources has been largely ignored, argues David Sedlak, professor of environmental engineering at the University of California at Berkeley. ’Dairy wastewater, aquaculture effluent and even spawning fish can lead to detectable concentrations of steroid hormones in surface waters,’ he and his colleagues report. They believe that in certain watersheds, these sources may be as or more important than wastewater coming out of sewage plants.

Sedlak’s latest research takes a look at steroid pollution from three sources in central California - dairy farms, fish hatcheries and the spawning site of a natural population of salmon. Analysis of water samples from these sites using gas chromatography-tandem mass spectrometry has produced some disturbing results.

Steroid concentrations of just 1 ng/L can cause feminisation of male fish. But in some samples of wastewater from US dairy farms, concentrations can be as high as 650 ng/L, reports Sedlak. Although the steroid concentration in wastewater from aquaculture operations is relatively low, ranging from 0.1 ng/L to 0.8 ng/L, it could also make a contribution to steroid levels in rivers. ’They are potentially significant because . aquaculture effluents are often discharged to receiving waters with little or no treatment,’ they say. Natural fish populations - like Chinook salmon, which congregate in their thousands to spawn - might also add to the steroid load, they suggest. ’Sources of steroid hormones other than municipal wastewater effluent may need to be considered when efforts are made to predict or control concentrations of steroid hormones in surface waters,’ they conclude.

Such findings have stimulated the UK’s Department for the Environment, Food and Rural Affairs (Defra) to fund a small pilot study to see if a similar situation exists in the UK. This autumn, a survey will be carried out on surface water surrounding 10 livestock farms where the potential for pollution is high, says Peter Matthiessen, professor of environmental chemistry and pollution at the Centre for Ecology and Hydrology (CEH) at Lancaster, UK. These will be worst-case scenarios, where there is a high density of livestock and a significant risk of rainwater running straight into waterways. Passive lipophilic samplers will catch estrogens and androgens and yeast cells modified to express estrogen receptors and androgen receptors will be used to screen for these steroids.

This study should reveal whether we have to look more closely at this source of steroid pollution, says Matthiessen. ’If we do, then we’ll obviously have to go on to do a much more unbiased survey to see how widespread is the problem.’ A report of the findings is expected in March 2005.

Nobody is ruling out these alternative sources of steroid pollution, says John Sumpter, head of the Fish Physiology Research Group at Brunel University, UK. However, their contribution, if any, is likely to be localised and small compared to human sources, he says. ’In the UK and in much of Europe, the main contributors to steroid[s] . in rivers are much more likely to be people than farm animals,’ he says.

Henry Nicholls