Tests were carried out on water from the River Thames
The technique can also be used to monitor oestrogen levels in water supplies destined for human consumption.
Small quantities of oestrogens are excreted from the body and enter the sewage system.
These very low levels of oestrogens have been shown to be responsible for signs of sex changes in male fish in rivers to which sewage is discharged - they begin to show some female characteristics.
There is also concern that they may be having a detrimental effect on male fertility by being recycled back into the human food chain. They have even been linked to an increase in testicular cancer.
Highly sensitive
Scientists at the University of the West of England (UWE) have developed highly sensitive chemical analysis procedures that can detect minute traces of these hormones.
The project is a collaboration between UWE and the
Environment Agency, and involves taking samples of water from the Thames in London.
The samples are separated into their constituent parts using a technique called gas chromatography-negative chemical ionisation mass spectrometry.
The techniques developed can also distinguish whether the hormones present are naturally occurring or result from use of the contraceptive pill.
Project leader Dr David McCalley said: "We can now detect quantities of oestrogens down to levels equivalent to a pinch of sugar in an Olympic swimming pool.
"Our method is sensitive enough to allow direct chemical measurements of oestrogens in rivers, rather than measuring them indirectly through their biological effects.
"We discovered that the largest concentrations in the River Thames are of naturally produced oestrogens.
"We have not been able to detect any synthetic oestrogens, which would derive from the pill."
Dr McCalley said that the levels of oestrogen detected were above those needed to cause sex changes in fish.
The samples were taken from the lower reaches of the Thames. Dr McCalley stressed that the water in the higher reaches of the river, from where it is extracted for drinking purposes, was likely to be cleaner.
However, he told BBC News Online: "There is a real risk that discharges of oestrogen do perhaps find their way into drinking water.
"Our detection method could certainly be used to monitor levels in drinking water.
"At present there are no standards laid down for what levels of oestrogen are permissible in water, but now we have developed a way to monitor these levels it might lead to standards being set."
Details of the project have been published in the Journal of Chromatography A.