Powerful doses of the female hormone oestrogen are creating hermaphrodite fish in the River Blackwater, says an Environment Agency study.

But despite assurances from the agency and the water companies involved, environment groups fear men's fertility could also be affected.

Research to be published shortly by the Environment Agency identifies the Blackwater among ten English rivers where feminised "intersex" roach had been found with eggs in their testes and female reproductive ducts.

The researchers blame a powerful form of oestrogen from the contraceptive pill entering rivers through sewage works but have no evidence that it has an effect on men.

Essex and Suffolk Water, which supplies Maldon's water from the Blackwater and elsewhere, and Anglian Water, which processes the district's sewage, both say humans aren't affected.

Anglian Water admits strange things are happening to fish but says the cause has not been identified.

Both firms said that filtration processes would stop any harmful substances getting into the water supply.

Published Thursday, March 21, 2002