Two of the discharge sites are off popular bathing beaches in Ayrshire. But the Scottish Environment Protection Agency, (Sepa) which is conducting the research, said that the amount of dilution was "enormous" and there was no risk to bathers.
The Sepa study is one strand in a vast amount of work worldwide to determine the extent of pollution by hormone disrupting chemicals and its effect on creatures from microscopic inhabitants of the seabed to human beings.
The discovery of "feminised" fish in the river Aire in Yorkshire - female fish hormones found in males - led to a request last year by the Environment Agency for the textile industry to stop using the most suspect chemicals.
Feminised fish were also found in other English rivers near sewage discharges, though a link between the chemicals and the sex change has not been proved.
The Sepa study focused on two classes of chemical compounds - alkyl phenol ethoxylates (APEs), used as detergents in a wide range of processes, including textiles and carpet manufacture and industrial cleaning, and phthalates, used as a softening agent in producing plastics, paints and cosmetics.
During the summer, 84 samples were taken from sea outfalls and other discharge points around Scotland. Of these, 13 were assessed by Sepa as possibly at times exceeding the level at which the compounds "may be capable of producing hormone disrupting effects".
The environmental pressure group Greenpeace yesterday called on the Government to advance its target of phasing out the use of APEs by 2000.
"The discharge of chemicals which can damage our hormones is unacceptable," said Peter Roache, a Greenpeace toxics campaigner.
Dr Gerry Best, head of chemistry for Sepa's west region, said the results had to be taken in context. "We have found no effects which can be attributed to hormone disrupting chemicals, nor are we aware of any feminised fish in Scotland."
The next stage of Sepa's work will be to examine tiny shrimp-like creatures in the seabed sediment around the sewage discharge to see if there are any signs of the intersexuality reported in scientific literature.
The agency is also working with industry and water authorities on safer alternatives and reducing discharges.
Laboratory tests at Brunel University in London showed that male fish exposed to sewage treatment effluents containing APEs and phthalates produced a protein called vitellogenin, which is present in female fish for producing eggs.
But John Sumpter, the professor of animal physiology who heads the work at Brunel, said yesterday that there was not enough information to judge the effect in the wild.
"There is genuine concern about these chemicals, including people who are concerned about human exposure to them, but there is not enough information to know whether it's real or not," Professor Sumpter said.
"As with BSE, there's only one way forward, and that is research."Reuse content