The Environmental Protection Agency revealed yesterday that a water test site on the Liffey had shown effects of the presence of endocrine disrupting chemicals (EDCs) - the chemicals which can cause feminine features on male fish.
The phenomenon, an interference with hormonal functions in animals leading to reproductive anomalies, is well documented in the US and on the Continent, where fish have developed both male and female genitalia.
The EPA water quality report 2001-03 published yesterday acknowledged concerns about similar effects on humans due to exposure to drinking water.
The effect on the fish results from the ability of some syntectic chemical compounds to interfere with the activity of the female reproductive compound oestrogen.
The agency said indications of an early EDC effect in fish below the Oberstown Sewage Treatment plant on the Liffey had been discovered as part of a recently-completed study it had commissioned from the Cork Institute of Technology.
While the study found there was no instance of simultaneous presence of male and female tissue, a "bio marker" of exposure to EDCs was found in a number of brown trout sampled below the treatment plant.
A range of analytical techniques including blood and histological examination were carried out on the fish, according to the EPA report: "The results showed that histological examination of the gonads in wild fish did not yield any evidence of intersex (the presence of both sets of genitalia) in any of the water bodies surveyed." However, the report continues that in the one instance referred to "elevated levels of lipoprotein vitellogenin, a widely-used bio marker of fish exposed to oestrogens, was found."
The report notes that the conclusion "is supported from an effluent study where the highest oestrogenic equivalent concentration was found in Oberstown effluent". The levels of oestrogen, it was noted, were six times those recorded at the Leixlip waste water treatment plant, also on the Liffey and with comparable loading.
Ultimately, the report concluded that as the "half life" of vitellogenin is relatively short "the exposure to EDCs at Oberstown may have been relatively transient".
The conclusion is no doubt a relief to the citizens of west Dublin but the EPA water quality in Ireland report does not end there: "It is clear that further investigations are warranted both at this site and at other locations with similar sewage inputs."
