- Research has shown that a large proportion
of male fish in some British rivers are changing sex through exposure to
- Chemicals from sewage treatment plants
and factories are causing male fish to produce eggs. The chemicals act
like the hormone, oestrogen, which is normally produced in the ovaries
of female animals.
- The Environment Agency and scientists
from Brunel University examined 2000 male roach taken from eight rivers.
- They found that between 25% and 60% of
them had produced eggs in their testes, and in some sites downstream of
sewage treatment plants, all male fish had an 'inter-sex condition'.
- Although it was already known that oestrogen
in river water could feminise male fish, the researchers said they were
surprised by the extent and severity of the effect.
- According to the agency it is now clear
that effluent from sewage treatment plants does contain substances that
change the hormones in fish, although further research is needed to determine
exactly which pollutants are responsible for the changes.
- Oestrogen-type substances exert a powerful
effect at very low concentrations and fears have been raised that small
amounts could find their way into domestic water supplies.
- Dr Jean Ginsburg, a hormone specialist,
said that any possibility of such substances entering the food chain is
reason enough to implement tougher standards.
- "What we ought to be doing is adopting
what is called the precautionary principle," she said.
- "That means [that] when there is
sufficient evidence for cause for alarm, we take steps to avoid it."
- The Environment Agency says it now wants
water companies to investigate ways of removing oestrogen-type substances
- Jan Pentreath, from the agency, said:
"We want the water industry to look at this carefully and see if there
is something they can do.
- "We want industry to consider ways
of phasing [the chemicals] out, finding alternatives, or at the very least
minimising the risk of them entering the environment."