More than 80% of the male bass fish in Washington's major river are
now exhibiting female traits such as egg production because of a "toxic
stew" of pollutants, scientists and campaigners reported yesterday.
Intersex fish probably result from drugs, such as the contraceptive pill, and other chemicals being flushed into the water and have been found right across the US.
The Potomac Conservancy,
which focuses on Washington DC's river, called for new research to
determine what was causing male smallmouth bass to carry immature eggs
in their testes. "We have not been able to identify one particular
chemical or one particular source," said Vicki Blazer, a fish biologist
with the US geological survey. "We are still trying to get a handle on what chemicals are important."
But
she said early evidence pointed to a mix of chemicals - commonly used
at home as well as those used in large-scale farming operations -
causing the deformities. The suspect chemicals mimic natural hormones
and disrupt the endocrine system, with young fish being particularly
susceptible.
The chemicals could include birth control
pills and other drugs, toiletries especially those with fragrances,
products such as tissues treated with antibacterial agents, or goods
treated with flame retardants that find their way into waste water. However, Blazer also pointed to runoff from fertilisers and pesticides from agricultural areas.
About 5 million people live in the greater Washington area, and 90% of them get their drinking water from the Potomac.
There is evidence that the anomaly is not confined to the Potomac, one of the largest rivers on America's Atlantic coast.
A
report last year by the US geological survey found intersex fish in a
third of 111 sites tested around the country. Of the 16 fish species
studied, the condition was most common in smallmouth and largemouth
bass and among males, although researchers also discovered the
occasional female fish with male characteristics. The researchers
studied sites along some of America's greatest rivers from the
Mississippi to the Rio Grande.
"We need to get these
toxins out of our river water," said Hedrick Belin, the president of
the Potomac Conservancy. The campaign group called for $3m (£1.9m) in
research over three years on endocrine disrupters on their effects on
fish. It also called on the authorities to involve pharmaceutical
companies in the safe disposal of drugs, and to invest in technology
that can filter out endocrine disrupting compounds.