[Pharmwaste] Gender-bending pollutants changing sex of clams, scientists say

[Tenace, Laurie]

http://www.guardian.co.uk/science/story/0,,1761306,00.html


Gender-bending pollutants changing sex of clams, scientists say 

Ian Sample, science correspondent
Wednesday April 26, 2006
The Guardian 


Scientists working along the south-west coast of Britain have discovered
widespread evidence of chemicals disrupting the sexual development of
sensitive marine organisms.
In a study published today, the researchers report the first cases in which
hormone-disrupting pollutants are believed to be responsible for a
gender-bending effect on marine invertebrates living in British estuaries.
The finding has caused alarm because the affected species are crucial for the
health of the ecosytem, in some cases forming the staple diet of many larger
animals.

Researchers at the Marine Biological Association in Plymouth examined clams
in estuaries from Southampton to the Severn and found that males at 17 of 23
sites suffered a condition called "intersex", where their testes contain both
sperm and eggs. In some cases the male sexual organs contained thousands of
eggs and up to 60% of clams were affected.

Some scientists fear that the species may become so badly malformed that they
will be unable to reproduce. If that causes a significant drop in their
numbers, there will be too little food for animals that feed on them, such as
plovers, bar-tailed godwits and other wading birds.

Bill Langston, who led the study, said any knock-on effects could be hard to
predict. "Invertebrates ... support the whole ecosystem by being at the
bottom of the food chain. If something goes wrong at the bottom of the chain,
there's a risk it could be serious for other species higher up," he said. One
concern is that the clams concentrate the chemicals in their flesh, and so
other animals eating them could also begin to show signs of feminisation.

Dr Langston's team became aware of the problem when they started to identify
the sex of clams in the Devon Avon. The researchers chose the site in the
hope that it would be free of chemicals that might interfere with tests on
the organisms.

According to the study, published in the journal Biology Letters today, the
most likely culprits are industrial hormone-mimicking chemicals, agricultural
chemicals, pesticides or natural oestrogen that has found its way into
estuaries after passing through sewage treatment works.

Tests conducted by the team show that exposing clams to estradiol, a natural
female hormone, or ethinyl estradiol, a similar compound used in the female
contraceptive pill, can trigger intersex.

Because there is little industry along the Avon estuary, Dr Langston said the
effect might be caused by large amounts of hormones excreted by cattle
grazing alongside estuaries.

Alastair Grant, director of the centre for ecology, evolution and
conservation at the University of East Anglia, said: "Something as
significant as large-scale sex change in an important estuarine organism
makes you think there are other effects on other organisms which we haven't
picked up yet. The worry is that it is the tip of the iceberg."


Laurie J. Tenace
Environmental Specialist
Florida Department of Environmental Protection
2600 Blair Stone Road, MS 4555
Tallahassee, Florida 32399-2400
PH: (850) 245-8759
FAX: (850) 245-8811
Laurie.Tenace at dep.state.fl.us  
 
view our mercury web pages at: 
http://www.dep.state.fl.us/waste/categories/mercury/default.htm 

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