Colorado, USA
— In 2004, David Norris reported that fish just
below the Boulder, Colo., Wastewater Treatment Plant's
outflow pipe were changing sex.
Two years later, the
University of Colorado integrative physiology professor
has expanded his study, which now involves one "Fish
Exposure Mobile" research trailer in operation and a
second on the way.
Science done in the
trailer has verified Norris' 2004 study and shown that
surprisingly low concentrations of treatment-plant
effluent can change male fish into females.
The 2004 study showed
that certain chemicals from pharmaceuticals and
personal-care products made it through the Boulder
Wastewater Treatment Plant and into Boulder Creek. Ninety
percent of the white suckers swimming downstream of the
plant were female. Upstream, there was an even
split.
"What we see in the fish
downstream is as if they are taking birth control pills,"
Norris said.
The female fish - both
the transsexuals and the original girls - had
smaller-than-average ovaries. The remaining males
produced less sperm, showing the water effluent also has
contraceptive effects, he said.
The chemicals are
believed to come from excreted birth-control hormones,
natural female hormones and detergents flushed down
toilets and drains. In the ecosystem, they are known as
endocrine disrupters, settling into cell receptors
intended for hormones and garbling the body's chemical
communications.
To bolster his evidence,
in 2005 Norris and colleague Alan Vajda, a CU research
associate, set up the Fish Exposure Mobile in a trailer
borrowed from the Colorado Division of Wildlife. U.S.
Geological Survey scientists Larry Barber and James Gray
also are working with Norris' team, and the city of
Boulder's cooperation also has been vital, the scientists
say.
Where Norris and Vajda
are what Barber called "world-class endocrinologists,"
Barber and Gray are chemists who have advanced detection
techniques to the point they can spot human estrogen in
concentrations as low as 0.2 parts per
trillion.
They needed such
exactitude because human estrogen, or 17 beta estradiol,
affects fish at concentrations as low as one part per
trillion - the equivalent of a pinch of salt in an
Olympic pool, Norris said.
Barber said volumes of
human estrogen in the pure treatment-plant effluent range
from one part per trillion to about 10 parts per
trillion.
The Fish Exposure Mobile,
parked next to the creek on sewage treatment plant
property, pulls water directly from the plant's outflow
pipe and can dilute it using precise volumes of upstream
Boulder Creek water.
Fathead minnows swim in
two identical tanks inside, each 200 gallons. One fills
with upstream creek water; the other with varying degrees
of wastewater plant effluent. Such control lets
researchers see how fish react to varying effluent
concentrations.
They aimed to create a
controlled experiment and confirm if estrogen and other
compounds from the treatment plant were responsible for
the fish sex change.
"The males were feminized
in seven days," Norris said. "You don't need a Ph.D. to
sex them."
The males have bumps on
the forehead and often attack each other. The fish
exposed to the effluent water lost their bumps and acted
like girls. It confirmed effluent to be the
culprit.
Diluting the treatment
plant's effluent 50 percent feminized breeding male fish
in a week to 15 days, Norris said. Some of the effects
remained evident even when the wastewater plant effluent
was diluted 75 percent.
"We were excited to get
these results, but at the same time we're a little bit
appalled at what we've seen," Norris said.
Sheila Murphy, a
hydrologist with the U.S. Geological Survey in Boulder,
said the Fish Exposure Mobile work has been important to
counter skeptics who attribute transsexual fish in the
Potomac River and other waterways to temperature changes
or other environmental influences.
"What it's showing is
that it's indeed from the wastewater plant," Murphy
said.
