U.S. Water News Online
WASHINGTON -- Over the last two years, scientists working
on the Potomac River have netted 111 smallmouth bass with bizarre
sexual traits. The fish were males but had eggs growing inside their
Researchers found many of these gender-bending bass downstream
from sewage treatment plants in water tinged with a chemical called
ethinylestradiol -- the active ingredient in birth control pills.
More studies are necessary, biologists say, but evidence is
mounting that trace levels of prescription drugs in rivers and
streams may be harming fish, tadpoles, frogs, mussels and oysters.
The pharmaceuticals are passing unaltered through people's bodies and
sewage plants into waterways.
In Georgia and Mississippi, scientists recently discovered that
the antidepressant Prozac, in water downstream from sewage plants,
can kill tadpoles, stunt the growth of others and befuddle the
survivors so they swim in circles and can't flee from predators.
In Pennsylvania, a biologist reported that small amounts of Prozac
may cause mussels and clams to discharge their sperm and eggs
prematurely, dooming their offspring. And in Texas, a researcher
found that the sexual organs of male minnows shrank when they were
lowered into a river tainted with birth control drugs.
"We might just be seeing the tip of the iceberg in terms of the
cumulative impact of all this," said Dr. Thomas Burke, associate
chairman of health policy at the Johns Hopkins School of Public
He said concerns about pharmaceutical pollution are likely to
become more urgent as a growing human population consumes a
multiplying number of medications.
"This is an important area we have to study more," Burke said.
The U.S. Environmental Protection Agency is working with other
federal offices to investigate whether the government should require
better sewage filtration systems to remove drugs before water is
discharged, according to the agency.
Pharmaceuticals are not regulated as pollutants, and most sewage
plants are not designed to break them all down.
One stumbling block to adding better filtration systems is the
cost, which could reach $100 million to install advanced technology
on each large sewage treatment plant, said Shane Snyder, research
manager at the Southern Nevada Water Authority.
"The water industry has no problem spending the public's money to
put in new [filter] technology," Snyder said. "But the cost might
mean that fewer schools can be built or fewer hospitals."
Vicki Blazer, a fish pathologist with the U.S. Geological Survey,
began investigating smallmouth bass in the Potomac River a few years
ago when fishermen reported their catch was falling.
She worked with natural resources officials in Maryland and West
Virginia, who used devices that fired electric shocks into the
Potomac River to stun hundreds of fish in 2003 and 2004.
Blazer said she dissected 184 male bass, and found that 111 of
them -- or about 60 percent -- had eggs growing inside their sexual
organs. All nine male bass netted downstream from the Hagerstown
sewage plant had this sexual abnormality. Fish like these almost
never show up in clean rivers, she said.
Blazer is looking into the possibility that the birth control
drugs caused the sexual confusion. She also found several other
pollutants in the river, including triclosan, a disinfectant used in
soap, and trifluralin, a farm pesticide. Any of these chemicals could
be disrupting fish hormonal systems, she said.
In an effort to pin down which is causing the mutations, Blazer's
colleagues have shocked an additional 100 fish during the last month
at five places along the lower Potomac River in Maryland, including
downstream from the Blue Plains sewage treatment plant near
The study is important, Blazer said, because fish with deformed
sex organs might not reproduce as well. People also draw drinking
water from the Potomac, and the same chemicals that could be harming
fish populations might also be affecting humans, she said.
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