[Pharmwaste] Sex reversal in fish linked to chemical cocktail -
Laurie.Tenace at dep.state.fl.us
Mon Mar 2 10:27:41 EST 2009
Sex reversal in fish linked to chemical cocktail.
Mar 02, 2009
Jobling, S, RW Burn, K Thorpe, R Williams and C Tyler. Statistical modeling
suggests that anti-androgens in wastewater treatment works effluents are
contributing causes of widespread sexual disruption in fish living in English
rivers. Environmental Health Perspectives doi:10.1289/ehp.0800197.
Synopsis by Benson T. Akingbemi and Carys L. Mitchelmore
Research using a powerful statistical model suggests that chemical mixes in
wastewater feminize male fish.
Scientists in the United Kingdom report that more than one type of hormonally
active chemical -- not just those that act like estrogen -- play a role in
sex reversal of male fish. Like estrogenic compounds, these other pollutants
are also found downstream of wastewater treatment plants in rivers across the
Male fish living in water contaminated with female hormones (or estrogen
mimics) can become feminized, developing female sex characteristics and
behaviors. Only compounds acting like the natural estrogen hormone estradiol
were thought to cause this type of sex reversal in male fish.
This study shows that is not the case and affirms that male fish are also
feminized by compounds that disrupt -- or possibly block -- the male sex
hormones. These compounds are described as antiandrogens.
This is one of the first studies to link antiandrogens alone, and in concert
with estrogenic compounds, with fish feminization. Much prior research has
focused on the ability of estrogenic compounds to increase estrogen hormone
actions that can bypass male development and lead to female characteristics.
Normally, testosterone and other androgens jump start and then guide the
reproductive tract development that gives rise to the male sex organs.
Antiandrogens can derail this process, preventing male attributes from
developing and allowing the female versions to develop instead.
Antiandrogens are widespread in the environment and their effects on
wildlife, and perhaps people, are possibly underestimated. Drugs used to
treat prostate cancer such as flutamide and bicalutamide and several
chemicals present in the environment including the antifungal herbicide
vinclozolin and phthalates used in the manufacture of plastics, paints, and
perfumes are known to act as antiandrogens.
Male fish turning into females is of concern for the fish and for fish
populations. But, it also has implications for humans. Reproductive problems
-- collectively called testicular dysgenesis syndrome -- are on the rise in
men living in industrialized countries. Low sperm quality/quantity, cancers
and infertility are some of the symptoms.
In rats, similar types of abnormal male reproductive development is readily
caused by exposure to antiandrogenic chemicals.
Given the similarity in reproductive hormones and their functions across
vertebrates, removing or reducing environmental contaminants linked to male
abnormalities should be a high priority.
In the study, the researchers used data on water chemistry and fish
abnormalities collected by the UK's Environment Agency, as well as sampling
additional fish, at 30 different sites. The wastewater was analyzed for
certain chemical levels and its estrogenic, antiestrogenic, androgenic and
antiandrogenic activity. Fish were considered abnormal if they had higher
than normal blood hormone levels, eggs in testis and/or abnormal reproductive
The authors plugged the data into sophisticated statistical tools to examine
the association between estrogenic and antiandrogenic chemicals and several
biological markers of feminization in fish.
Anti-androgenic activity, in addition to the estrogenic, was found in nearly
all of the sewage treatment effluent tested. The model demonstrated that
"feminizing effects in wild fish could be best modelled as a function of
their predicted exposure to both anti-androgens and estrogens or to
Waste Reduction Section
Florida Department of Environmental Protection
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