Study Links Water Pollution
With Declining Male Fertility
New research strengthens the link between water pollution and
rising male fertility problems.
The study, by Brunel University, the Universities of Exeter and
Reading and the Centre for Ecology & Hydrology, shows for
the first time how a group of testosterone-blocking chemicals
is finding its way into UK rivers, affecting wildlife and potentially
The research was supported by the Natural Environment Research
Council and is now published in the journal Environmental Health
The study identified a new group of chemicals that act as anti-androgens.
This means that they inhibit the function of the male hormone,
testosterone, reducing male fertility. Some of these are contained
in medicines, including cancer treatments, pharmaceutical treatments,
and pesticides used in agriculture. The research suggests that
when they get into the water system, these chemicals may play
a pivotal role in causing feminising effects in male fish.
Earlier research by Brunel University and the University of Exeter
has shown how female sex hormones (estrogens), and chemicals that
mimic estrogens, are leading to feminisation of male
fish. Found in some industrial chemicals and the contraceptive
pill, they enter rivers via sewage treatment works. This causes
reproductive problems by reducing fish breeding capability and
in some cases can lead to male fish changing sex.
Other studies have also suggested that there may be a link between
this phenomenon and the increase in human male fertility problems
caused by testicular dysgenesis syndrome. Until now, this link
lacked credence because the list of suspects causing effects in
fish was limited to estrogenic chemicals whilst testicular dysgenesis
is known to be caused by exposure to a range of anti-androgens.
Lead author on the research paper, Dr Susan Jobling at Brunel
Universitys Institute for the Environment, said: We
have been working intensively in this field for over ten years.
The new research findings illustrate the complexities in unravelling
chemical causation of adverse health effects in wildlife populations
and re-open the possibility of a human wildlife connection
in which effects seen in wild fish and in humans are caused by
similar combinations of chemicals. We have identified a new group
of chemicals in our study on fish, but do not know where they
are coming from. A principal aim of our work is now to identify
the source of these pollutants and work with regulators and relevant
industry to test the effects of a mixture of these chemicals and
the already known environmental estrogens and help protect environmental
Senior author Professor Charles Tyler of the University of Exeter
said: Our research shows that a much wider range of chemicals
than we previously thought is leading to hormone disruption in
fish. This means that the pollutants causing these problems are
likely to be coming from a wide variety of sources. Our findings
also strengthen the argument for the cocktail of chemicals in
our water leading to hormone disruption in fish, and contributing
to the rise in male reproductive problems. There are likely to
be many reasons behind the rise in male fertility problems in
humans, but these findings could reveal one, previously unknown,
Bob Burn, Principal Statistician in the Statistical Services
Centre at the University of Reading, said: State-of- the-
art statistical hierarchical modelling has allowed us to explore
the complex associations between the exposure and potential effects
seen in over 1000 fish sampled from 30 rivers in various parts
The research took more than three years to complete and was conducted
by the University of Exeter, Brunel University, University of
Reading and the Centre for Ecology & Hydrology. Statistical
modelling was supported by Beyond the Basics Ltd.
The research team is now focusing on identifying the source of
anti-androgenic chemicals, as well as continuing to study their
impact on reproductive health in wildlife and humans.