10/05/2006 - Evidence
is surfacing of a disturbing trend where industrial
chemicals are meddling with evolution and skewing
the balance of boys and girls born every year.
Nature’s way of perpetuating
the human species has been to balance the ratio
of boys and girls born every year, with a consistent
ratio of approximately 106 boys for every 100
girls, (51.4%) worldwide. However, it appears
that in the world’s richest countries the proportion
of boys born has been declining. This change has
been more marked in areas near chemical plants.
Fewer boys in Italy
One of the first cases where
this trend was noted was in Europe: in Seveso
in Italy, after an explosion in a herbicide manufacturing
plant in 1976 contaminated the local population
with the chemical tetracholorodibenzo-p-dioxin
(TCDD). Birth statistics show that for 20 years
following the explosion, TCDD has acted as a sex-bending
chemical as fewer boys than girls have been born
amongst those families living near the plant.
Professor Paolo Mocarelli, of
the Hospital of Desio, Desio-Milan in Italy, who
has spent many years studying the effects of dioxins,
and carried out the studies following the Seveso
accident explained their significance: “This was
the first time anyone had observed the effects
of TCDD. Before this no one had realised it could
affect sexual ratios in this way”.
As Professor Mocarelli described,
“Following the accidence this dioxin was spread
over a wide area. In the early days it fell on
crops, which were consumed by the local population
and also they inhaled it or absorbed it through
their skin”.
Professor Mocarelli and his
team studied the 239 men and 296 women who had
been exposed to the chemicals in families who
gave birth during the next two decades and found
they produced 346 girls, but only 328 boys. The
researchers analysed the serum samples from all
these parents and discovered that the TCDD pollution
in the exposed men was to blame for the falling
rates of boys born, as the higher rate of the
TCDD concentration levels in the men, the more
likely that their children would be girls.
TCDD is a known endocrine disruptor
which interferes with the body’s reproductive
functions, particularly in women. However, the
study found that the chemical did not affect the
exposed female population’s reproduction patterns.
“We were very surprised to find the effects passed
through the fathers”, said Professor Mocarelli,
“as it is more common for endocrine disruptors
to affect the female”.
The research had two other significant
findings: first, even low TCDD levels – from about
20ng per kg bodyweight – had an effect. Secondly,
the effects have persisted over 20 years. Men
who were in their teens during the accident were
still producing fewer boys many years later, suggesting
that the effects of being exposed to TCDD may
last for years. As Professor Mocarelli explained:
“We also found that the contamination was stronger
the younger the men, as the young of any species
are more vulnerable”.
The lost boys of Canada
Another notorious case of chemicals
affecting the ratio of boys has occurred the other
side of the world, in Canada among the Chippewa
Indian population in Ontario, where only 35% of
the babies born are boys.
The Indians’ community which
borders on the Great Lakes, has been increasingly
encircled by Ontario’s ‘Chemical Valley’, where
factories produce 40% of Canada’s output of plastics,
synthetic rubber and other chemicals. Unfortunately
they belch out huge amounts of chemical pollutants
at the same time. Scientists have described the
levels of contamination as “incredible” and fish
and wildlife in Lake Huron, adjoining the Chippewa
Indians’ land have also been exhibiting sexual
changes.
As community members became
increasingly concerned about the decreasing numbers
of boy babies they approached researchers from
Ottawa University. The subsequent research has
shown a significant decline in the number of male
births beginning in the early 11000s, immediately
following a fire and chemical release at a chemical
plant in 1993.
As only families downwind of
the chemical plants are producing so few boys
it appears that chemicals must be to blame. Professor
Shanna Swan, an epidemiologist and Director of
the Centre for Reproductive Epidemiology at the
University of Rochester School of Medicine and
Dentistry, known for her work on the impact of
environmental exposures on male and female reproductive
health, believes that low levels of exposure to
chemicals such as PCBs and dioxins may explain
why the male birth rate is falling in industrialised
countries.
Nordic countries also
producing fewer males
A further study, this time in
the Nordic countries, also reports a decline in
the ratio of baby boys born in Europe. Danish
scientist Dr. Henrik Møller has found that
the rate of male babies in Denmark, Finland, Norway
and Sweden has been dropping slowly since 1945.
The study, which also tracks
the growing incidence of testicular cancer in
these countries, finds that this decline in male
births is more marked where men who fathered the
children had been diagnosed with testicular cancer
up to two years previously. According to Professor
Møller: “Among the children of the 514
testicular cancer cases, there were 252 boys and
288 girls - giving a sex-ration of 47%”. Again
this is below national ratios of 51.4%.
Worldwide Contamination
These studies all point to a
worrying increase in the effects of chemical pollution
on reproduction. As Professor Mocarelli says,
“While the Seveso study was the first scientific
study to track these effects, now it is accepted
that this is occurring worldwide – among populations
exposed to TCDD as diverse those who developed
chloracne in Austria, among the Inuit and among
Russians close to the city of Ufa and in other
locations”.
It is the future of humans and
wildlife what is at stake, and urgent measures
are needed to stop the uncontrolled spread of
chemical contamination and its potential effects
on humans and wildlife. The European Union has
now a unique chance to take global leadership
in the strive for safer chemicals.
If the text of the new
EU chemicals law (REACH) were strengthened, it
could make a significant contribution towards
global protection against hazardous chemicals.
