29 May 2003
chemicals are causing serious problems for wild animals
by Alok Jha
reads like the line-up for some grotesque travelling circus show:
female, pseudo-hermaphrodite polar bears with penis-like stumps;
panthers with atrophied testicles; male trout and roach with eggs
growing in their testes. But all these abnormalities are cropping
up in wild animal populations, and opinion as to why is converging:
our awesome appetite for artificial chemicals is slowly poisoning
week the WWF warned that evidence for environmental problems caused
by man-made chemicals is mounting fast. A group of 60 scientists
from around the world has signed a declaration calling for action.
humans have designed and made a staggering number of chemicals to
help us live our lives. Between 1930 and 2000, the annual production
of man-made chemicals increased from 1m to 400m tonnes a year. We
have invented some 80,000 new chemicals just in the past 50 years.
Though we may encounter them every day, they are mostly invisible.
Take bisphenol A, a suspected hormone disrupter: 700,000 tonnes
are produced every year in the EU alone and used in everything from
cleaning metals to producing babies' bottles. Others we slather
over ourselves every day - phthalates and parabenes in cosmetic
creams for example. Yet more are in the objects around us, such
as brominated flame retardants on our sofas. All these chemicals
are finding their way into the wider environment.
WWF has identified two specific types of chemicals affecting wildlife.
first are the persistent bioaccumulative chemicals. These can stay
in the environment for long periods and do not break down easily.
They build up in animal tissue and can pass up the food chain or
to successive generations through the placenta or by suckling. Examples
include toxic pesticides such as DDT, which has been banned but
lingers in ecosytems.
second type are the endocrine disrupting chemicals, which interfere
with hormonal action. "When you look at the structure of a
hormone molecule such as testosterone, they have these circular
links of carbon and it's exactly that sort of pattern that's present
on a lot of the pesticides like PCBs," says Andrew Derocher,
a professor of biology at the University of Alberta. Over time,
animals have evolved ways of dealing with naturally occuring chemicals
invading their bodies. But the speed at which man-made chemicals
have been invented and then released into the environment has had
devastating effects. "No organism has evolved to deal with
these human produced chemicals," says Decrocher.
an organism cannot tell the difference between a pollutant molecule
and, say, one of its own hormone molecules. As a result, the natural
mechanisms for dealing with the invading molecules go into overdrive
and may break down more than just pollutants. The result is an imbalance
and, since hormones regulate things like growth and body development,
abnormalities are almost inevitable. But actually proving that the
abnormalities seen in animals are directly related to particular
chemicals is not easy. Decrocher calls the research "correlative
science" and compares it to the argument about smoking - no
one has proved that smoking causes cancer but researchers agree
that the incidences of cancer are at higher levels than in smokers
than non smokers.
has been studying polar bears for the past 20 years and is convinced
that environmental pollutants have had serious effects. "The
more polluted a bear is, the less of an immune response it can generate
to immune challenge," he says. He blames the effect on PCBs,
which persist in the environment decades after they were banned.
on North Sea seals shows adverse health effects as a result of chemicals
present in their local environment. Gwynne Lyons, a toxics science
and policy advisor to the WWF, cites work carried out by Dutch scientists
in the 1990s. "Seals fed on conta minated herring caught off
the Netherlands, where you've got European rivers coming into the
sea, have only had half the breeding success of those fed fish caught
in the north Atlantic, in the open ocean," she says. The former
also had suppressed immune responses. This pollution is believed
to have been an indirect cause in the death of more than a thousand
seals from the distemper virus last summer.
course, humans are just another animal at the top of the food chain.
"If we were exposing the population to harmful levels of chemicals
that can mimic oestrogen and chemicals that can block the action
hormones, the effect you'd see is an increase in hormone-related
cancers - cancer of the breast, prostate, the testes," says
Lyons. "And you would expect to see an increase in birth defects,
the reproductive tract, undescended testes. You might also expect
girls coming to puberty earlier. All those effects do seem to be
happening." A lot of the 300 or so man-made chemicals found
in humans are those that have been banned for decades - PCBs and
other pesticides like DDT. "You can't turn off the exposure
tap overnight," says Lyons.
the thousands of chemicals traded within the EU today, there is
not enough data to make safety assessments on 86% of them. For its
part, the EU recently named 30,000 of the most common chemicals
it wants to test for safety. The WWF broadlysupports the plans but
is adamant that any chemicals appearing persistent or bioaccumulative
should be banned straight away.
those producing the chemicals have a more conservative stance. "It's
so difficult to generalise about so many different chemicals with
so many different applications," says a spokesperson for the
Chemical Industries Association. The CIA argues that groups call
for bans on chemicals because it is easier than investigating them
Kortenkamp, a toxicologist at the University of London School of
Pharmacy, agrees more research must be done but adds that it is
not too early for action. "In a strict scientific sense, we
don't have proof but I firmly believe there are warning signs and
if we wanted to we could act on them now."
consultation on chemicals: http://europa.eu.int/comm/enterprise/chemicals/chempol/whitepaper/reach.htm
chemicals declaration: http://wwf.org.uk/chemicals/declaration.asp