Tales from a poisoned planet
A report by Alok Jha
29th May 2003
Man-made chemicals are causing serious problems for wild animals.
It 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 the planet.
This 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.
We 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.
The WWF has identified two specific types of chemicals affecting wildlife.
The 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 ecosystems.
The 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 occurring 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.
Physiologically, 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.
Derocher 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.
Research 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 contaminated 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.
Of 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.
Of 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 broadly supports the plans but is adamant that any chemicals appearing persistent or bio accumulative should be banned straight away.
Inevitably, 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 further.
Andreas 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."
EU consultation on chemicals: