Many pesticides are now suspected endocrine disruptors
– chemicals that lead to an increase in birth defects, sexual
abnormalities and reproductive failure. Nikki van der Gaag
interviews Dr Theo Colborn, whose groundbreaking
work has unearthed a growing menace.
I had been looking forward to this interview for several weeks.
‘Oh.’ The disappointment must have been obvious in my voice because the person on the other end of the phone hastened to cheer me up. ‘It’s OK. She’s expecting your call. But she is not well and is at home today.’
‘Should we fix another time?’
‘No. She wants to talk to you. She just didn’t want to pass any infection on to people in the office.’
That, I decide later, is probably typical of Theo Colborn. Kind-hearted but sharp, she has an enthusiasm coupled with the kind of intellectual rigour that made me realize why people take what she says very seriously.
She was a latecomer to the world of science, only going back to college in 1982 at the age of 51. She had previously been a pharmacist, a sheep farmer and a student of ecology. She is a mother of four and a grandmother.
The voice on the other end of the phone is soft but assertive, if a little croaky.
How did you become involved in this research?
By accident. I was working in Washington on a one-year fellowship which was just ending and I was asked to be the scientist on an American/Canadian team investigating the state of the environment in the Great Lakes area around Michigan. There was little information on the health of people living in that area, which had been known to be heavily polluted.
What I found was amazing. There was lots of research on individual species, but nothing that looked at the Lakes as a whole. People had been fooled into thinking that things were OK because they were only looking at adult animals. Because not that many had actually died people thought things were fine.
The US and Canada assumed the water was clean and spent $50 million a year putting uncontaminated fish back into the lakes.
But things weren’t fine. Not at all. No-one had thought to look at the offspring of the eagles or the gulls or the trout – or indeed the people living around the waters. We found other problems, all of which seemed to be related to hormones. Male animals for example were not reaching sexual maturity. Many species had thyroid problems. Some adults simply abandoned their young or the babies died unexpectedly, in large numbers, for unknown reasons. Birds were born deformed with crossed bills, missing eyes and clubbed feet.
And this is where alarm bells began to ring for me. If babies were being affected then these chemicals must have the ability to cross the placenta. We came to recognize that a crucial barrier had been broken – a barrier as significant as the breaching of outer space. It was the barrier of inner space. These chemicals were getting through the placenta and reaching foetuses in the womb and the eggs of birds and fish.
This meant that all aspects of development were likely to be affected – including intelligence. Of course we couldn’t test the intelligence of the animals but we did find out that babies of mothers who had eaten fish from the Great Lakes had lower intelligence than those whose mothers had not eaten fish – as well as lower birth weight and a host of other problems. And the mothers didn’t have to eat large quantities of fish; two to three meals a month were sufficient to affect the babies in the womb.
So how did people react to these findings?
It was not an easy message to get across. We were challenging all the traditional methods of testing for poisons. All the assessments of risk were based on the likelihood of contracting cancer. They didn’t take other risks into account. And yet we were finding increasing evidence that these chemicals could not only reach the foetus but also that many of them were able to mimic natural hormones – with disastrous effects on the endocrine system which controls sexual development.
So the safe levels that are set at the moment are still based on the risk assessments of cancer?
Yes. And without recognizing just how little it takes to disrupt development. Look, we know that all it takes is a tenth of a trillionth of a gram of free estrogen hormones for a male mouse to develop problems. It takes 2.6 parts per trillion of a chemical called T-4 in the womb for a child to be born with an IQ which is 4 points lower than it should be.
So how can you know all this for sure? How can you test for effects on unborn children or on things which might affect two or three generations?
Of course this is difficult to test. But we know that some chemicals bioaccumulate – that is, they build up in the body and can be stored for a long time in body fat. Many other chemicals are very much a part of our daily lives. They include certain pesticides and also some plastics. And the combination of two or more of these can be even stronger.
They can also spread to other places, can’t they?
Yes. High levels are found for example in the Arctic in the bodies of Inuit people, polar bears and other wildlife who have never gone near such chemicals.
Let me explain. Take the flood in Mississippi in 1996. We can see from aerial photos that the floodwater flowed down the rivers and out into the Gulf of Mexico. Then the currents took them across the north Atlantic via the Gulf Stream. Six weeks later they were off the coast of Newfoundland. The rivers, seas and oceans are not separate. They mix together. Air too flows from one place to another. And they stay around a long time. Many of these chemicals take a very long time to break down in the body. DDT for example has a half-life of 57 years in temperate zones.
Hormones get their name from the Greek word meaning ‘to urge on’. They are chemical messengers produced and released into the bloodstream by organs known as the endocrine glands. These include the testicles, the ovaries, the pancreas, the adrenal glands, the thyroid, the parathyroid and the thymus. These play a crucial role in helping the foetus to grow in the womb, in the development of the baby and young child, and in the sexual development of both male and female.
Endocrine-disrupting chemicals interfere with these hormones, most crucially at the stage when the baby is developing in the womb. But they can also mimic the hormone or block or stimulate its action in adults. So, for example, the pesticide endosulfan affects the body’s oestrogen. Amitrole can affect levels of hormones in the thyroid gland and a number of organophosphate and carbamate pesticides have been linked to lower sperm counts.
How about the effects in the developing world?
Well the direct effects of people using some of these chemicals are terrible. It is particularly bad for farm workers in the Third World who don’t have the protective clothing or the ability to protect themselves.
But it is very difficult to get accurate statistics of people who have died or suffered ill-effects from chemical use. Many people in the fields have to move about to find work and because they don’t stay in one place no-one can trace them to test what has happened.
Even when this is possible, research at the moment is only looking at the effects on adult workers. No-one is studying the children. But the evidence is there. We know that if adults are affected then the children are probably even more so because they get doses in the womb as well as doses after they are born and their bodies are also that much smaller.
So what can be done?
The most important thing is to find alternatives. As a priority there needs to be a crash programme of research for new ways of controlling diseases like malaria and dengue fever because people are still having to use insecticides like DDT to kill mosquitoes. This will be expensive and the pharmaceutical companies are not going to foot the bill. So governments have to take responsibility. There are already a number of initiatives: for example, the one to ban POPs (see PICs, POPs and the Pesticide Code) many of which are pesticides. But progress is difficult. Russia for example doesn’t want to stop producing PCBs, a family of synthetic chemicals used to insulate electrical equipment.
What about at an individual level?
One of the things I always tell people is to buy organic. This is not only good for the consumer’s health but it means that the people growing the food don’t have to put up with the chemical doses either. I think there is growing awareness of this in Europe. People here in the US still don’t understand what I mean when I talk about this as a kind of altruism; one which also helps the people who actually work in the fields.
The other thing I tell people is to avoid eating fatty foods because many of the persistent fat-soluble chemicals are found in body fats. Eat more beans!
Our Stolen Future, the book you co-authored on endocrine disruptors, has been hailed as the second Silent Spring. What impact do you think it has had?
Well, it has been translated into 18 languages. The Japanese in particular are very interested. Japan has put a lot of money into research on endocrine disruptors – far more than we have here in the US, where the focus is on treatment and cures instead of prevention. Society is going to have to get its values straight. And the US needs to begin by spending money to determine how to practise prevention rather than hopelessly looking for cures that come too late to stop the irreversible damage of endocrine disruption.
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