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The Precautionary Principle

The Institute of Science in Society

Science Society Sustainability

This article can be found on the I-SIS website at http://www.i-

ISIS Press Release 09/01/06

Lectures in The Philippines

By Dr. Mae- Wan Ho and Prof. Peter Saunders in universities and open forums in Luzon and Mindanao 11-16 December 2005

The Precautionary Principle

Prof. Peter Saunders

Institute of Science in Society and King’s College London


The precautionary principle is really just a statement that we shouldn’t introduce a new technology or continue with an old one unless we’re convinced it’s safe both for us and for the environment. If we’re not sure, we wait until we are. We don’t just charge ahead and hope for the best.

This is obvious common sense, but many powerful people oppose it, often because they or their friends want to make money out of products that appear likely to be - or even are known to be - hazardous. I list and refute the arguments most often used against the precautionary principle. I describe one example - asbestos - where failure to apply the principle resulted in a massive cost in lives and money,

and show how the principle could and should be applied in the cases of Bovine Somatotropin (currently before the WTO) and GMOs.

When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically. In this context the proponent of an activity, rather than the public, should bear the burden of proof.

The Wingspread Declaration [1]

The Precautionary Principle applies “where preliminary objective scientific evaluation indicates that there are reasonable grounds for concern …”

The European Commission [2]

It’s just common sense

The precautionary principle is really just a statement that we shouldn’t introduce a new technology or continue with an old one unless we’re convinced it’s safe both for us and for the environment. If we’re not sure, we wait until we are. We don’t just charge ahead and hope for the best.

Now you might think that this was such an obviously sensible idea that no one could possibly disagree. Unfortunately, there are many who do. That’s usually because they or the people who support them want to make profits out of things that might be very dangerous: for instance, asbestos, tobacco and GMOs.

They insist on what we might call the anti-precautionary principle: what they are producing must be permitted unless and until it can be proven to be dangerous. What is more, they set a very high standard of proof: the tobacco companies are still advertising and selling cigarettes despite the overwhelming evidence that smoking, even passive smoking, contributes to many serious diseases, not only lung cancer, and significantly shortens life expectancy.

Because these people represent big corporations, well- financed think tanks, and university departments, they have a lot of influence. So we can’t assume that just because the precautionary principle is common sense our governments are going to adopt it. We’re going to have to convince them, and to do that we have to be clear in our own minds about what it is and how it works.

The burden of proof

The precautionary principle is like the legal principle of the burden of proof. In a criminal court, the two sides are not on equal terms. The defendant doesn’t have to prove he is innocent. He doesn’t have to prove anything. The prosecution must prove he is guilty “beyond reasonable doubt.” If they cannot, he goes free.

The reason for this deliberate bias is that while we hope that our courts will convict the guilty and acquit the innocent, they won’t always get it right, and we have to think about what will happen then. Most people would agree that while it is bad that a crime should go unpunished, it is much worse that an innocent person should be convicted. So just thinking that someone is probably guilty isn’t good enough. The jury may only convict if they are really convinced he is, beyond reasonable doubt.

In exactly the same way, the precautionary principle says that if we have good scientific grounds for being concerned that something presents a serious danger to health or the environment, then we do not have to prove that it is dangerous before we can justify banning it. It is the people who want to use and profit from the technology that have to prove it is safe. Of course they don’t have to provide absolute proof – there are no absolutes in science any more than in the courtroom – but they have to demonstrate safety beyond reasonable doubt. And we bias the decision in that direction because the damage that can be done if a technology turns out to be unsafe can be so much greater than what we stand to lose by waiting until we are sure it is safe, or can be made so.

Common criticisms refuted

Opponents of the precautionary principle have a number of standard objections that they generally raise when attacking it. They are all easily refuted, and I’m not even sure if the people that put them forward really believe them, but it’s as well to go through the ones that are most often used.

1. “The precautionary principle is useless because it does not lead to decisions.” The principle is not a formula for making decisions. Decisions are made by people exercising their judgement, and the precautionary principle is just one of the things they should take into account. A judge will explain the concept of the burden of proof to the jury, but they still have to decide whether the defendant is guilty beyond reasonable doubt, and even what level of doubt they are prepared to accept as reasonable. In the same way, even if we accept the precautionary principle, we must still weigh up the evidence as best we can and decide for ourselves.

2. “The precautionary principle does nothing that is not already covered by risk assessment.” Risk assessment involves multiplying the probability that something happens by the cost if it does. The precautionary principle comes into play when we are not able to estimate one or both of these factors at all, or with any degree of accuracy.

3. “The precautionary principle is too weak. It would make no difference at all to policy.” I shall show later how using the precautionary principle would have made a major difference to policy on asbestos (as it would have on many other issues) and would make a difference now if applied to BST and GMOs.

4. “The precautionary principle is too strong. It would stop all progress”. In practice, the Precautionary Principle would not affect most innovations at all. In most other cases, it would mean only a short delay while the technology was properly tested. (Even with the burden of proof on the prosecution, many people do get convicted!)

5. “The precautionary principle is anti- scientific.” Nothing could be further from the truth. The precautionary principle applies only when there are good scientific grounds for concern. It then requires that more good science be done to address those concerns. What is anti-scientific is to assure the public that something is safe when you have no evidence to back up your claim.

6. “The precautionary principle is merely a cover for protectionism.” Anything that involves regulation can be used to block imports. Here, however, the innovator has the opportunity to have the ban lifted by providing convincing scientific evidence that what he wants to export is safe.

7. “These issues should be decided in the courts.” The precautionary principle is not an alternative to the courts; like the burden of proof it is a principle that the courts can and should use.


I’ll now discuss three examples. The first illustrates clearly what can happen when the precautionary principle is not used; the other two are current issues where using the principle would make a real difference.


Everyone knows that asbestos is very dangerous and that it is still being removed from buildings some of which are no more than 30 years old. Most people probably believe that the danger was only recently discovered and that action was taken as soon as it was. Actually it wasn’t quite like that [3].

Asbestos was first mined in Canada in 1879. It was soon noticed that people who worked with asbestos tended to suffer from respiratory diseases, and in 1898 an English factory inspector, Lucy Deane, observed that these were more serious than what she saw in other workers who worked in dusty conditions. She was also able to discover why: asbestos fibres are sharp and so likely to damage the lungs.

Nothing was done about her report, and even in 1917, when more evidence had accumulated, the UK Factory Department decided that there was no need to take any action. In the very next year, however, insurance companies in the USA and Canada started to refuse cover to asbestos workers, “due to the assumed injurious conditions in the industry”.

Note the parallel with GMOs today. We are being assured by the biotech industry and by our governments that GMOs are safe, yet at the same time the industry is refusing to accept any liability if they are not, and insurance companies are refusing to provide cover. A clear example of what happens when, as the Americans say, you ask someone to put his money where his mouth is.

For most of the rest of the twentieth century, the evidence against asbestos steadily built up. It became clear that not only people who worked with asbestos but also their families and others who came in contact with it were at risk. Yet far too little was done, and then only in the factories. It wasn’t until 1982 that the British government started to restrict the use of asbestos and look for alternatives, and only in 1998, the one hundredth anniversary of Lucy Deane’s report, was asbestos banned altogether in the UK and France.

Even then, the Canadian government went to the World Trade Organisation to have the ban declared an artificial restraint of free trade. The WTO rejected the appeal – it is hard to see how even the WTO could have done anything else in view of the overwhelming evidence – but this is a very clear example of how an industry can put profit ahead of safety and how a government can support it.

Throughout the whole of the twentieth century, governments consistently took an anti-precautionary approach to asbestos. They waited for undeniable evidence of harm before taking any action, which meant they always acted far too late.

What would have happened if they had applied the precautionary principle? We don’t know, because we can’t say when they would have banned asbestos or at least regulated its production and use. That would have been a matter of judgement at the time.

We also do not have anything like full records of the number of deaths due to asbestos or the cost of removing it from places where it was used. Some partial data are, however, available and they give us an indication of the scale of the problem. For example, it has been estimated that between 1979 and 2001, over 200,000 people died in the USA from diseases caused by asbestos. It has also been estimated that there are about 250,000 mesothelioma deaths still to come in the EU even though asbestos is no longer used; this is because the disease takes so long to develop. The long time lag between first exposure and the actual onset of the illness is yet another argument in favour of a precautionary approach.

As for the financial loss, the Dutch have estimated that if they had banned asbestos in 1965, when the mesothelioma evidence had been widely accepted, instead of in 1993, they would have saved about $20 billion in construction and compensation costs. That’s for one small country and assuming action was taken considerably later than a precautionary approach would have implied, so you can imagine what the total must be.


Bovine somatotropin, commonly known as BST, is a growth hormone frequently given to cattle in the USA. The European Union prohibits the import of products from these cattle on health and safety grounds. In 1996, the United States appealed to the World Trade Organisation, claiming that the EU’s ban was an unfair restraint of trade.

Let’s see how the precautionary principle operates. Are there good scientific grounds for concern? There certainly appear to be, because we always have to be cautious where hormones are involved. They are signal substances, telling the body to do something rather than doing it themselves, and that means they can have major effects even at very low dosages. And while BST normally acts in cattle, hormones are not necessarily species specific, which means BST might act in humans as well.

When we look into the situation more closely, however, things look a bit better, at least initially. Most of the BST in milk is destroyed by pasteurisation. What’s more, any that survives can’t function as a growth hormone in humans because the molecule is the wrong shape and doesn’t bind to the appropriate receptors.

On the other hand, BST stimulates the production of ‘insulin-like growth factors’ in cattle, and these are not destroyed by pasteurisation. In humans, high levels of IGF-1 are associated with a greater risk of cancer [4]. At present, we don’t know whether it increases the risk or whether it is merely a marker for cancer risk – i.e. we don’t know if it is cause or effect – but it’s clearly something to be concerned about.

There is also the problem that hormones often play more than one role. Even if we know their chief function we may have no idea what else they do. So the fact that BST can’t act as a growth hormone in humans doesn’t mean that it doesn’t act in humans at all.

As in conventional risk assessment, we have to look at the other side as well. How great a risk we are willing to take naturally depends on the cost of not taking it. There is no shortage of milk in the EU; on the contrary, the EU has had to impose quotas to reduce milk production by its own farmers.

Is BST a hazard to human health? We don’t know. We don’t even know how likely that is. But that’s precisely the point. If we were sure it was dangerous, there’d be no argument. It’s when we aren’t sure that the precautionary principle comes into play.

Here it surely leads us to conclude that on the basis of the evidence currently available, the EU is justified in not permitting the import of milk from BST treated cattle.

The WTO, however, generally applies the anti-precautionary principle. It therefore ruled that it was up to the EU to prove that BST is hazardous to human health and gave the EU a year to do this. Not surprisingly, the EU was not able to comply, largely because whatever harmful effects there are probably can’t be seen in such a short time, even if we knew exactly what we were looking for, which of course we don’t. After all, both asbestos and smoking can take 20 years or more to act, and here one of the chief concerns is the possible effect of ingesting small quantities of IGF-1 over a long period of time. In the end, the ban was allowed to stand, but only for the time being; the US is still trying to get it removed.

I was recently arguing with a leading British opponent of the precautionary principle. I asked him several times, in different ways, if he thought the WTO was right to insist that the EU drop its ban on BST. He steadfastly refused to give me an answer, which I’m sure was because he agreed the WTO was wrong but didn’t want to admit that the precautionary principle can really work.

Finally, he said that it didn’t matter whether we accepted the precautionary principle or not because the Americans had told him that whatever the WTO decided, they’d force BST products into the EU one way or another. That tells you where the opponents of the precautionary principle really stand. They’re not interested in the logic of the case. They just want to foist their products on us by whatever means they can. That is exactly what they are doing with GM crops.


I’m not going to say much about GMOs because Mae Wan Ho will be dealing with them in some detail. As she’ll explain, there are many good reasons for being concerned about GMOs: it is an inherently hazardous technology, the risks of horizontal gene transmission, allergic effects, and so on [5].

I’d like to comment on one further issue however, diversity. Here in the Philippines there are thousands of varieties of rice. If you were to switch to GM rice, there would be at most a handful. The biotech companies aren’t going to genetically modify large numbers of varieties, and there wouldn’t be time for local types to evolve, even if farmers were allowed to keep their seeds – which of course they are not.

This could leave the Philippines highly vulnerable to any new pest or disease that might appear. Remember, GM crops have been engineered to be resistant to one particular challenge: a particular pest or a particular disease. They are at least as vulnerable to other pests and diseases as conventional crops, which makes relying on a single variety a very risky strategy.

It’s worth bearing in mind that one of the reasons the famine in Ireland in the 19th century was so devastating was that the country was very heavily dependent on the potato, which is not indigenous to Ireland. It had been brought to Europe comparatively recently from Peru. With little or no diversity when the blight arrived, almost the entire crop was destroyed.

The precautionary principle does not lead to the conclusion that we should stop all research into GMOs. If we think that genetic engineering has the potential to improve crops, and it may well have, then there’s no reason not to carry out research, providing we do it in enclosed laboratories and greenhouses. The objection is to releasing GMOs into the environment when there are so many unanswered questions concerning their safety and their effect on the environment in general and other crops in particular. We ought to be doing more research into understanding what happens in genetic engineering and finding better and safer ways of doing it, and of course devoting far more of our time, effort and resources to discovering how we can improve our farms and our crops without using GMOs (many examples in successive issues of Science in Society, especially #17, 23 and 28) [6-14].


In short, there’s nothing difficult about the precautionary principle. It’s just common sense. The only problem is getting our governments to accept that, and to act on it.

A fully referenced version of this paper is posted on ISIS members’ website. Details here

Making the World Sustainable &GM- Free

Dr. Mae-Wan Ho

Institute of Science in Society, PO Box 32097, London NW1 0XR, UK

Lecture tour in the Philippines 6-19 December 2005


Decades of an “environmental bubble economy” built on the over-exploitation of natural resources has accelerated global warming, environmental degradation, depletion of water and oil, and falling crop yields, precipitating a crisis in world food security with no prospects for improvement under the business as usual scenario.

Genetically modified crops promoted to “feed the world” have the worst features of industrial monocultures and are proving inherently hazardous to health. They are a dangerous diversion from the urgent task of getting our food system sustainable in order to really feed the world. Expanding the cultivation of GM crops across the world is a recipe for global biodevastation, massive crop failures and global famine.

There is a wealth of knowledge for making our food system sustainable that not only can provide food security and health for all, but can also effectively mitigate global warming by preventing greenhouse gas emissions and creating new carbon stocks and sinks.

One of the greatest obstacles to implementing the knowledge is the dominant economic model of unrestrained, unbalanced growth that has precipitated the present crisis. I describe a highly productive integrated farming system based on maximising internal input to illustrate a theory of sustainable organic growth as alternative to the dominant model.

The complete paper with references posted on ISIS members’ website. Details here

This article can be found on the I-SIS website at http://www.i-

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