Ban first, ask questions later – is this the way to apply the precautionary principle?

In 1992, a major meeting of world leaders in Rio de Janeiro agreed that, when a possible threat to the environment was identified, "lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures".

This UN definition of the 'precautionary principle' has been popularly translated using a triple negative: not having proof is not a justification for not taking action.

The EC Treaty states that all environmental policy decisions must be based on this precautionary principle. But wider use of the principle, particularly when it comes to health research, remains a source of controversy.

Europe's trading partners have complained about the EU's use of the precautionary principle to keep out, for example genetically modified products or hormone-treated meat. But on the other side of the argument health campaigners in Europe counter that if the precautionary principle were properly applied then regulation would be even tighter.

Diana Smith of the European Public Health Alliance Environment Network (EEN) said the precautionary principle should prevent research being used as an alternative to tough action.

She said: "We [as the EEN] often feel the balance is swinging the other way because profit is put before health."

"For example, if limited research suggests a chemical in a drink is carcinogenic, instead of looking for further research to establish the link we should take immediate action to withdraw the chemical - and, in the short-term, the drink."

Exceptions could be made to this rule, she explained, if the known benefits of a chemical outweighed the risk. "If something is shown to cause a mild skin rash, but it also halves malaria cases, then obviously we would keep it."

Smith said strict application of the precautionary principle would not block important scientific discoveries. If there were a chance a chemical would be beneficial in the future, she predicted, research would still go on even when the chemical was withdrawn from the market.

But John Adams, professor at University College, London, one of the first directors of environmental group Friends of the Earth, warned that over-use of the precautionary principle could be a barrier to research and would block European efforts to become more competitive.

"I am not against the precautionary principle per se," he explained, "I am opposed to its extension to extreme conclusions. A huge number of things that are very useful and that we have learned to cope with would not be allowed if the precautionary principle were applied to them."

On the list of very useful things, he said, is aspirin. Long-term benefits were not in this case revealed by early research. Originally seen just as a pain-relief drug, aspirin has since been found to reduce the risk of heart disease and deep- vein thrombosis.

But modern research also suggests that taking aspirin can in some cases cause abdominal bleeding. If discovered today, said Adams, the painkiller would be subjected to multi-million euro safety tests and, if approved at all, would only be available on prescription.

"If you make the world failsafe you end up able to do nothing at all," said Adams, the author of cultural analysis Risk. "Applied with enough imagi- nation, the precautionary principle would bankrupt governments."

In 1992, a major meeting of world leaders in Rio de Janeiro agreed that, when a possible threat to the environment was identified, "lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures".