The "precautionary principle" says that when an activity may threaten human health or the environment, precautionary measures should be taken -- even if some cause and effect relations are not established scientifically.

However, using this principle could increase risks to public health and the environment if it is only applied to the potential harms, but not the possible consequences of the precautionary measures themselves.

• For instance, requiring developing countries to reduce greenhouse gas emissions to combat global warming may retard economic growth, leading to greater hunger, poorer health and higher mortality.

• And higher oil and gas prices could increase hunger and delay the switch from solid fuels to more environmentally benign fuels for heating and cooking.

To ensure that policies do not create greater harm than the harm avoided, say experts, we need some criteria to evaluate potential threats. Thus,

• Threats to human health, especially the threat of death, should take precedence over threats to the environment.

• More immediate threats should be given priority over threats that could occur later.

• Threats of harm that have a higher certainty should take precedence over those that are less certain.

• For threats that are equally certain, more weight should be given to those that have a higher expected cost -- which might be measured in expected deaths or lost biodiversity, for instance.

• If the technology is available to adapt to the adverse consequences of a policy, the harm can be discounted to that extent.

• Irreversible or persistent potential harms should be given greater priority over temporary or reversible ones.

When applied to global warming, these criteria indicate we should focus on solving current problems that may be aggravated by climate change, and on increasing society's adaptability and decreasing its vulnerability to environmental problems.

Source: Indur M. Goklany, "Applying the Precautionary Principle to Global Warming," Policy Study Number 158, November 2000, Center for the Study of American Business, Washington University, Campus Box 1027, One Brookings Drive, St. Louis, Mo., 63130, (314) 935-5630.