What is the precautionary principle?

There are lots of different definitions of the precautionary principle (and no single agreed one), but the essence is captured in the 1992 Rio Declaration on the Environment:

“Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.”

We list here some other definitions of the precautionary principle from various international statements.

When does the precautionary principle apply?

The European Commission suggest the precautionary principle may apply when:

“preliminary objective scientific evaluation indicates that there are reasonable grounds for concern”

The World Health Organization are moving away from the idea of “triggering” or “invoking” precaution at all, rather seeing it as an approach that should underpin all risk assessment.

What does it require?

There have recently been two detailed discussions of the precautionary principle and how it might be applied in practice: one by the European Commission and the other by a UK Government committee. The European Commission summarise the application of the precautionary principle:

Where action is deemed necessary, measures based on the precautionary principle should be, inter alia:

  • Proportional to the chosen level of protection
  • non-discriminatory in their application
  • consistent with similar measures already taken
  • based on an examination of the potential benefits and costs of action or lack of action (including, where appropriate and feasible, an economic cost/benefit analysis)
  • subject to review in the light of new scientific data, and
  • capable of assigning responsibility for producing the scientific evidence necessary for a more comprehensive risk assessment. More on what these actually mean

Has a precautionary approach been adopted for EMFs?

Expand any of the boxes below for details of how precaution has been applied to EMFs in different parts of the world.

Taking precautions for yourself

This page is a discussion of the precautionary principle.  If you decide for yourself that you want to reduce your own exposure as a precautionary measure, we provide some helpful information.

Examples of precaution applied to other issues

Two publications give interesting and contrasting case studies of other issues where there has been scientific uncertainty.

The European Environment Agency report is called ”Late lessons from Early Warnings” and gives examples where it suggests early action could have prevented health or environmental problems.

By contrast, the American Council on Science and Health publish “Facts Versus Fears”, which gives examples where it suggests claims of health risks turned out to be unfounded or exagerated.

SAGE and precaution in the UK

The precautionary measures that exist in the UK resulted from a stakeholder group SAGE - see much more on this

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Precaution applied to EMFs in the UK

The UK has gone down the route of deciding which specific precautionary measures should or should not be applied in regard to EMFs.  These decisions were made by the Government acting on the recommendations of the stakeholder group SAGE.

The measures

For high-voltage power lines, the only precautionary measure is optimum phasing, a design feature of double-circuit lines that reduces the fields.

For house wiring and for low-voltage distribution, there are multiple measures, but mainly endorsing existing best practice rather than introducing new measures.

How this came about

In March 2004, the NRPB recommended to Government:

“The government should consider the need for further precautionary measures in respect of exposure of people to EMFs. In doing so, it should note that the overall evidence for adverse effects of EMFs on health at levels of exposure normally experienced by the general public is weak. The least weak evidence is for the exposure of children to power frequency magnetic fields and childhood leukaemia.” more on the NRPB recommendations 

The Government response said:

“Government has recently engaged in preliminary stakeholder discussions to consider power lines and NRPB advice suggests that this process should be continued, focussing on the possible health effects of continuous low level exposure to power frequency electromagnetic fields.
The Government will be exploring further the practical applications of precautionary measures within a stakeholder engagement process. This will be the subject of wide consultation and will explore any risks and benefits arising in the same manner as a Regulatory Impact Assessment.”

The stakeholder discussions referred to became known as SAGE – stakeholder advisory group on ELF EMFs. The SAGE First Interim Assessment contains detailed analyses of possible precautionary measures for power lines and for house wiring, and the Second Interim Assessment for low-voltage distribution. In both cases Government issued responses detailing which measures would be adopted and which not.

More here on SAGE.  

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Precaution applied to EMFs in the UU

The EU regards the 1999 Recommendation as sufficiently precautionary.

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Precaution applied to EMFs in other countries

Some individual countries have adopted precautionary measures: Switzerland and Italy have precautionary exposure limits, and some of the Scandinavian countries have general precautionary policies. In parts of America and Australia, “prudent avoidance” measures are sometimes taken.

See a summary of countries in the EU and in the world as a whole grouped according to whether they have precautionary measures.

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What WHO says about precaution

WHO issued a Monograph and factsheet in 2007 which contain recommendations on precaution:

"When constructing new facilities and designing new equipment, including appliances, low-cost ways of reducing exposures may be explored. Appropriate exposure reduction measures will vary from one country to another. However, policies based on the adoption of arbitrary low exposure limits are not warranted."

More on the WHO recommendations on precaution.

WHO has been developing a Precautionary Framework which gives both general principles for applying the precautionary principle, and specific guidance on applying it to ELF and RF EMFs.

The latest draft Framework was released in October 2004. The key conclusions are:

“Under the WHO Precautionary Framework, [childhood leukaemia] warrants a thorough consideration of precautionary measures including detailed cost-benefit or cost-effectiveness analyses”


“…even after fully allowing for the legitimate desire by society to err on the safe side, it seems likely that only very low-cost measures will be justified.”

The draft Framework is no longer available on the WHO web site but much of its thinking has been incorporated in the Environmental Health Criteria.