Exposure limits

Guidelines and limits on safe levels of exposure
Various bodies in the UK and round the world have issued guidelines on safe levels of exposure to EMFs. We give details here of some of them. Most of them are designed to prevent induced currents having effects on the body.

The NRPB Guidance
The National Radiological Protection Board (NRPB) is the independent body charged by the UK Parliament with giving advice on EMFs, including advice on safe levels of exposure.

On 1 April 2005, the NRPB joined the Health Protection Agency, becoming the Radiation Protection Division.

Until 2004, the NRPB published its own exposure guidelines, last revised in 1993 (more detail on the 1993 NRPB Guidelines). In March 2004, it published new Advice on limiting exposures to EMFs. This Advice recommends that the UK adopts levels published internationally by ICNIRP, the International Commission on Non-Ionizing Radiation Protection (more detail on the 2004 NRPB Advice).

In August 2004, in response to the NRPB’s recommendation, the Parliamentary Under Secretary for Public Health (Melanie Johnson) wrote to the Chairman of the NRPB welcoming the new advice. The letter included a 10 point annex describing the way Government intends to implement the NRPB advice. It points to the need for inter-departmental working and introduces the initial plans for a wider stakeholder process in order to consider the possible need for further precautionary measures in respect of extremely low frequency (ELF) electromagnetic fields (EMF).

The key statement about implementation is:
“… the Government expects the NRPB guidelines to be implemented in line with the terms of the EU Recommendation, that is, taking account of the risks and benefits of action. Preliminary discussions have already taken place to identify what reasonable actions might be taken.”

Comparison of NRPB and ICNIRP Guidelines

The ICNIRP limit for the public is a factor of 5 lower than the 1993 NRPB Guidelines.

In practice, the reference levels are set well below the basic restriction so as to include a margin, and the ICNIRP basic restriction for the general public actually corresponds to fields of 360 µT and 9.5 kV m^-1 on current understanding more on how these figures are derived

The ICNIRP Guidance
ICNIRP are the International Commission on Non-Ionizing Radiation Protection. They issued guidelines on exposures in 1998.

Importantly, their guidelines are not intended to be a complete system for protecting the public that should be applied in different countries as it stands. They say that their guidance considers only the science, and Governments will need to look at other factors before deciding whether and how to implement the guidelines.

The ICNIRP guidelines are similar in many respects to the 1993 NRPB guidelines. For occupational exposures at power frequencies they have the identical basic restriction, 10 mA m. For the general public, they apply an extra factor of 5, giving a basic restriction of 2 mA m. They also calculate the investigation levels in a different way, resulting in lower numbers, but these are not the actual limits, they are simply guidance figures for when it is necessary to investigate the basic restriction. ICNIRP’s reference levels are 500 µT and 10 kV m for workers and 100 µT and 5 kV m for the public. More on how investigation levels are calculated.

The EU Recommendation
The EU issued a Recommendation in 1999. This is a recommendation to Governments to implement exposure guidelines. It does not apply directly to industry or members of the public.

The numbers in the EU Recommendation are identical to those in the ICNIRP Guidelines. However, the EU Recommendation says they should be applied only when the time of exposure is significant, and only after Governments have considered both the risks and benefits in deciding whether action is required or not. More on developments on EMFs in Europe.

European Physical Agents Directive
In April 2004, the European Union adopted a Directive on occupational exposure to EMFs. This basically gives force to the ICNIRP exposure levels. The UK has until 2008 to bring it into UK law. More on the Directive.

Other countries
Some countries have exposure limits, some do not. Eurelectric maintains a compilation of power-frequency exposure limits in different countries. The World Health Organization also has a database of exposure standards.

Some countries have attracted particular interest because of the situation regarding exposure limits in them:

• Australia
• Italy
• Switzerland

Other frequencies
The NRPB and ICNIRP guidelines cover a wide range of frequencies, not just power frequencies. Microwave Consultants Limited offer a calculator to discover the guideline values at any chosen frequency.

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