ICNIRP 1998

ICNIRP are the International Commission on Non-Ionizing Radiation Protection. They issued guidelines on exposures in 1998. (In 2009 they issued a draft revision for consultation - see more detail on this.)

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.  Thus, for example, the EU Recommendation uses the numbers out of ICNIRP but expects them to be applied only where the time of exposure is significant.

For occupational exposures at power frequencies the basic restriction is 10 mA m-2. For the general public, they apply an extra factor of 5, giving a basic restriction of 2 mA m-2.  They subsequently clarified that these basic restrictions apply to the central nervous system, not to the whole body.

They also give investigation levels. 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-1 for workers and 100 µT and 5 kV m-1 for the public.  The fields required to produce the basic restriction are higher:

Occupational exposure:

Basic restriction: 10 mA m-2 in the central nervous system
Magnetic fields
Electric fields

ICNIRP reference level: 500 µT

Field actually required: 1800 µT

ICNIRP reference level: 10 kV m-1
Field actually required: 46 kV m-1

These values are for 50 Hz - see here for the values at 60 Hz

Public exposure

Basic restriction: 2 mA m-2 in the central nervous system
Magnetic fields
Electric fields

ICNIRP reference level: 100 µT
Field actually required: 360 µT

ICNIRP reference level: 5 kV m-1
Field actually required: 9 kV m-1

These values are for 50 Hz - see here for the values at 60 Hz

* The Dimbylow calculations give a value of 9.2 kV m-1. HPA suggest 9 kV m-1 which includes a further small margin.