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 followed by new guidance in 2010)
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:
Basic restriction: 10 mA m-2 in the central nervous system
ICNIRP reference level: 500 µT
ICNIRP reference level: 10 kV m-1
Basic restriction: 2 mA m-2 in the central nervous system
ICNIRP reference level: 100 µT
ICNIRP reference level: 5 kV m-1
* The Dimbylow calculations give a value of 9.2 kV m-1. HPA suggest 9 kV m-1 which includes a further small margin.
The values at other frequencies
We concentrate on this site in general and this page in particular on the limits at power frequencies. But ICNIRP covers a range of frequencies. The following graphs show the reference levels from 0.1 Hz to 100 kHz (solid lines are occupational, dotted lines public). See also an interactive comparison of ICNIRP 1998, ICNIRP 2010 and ICES across a range of frequencies.
Are these limits still current?
ICNIRP themselves see these 1998 limits as superseded by their 2010 limits. But given how many countries use the 1998 limits or variants of them, it seems they will be around for a while.