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Bioelectromagnetism

TABLE 7.1 Limits of Exposure to Static Magnetic Fields in the ICNIRP Guidelines for Static Magnetic Fields^a

Exposure Characteristics

Magnetic Flux Density

Occupational^b

Exposure of head and of trunk

2 T

Exposure of limbs^c

8 T

General public^d

Magnetic fux density

400 mT

Source: Reproduced from ICNIRP, Health Physics 96: 504–514, 2009.

a ICNIRP recommends that these limits should be viewed operationally as spatial peak exposure limits.

b For specifc work applications, exposure up to 8 T can be justifed, if the environment is controlled and appropriate work

practices are implemented to control movement-induced efects.

c Not enough information is available on which to base exposure limits beyond 8 T.

d Because of potential indirect adverse efects, ICNIRP recognizes that practical policies need to be implemented to prevent

inadvertent harmful exposure of persons with implanted electronic medical devices and implants containing ferromag­

netic material, and dangers from fying objects, which can lead to much lower restriction levels such as 0.5 mT.

Te ICNIRP provides guidelines for static magnetic felds (ICNIRP, 2004). Te guidelines were orig­

inally established in 1994 and revised in 2004. Te exposure limit values are tabulated in Table 7.1.

Separate limits are given for occupational exposure and general public exposure, and the limits for

occupational exposure are applied to those individuals who are exposed to static magnetic felds as a

result of performing their regular or assigned job activities, while the limits for general public exposure

are applied to the entire population. Te limit for occupational exposure of the head and trunk should

not exceed a spatial peak magnetic fux density of 2 T. Exposure up to 8 T can be permitted if the envi­

ronment is controlled and appropriate work practices are implemented to control movement-induced

efects.

Exposure limits for occupational exposures: It is recommended that occupational exposure of the

head and trunk should not exceed a spatial peak magnetic fux density of 2 T except for the following

circumstance: for working application for which exposure above 2 T are deemed necessary following,

exposure up to 8 T can be permitted if the environment is controlled and appropriate work practices are

implemented to control movement-induced efects. Sensory efects due to the movement in the feld can

be avoided by complying with basic restrictions set in the extremely low-frequency guidelines. When

restricted to the limbs, maximum exposures of up to 8 T are acceptable (ICNIRP, 2010).

Exposure limits for general public exposures: Based on scientifc knowledge on the direct of static

felds on humans, acute exposure of the general public should not exceed 400 mT (any part of the body).

However, because of potential indirect adverse efects, ICNIRP recognizes that practical policies need

to be implemented to prevent inadvertent harmful exposure of people with implanted electronic medi­

cal devices and implants containing ferromagnetic materials, and injuries due to fying ferromagnetic

objects, and these considerations can lead to much lower restriction levels, such as 0.5 mT (IEC, 2002).

Te exposure limits to be set with regard to these non-biological efects are not, however, the duty of

ICNIRP (CINIRP, 2010).

ICNIRP recommends that the use of these guidelines should be accompanied by appropriate protec­

tive measures. Tese measures need to be considered separately for public places and for workplaces.

For public places, exposures to static magnetic felds are likely to be very low and infrequent. On the

other hand, strong static felds may be regularly encountered for workplaces (ICNIRP, 2009). Tere are

three main areas of concern: for members of the public, there is a need to protect people with implanted

medical devices against possible interference and against forces on implants containing ferromagnetic

material. In addition, in some specifc situations, there is a risk from fying ferromagnetic objects such

as tools. Tird, in work situations involving exposure to very high felds, there is a need for a set of site-

specifc work procedures intended to minimize the impact of transient symptoms such as vertigo and

nausea (ICNIRP, 2009).

ICNIRP provides additional guidelines for the protection of workers moving in static magnetic felds

or being exposed to magnetic felds with frequencies below 1 Hz (ICNIRP, 2014). Tis was aimed at