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Safety and Electromagnetic Field Guidelines

TABLE 7.5 Basic Restrictions in ICNIRP Guidelines for Electromagnetic Field Exposure from 100 kHz to

300 GHz, for Averaging Intervals ≥6 Minutes

Exposure

Whole-Body

Local Head/

Local Limb

Local Sab

Scenario

Frequency Range

Average SAR (W/kg)

TorsoSAR (W/kg)

SAR (W/kg)

(W/m²)

Occupational

100 kHz to 6 GHz

0.4

10

20

NA

>6 to 300 GHz

0.4

NA

NA

100

General

100 kHz to 6 GHz

0.08

2

4

NA

public

>6 to 300 GHz

0.08

NA

NA

20

Source: Reproduced from ICNIRP, Health Physics 118:483–524, 2020.

Notes:

1. “NA” signifes “not applicable” and does not need to be taken into account when determining compliance.

2. Whole-body average SAR is to be averaged over 30 minutes.

3. Local SAR and Sab exposures are to be averaged over 6 minutes.

4. Local SAR is to be averaged over a 10-g cubic mass.

5. Local Sab is to be averaged over a square 4 cm² surface area of the body. Above 30 GHz, an additional constraint is

imposed, such that exposure averaged over a square 1 cm2 surface area of the body is restricted to two times that of the

4 cm² restriction.

DRL is defned in terms of internal electric feld (in situ electric feld). Te exposure limit is based on

dosimetric thresholds for established adverse health efects expressed as in situ electric feld strength (0Hz

to 5 MHz). Separate limits are given for “brain,” “heart,” “limb,” and “other tissues.” In the frequencies

above 100 kHz, RF-specifc basic restrictions need to be considered additionally, SAR (100 kHz to 6 GHz), or

epithelial power density (6 GHz to 300 GHz) and which provides an adequate margin of safety (IEEE, 2019).

ERL provides an adequate margin of safety against established adverse health efects. It is expressed

as the metric appropriate to the frequency and temporal characteristics of the exposure under consid­

eration. ERL is the maximum exposure level relative to ambient electric and/or magnetic feld strength

or power density, induced and/or contact current, or contact voltage which means that the ERL is mea­

sured, estimated, or derived from the DRL (in situ electric feld, SAR, or epithelial power density).

Te DRL is a limit expressed in terms of feld strength in the body, SAR, or power density in the epithe­

lium, and can be considered to be roughly equivalent to the basic limit of the ICNIRP guideline. ERL is the

level indicated by measurable electric felds, magnetic feld, power density, induced in the limb, contact cur­

rent, and contact voltage. ERL can be considered equivalent to the reference level of the ICNIRP guidelines.

Te exposure limits in the low-frequency range are determined based on the threshold of electro-

stimulation, which is manifested by the excitation of nerves and muscle, as well as by the alteration of

neural synapse activity. Te major part of the scientifc base is from Reilly’s comprehensive work in

electrostimulation (Reilly, 1998).

Te ERL for magnetic feld exposure are provided separately for exposure of “head and torso” and

for “the limbs.” Te ERLs are derived analytically from the DRL by assuming simple induction models

(several sizes of homogeneous ellipsoids representing each part of the human body) that have an ana­

lytical solution for the uniform magnetic feld exposure (IEEE, 2019). Safety factors that are applied to a

median adverse reaction threshold are considered in the derivation of the ERLs.

Te ERL for electric feld exposure is provided separately for exposure of “head and torso” and for

“the limbs.” Unlike the magnetic feld exposure, the ERLs for electric feld exposure are limited by indi­

rect electrostimulation (contact current and spark discharge). Tis is because the environmental electric

feld level for the indirect electrostimulation is signifcantly lower than that inducing DRL level in situ

electric felds.

Te ERL for contact current is also provided in the IEEE safety standard for frequencies 0 Hz to

5 MHz based on the electrostimulation efects. Tese contact current limits apply to a freestanding indi­

vidual who is insulated from the ground while touching a grounded conductor. Tese limits might not

protect against aversive sensations from spark discharge just prior to direct contact or upon release from

the grounded conductor.