Directive 2004/40/EC of the European Parliament and of the Council (repealed)Show full title

A. EXPOSURE LIMIT VALUES

Depending on frequency, the following physical quantities are used to specify the exposure limit values of electromagnetic fields:

• exposure limit values are provided for current density for time-varying fields up to 1 Hz, to prevent effects on the cardiovascular and central nervous system,

• between 1 Hz and 10 MHz exposure limit values are provided on current density to prevent effects on central nervous system functions,

• between 100 kHz and 10 GHz exposure limit values on SAR are provided to prevent whole-body heat stress and excessive localised heating of tissues. In the range 100 kHz to 10 MHz, exposure limit values on both current density and SAR are provided,

• between 10 GHz and 300 GHz an exposure limit value on power density is provided to prevent excessive tissue heating at or near the body surface.

Table 1: Exposure limit values (Article 3(1)). All conditions to be satisfied

Frequency range	Current density for head and trunkJ(mA/m2)(rms)	Whole body average SAR(W/kg)	Localised SAR(head and trunk)(W/kg)	Localised SAR(limbs)(W/kg)	Power densityS(W/m2)
Up to 1 Hz	40	–	–	–	–
1 - 4 Hz	40/f	–	–	–	–
4 - 1 000 Hz	10	–	–	–	–
1 000 Hz – 100 kHz	f/100	–	–	–	–
100 kHz – 10 MHz	f/100	0,4	10	20	–
10 MHz –10 GHz	–	0,4	10	20	–
10 – 300 GHz	–	–	–	–	50

Notes:

1. f is the frequency in Hertz.

2. The exposure limit values on the current density are intended to protect against acute exposure effects on central nervous system tissues in the head and trunk of the body. The exposure limit values in the frequency range 1 Hz to 10 MHz are based on established adverse effects on the central nervous system. Such acute effects are essentially instantaneous and there is no scientific justification to modify the exposure limit values for exposure of short duration. However, since the exposure limit values refer to adverse effects on the central nervous system, these exposure limit values may permit higher current densities in body tissues other than the central nervous system under the same exposure conditions.

3. Because of the electrical inhomogeneity of the body, current densities should be calculated as averages over a cross-section of 1 cm perpendicular to the current direction.

4. For frequencies up to 100 kHz, peak current density values can be obtained by multiplying the rms value by (2)½.

5. For frequencies up to 100 kHz and for pulsed magnetic fields, the maximum current density associated with the pulses can be calculated from the rise/fall times and the maximum rate of change of magnetic flux density. The induced current density can then be compared with the appropriate exposure limit value. For pulses of duration t_p, the equivalent frequency to apply for the exposure limit values should be calculated as f=1/(2t_p).

6. All SAR values are to be averaged over any six-minute period.

7. Localised SAR averaging mass is any 10 g of contiguous tissue; the maximum SAR so obtained should be the value used for estimating exposure. These 10 g of tissue are intended to be a mass of contiguous tissue with nearly homogeneous electrical properties. In specifying a contiguous mass of tissue, it is recognised that this concept can be used in computational dosimetry but may present difficulties for direct physical measurements. A simple geometry such as cubic tissue mass can be used provided that the calculated dosimetric quantities have conservative values relative to the exposure guidelines.

8. For pulsed exposures in the frequency range 0,3 to 10 GHz and for localised exposure of the head, in order to limit and avoid auditory effects caused by thermoelastic expansion, an additional exposure limit value is recommended. This is that the SA should not exceed 10 mJ/kg averaged over 10 g of tissue.

9. Power densities are to be averaged over any 20 cm² of exposed area and any 68/f^1,05-minute period (where f is in GHz) to compensate for progressively shorter penetration depth as the frequency increases. Spatial maximum power densities averaged over 1 cm² should not exceed 20 times the value of 50 W/m².

10. With regard to pulsed or transient electromagnetic fields, or generally with regard to simultaneous exposure to multiple frequency fields, appropriate methods of assessment, measurement and/or calculation capable of analysing the characteristics of the waveforms and nature of biological interactions have to be applied, taking account of European harmonised standards developed by CENELEC.