Administrative Rule no. 1421/2004, of 23 November

Presidência do Conselho de Ministros e

Ministérios da Defesa Nacional das Cidades, Administração Local, Habitação e Desenvolvimento Regional, da Ciência, Inovação e Ensino Superior, da Saúde e das Obras Públicas Transportes e Comunicações

Administrative Rule

(This is not an official translation of the law)

Decree-Law no. 11/2003, of 18 January, governs the approval from the municipality concerning the installation and functioning of support infrastructures for radiocommunication stations and respective accessories, adopted in Decree-Law n. º 151-A/2000 of 20 July, and provides mechanisms for the setting of reference levels on exposure of the general public to electromagnetic fields (0 Hz to 300 GHz), such levels being settled by joint administrative rule, pursuant to article 11 of that statutory instrument.

In compliance with the mentioned legal provision, the Government has accepted the proposal presented by the interministerial working group appointed by joint order no. 8/2002, of 7 January, for the establishment of a framework of basic restrictions and level references as regards the exposure of the population to electromagnetic fields, which adopts Council Recommendation 1999/519/EC, of 12 July.

These basic restrictions were adopted and reference levels were determined assuming the need to protect public health against the proven harmful effects of the exposure to electromagnetic fields, based on the best currently available scientific data and guidelines in this matter. Thus, the evolution of technology and scientific knowledge on this subject shall be duly taken into consideration for a potential review of levels herein set up.

Therefore:

The Government, through its Ministers of State, of National Defence and Sea Affairs, for Towns, Local Administration, Housing and Regional Development, for Science, Innovation and Higher Education, for Health, for Public Works, Transport and Communications and Assistant to the Prime Minister, hereby orders that basic restrictions are adopted and that reference levels on exposure of the general public to electromagnetic fields (0 Hz to 300 GHz) are set up, such reference levels being included in annex to the present statutory instrument, of which they are an integral part.

On 2 November 2004.

The Minister of State, of National Defence and Sea Affairs, Paulo Sacadura Cabral Portas. - The Minister for Towns, Local Administration, Housing and Regional Development, José Luís Fazenda Arnault Duarte. – The Minister for Science, Innovation and Higher Education, Maria da Graça Martins da Silva Carvalho. – The Minister for Health, Luís Filipe da Conceição Pereira. – The Minister for Public Works, Transport and Communications, António Luís Guerra Nunes Mexia. – The Minister Assistant to the Prime Minister, Henrique José Monteiro Chaves.

ANNEX

I - Definitions

For the purposes of the present Administrative Rule, the term «electromagnetic fields» (EMF) shall include static fields, extremely low frequency (ELF) fields and radio frequency (RF) fields, including microwave, comprising frequency ranges from O Hz up to 300 GHz.

A) Physical quantities

In the context of the exposure to EMF, the following eight physical quantities usually apply:

Contact current (I(index C)) between a person and an object is expressed in amperes (A). A conductive object in an electric field can be charged by the field;

Current density (J) is defined as the current flowing through a unit cross section perpendicular to its direction in a volume conductor such as the human body or part of it, expressed in amperes per square metre (A/m2);

Electric field strength is a vector quantity (E) that corresponds to the force exerted on a charged particle regardless of its motion in space. It is expressed in volts per metre (V/m);

Magnetic field strength is a vector quantity (H), which, together with the magnetic flux density, specifies a magnetic field at any point in space. It is expressed in amperes per metre (A/m);

Magnetic flux density is a vector quantity (B), resulting in a force that acts on moving charges, expressed in teslas (T). In free space and in biological materials, magnetic flux density and magnetic field strength can be interchanged using the equivalence 1 A/m = 410(raised to power -7)T;

Power density (S) is the appropriate quantity used for very high frequencies, where the depth of penetration in the body is low. It is the radiant power incident perpendicular to a surface, divided by the area of the surface and is expressed in watts per square metre (W/m2);

Specific energy absorption (SA) is defined as the energy absorbed per unit mass of biological tissue, expressed in joules per kilogram (J/kg). In this Administrative Rule it is used for limiting non-thermal effects from pulsed microwave radiation.

Specific energy absorption rate (SAR) averaged over the whole body or over parts of the body, is defined as the rate at which energy is absorbed per unit mass of body tissue and is expressed in watts per kilogram (W/kg). Whole body SAR is a widely accepted measure for relating adverse thermal effects to RF exposure. Besides the whole body average SAR, local SAR values are necessary to evaluate and limit excessive energy deposition in small parts of the body resulting from special exposure conditions. Examples of such conditions are: a grounded individual exposed to RF in the low MHz range and individuals exposed in the near field of an antenna.

Of these quantities, magnetic flux density, contact current, electric and magnetic field strengths and power density can be measured directly.

B) Basic restrictions and reference levels

For the application of restrictions based on the assessment of possible health effects of electromagnetic fields, differentiation should be made between basic restrictions and reference levels.

Note. - These basic restrictions and reference levels for limiting exposure have been developed following a thorough review of all published scientific literature. The criteria applied in the course of the review were designed to evaluate the credibility of the various reported findings; only established effects were used as a basis for the proposed exposure restrictions. Induction of cancer from long-term EMF exposure was not considered to be established. However, since there are safety factors of about 50 between the threshold values for acute effects and the basis restrictions, this Administrative Rule implicitly covers possible long-term effects in the whole frequency range.

Basic restrictions - restrictions on exposure to time-varying electric, magnetic, and electromagnetic fields which are based directly on established health effects and biological considerations are termed "basic restrictions". Depending upon the frequency of the field, the physical quantities used to specify these restrictions are magnetic flux density (B), current density (J), specific energy absorption rate (SAR), and power density (S). Magnetic flux density and power density can be readily measured in exposed individuals.

Reference levels - these levels are provided for practical exposure-assessment purposes to determine whether the basic restrictions are likely to be exceeded. Some reference levels are derived from relevant basic restrictions using measurements and/or computational techniques and some reference levels address perception and adverse indirect effects of exposure to EMFs. The derived quantities are electric field strength (E), magnetic field strength (H), magnetic flux density (B), power density (S), and limb current (IL). Quantities that address perception and other indirect effects are (contact) current (I(index C)) and, for pulsed fields, specific energy absorption (SA). In any particular exposure situation, measured or calculated values of any of these quantities can be compared with the appropriate reference level. Respect of the reference level will ensure respect of the relevant basic restriction. If the measured value exceeds the reference level, it does not necessarily follow that the basic restriction will be exceeded. Under such circumstances, however, there is a need to establish whether there is respect of the basic restriction.

Quantitative restrictions on static electric fields are not given in this Administrative Rule. However, it is recommended that annoying perception of surface electric charges and spark discharges causing stress or annoyance should be avoided.
Some quantities such as magnetic flux density (B) and power density (S) serve both as basic restrictions and reference levels, at certain frequencies (see parts II and III).

II - Basic Restrictions

Depending on frequency, the following physical quantities (dosimetric/exposimetric quantities) are used to specify the basic restrictions on EMF:

Between 0 and 1 Hz basic restrictions are provided for magnetic flux density for static magnetic fields (0 Hz) and current density for time-varying fields up to 1 Hz, in order to prevent effects on the cardiovascular and central nervous system;

Between 1 Hz and 10 MHz basic restrictions are provided for current density to prevent effects on nervous system functions;

Between 100 kHz and 10 GHz basic restrictions on SAR are provided to prevent whole-body heat stress and excessive localised heating of tissues. In the range 100 kHz to 10 MHz, restrictions on both current density and SAR are provided;

Between 10 GHz and 300 GHz basic restrictions on power density are provided to prevent heating in tissue at or near the body surface;

The basic restrictions, given in Table 1, are set so as to account for uncertainties related to individual sensitivities, environmental conditions, and for the fact that the age and health status of members of the public vary.

TABLE I
Basic restrictions for electric, magnetic and electromagnetic fields (0 Hz to 300 GHz)

(see table in the original document)

Notes

1. f is the frequency in Hz.

2. The basic restriction on the current density is intended to protect against acute exposure effects on central nervous system tissues in the head and trunk of the body and includes a safety factor. The basic restrictions for ELF fields 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 basic restrictions for exposure of short duration. However, since the basic restriction refers to adverse effects on the central nervous system, this basic restriction may permit higher current densities in body tissues other than the central nervous system under the same exposure conditions.

3. Because of electrical inhomogeneity of the body, current densities should be averaged over a cross section of 1 cm² perpendicular to the current direction.

4. For frequencies up to 100 kHz, peak current density values can be obtained by multiplying the effective value by –2(~1 – 414). For pulses of duration t(index p), the equivalent frequency to apply for basic restrictions should be calculated as i = 1/(2 - t(index p)).

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 basic restriction.

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

7. Localised SAR averaging mass is any 10g of contiguous tissue; the maximum SAR so obtained should be the value used for the estimation of exposure. These 10g 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 pulses of duration t(index p) the equivalent frequency to apply in the basic restrictions should be calculated as f = 1/(2 - t(index p)). Additionally, for pulsed exposures, in the frequency range 0,3 GHz to 10 GHz and for localised exposure of the head, in order to limit and avoid auditory effects caused by thermoelastic expansion, an additional basic restriction is recommended. This is that the SA should not exceed 2mJ kg averaged over 10 g of tissue.

III - Reference Levels

Reference levels of exposure are provided for the purpose of comparison with values of measured quantities. Respect of all recommended reference levels will ensure respect of basic restrictions.

If the quantities of measured values are greater than the reference levels, it does not necessarily follow that the basic restrictions have been exceeded. In this case, an assessment should be made as to whether exposure levels are below the basic restrictions.

The reference levels for limiting exposure are obtained from the basic restrictions for the condition of maximum coupling of the field to the exposed individual, thereby providing maximum protection. A summary of the reference levels is given in Tables II and III. The reference levels are generally intended to be spatially averaged values over the dimension of the body of the exposed individual, but with the important proviso that the localised basic restrictions on exposure are not exceeded.
In certain situations where the exposure is highly localised, such as with hand-held telephones and the human head, the use of reference levels is not appropriate. In such cases respect of the localised basic restriction should be assessed directly.

TABLE II
Field levels

Reference levels for electric, magnetic and electromagnetic fields (0 Hz to 300 GHz, unperturbed effective values)

(see table in the original document)

Notes

1. f, as indicated in the frequency range column.

2. For frequencies between 100 kHz and 10 GHz, S(index eq), E(raised to power 2), H(raised to power 2), and B(raised to power 2) are to be averaged over any six-minute period.

3. For frequencies exceeding 10 GHz, S(index eq), E(raised to power 2), H(raised to power 2), and B(raised to power 2) are to be averaged over any 68/f (raised to power 1.05) minute period (f in GHz).

4. No E-field value is provided for frequencies (less than) 1 Hz, which are effectively static electric fields. For most people the annoying perception of surface electric charges will not occur at field strengths less than 25 kV/m. Spark discharges causing stress or annoyance should be avoided.

No higher reference levels on exposure to ELF fields are provided when exposures are of short duration (see note 2 of Table I). In many cases, where the measured values exceed the reference level, it does not necessarily follow that the basic restriction will be exceeded. Provided that adverse health impacts of indirect effects of exposure (such as microshocks) can be avoided, it is recognised that the general-public reference levels can be exceeded provided that the basic restriction on the current density is not surpassed. In many practical exposure situations external ELF fields at the reference levels will induce current densities in central nervous-system tissues that are below the basic restrictions. Also it is recognised that a number of common devices emit localised fields in excess of the reference levels. However, this generally occurs under conditions of exposure where the basic restrictions are not exceeded because of weak coupling between the field and the body.

For peak values, the following reference levels apply to the E-field strength (V/m), H-field strength (A/m) and the B-field ((mi)T):

For frequencies up to 100 kHz, peak reference values are obtained by multiplying the corresponding effective values by –2 (~1 - 414). For pulses of duration t(index p) the equivalent frequency to apply should be calculated as f = 1/(2 t(index p));

For frequencies between 100 kHz and 10 MHz peak reference values are obtained by multiplying the corresponding effective values by 10, where = [0,665 log (f/10(raised to 5)) + 0,176], f in Hz;

For frequencies between 10 MHz and 300 GHz peak reference values are obtained by multiplying the corresponding effective values by 32.

Generally, with regard to pulsed and/or transient fields at low frequencies, there are frequency-dependent basic restrictions and reference levels from which a hazard assessment and exposure guidelines on pulsed and/or transient sources can be derived. A conservative approach involves representing a pulsed or transient EMF signal as a Fourier spectrum of its components in each frequency range, which can then be compared with the reference levels for those frequencies. The summation formulae for simultaneous exposure to multiple frequency fields can also be applied for the purposes of determining compliance with the basic restrictions.

Although little information is available on the relation between biological effects and peak values of pulsed fields, it is suggested that, for frequencies exceeding 10 MHz, S (index eq) as averaged over the pulse width should not exceed 1000 times the reference levels or that field strengths should not exceed 32 times the fields strength reference levels. For frequencies between about 0,3 GHz and several GHz and for localised exposure of the head, in order to limit or avoid auditory effects caused by thermoelastic expansion, the specific absorption from pulses must be limited. In this frequency range, the threshold SA of 4mJ/kg - 16 mJ kg necessary for producing this effect corresponds, for 30 (mi)s pulses, to peak SAR values of 130 W/kg to 520 W/kg in the brain. Between 100 kHz and 10 MHz, peak values for the fields strengths are obtained by interpolation from the 1,5 kHz fold peak at 100 kHz to the 32 kHz fold peak at 10 MHz.

Contact currents and limb currents. For frequencies up to 110 MHz additional reference levels are recommended in order to avoid hazards due to contact currents. The contact current reference levels are presented in Table III. The reference levels on contact current were set to account for the fact that the threshold contact currents that elicit biological responses in adult women and children are approximately two-thirds and one-half, respectively, of those for adult men.

TABLE III
Reference levels for contact currents from conductive objects (f in kHz)

(see table in the original document)

For the frequency range 10 MHz to 110 MHz, a reference level of 45 mA in terms of current through any limb is recommended. This is intended to limit the localised SAR over any six-minute period.

IV - Exposure from sources with multiple frequencies

In situations where simultaneous exposure to fields of different frequencies occurs, the possibility that these exposures will be additive in their effects must be considered. Calculations based on such sum up of effects should be performed separately for each effect; thus separate evaluations should be made for thermal and electrical stimulation effects on the body.

Basic restrictions

In the case of simultaneous exposure to fields of different frequencies, the following criteria should be satisfied in terms of the basic restrictions: