A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A

AC current:

AC current: A current that alternates between positive and negative values. The current provided by the electrical supply network is an AC current of sinusoidal appearance, with a period of 20 milliseconds which corresponds to a frequency of 50 Hz (in Europe ).

Note: The period is the reverse of the frequency: 1/50 = 0.02 s or 20 ms

Association:

A relationship, generally shown by statistical tests, between an exposure and an effect on health. This does not imply a link between the cause and the effect.

Biais:

A systematic error in the processing of an epidemiological study that leads to false results.

Bias of confounding or confounding factor:

A confounding factor occurs when the association observed between the exposure and the disease is influenced by variables other than the one studied. In the case of studies concerning the role of electromagnetic fields in the development of cancers, the confounding factor could be the exposure to chemicals or tobacco smoking.

Calcium messenger:

The Ca++ ion plays the role of a messenger between the external medium of the cell and the cell itself. It penetrates the cell through channels, and binds to proteins to intervene in the cell's metabolic activity.

Causal factor:

A factor playing a direct role in the onset of a disease. It must be either necessary or sufficient to cause the disease. Several criteria are used to decide if a risk factor plays a causal role:

• the exposure factor precedes the effect,
• the relationship is found in various studies and the relative risk is high,
• there is a dose effect relationship,
• there is coherence with medical and biological knowledge (animal and cellular studies),
• significant biases were correctly controlled (in particular confounding factors),
• the effect attributed to the supposed cause is specific.

In causality studies, epidemiology strength is that it provides results pertinent to human health. Its weakness is that it is a science of observation, not of experimentation. That is why multiple precautions must be taken before being able to show causality.

Carcinogen:

Any element that can cause or support the development of a cancer.

Carcinogenesis:

A set of mechanisms and stages in the development of a cancer.

Case control study:

An epidemiological study that compares a group of sick persons with a group of healthy ones. One seeks to know if the two groups have a different exposure to certain factors such as, for example, magnetic fields.

Cellular membrane:

The cell's " envelope " which is made up of a double layer of lipids, protein and cholesterol. It is the intermediary between the external medium and the cell. Any substance entering or exiting the cell must cross this membrane.

Chromosome:

An element of cell nucleus. Chromosomes, which are composed of genes, are the components of heredity.

Circadian (rhythms):

Rhythms associated with the 24-hour cycle of the Earth's rotation.

Cohort study (exposed versus unexposed):

An epidemiological study that compares a group exposed to the studied factor with a group as similar to the first as possible, except that they have not been exposed to the factor. The frequencies of the diseases that occur in these two groups are then compared.

Conductivity:

The conductivity of a material indicates the degree of facility to which current flows through the material. Conductivity is the opposite of resistivity (the latter is expressed in W.m).

Confidence interval:

A 95 % confidence interval specifies a higher and lower limit inside of which the probability of finding the actual value of the measured variable is 95 %. The size of the confidence interval, that is to say, the estimate's precision is related to the size of the studied sample: the larger the sample's size, the smaller the interval and the more precise the estimation.

Contact current (Ic):

Contact current is a current that runs through the body between two points of contact (generally, a hand and a foot or between both hands / feet) with electrical conductors at different potentials (a device and the floor, a tap and the floor a heater and the floor...) while this voltage is first of all not obvious since no object is connected to a voltage source.

Contact current is a current that flows all the time during the contact, thus it is neither a transitory phenomenon, nor an impulse. This current is at power frequency (50 Hz in Europe).

For safety purposes related to electrocution risks, residential electric wiring are protected against contact currents when they exceed 30 mA (bathrooms), or even 300 mA. This measure aims to protect from ventricular fibrillation risks.

However, contact current intensity is generally weak in well-designed house wiring in good maintenance. Let's also add that shoes partly insulate from the ground and, by the way, limit contact currents.

Very often, contact currents are not perceived (the perception threshold of human being is around 0.2 to 0.4 mA; source : ICNIRP, 2001 (http://www.icnirp.de/documents/emfgdl.pdf). Exceeding perception threshold does not directly trigger the circuit-breaker. However, if a problem arises with the washing machine, for example, the differential will work if the current exceeds 30 mA to avoid any direct health hazard.

It would be mistaken to believe protecting our house wiring to levels lower than 30 mA because inopportune triggering would be too numerous.

Remarks :

- Contact current is another source of current that can flow through the human body, different from the one related to ambient electromagnetic fields (called induced current).

- Contact current neither means there is a contact with active parts (contact with live parts), nor electrostatic discharges (ESD).

Current:

Electrical current is a physical phenomenon caused by the displacement of a charge (ion or electron). In the case of a metal conductor, electrons play the main part in the current. The current's intensity is the quantity of charge that passes in a conductor per unit of time. The current's intensity is measured in amperes (A).

DC current:

A current whose value is constant e.g. the current output by a battery.

DNA:

DNA is the abbreviation for desoxyribonucleic acid. It is a giant molecule composed of two chains in a double helix. It is the principal component of chromosomes, which are in the nucleus of the cell; DNA supports the genetic code.

Density of current:

The density of current is the intensity of the current per unit area and, is measured in amperes per square meter (A/m2).

Dose:

A dose is a quantity measured in specific units of energy received.

Dose effect (relationship):

A relation that exists when the relative risk or the odds ratio increases with intensity or duration of exposure to the studied factor.

Electric field (E):

Static electric field: A state of the region in which stationary charged bodies are subject to forces by virtue of their charges.

The electric field is a field vector (i.e. a collection of values and directions for all points of a given space), just like the terrestrial field of gravity. Its direction depends on the electric charges present. The value and direction of the electric field at a given space location is obtained by placing a virtual positive unit electric charge at that location: the electric field at this point is the force (expressed in newtons) acting on this virtual charge. (F=qE with q = 1 coulomb).

Any electric charge " q " (unit : coulomb) creates an electric field " E " in the space that surrounds it. The intensity of the electric field is expressed in volts per meter (V/m).

The electric field is perpendicular to an equipotential surface, e.g. the ground (assumed perfectly conducting) or an electrically conductive surface. Within a perfectly conducting object (e.g. a metal cage), the electric field is equal to zero if there are no internal sources within the object. The human body, for example, being a relatively good conductor, has an internal electric field nearly equal to zero (magnitude of mV/m), even if one plunges it into an intense external field of several kV/m say, 6 orders of magnitude stronger. An electrical current passing through an imperfect conductor also creates an electric field in the direction of the current.

A didactic explanation is proposed in the heading " Basic notions "

Electromagnetic compatibility:

According to Council Directive 89/336/EEC of 3 May 1989
electromagnetic compatibility is the capability of a device, unit of equipment or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment.

Electromotive force:

The electromotive force of a device corresponds to the work per unit charge needed to conduct this charge in a closed loop. It is also the potential difference (in volts) induced or imposed that supplies a circuit.

Electrostatic discharges:

Electrostatic discharges are observed during the counterbalancing of potential between two bodies, initially at a potential difference. The almost instantaneous discharge (within a few billionth of a second) brings only momentary discomfort, related to a burning sensation that comes from the passage of an intense but short shock. This type of contact current is never the origin of real disorders, considering its short duration. It is typically the discomfort observed when touching a metallic object (door or car handles) under particular circumstances.

(see a graph showing the difference between a leak current and an electrostatic discharge)

ELF:

Extremely Low Frequency.

Electric energy:

It is the product of the power with the number of hours in operation. It is expressed in kilowatt hours (kWh) at the domestic level and in Terawatt hours (TWh) at the entire country level . The average annual consumption for a Belgian household is 4000 to 6000 kWh. Belgium consumed approximately 80 TWh in the year 2000 (more or less one-third for domestic use).

Exposure:

Exposure is the condition of being subjected to a factor. Measurement of exposure can be carried out in a direct way with a measuring apparatus. It can also be evaluated in an indirect way by a calculation method or an estimate. In the case of magnetic fields, two methods of indirect measurement are frequently used: the " wiring code " for studies in the general population and professional title for studies in the occupational environment.

F

Fault current:

This is an abnormal current, usually of high intensity (several thousands of amperes), which runs through a network after the occurrence of a default.

The default can be a contact between phases, between a phase and the ground, between a phase and the neutral. The contact is usually (but not always) of weak impedance. This fault current is often referred to short-circuit current (the circuit is “shorter” as it no longer passes through the load).

The value of the short-circuit current depends on the upstream network and not on the load. It is the network that flows in the short-circuit: in high voltage, short-circuits can reach up to 63.000 amps. In low voltage (domestic network), we can have short-circuit currents of a few thousand amps, depending on the proximity and the kind of transformers.

The hazards of short-circuit currents are, firstly, the risk of indirect contact with people (only in high voltage) and, secondly, fire and overheating of the cable insulation (accelerated aging), a resulting imbalance in voltage and associated risks. Effects related to Laplace 's mechanical forces (attraction if the current flows in the same direction in both conductors involved and repulsion in the opposite case) can also occur. These are generally negligible at low voltage but can be significant at high voltage and are a key element in the design of high voltage structures.

They are protected by protection devices like fuses or circuit breakers that should quickly open the circuit to limit the effects.

Note that most default currents (e.g. a short-circuit between phase and neutral) in our homes does not trigger a differential protection because up and down currents within the circuit remain identical.

Fibrillation:

Fibrillation is a very fast and irregular succession of stimuli, leading to the disappearance of any coordinated and effective contraction of auricular cardiac fibres (auricular fibrillation) or ventricular fibres; ventricular fibrillation is equivalent to heart failure.

Frequency:

The number of identical regular cycles during one second. Frequency is expressed in hertz (Hz). It is the inverse of the period, which is expressed in seconds : 1 Hz = 1/s.

Gene:

The segment of DNA in the chromosome that transmits hereditary characteristics.

Hormone:

A substance produced by an endocrine gland; it is transported by the blood towards other organs or tissues where it exerts its influence on biochemical processes.

I

Incidence:

Incidence is the number of new cases of a disease appearing in a given population during a given period. Incidence measures the risk of a disease.

Induced current in the human body

Leak induced current is a current that flows through the human body without an electrical conductor being touched.

The human body is roughly a salt water ball, quite a good electric conductor. If we plunge such a body in a variable electromagnetic field (for example with a 50Hz sinwave like power frequency), it will be travelled by a current at the same frequency than the one of the ambient field. This current makes closed loops inside the body.

In low frequency fields (ELF), the electric field E and the magnetic induction field B are separately considered.

• Variable external electric field E (ambient) (expressed in kV/m) will be highly perturbed by the presence of this electrical conductor, surface charges will appear at the surface to attempt to cancel the electric field inside the body, without, however, totally succeeding in doing this seeing that the body is not a perfect conductor (electrical conductivity of internal part of the body varies according to tissues).

It is considered that an electric field inside the body can be reduced (in comparison with the external ambient field) from a one million factor, thus only some mV/m remain inside the body for some external kV/m. Induced current inside the body is related to an internal electric field by Ohm's law (that connect current density, electric field and tissue conductivity).

• Variable external magnetic induction field B (expressed in microTesla) is slightly disrupted by the presence of an electrical conductor. The reaction inside the conductor is made as the appearance of a loop of current that will attempt to cancel the applied external field. Again, this induced current is related to internal electric field by Ohm's law.

Induced current by an electric field and a magnetic field can overlap but it is quite complex seeing that the direction of these induced currents (parallel to internal electric field) are not the same depending on whether they are induced by E or B because of substractional or additional effects.

Initiation of cancer:

The transformation process of a healthy cell into a cancerous cell. The initiating agent causes permanent damage to the cell's genetic material.

Intensity - Potential difference:

One can compare intensity to the current of a river. The flow (i.e. water quantity per unit of time) would be analogous to the intensity expressed in amperes (A). The pressure would be the potential difference expressed in volts (V). As there can exist pressure (e.g. through a difference in level) without a corresponding water circulation, one can detect electricity without a corresponding circulation of electrons. Thus the terminal voltage of a plug is present if a light is switched on or off. On the other hand, one can not detect intensity (of the current) if the appliance is switched off.

In vitro (study):

A study carried out in a laboratory using cells or tissues. The term " in vitro " refers to the observation of phenomena " under glass " (i.e. in the tubes or the dishes of the laboratory).

In vivo (study):

A study based on the observation of phenomena occurring in living organisms. Example: studies carried out on animals in a laboratory.

Ionization:

A process at the end of which an atom or a neutral molecule becomes electrically charged, positive or negative. The energy of ionisation is the energy necessary to extract an electron from an atom, ion or molecule.

Latency (period of):

The time that passes between the moment of exposure to pathogenic factors (biological, chemical, traumatic, or psychological) and the appearence of the first signs or symptoms of the disease.

Leak current:

Leak current is first of all a current … of leakage! It means that we neither speak about fault current (which causes an over-current that triggers the protection), nor contact current (which is the one that can run through a person, it depends on the impedance (*) of the person who makes the contact and the grounding of the apparatus), nor electrostatic discharge (see a graph showing the difference between a leak current and an electrostatic discharge). Its value is usually limited to few microamps, or even few milliamps.

(*) Electrical impedance measures the opposition of an electrical circuit to the flow of an alternating sinusoidal current. It is denoted by Z and its unit is the ohm.

It is a weak current, which escapes from the network (and wirings), and flows out the electrical installation, in the absence of a default in the electrical circuit. It is not incompatible with an apparently normal functioning of electrical appliances. It sometimes increases with time due to deteriorating insulation (cf. “More technically…”).

The leakage of current can exist because an impedant “link” (which means with a high impedance but not infinite) exists between the live parts of a circuit and the mass of the apparatus (e.g. the frame of a washing machine). This current only exists in a closed electrical circuit; the closing of the circuit can be made through various manners:

• If the impedance of this link is very high, for example higher than some tens of MΩ (million of ohms) in our domestic wiring at 230 V, the leak current will be extremely weak: 100 microamps of “leakage” if the impedance between the active cable and the “mass” is 2.3 MΩ.
• If the impedance is weaker, the « mass » of the apparatus (here the frame of the washing machine) is put under voltage. The leak current can become important (e.g. a few mA (milliamps)). To avoid putting masses under voltage, regulations impose their grounding (ie the one of the frames). In this case, the frame is almost placed to the ground voltage (reference), given the very low impedance of the grounding wire and the ground (typically 10 to 20 ohms). To do so, a current (of leakage if the impedance of the insulation failure is high enough, otherwise we may have a short-circuit) will flow through the grounding wire. The exact voltage of the mass is then the product of the leakage current with the impedance of the grounding, which means here 100 mV for 10 mA and 10 Ω of grounding.
  Note that to have a leak current of 10 mA in this case, the impedance due to the loss of insulation must be of the order of 23 kΩ. Such currents are rare in a well-insulated installation but may also be due to the presence of noise filters (capacitors between live conductors and the mass).

In the absence of grounding, the frame will be put under a voltage different from the ground waiting for a « client » that will make the link to the ground. This is dangerous because the grounding can be made when a person enters in contact with the frame and this person will be travelled by a current (of contact in this case).

Note : a leak current of 10 mA does not mean that the contact current will be of 10 mA because the contact current depends on additional impedances for closing the loop, ie the impedance of the person, the impedances of the contacts (hand-frame and feet-ground) and the impedance of the circuit through the ground.

Leak current frequencies are frequencies of basal current. That way, we can consider that leak current is mainly 50 Hz (in Europe ), which corresponds to a period of 20ms. There are also 50 Hz harmonics running (especially 5, 7, 11) but with lower amplitudes.

As seen above, dangers of leak currents are linked to people safety. Differential protection is used to protect us from current differences in the circuit. Typically the risk is limited to 30 mA in the bathroom and 300 mA in general for entire installations (note that only 30 mA differentials directly protect people; those of 300 mA are mainly used to avoid risks of overheating and fire).

There is virtually no risk of fire with leakage currents. Fuses and circuit breakers do not respond to current leakage.

More technically …

The leakage current has resistive and capacitive components :

• The capacitive component always exists and is related to the fact that a part of the current (AC) escapes from the cables, even healthy by capacitive effect (but this value is very weak, maximum order of few tens of micramps for a dwelling).
• The resistive component comes from the partial degradation of cable insulation (if the damage is total, it is a short-circuit with a fault current). This partial degradation give a non-infinite impedance between the live parts of the cable and the outside. This allows a “leakage” of the current outside the network.

The leak current needs to be channeled on one hand and limited in amplitude on another hand:

• Channeled to avoid metallic pieces being put under voltage. This is the role of the grounding systems of the apparatuses.
• Limited for 2 reasons (i) ensure that the putting under voltage of metallic masses, if unavoidable, remains limited in amplitude, and (ii) prevent such a current to generate an electric shock / electrocution of a person / animal that could be crossed trough by this current.

Leukaemia:

Disease characterized by an abnormal proliferation of white globules in blood and bone marrow.

Lymphocyte:

The variety of white globules (leucocytes) in charge of cellular immunity.

 

Magnetic field (H):

The magnetic field H (which is expressed in A/m) is related to the magnetic induction field B (expressed in teslas or T) by a physical size characteristic of the medium in which the field exists. This physical size is called the magnetic permeability of the medium. It is expressed in henry per meter (H/m) and is often represented by the letter µ. In the majority of materials (e.g. air, vacuum, gas, copper, ground), this size is a constant with a value of 1.25666 10^-6 H/m. It differs from this value in materials known as ferromagnetic (used for magnets, sheets of transformers), in which case this value can be several tens of thousands of times greater. B=µH

The lines of field and induction field can thus be very different in the presence of ferromagnetic materials.

Magnetic flux density:

Magnetic flux density is another term for the " magnetic induction field ".

Magnetic induction field (B):

In the literature, One readily speaks of magnetic field instead of the adequate expression " magnetic induction field ". Electric charges at rest generate an electric field. Moving charges (i.e. electrical current) create a magnetic field, known as a magnetic induction field.

B-field is expressed in Tesla (T) in International Unit. However, it is often expressed in mT (milliTesla) or µT (microTesla) to avoid too much null values in figures. In the literature, we can also see Gauss (G). The conversion is as follow: 1 Tesla= 10.000 Gauss or 1 µT = 10 mG.

Magnetic permeability of a material :

The magnetic permeability of a material is the capability of this material to channel magnetic induction, in other words, to concentrate magnetic flux lines and thus to increase the value of magnetic induction. It means that this value depends on the material in which it is produced.

The chanelling of the magnetic field in a material which is also a conductor is especially reduced, because of induced current when frequency of field variation, permeability and conductivity are high.

In fact, magnetic field H and magnetic induction field B are linked, in a given material, by the equation :

B = µ * H

where µ is the magnetic permeability of the material (in Henry/meter).

The magnetic permeability of a material (µ) is expressed by the product of vacuum permeability (µ₀, in Henry/meter) and relative permeability (µ_r, without dimension) :

µ=µ₀ * µ_r

- µ₀ is a universal constant, equal to 4 π *10 ^-7 H/m
- µ_r depends on the material.

In air, a vacuum, gas, copper, aluminium, earth and other materials, µ_r is equal to 1. These materials do not lead to a chanelling of the magnetic field.

Different kind of materials

We can distinguish diamagnetic (Silver, Copper, Water, Gold, Lead, Zinc ...), paramagnetic (Air, Aluminium, Magnesium, Platinum...) and ferromagnetic (Cobalt, Iron, Mumetal, Nickel ...) materials.

In general, diamagnetic and paramagnetic materials present permeability values close to 1. Thus, the absolute permeability µ of diamagnetic and paramagnetic materials is practically equal to the one of the vacuum, i.e. 4 π *10 ^-7 H/m.

The permeability of ferromagnetic materials is not constant but depends on the magnetic field H. For low values of H, µr can be very high, but it decreases with H value and can become equal to 1 above a certain threshold, because of a saturation. For this reason, we indicate maximal values of relative permeability in the table below.

Table - Relative magnetic permeability of ferromagnetic
materiels at 20°C

Ferromagnetic material	Relative magnetic permeability (µr) (max value)
Cobalt= Iron= Mumetal= Nickel=	250 10 000 100 000 600

Influence of temperature

A particular temperature exists, called Curie temperature (Tc) or Curie point, above which ferromagnetic materials lose their ferromagnetic property :

• Cobalt : 1115°C
• Iron : 770°C
• Mumetal : 380 °C
• Nickel : 358°C

Above the Curie temperature Tc, ferromagnetic materials become paramagnetic.

Further information:

• http://en.wikipedia.org/wiki/Curie_temperature
• http://www.goodfellow.com/csp/active/static/F/Mumetal.HTML

Origins of magnetic properties of materials

To understand differences in relative permeability, it is necessary to start from characteristics of atoms constituting materials. Either solids, liquids or gas, materials are constituted of molecules, which are made up of atoms.

An atom contains a central nucleus with orbiting electrons. Electrons move around the nucleus. Moreover, we can say figuratively that they also turn around themselves. This is this rotation of electrons or SPIN that gives magnetic properties to materials.

For further information on this subject, we advise you to follow the links below :

• http://en.wikipedia.org/wiki/Spin_%28physics%29
• http://en.wikipedia.org/wiki/Quantum_mechanics
• http://www.cvgg.org/vincent/Cours_electricite_et_magnetisme/
• http://www.rareearth.org/magnets_magnetism.htm

Melatonin:

A hormone, secreted by the pineal gland, which plays a role in the regulation of the waking-sleeping cycle.

Neuroendocrinal:

Relating to hormones secreted under the influence of the central nervous system.

Neuro - hormone:

A hormone secreted by the central nervous system. As the pineal gland is part of this system, melatonin is a neuro - hormone.

Occupational exposure:

Exposure to one or several risk factors during occupational activity.

Odds ratio:

The measurement of association between a factor and a disease that results from case control study. If the factor is a risk factor, the odds ratio (OR) will be significantly greater than 1.

Ohm's law:

Ohm's law explains the relationship between voltage and current that it produces.

To understand the relationship, let's take the example of water spurted out from a high pressure washer. The hosepipe section is very small. When the washer is turned off, the rate of water flow is weaker at the output of the hosepipe than directly at the tap. This decrease arises from the resistance of the hosepipe to water flow.

When the washer is turned on, pressure is enhanced at the input of the hosepipe and by the way the rate of water flow is increased through it.

In electricity, voltage V plays the role of pressure and the current i is equivalent to the rate of the flow. In the same way that hosepipe gives a certain resistance to water flow, each material gives a certain resistance R to charged particles moving which constituted it and these notions are linked to Ohm's law:

V = R x i

... so that, as in the example above, every enhancement of resistance causes under constant pressure a reduction of current and every enhancement of voltage causes an increase of current.

Ornithin 0 decarboxylase (ODC):

An enzyme taking part in the process of cell multiplication.

Pineal gland:

The pineal gland is an endocrine gland located in the middle of the brain. It secretes melatonin during the night.

Potential difference:

see Intensity - Potential difference

Power:

The energy generated or consumed per unit time. The unit of power is a watt (W). Electric power is calculated by multiplying the current intensity by the potential difference.

Power frequency:

In Europe, electricity is transported and distributed with a frequency of 50 cycles per second (50 Hz). In North America, the electricity distribution network functions at 60 Hz. The frequency of 50 Hz (or 60 Hz) is called the " power frequency ".

Power of the power stations:

Power stations generate significant power (expressed in millions of watts: MW). In Belgium, the working capacity installed is around 15600 MW (value 1999). This power is delivered on consumers' demand. In 2004, the maximum demand took place on December 20 and was measured at 13708 MW . The minimum demand took place on August 1 and was measured at 6046 MW at 7:00 AM. These extreme values show how electric consumption can fluctuate in Belgium.

The yearly consumption of an average household of 4 people is around 6000 kWh; this amounts to an average of 0.685 kW of power required, since a year corresponds to 8760 hours. However, the peak value can exceed 3 to 6 kW for short periods.

In 2004, the annual overall consumption for Belgium was 86 587 GWh. Consumption increased by 1.03 % compared with 2003. The increase is similar to that of the previous year. Since power is related to the product of intensity and current, one can conclude that, on average, the intensities increase on a consistent basis. The levels of potential difference of the electric energy network have been fixed for many years and are practically identical in connected European countries.

Prefixes of units:

Pico p 10^-12 (thousandth of billionth)
Nano n 10^-9 (billionth)
Micro µ 10^-6 (millionth)
Milli m 10^-3 (thousandth)
Kilo k 10³ (thousand)
Mega M 10⁶ (one million)
Giga G 10⁹ (one billion)
Tera T 10¹² (thousand billion)

Prevalence:

The total number of cases of a disease existing at a given time in a given population.

Promotion of cancer:

The process of development of tumours starting from cancerous cells.

Pulsated (wave):

See Wave forms.

Relative risk (RR):

A measurement of association between a factor and a disease in the case of a cohort study. If the factor is a risk factor, the relative risk (RR) will be significantly greater than 1.

Residential exposure:

The e xposure to risk factors in and around a place of residence.

RGIE:

The General Regulation of Electrical Installations to include certain lines of transport and electrical energy distribution. This regulation was made compulsory by the royal orders of March 10, 1981 (Belgian Monitor, April 23, 1981) and September 2, 1981 (Belgian Monitor, September 30, 1981).

See the website of the FPS Economy, SMEs, independent Professions
and Energy :
http://economie.fgov.be/Default.htm (in French or in Dutch)
(Onglet Energie - Electricité - Contrôle des installations électriques)
(Energie - Elektriciteit - Controle van de elektrische installaties)

RGPT:

General Regulation of Worker Protection.

The RGPT is a subdivision of social legislation governing relations between employers and workers. Social, medical and technical inspectors are qualified to note infractions, and thus have the right to inspect all companies and documents. A collection of regulations, taken mainly pursuant to the law on security (1952) and the law on the well being of workers (1996), the RGPT took form after the Second World War by the Regent's Orders of February 11, 1946 and September 27, 1947. In order to respect the European regulation and because it became illegible, the RGPT was revised in 1993 and is being progressively integrated into the Code on Well being.

ref: http://www.employment.belgium.be/home.aspx
http://www.emploi.belgique.be/detailA_Z.aspx?id=1008 (in French)
http://www.werk.belgie.be/detailA_Z.aspx?id=1008 (in Dutch)

Risk:

The probability of a given disease appearing in a given population within a given time period.

Risk factor:

A risk factor modifies the probability of disease onset. It is a statistical concept that does not imply a causal role for this factor. It is sufficient that the relative risk or odds ratio be significantly different from 1. The existence of a statistical relationship is not sufficient to conclude that a causal relationship exists.

RNA, messenger RNA:

RNA is the abbreviation for ribonucleic acid. RNA is a molecule formed of only one helix: it allows the synthesis of proteins in cells. RNA can have several functions. The messenger RNA, in particular, transmits genetic code information which is copied from the DNA in the nucleus to the cytoplasm of the cell in order to synthesize proteins.

Root mean square value (RMS):

A representative value of a quantity that varies in time (e.g. an AC current, an alternating voltage, an electric field, or a magnetic field). As these values vary continuously, it is necessary to establish a typical value. Physicists created the RMS, which is an image of continuous size that is equivalent to the true non-continuous quantity in terms of energy. The effective value of a quantity oscillating in a sinusoidal way is equivalent to its peak value divided by the square root of 2 (approx. 1.41).

Sinusoidal (wave):

See Wave forms

Static magnetic field:

The expression " static magnetic field " is equivalent to " continuous magnetic field ".

Statistically significant difference:

A statistical test makes it possible to calculate the probability that a difference observed between two groups is random rather than due to an exposure factor like magnetic fields. Conventionally, the difference is considered as significant if this probability (indicated in publications by the letter p) is lower than 5 %. Otherwise, it is impossible to decide whether there is an effect or an absence of effect. The smaller p is, the higher the probability of a relationship between the factor and the disease. Note however that a statistically significant difference does not prove a causal relationship.

Teratogenic:

Abnormalities produced during embryonic development leading to foetal malformations.

Three-phase current:

A configuration of three conducting wires wherein each one functions with the same alternating voltage, and generally transports the same AC current, but were the three currents are phase-shifted by a third of a period compared to each other. This means that the sum of the three currents is zero at every moment. A three-phase configuration makes it possible to transmit the same energy as with three identical circuits of a single wire each (compared to the same circuits with two wires each), thereby saving in 50 % in materials.

The three waves (A,B,C) represent the voltages (and currents) in a three-phase system.
Source : CIGRE

A set of cells of comparable nature that are specialised to perform the same function. Tissues form organs.

 

Waves forms:

Sinusoid: an oscillating curve resembling the sine function.

Pulsated wave: a curve that does not oscillate in a sinusoidal way. Rather, it provides impulses of short durations, similar in form to a saw's teeth.