ELECTROMAGNETIC 0 Hz 300 GHz Field characterization & occupational exposure sources Laura FILOSA
1. Organization of the NIR Module 2. European frame introduction 3. Electromagnetic field characterization 4. Occupational emf sources
TODAY, 12 May TOMORROW, 13 May Electromagnetical Fields EMF Artificial optical radiation AOR
The object of this Directive is to introduce general principles Council concerning Directive 89/391/EEC the prevention of 12 June of 1989 occupational on the risks, introduction the protection of measures of safety to and encourage health, improvements the elimination of risk and in the accident safety factors, and health the of informing, workers at consultation, work balanced participation in accordance with national laws and/or practices and training of workers and their representatives, as well as general guidelines for the implementation of the said principles.
2002 2003 2004 2006
2004 PASSING EMF DIRECTIVE 2008 AMENDMENT TO EMF DIRECTIVE 30/4/2010 Proposal of new directive to EU Council 2011 NEW EMF European Directive 2011 / XX / EC COME INTO FORCE
Deadline postponed MAGNETIC RISONANCE PROBLEMS RELATED TO SOME INDUSTRIAL APPLICATIONS DIFFICULT IMPLEMENTATION IN SME
Protection of Workers Exposed to EMF in the European Union: Directive 2004/40/EC 1. The philosophy behind? 2. Possible implementation problems?
1. Organization of the NIR Module 2. European frame introduction 3. Electromagnetic field characterization 4. Occupational emf sources
Electric and magnetic phenomena Electric field Magnetic field Is generated by Is a region of space where forces are present, which have effects on (Every object on which is present) a net electric charge (Other objects possessing) net electric charges (Every conductor on which is flowing) an electric current (Other conductors on which are flowing) electric currents
The Maxwell s system of equations E E 0 t B E J t B B They link the field quantities, their sources and the characteristics of materials
The Maxwell s system of equations in quasi-static conditions (static or extremely low frequency fields) E 0 E B B 0 J Electric and magnetic fields are decoupled. Electric and magnetic fields are due to material sources: Electric charge for the electric field; Electric current for the magnetic field.
Characteristic parameter of waves Period T: It is the duration of a repeating event per unit time Wavelenght l: It is the spatial period of the wave the distance over which the wave s shape repeats Frequency l: It is the number of occurences of a repeating event per unit time. It is also referred to as temporal frequency Amplitude A: It is related to its intensity wich is power per unit It is related to energy carried from the wave.
Units of measurement and symbols Quantity Unit of meas. Symbol Frequency hertz f [Hz] Wavelength meter λ [m] λ*f = c (speed of light, approx. 3x10 8 m/s in vacuum and air) Although biological effects of EM fields dramatically depend on frequency, the frequency itself is not a direct measure of radiation intensity. Safety standards and guidelines always specify limits which depend on frequency in a complex way. The wavelength is the reference to describe the structure of the EM field as a function of distance from its source.
Units of measurement and symbols Quantity Unit of meas. Symbol Electric field volt/meter E [V/m] Magnetic field ampere/meter H [A/m] Magnetic flux density tesla gauss (obsolete) B [T] B [G] 1 G = 100 μt, 1 μt = 10 mg, 1 T = 10000 G 1 A/m is approximately equivalent to 1,2 μt Power density watt/squaremeter S [W/m 2 ]
The structure of the EM field as a function of distance from the source CHARGE VOLTAGE ELECTRIC FIELD Decays as 1/d 2 ELECTRIC FIELD 1/d CURRENT MAGNETIC FIELD Decays as MAGNETIC FIELD 1/d 2 SOURCE ELECTRIC AND MAGNETIC REACTIVE FIELDS ELECTROMAGNETIC RADIATIVE FIELDS EM WAVE
Quantistic energy Wave lenght Frequency Frequencies bands definition Gamma rays, Cosmic rays 12 ev 100 nm X Rays Ultraviolet rays Visible radiation Infrared radiation EHF VHF, UHF MF, HF VLF, LF
Why 12 ev? ATOMS IONIZING ENERGY [ ev ] l [ nm ] Caesium 3.9 318 Carbon 11.3 110 Hydrogen 13.6 91 Oxygen 13.8 93 Azote 14.3 56 Helium 24.8 50 ONLY STARTING FROM UV RADIATIONS THERE IS THE CHANCE TO IONIZING THE BIOLOGICAL MATTER
1. Organization of the NIR Module 2. European frame introduction 3. Electromagnetic field characterization 4. Occupational emf sources
Natural static electric field
45 50 T 130 V/m 100 V/m 20 kv/m
Low and intermediate frequency sources
High frequency sources
Main occupational EM sources
Industrial and sanitary applications of EM heating Industrial EM heating: useful in production processing requiring a fast and efficient heating (hardening and other metallurgic treatments, plastic welding and sealing, wood gluing, food and wood sterilization, cooking, drying of ceramics). Sanitary electromagnetic heating: marconi-therapy (short-wave diathermy), radar therapy (microwave).
600 V H < 30 V/m up to 500 kv 20 Kv / m 10-500 kv/m
DC SUPPLY derived From alternating current by rectification, so also AC harmonic components can exist Electrolytic process Permanent magnet < 100 mt
< 0.1-30 T < 10 V/m
Electric and magnetic field strengths under overhead transmission lines OVERHEAD TRANSMISSION LINE ELECTRIC FIELD STRENGTH [kv / m] MAGNETIC FLUX DENSITY [ T] 110 kv 240 kv 400 kv 765 kv 0.5-2 3-5 6-10 10-12 2-5 5-10 10-15 30-40 Depending on the line design and current, electric and magnetic fields generally fall to background strengths at distances of about 50-100 m
Electric and magnetic field strengths measured at an electricity production plant ELECTRIC FIELD STRENGTH [kv / m] MAGNETIC FLUX DENSITY [ T] Control room Power station Substation 1.5 6 24 75 150 400 Exposure limit 10 kv / m 500 T
Only detect Detect and convey information manual gate 1. 10Hz-20kHz 2. 20-235 khz 3. 1-20 MHz 4. 0.8-2.5 GHz 1. Hz-500 khz 2. 2-30 MHz 3. 850-950MHz 2.45 GHz 5.8 GHz
Examples of EAS, RFID and MD systems System Frequency Comments EAS 10 Hz 135 khz 1-20 MHz 0.8-2.5 GHz Anti-theft system in shops Anti-theft system in shops Microwave EAS systems in shops RFID MD 1 Hz 500 khz 2-30 MHz 850-950 MHz, 2.45 GHz, 5.8 GHz 0.24 8 khz 10 khz- 2 MHz Access control, library systems, item tracking Access control, smart cards Train monitoring, toll collection systems Airport and prison control system Handheld metal detectors
Peak magnetic flux densities measured within EAS gates FREQUENCY B PEAK [ T] REFERENCE LEVEL [ T] Distance from transmitter [cm] 73 Hz 219 Hz 230 Hz 535.7 Hz 5-7.5 khz 58 khz 146 122 93 72 43 62-65 484 161 154 66 44 44 31 36 42 36 48 36 Below 100 khz, peak reference values for pulsed fields are obtained by multiplying the rms-values by V2
APPLIED TO HEAT WOOD (GLUE DRYERS) OR WELD PLASTIC (PLASTIC SEALERS) BY APPLYING A STRONG RF FIELD BETWEEN METAL ELECTRODES. Frequency range: 10-110 MHz 13.56 MHz 27.12 MHz 40.68 MHz
PROCESS THAT GENERATE HEATH USING ALTERNATING CURRENT FLOWING THROUGH LARGE COILS FORGING, SURFACE HARDENING, BENDING PIPES 50 Hz 8 MHz INDUCTION FURNACES ARE THE MOST POWERFUL SOURCES OF MAGNETIC FIELDS IN INDUSTRY
INDUSTRIALLY USED FOR DRYING OF WATER DAMAGES IN FLOOR OR WALLS 915 MHz 2450 MHz Power density of MW radiation is HIGH and furthermore presence of stray fields Should be used only by well trained users
GAS WELDING LASER WELDING ELECTRIC WELDING
ELECTRIC ARC WELDING PROCESSES ARE USED TO FUSE METAL PIECES TOGETHER ACCORDING THE TYPES OF WELDING PROCESS (ARC, RESISTANCE, HIGHER FREQUENCY, ELECTRON BEAM WELDING) ACTION VALUES COULD BE EXCEEDED
Three environments in which workers may be exposed to strong magnetic field: EXAMPLES ARE THE ELECTROLYSIS OF BRINE TO PRODUCE CHLORINE GAS AND CAUSTIC SODA & THE EXTRACTION OF METALS SUCH AS ZINC, CADMIUM, AND ALLUMINIUM FROM ORES DISSOLVED IN WATER AND ACID SOLUTIONS & SURFACE TREATMENT (ZINC COATING, CHROMIUM PLATING) Transformer rectifier room Bus bar Electrolysis hall
MAINLY THERE ARE THREE APPLICATION IN MEDICINE OF INTEREST: Physioterapic use of diathermy Surgical diathermy Magnetic Resonance Imaging
IN MEDICAL CLINICS RF ARE USED IN PHYSIOTHERAPY IN SHORTWAVE OR MICROWAVE DIATHERMY TREATMENT Physiotherapist using a pulsed shortwave diathermy device for pain relief APPLICATION ARE OPEN AND POSSIBLE OVEREXPOSURE OF STAFF CAN OCCURE SHORTWAVE 27 MHz MICROWAVE 2.45 GHz
RF ENERGY IS USED TO CUT AND TO COAGULATE, AND SINCE UNSHIELDED ELECTRODES ARE USED THE FIELD ARE RATHER INTENSE AND SPECIAL ATTENTION IS NEEDED TO ENSURE COMPLIANCE WITH DIRECTIVE ON OCCUPATIONAL EXPOSURE
STATIC MAGNETIC FIELD RF FIELDS GRADIENT MAGNETIC FIELDS
LET CONSIDER 3 GROUPS: 1. TWO-WAY COMMUNICATION TRANSMITTERS 2. ONE-WAY BROADCASTING TRANSMITTERS 3. RADARS
Mobile telephony: GSM and UMTS base stations TETRA transmitters GSM telephones UMTS telephones TETRA hand portable & vehiclemounted transmitters Wireless communication: WLL beam transmitters broadcasting Radar
ANTENNAS OF BROADCAST RADIO & TV STATIONS ARE THE MOST POWERFUL SOURCES OF ENERGY INTENTIONALLY RADIATED INTO AIR
DESIGNATION LF (long) MF (medium) HF (short) VHF UHF FREQUENCY RANGE 30-300 khz 300-3000 khz 3-30 MHz 30-300 MHz 0.3-3 GHz APPLICATION AM radio transmitters AM radio transmitters AM radio transmitters FM radio transmitters Television transmitters Frequency bands for broadcast radio and TV transmitters
l.filosa@ inail.it