“Gheorghe Asachi” Technical University of IasiFaculty of Chemical Engineering and

Environmental Protection Section: Environmental Management

and Sustainable Energy

Biological effects of Electromagnetic Fields on Human’s health

Supervisor:

  Prof.dr.ing.Valeriu David Students:

Vitelaru Razvan

Zara Maria

Iasi, 2014

CONTENT

1. Introduction2. Mechanism of propagation3. Electromagnetic field4. Classification of electromagnetic waves5. Source of electromagnetic pollution6. Measuring system7. Biological effects of electromagnetic fields 8. Conclusions9. References

1. INTRODUCTION

Electromagnetic radiation (EM radiation or EMR) is a fundamental phenomenon of

electromagnetism, behaving as waves and also as particles called photons which travel through

space carrying radiant energy. In a vacuum, it propagates at the speed of light, normally in

straight lines. EMR is emitted and absorbed by charged particles. As an electromagnetic wave, it

has both electric and magnetic field components, which synchronously oscillate perpendicular to

each other and perpendicular to the direction of energy and wave propagation.

In classical physics, EMR is produced when charged particles are accelerated by forces

acting on them. Electrons are responsible for emission of most EMR because they have low

mass, and therefore are easily accelerated by a variety of mechanisms. Quantum processes can

also produce EMR, such as when atomic nuclei undergo gamma decay, and processes such as

neutral pion decay.

EMR carries energy sometimes called radiant energy through space continuously away from

the source (this is not true of the near-field part of the EM field). EMR also carries both

momentum and angular momentum. These properties may all be imparted to matter with which

it interacts. When created, EMR is produced from other types of energy and it is converted to

other types of energy when it is destroyed.

Electromagnetic waves are transverse waves where the magnetic component and the electric

component, the electric and magnetic vectors are perpendicular to each other to the direction of

propagation. From the point of view of the wave spectrum of electromagnetic radiation

extending from long radio waves characterized by low frequency and large wavelength (km) to

high-energy rays, the high frequencies and smaller wavelengths.

In the spectrum of electromagnetic radiation, X-rays and Γ only satisfy the condition that the

wavelength should be less than 100 nm, so that only they can produce ionization of the atoms

constituting the main living matter. Therefore, X-rays and γ are called ionizing radiation.

Radiation of wavelength less than 100 nm from UV (ultraviolet) ones (100-190 nm) and going

for long radio waves are non-ionizing radiation. Ionizing radiation ranging from the visible to

the very low frequency (ELF-Extremely Low Frequency) waves produced by mobile phone base

stations are non-ionizing radiation.

The main sources of radiofrequency electromagnetic fields are antennas that emit radio and

television programs, mobile antennas, communication antennas (army, air traffic, police, fire or

emergency services), mobile devices, surveillance installations movement, microwaves, antennas

fixed wireless phones, security systems and more. Computer monitor, CRT is a source of

electromagnetic radiation from the cathode ray tube, and the most dangerous are extremely low

frequency radiation. Cells exposed to this type of radiation long suffering and in addition

dysfunction may occur metabolism disorders.

2. Mechanism of propagation

Electromagnetic waves are waves which can travel through the vacuum of outer space.

Mechanical waves, unlike electromagnetic waves, require the presence of a material medium in

order to transport their energy from one location to another. Sound waves are examples of

mechanical waves while light waves are examples of electromagnetic waves.

Electromagnetic waves are created by the vibration of an electric charge. This vibration

creates a wave which has both an electric and a magnetic component. An electromagnetic wave

transports its energy through a vacuum at a speed of 3.00 x 108 m/s (a speed value commonly

represented by the symbol C). The propagation of an electromagnetic wave through a material

medium occurs at a net speed which is less than 3.00 x 108 m/s. This is depicted in the animation

below.

The mechanism of energy transport through a medium involves the absorption and

reemission of the wave energy by the atoms of the material. When an electromagnetic wave

impinges upon the atoms of a material, the energy of that wave is absorbed. The absorption of

energy causes the electrons within the atoms to undergo vibrations. After a short period of

vibrational motion, the vibrating electrons create a new electromagnetic wave with the same

frequency as the first electromagnetic wave. While these vibrations occur for only a very short

time, they delay the motion of the wave through the medium. Once the energy of the

electromagnetic wave is reemitted by an atom, it travels through a small region of space between

atoms. Once it reaches the next atom, the electromagnetic wave is absorbed, transformed into

electron vibrations and then reemitted as an electromagnetic wave. While the electromagnetic

wave will travel at a speed of c (3 x 108 m/s) through the vacuum of interatomic space, the

absorption and reemission process causes the net speed of the electromagnetic wave to be less

than C. This is observed in the figure below.

The actual speed of an electromagnetic wave through a material medium is dependent upon the

optical density of that medium. Different materials cause a different amount of delay due to the

absorption and reemission process. Furthermore, different materials have their atoms more

closely packed and thus the amount of distance between atoms is less. These two factors are

dependent upon the nature of the material through which the electromagnetic wave is traveling.

As a result, the speed of an electromagnetic wave is dependent upon the material through which

it is traveling.

3. Electromagnetic field

Electric field and magnetic field are two aspects of a form of existence of matter, which is

called the electromagnetic field. The fact that a changing magnetic flux through the area is

bordered by a conductive coil produces in the mind, an electromotive induction shows that a

changing magnetic field creates an electric field. The result can be generalized in the sense that

everywhere in space, there is a time-varying magnetic field, an electric field arises. Also an

electric induction variable gives rise to a magnetic field (the principle of electromagnetic theory

established by physicist James Clark Maxwell in 1864).

The electromagnetic field is a field rotation and propagate in space in the form of

electromagnetic waves with a speed that depends on the permittivity and permeability of the

medium considered. Wave frequency is equal to the frequency obtained by moving electrons.

The higher the frequency, the more energy is transported in the same time frame. Analogous to

what happens in the elastic waves can be defined a size called wavelength electromagnetic

waves, and is equal to the distance they propagate electromagnetic field during a period of

oscillation of the dipole.

4. Classification of electromagnetic waves

Radio waves (where long, medium, short, ultra, microwave) are issued by oscillations of

electrons emitting antennas used in radio and microwave systems (television, radar). The radar

used to determine the vehicle speed based on the fact that the frequency of oscillations received

observer is greater if the source is near him and less if the source moves away. Source that emits

electromagnetic wave trains is placed in a police car stationed at the side of the road. Reflected

wave approaching vehicle which is received as a wave emitted by a mobile source with increased

frequency. Received wave is composed of a constant frequency wave phenomenon beats, and by

measuring the frequency change with beatings, determine the speed of the car that passes the

radar.

Infrared waves are electromagnetic waves emitted by warm bodies, being one of the three

categories are divided solar radiation (infrared radiation, visible light and ultraviolet radiation).

They are obtained by oscillations of molecules, atoms and ions, and their amplitudes depend on

the temperature of the electron transitions bodies and inner shells of atoms with lower energy

levels . They are strongly absorbed by water or other substances, including the human body and

produce heating of them. Radiation is used in various heating and drying processes, in building

detectors with infrared light sensitive film to retain pictures on infrared light to heat photocopies.

Visible waves are perceived by the human eye. Are emitted by the sun, stars, incandescent

filament lamps whose temperature can reach (2000 - 3000) ˚ C, gas discharge tubes, electric arcs.

Light emission is obtained after electronic transitions lower energy levels of atoms.

Ultraviolet radiation from the sun, stars, strong bodies and mercury vapor heated in special

quartz glass tubes (not absorbs this radiation). Radiation contained in sunlight are absorbed

mostly in the upper atmosphere (ozone layer) as altitude increases, the ultraviolet radiation is

greater. They lead to changes in the skin: pigmentation, burning, cancer, UV light helps form

vitamin D and kills bacteria, It is also useful in dermatology, and fluorescent lighting

installations in industrial numbering. Radiation are obtained following electron transitions to

higher energy levels to lower energy levels.

X-radiation (composed of X-rays) is a form of electromagnetic radiation. Most X-rays have

a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30

petahertz to 30 exahertz (3×1016 Hz to 3×1019 Hz) and energies in the range 100 eV to 100 keV.

X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma

rays.

X-rays have high frequencies and are used for the medical X-rays as are absorbed differently by

the muscles and bones and impress photographic plates. Radiation is also used for therapeutic

purposes because it helps fight cell growth diseased tissue.

Cosmic radiation and γ rays are emitted in nuclear decay processes and nuclear reactions in

the sun, the stars (they are absorbed by the atmosphere) and land-based nuclear reactors. Are the

most penetrating, with the highest frequencies and energies. They are used in flaw detection,

sterilization and medicine (treatment of cancer).

5. Source of electromagnetic pollution

Natural source of radiation

Atomic radioactive minerals are one of natural sources of radioactive pollution. During

mining of uranium, radon gas is constantly released into the air. The parent of radon-222

(t½ = 3.82 days) is radium 226 which has a half-life of 1602 years. Radium-226 is widely

distributed in rocks, sediments and soils along with isotopes of uranium.

Cosmic rays are high energy ionizing electromagnetic radiation. The cosmic rays

originate from the stars in our galaxy by virtue of nuclear reactions primarily in their

cores. The cosmic rays are constantly reaching the earth from outer space.

Naturally occurring radioisotopes such as radon-222 found in soil in small quantity is

another source of radioactive radiations.

Radioactive elements which like uranium, thorium, radium, isotopes of potassium (K-40)

and carbon (C-40) occur in the lithosphere.Potassium-40 contributes radioactivity to all

potassium containing systems in the soil. Crops grown on such soil contain radioactive

elements like carbon-14 and potassium-40. Water gets contaminated with various

radionuclides when it runs through soils and rocks containing radioactive minerals.

Anthropogenic source of radiation

Diagnostic medical applications : Radiations are employed for diagnostic and therapeutic

applications. X -rays are used in general radiology and CT scan. Gamma rays are used in

treatment of cancer. In all these procedures we are exposed to varying doses of radiations.

Nuclear Tests : Nuclear explosion tests especially when carried out in the atmosphere are

a major cause of radiation pollution. It is responsible for increasing the background level

of radiation throughout the world. During atmospheric nuclear explosion tests, a number

of long-lived radionuclides are released into the atmosphere. This radioactive dust (also

known as radioactive fall out) gets suspended in air at a height of 6 to 7 km above the

earth’s surface and is dispersed over long distances by winds from the test site. These

radionuclides often settle down by rain and get mixed with soil and water. From there

they can easily enter the food chain and finally get deposited in the human body where

they cause serious health hazards. Some of the radioactive isotopes given off during

nuclear test affect the human body.

Nuclear Reactors : Radiations may leak from nuclear reactors and other nuclear facilities

even when they are operating normally. It is often feared that even with the best design,

proper handling and techniques, some radioactivity is routinely released into the air and

water.

6. Measuring system

Electromagnetic field measurements are measurements of ambient (surrounding)

electromagnetic fields that are performed using particular sensors or probes, such as EMF

meters. These probes can be generally considered as antennas although with different

characteristics. In fact probes should not perturb the electromagnetic field and must prevent

coupling and reflection as much as possible in order to obtain precise results.

There are two main types of EMF measurements:

broadband measurements performed using a broadband probe, that is a device which

senses any signal across a wide range of frequencies and is usually made with three

independent diode detectors;

frequency selective measurements in which the measurement system consists of a field

antenna and a frequency selective receiver or spectrum analyzer allowing to monitor the

frequency range of interest.

Measurements of the EMF are obtained using an E-field sensor or H-field sensor which can

be isotropic or mono-axial, active or passive. A mono-axial, omnidirectional probe is a device

which senses the Electric (short dipole) or Magnetic field linearly polarized in a given direction.

Using a mono-axial probe implies the need for three measurements taken with the sensor axis

set up along three mutually orthogonal directions, in a X, Y, Z configuration. As an example, it

can be used a probe which senses the Electric field component parallel to the direction of its axis

of symmetry. In these conditions, where E is the amplitude of incident electric field, and θ is the

amplitude of the angle between sensor axis and direction of electric field E, the signal detected is

proportional to |E| cos θ (right).

Electromagnetic field projection on an orthogonal reference frame

An isotropic (tri-axial) probe simplifies the measurement procedure because the total field

value is determined with three measures taken without changing sensor position: this results

from the geometry of the device which is made by three independent broadband sensing

elements placed orthogonal to each other. In practice, each element’s output is measured in three

consecutive time intervals supposing field components being time stationary.

To measure the Electromagnetic field we can use an EMF meter that is a scientific

instrument for measuring electromagnetic fields. Most meters measure the electromagnetic

radiation flux density (DC fields) or the change in an electromagnetic field over time (AC fields),

essentially the same as a radio antenna, but with quite different detection characteristics.

EMF meter

The two largest categories are single axis and tri-axis. Single axis meters are cheaper than

a tri-axis meters, but take longer to complete a survey because the meter only measures one

dimension of the field. Single axis instruments have to be tilted and turned on all three axes to

obtain a full measurement. A tri-axis meter measures all three axes simultaneously, but these

models tend to be more expensive.

Electromagnetic fields can be generated by AC or DC currents. An EMF meter can measure

AC electromagnetic fields, which are usually emitted from man-made sources such as electrical

wiring, while gaussmeters or magnetometers measure DC fields, which occur naturally in Earth's

geomagnetic field and are emitted from other sources where direct current is present.

7. Biological effects of electromagnetic fields

Electromagnetic energy can be emitted as waves by many natural and artificial sources.

These waves consist on oscillating electric and magnetic fields that influence each other and

affect in different ways the biological systems, such as cells, plants, animals and human beings.

To better comprehend this reciprocal influence it is necessary to know the physical properties of

the electromagnetic waves.

The electromagnetic waves can be characterised by their wavelength, frequency or energy.

These three parameters are directly related to each other. The values of these quantities

determine the way the EMF can affect a biological system.

The frequency of a electromagnetic wave is defined as the number of times the (electric or

magnetic) fields changes its sign at a given point per time unit. The Frequency is measured on

Hertz (Hz), or times per second.

The wavelength of a electromagnetic wave is inversely proportional to the frequency of the

wave, being the proportionality constant the speed of the wave in the medium (usually the

medium is considered to be vacuum, then the speed corresponds to the speed of light c = 3x108

m/s). It is easy to see that the highest the frequency, the smaller the wavelength. As an example,

a typical microwave furnace emits a wave of 2450 million Hz (or 2.54 GHz), corresponding to a

wavelength of 12 centimetres, while for amplitude modulated radio emissions (AM) the

frequency is about 1 million Hz (1 MHz), with a wavelength of about 300 metres.

The electromagnetic waves are formed by small packets of energy, called photons, that can

be considered to act as quasi-particles. The energy of a photon depends on its frequency (or

wavelength): the higher the frequency the higher the energy (and the smaller the wavelength).

The intensity of an electromagnetic wave is proportional to the number of photons.

The effects of the electromagnetic fields on biological systems is determined both by the

energy of the wave (the energy of the photons) and the intensity of the fields (the number of

photons on the wave).

In function of the frequency, the electromagnetic waves are usually classified on

electromagnetic fields or non-ionizing radiations, when the frequency is small, and

electromagnetic radiations or ionizing radiations, when the frequency is very high.

The ionizing radiations have a frequency high enough to produce the ionization of

molecules and atoms through the breaking of the chemical bonds of the molecules. Examples of

these radiations are the X-rays and radiations produced by radioactive sources.

The non-ionizing radiations (NIR) correspond to those waves of the electromagnetic

spectrum whose energy is too low to break the atomic bonds. Among these radiations are the

ultraviolet and visible light, the infrared radiation, the radiofrequency and microwave emissions,

the extremely low frequency fields and the static magnetic and electric fields.

The NIR, even at very high intensity, can not produce ionization in a biological system.

Nevertheless, these radiations have been proved to produce other biological effects, such as

heating, alteration of some chemical reactions or induction of electric currents on tissues and

cells.

The effects the electromagnetic waves can produce on a biological system are not always

pernicious to health, and sometimes they are even healthy. A biological effect is produced when

the exposition to electromagnetic waves cause any physiological change perceptible or

detectable on a biological system. A pernicious effect is produced when the biological effect

overpass the normal ability of the organism to compensate it and produces a pathological

process.

As previously commented, some biological effects can be innocuous, as the increase of

skin blood circulation in response to a slight warming. Some effects can even be beneficial or

healthy, as the use of solar radiation for the production of D vitamin by our bodies. Nevertheless,

other effects are harmful, as the burnings or the skin cancer produced by sun radiation.

Nowadays it is well established that radiofrequency fields (RFF) produce heating and induce

electric currents on biological systems. Moreover, other biological effects have also been cited,

though there are not fully proved. The main biological effects reported up to date, in function of

the wave frequency, are:

- RFF with frequency over 1MHz mainly produce heating by displacing ions and water

molecules on their medium. Even at very low field intensity, these waves cause heating,

which is absorbed and compensated by the body without noticing.

- Electromagnetic fields (EMF) with frequency below 1 MHz induce electric charges and

currents that can stimulate cells from some tissues as nerves and muscles. The human

body does have electric currents as a normal product of its chemical reactions. When the

electric currents produced by the EMF exceed significantly the natural currents produced

by the organism, harmful effects are possible.

- The main effect of electric and Magnetic fields with very low frequency on biological

system is the induction of electric charges and currents. It is highly improbable that these

effects can explain the reported sanitary effects, as the notified increase rate of cancer

cases on children due to exposition to ambient fields with very low frequency, as those

produced on high voltage lines.

- Static magnetic and electric fields induce electric charges and currents. The existence of

other possible harmful effects have been shown, though only at very high intensities,

difficult to find on normal life.

The electric fields do not penetrate on the organism as deep as magnetic fields do, but they

can be felt by the movement of the hair. Apart form the electric discharges of high electrostatic

fields, their effects on health are not remarkable.

Static magnetic fields show almost the same intensity inside and outside the body. When

these fields are very intense, they can alter the blood flow or modify the neuronal impulses, but

the intensity necessary to observe these effects is not found on normal life. It should be noticed

that there is not enough information about the effects of long, continuous exposure to magnetic

fields at levels found on labour environments.

International rules and directives have been adopted in order to assure that human exposition

to electromagnetic fields do not have any harmful effects and to avoid any electric interference

between EMF emitters/generators and other systems. To fix these rules, scientific committees

carry out a full revision of the scientific publications and investigations by, and made

recommendations to the different national and international organizations, who will then adopt

the appropriate prevention rules. The International Commission on Non Ionizing Radiation

Protection (ICNIRP) a non-governmental organization recognised by WHO, has established

international directives for the exposure limits of human beings to electromagnetic fields,

including UV radiation, visible light and infrared radiation.

8. Conclusions

The best way to understand the biological effects of electromagnetic fields is to cause dielectric

heating by touching or standing around an antenna while a high-power transmitter is in operation

it can be seen that this process can cause severe burns, kind of burns that are inside a microwave

oven.

The heating effect varies with the power and the frequency of the electromagnetic energy,

heating effect represents the specific absorption rate (W/kg).

The most acute exposures to harmful levels of electromagnetic radiation are immediately

realized as burns, but the biological effects due to chronic or occupational exposure may not

manifest effects for months or years.

Exposure to high-power radio frequency is known to create effects ranging from a burning

sensation on the skin and microwave auditory effect, to extreme pain at the mid-range, to

physical microwave burns and blistering of skin and internals at high power levels.

Very strong radiation can induce current capable of delivering electric shock’s to humans or

animals also can cause damage or destroy the electrical equipment.

The induction of currents by oscillating magnetic fields is also the way in which solar storms

disrupt the operation of electrical and electronic systems, causing damage to and even the

explosion of power distribution transformers, blackouts and interference with electromagnetic

signals (radio, TV, and telephone signals).

References

Bernhardt J H, Non-ionizing radiation safety: radiofrequency radiation, electric and

magnetic fields, Phys. Med. Biol. 37 807-844,  1992

Zhang,  Hong-qi Zhang., and W. Pan, Electromagnetic field of a vertical electric dipole

on a perfect conductor coated with a dielectric layer, Radio Sci., 37(4), 2002

World Health Organization, International Commission on Non-Ionizing Radiation

Protection (ICNIRP), Health issues related to the use of hand-held radiotelephones and

base transmitters, Health Physics, Vol.70, No.4, p. 587-593, 1996,  http://www.icnirp.org

Health effects from radiofrequency electromagnetic fields – Report of an Independent

Advisory Group on Non-Ionizing Radiation, 2003

http://www.bioone.org/bioone/7587&volume=162&issue=02&page=0219

http://www.icnirp.de/what.htm