Effect of non-ionizing electromagnetic field
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This document provides an overview of non-ionizing radiation and its biological effects on the human body. It discusses the electromagnetic spectrum and different types of non-ionizing radiation such as optical radiation, radiofrequency, microwaves, and electric and magnetic fields. The document outlines sources of non-ionizing radiation, potential biological effects including thermal and non-thermal interactions, and international standards and guidelines for limiting exposure to avoid known health risks.
![Radiofrequency and Microwave
RF radiations transmitted from base stations and mobile phones have received a
lot of attention. Typical locations where the public is exposed are at ground level,
in buildings beneath antennas and in buildings facing antennas mounted on masts
or other buildings.
NRPB has made many measurements of exposure levels at publicly accessible
locations around base stations. One study [12] reported measurements taken at
118 locations from 17 different base station sites. Average exposures were found
to be 0.00002% of the ICNIRP public exposure guidelines and at no location
were exposure found to exceed 0.02% of the guidelines.
The maximum exposure at any location was 0.00083 mWcm-2
(on a playing field
60 meters from a school building with an antenna on its roof). Typical power
densities were less than 0.0001 mWcm-2
(less than 0.01% of the ICNIRP public
exposure guidelines). (See Fig. 2) Power densities indoors were substantially less
than power densities outdoors. When RF radiation from all sources (mobile
phone, FM radio, TV, etc.) was taken into account the maximum power density at
any site was less than 0.2% of the ICNIRP public exposure guidelines](https://image.slidesharecdn.com/introduction-210509145408/85/Effect-of-non-ionizing-electromagnetic-field-18-320.jpg)
![ short-term: whole body 2 T; limbs 5 T
continuous exposure: 200 mT
(since these are for occupational exposure only, time-averaging is performed over the
working day.)
continuous exposure of the general public (except for those with pacemakers and other
implanted devices): 40 mT
continuous exposure of those with pacemakers and other implanted devices: 0.5 mT.
Guidelines for exposure to time-varying electric fields, magnetic fields, and electromagnetic
radiation
ICNIRP [3] guidelines are presented in terms of two levels of protection (Tables 3 & 4). The
conditions are:
All Specific Absorption Rate (SAR) values are averaged over any 6-min period and
localized SAR values are averaged over a 10g contiguous mass of tissue.
- For pulses of duration tp, the equivalent frequency is determined by 1/(2tp).
- For pulsed exposures in the frequency range 0.3 -10 GHz and for localized exposure of
the head, the specific absorption should not exceed 10 mJ kg-1
, averaged over 10 g tissue.
- For frequencies up to 100 kHz and for pulsed magnetic fields, the associated maximum
current density may be determined from the rise/fall times and maximum rate of change of
magnetic flux density.](https://image.slidesharecdn.com/introduction-210509145408/85/Effect-of-non-ionizing-electromagnetic-field-23-320.jpg)
Effect of non-ionizing electromagnetic field
- 1. Hazard Analysis & Safety Management 1 Md Jalaluddin Rayeen Senior Lecturer, Department of Electrical Engineering Hillside College of Engineering Subject Code: BEG424EL Fourth Year
- 2. CONTROL SYSTEM ENGINEERING Year Third Teaching Schedule (Hours /week) Lecture (Theory) Practical Tutorial Semester Fifth Credit Hour 3 - - Course Code BEG324EL Lecture Hour 3 3/2 1 Examination System Final Internal Assessment Total Marks Remarks Theory Practical Theory Practical Full Marks 80 - 20 25 125 Pass Marks 32 - 8 10 50 Duration 3 Hours - 3 Hours - - Course Objectives: To present the basic concepts on analysis and design of control system and to apply these concepts to typical physical processes.
- 4. Chapter 1: Effect of Non-ionizing Electromagnetic Fields on Human Body Radiation: Radiation is energy that comes from a source and travels through space and may be able to penetrate various materials - It travels as invisible waves - The frequency of these waves helps to determine field characteristics and how it can affect people -Electromagnetic spectrum, the entire distribution of electromagnetic radiation according to frequency or wavelength. Although all electromagnetic waves travel at the speed of light in a vacuum, they do so at a wide range of frequencies, wavelengths, and photon energies.
- 7. Types of Radiation There are two principle categories of radiation i. Ionizing Radiation ii. Non-ionizing Radiation i. Ionizing Radiation: Radiation with sufficient energy to cause a neutral atom to acquire positive or negative charge, that is having ability to create electrically charged ions capable of disrupting the process is called ionizing radiation - Ionizing radiation is found at extremely high frequency eg X-rays as seen in figure - The Higher the frequency , the greater the radiant energy associated with radiation
- 8. ii. Non-ionizing Radiation • Non-ionizing radiation (NIR) refers to any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atoms or molecules—that is, to completely remove an electron from an atom or molecule. • The NIR spectrum is divided into two main regions, Optical Radiations and Electromagnetic Fields. • The Optical can be further sub-divided into ultraviolet, visible, and infra-red • The Electromagnetic Fields are further divided into radiofrequency (microwave, very high frequency and low frequency radio wave)
- 9. • Non-ionizing radiation originates from various sources: • Natural origin (such as sunlight or lightning discharges etc.) And • Man-made (seen in wireless communications, industrial, scientific and medical applications). • The optical radiations are centred around visible light; those with higher energies are termed UV radiation and those with lower energies IR radiation. • Sources of UV radiation are the sun, arc welding, oxy- gas welding, sun lamps, lasers (UV), sterilization (germicidal) lamps, low pressure gas discharge lamps, high pressure discharge lamps. • Sources of IR radiation are from hot processes such as steelmaking, glassmaking, welding, and also lasers (IR). The application of laser as a coherent light source is increasing rapidly. • Medical applications include UV and neonatal Phototherapy, Surgical and laser Therapy
- 10. 10 Electromagnetic fields-Sources • Microwaves are used in telecommunications, radar/satellite links, mobile phones, microwave ovens, TV transmitters. RF is used in radio communications, visual display units, television sets. • • Extremely low-frequency (ELF) electric and magnetic fields (EMFs) surround electrical machinery, home appliances, electric wiring, and high-voltage electrical transmission lines and transformers. • Medical applications include: microwave hyperthermia, therapeutic and surgical diathermy, and magnetic resonance imaging (MRI).
- 12. BIOLOGICAL EFFECTS OF NIR • A biological effect occurs when a change can be measured in a biological system after the introduction of some type of stimuli. However, the observation of a biological effect, in and of itself, does not necessarily suggest the existence of a biological hazard or health effect. • A biological effect only becomes a safety hazard when it “causes detectable impairment of the health of the individual or of his or her offspring”. • Biological effects could be physiological, biochemical or behavioral changes induced in an organism, tissue or cell. • NIRs usually interact with tissue through the generation of heat. • The hazards depend on the ability to penetrate the human body and the absorption characteristics of different tissues. • There are still much uncertainties about the severity of effects of both acute and chronic exposure to various types of NIRs. • Generally the public is concerned about the risks from ELF, RF and MW. However, the greatest risk to the public probably arises from natural UV radiation.
- 13. • Damage from optical radiations is largely confined to the eye and skin, and fall into two categories – thermal damage and photochemical damage. • Despite having insufficient energy to ionise atoms, single photons of ultraviolet radiation can damage tissue through disruption of bonds within DNA molecules and give a long-term risk of cancer. • This must be borne in mind when determining allowable exposures. Visible light and IR only produce damage through high-intensity multi-photon interactions. • The biological effects induced are essentially the same for both, but lasers (coherent light) are capable of producing higher irradiances and can heat localized volumes of tissue to a high enough temperature to produce rapid physical change • The nature, extent, and physiological importance of biological effects from NIR exposures will depend on many factors such as the energy of the incident radiation (determines the penetration depth), the power density of the field or beam, source emission characteristics, duration of exposure, environmental conditions, and the spatial orientation and biological characteristics of the irradiated tissues (molecular composition, blood flow, pigmentation, functional importance, etc.). • Biological effects that result from heating of tissues by RF radiation are referred to as ‘thermal’ effects. The body has effective ways to regulate its temperature, but if exposures are too intense the body no longer copes
- 14. Biological Effects of NIR 14
- 17. EMISSIONS AND EXPOSURES Optical radiations Prolonged human exposure to solar UV radiation may result in acute and chronic health effects on the skin, eye and immune system. Sunburn and tanning are the best known acute effects of excessive UV radiation exposure; in the long term, UV radiation-induced degenerative changes in cells, fibrous tissue and blood vessels lead to premature skin ageing. UV radiation can also cause inflammatory reactions of the eye, such as photokeratitis. Chronic effects include two major public health problems: skin cancers and cataracts. Furthermore, a growing body of evidence suggests that environmental levels of UV radiation may increase the risk of infectious diseases and limit the efficacy of vaccinations. Sun protection programs are urgently needed to raise awareness of the health hazards of UV radiation, and to achieve lifestyle changes that will reverse the trend towards more skin cancers. Recently the Global Solar UV Index (UVI) was developed by the World Health Organization (WHO) in collaboration with the United Nations Environment Programmed (UNEP), the World Meteorological Organization (WMO), and the International Commission on Non- Ionizing Radiation Protection (ICNIRP). The UVI is a simple measure of the UV radiation level at the Earth’s surface and aims to aid public understanding of exposure levels and to raise public awareness of the risks of exposure
- 18. Radiofrequency and Microwave RF radiations transmitted from base stations and mobile phones have received a lot of attention. Typical locations where the public is exposed are at ground level, in buildings beneath antennas and in buildings facing antennas mounted on masts or other buildings. NRPB has made many measurements of exposure levels at publicly accessible locations around base stations. One study [12] reported measurements taken at 118 locations from 17 different base station sites. Average exposures were found to be 0.00002% of the ICNIRP public exposure guidelines and at no location were exposure found to exceed 0.02% of the guidelines. The maximum exposure at any location was 0.00083 mWcm-2 (on a playing field 60 meters from a school building with an antenna on its roof). Typical power densities were less than 0.0001 mWcm-2 (less than 0.01% of the ICNIRP public exposure guidelines). (See Fig. 2) Power densities indoors were substantially less than power densities outdoors. When RF radiation from all sources (mobile phone, FM radio, TV, etc.) was taken into account the maximum power density at any site was less than 0.2% of the ICNIRP public exposure guidelines
- 19. Electric and Magnetic Fields • Exposure can arise at home, work, or school and is measured using personal or environmental monitoring. • The Electric fields depend on the magnitude of the voltage and distance from the source. Generally, voltages are stable and remain the same; however electric fields are easily perturbed by many common objects. • Exposure to magnetic fields arises from power lines and the use of electrical appliances. Ambient fields from the supply to the house are always present and expose the whole body, whereas those from appliances are intermittent and expose part of the body. • The magnetic field strength depends upon the magnitude of the current and on the distance from the appliances.
- 20. STANDARDS AND GUIDANCE FOR NIR Standards and guidelines for limiting exposure and avoiding known adverse health effects have been drawn up by international and national bodies. These apply in general to characteristic parameters of the radiation field at the point in space where the individual can be or is exposed. They are based on biophysical models and on laboratory and field observations of the biological effects. The standards are limits for field parameters (e.g. to limit current density, SAR, and power density) which are designed to protect workers from potentially adverse effects of NIRs and to permit the general use of NIR under safe conditions, though there is no precise boundary between risk and no risk. The earliest recommendations for exposure limits for NIRs were established in the 1950s and 1960s for microwave and RF radiations generated by military radars and communication equipment. Recommendations for the protection of the eyes from lasers were established in 1970s. As concern for the increasing applications of all forms of NIRs, the International Non- Ionizing Radiation Committee (INIRC) was set up in 1977. In 1992 the INIRC was renamed the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The ICNIRP works closely with the World Health Organization (WHO) to assess health effects of NIRs and to develop international guidelines on limits to exposure and protection measures. Guidelines are often presented in terms of two levels of protection: basic restrictions-based directly on established health effects reference levels - derived from measurements and/or computed predictions. These provide for practical exposure assessment to determine whether the basic restrictions are likely to be exceeded.
- 21. If a reference level is exceeded, it does not necessarily follow that the basic restriction is exceeded. However, in such cases, compliance with the basic restriction must be tested. Guidelines often differentiate between occupational exposure and general public exposure: occupational/controlled exposures - appropriate when and can exercise control over it are exposed as a consequence of their employment. These limits also apply in situations when an individual is transient through a location where occupational/controlled limits apply provided he or she is made aware of the potential for exposure. general population/uncontrolled exposures - apply when the general public may be exposed or when persons who may not be fully aware of the potential for exposure or cannot exercise control over it are exposed as a consequence of their employment. Recommended exposure limit for RF radiation from mobile phone is given in Table
- 22. Table 2. Basic restrictions on exposure SAR* (W kg-1 ) recommended by NRPB and ICNIRP for workers and members of the public Worker Public Public NRPB/ICNIRP NRPB ICNIRP Whole body** 0.4 0.4 0.08 Head and trunk** 10 10 2.0 Limbs** 20 20 4.0 * SAR (specific energy absorption rate) is a measure of the rate at which energy is absorbed by unit mass of tissue in an electromagnetic field. It is measured in the units of watts per kilogram (W kg-1 ). ** For calculating SAR the averaging time is taken to be 6 minutes for all tissues. ICNIRP also uses 6 minutes for the whole body but NRPB uses 15 minutes. The averaging mass is taken to be 10 g by ICNIRP while NRPB uses 10 g for the head (and fetus) but 100 g for the trunk, limbs and neck. Guidelines for exposure to static magnetic fields Several guidelines have been proposed by international and national agencies based on criteria such as the need to limit currents induced by movement through the static magnetic field to levels less than those that occur naturally in the body or to limit those induced in the large vessels by blood flow to below levels that result in hemodynamic or cardiovascular effects. ICNIRP recommends limits on occupational exposure:
- 23. short-term: whole body 2 T; limbs 5 T continuous exposure: 200 mT (since these are for occupational exposure only, time-averaging is performed over the working day.) continuous exposure of the general public (except for those with pacemakers and other implanted devices): 40 mT continuous exposure of those with pacemakers and other implanted devices: 0.5 mT. Guidelines for exposure to time-varying electric fields, magnetic fields, and electromagnetic radiation ICNIRP [3] guidelines are presented in terms of two levels of protection (Tables 3 & 4). The conditions are: All Specific Absorption Rate (SAR) values are averaged over any 6-min period and localized SAR values are averaged over a 10g contiguous mass of tissue. - For pulses of duration tp, the equivalent frequency is determined by 1/(2tp). - For pulsed exposures in the frequency range 0.3 -10 GHz and for localized exposure of the head, the specific absorption should not exceed 10 mJ kg-1 , averaged over 10 g tissue. - For frequencies up to 100 kHz and for pulsed magnetic fields, the associated maximum current density may be determined from the rise/fall times and maximum rate of change of magnetic flux density.