EMF Levels & Safety
It can be very hard to say exactly what levels of EMF are safe, because safety in this arena is often a relative concept based on frequency, exposure time, and possibly individual sensitivity. Even then, studies are often considered inconclusive plus there is the potential for political and financial agenda to steer perception one way or the other.
In order to be fair and equitable while remaining informative, this page has been constructed to examine / compare / contrast various safety standards, average environmental levels and references along a continuum to better explain technical measurements in context.
Magnetic Fields Conversion Table
| Conversion Factors for Various Magnetic Field Strength Units | ||||||
| uT | mT | mA/m | A/m | mG | G | |
| 1 uT | 1 | 10-3 | 795.8 | 0.7958 | 10 | 0.01 |
| 1 mT | 103 | 1 | 7.96x105 | 795.8 | 104 | 10 |
| 1 mA/m | 1.26E-3 | 1.26E-6 | 1 | 10-3 | 1.26E-2 | 1.26E-5 |
| 1 A/m | 1.257 | 1.26E-3 | 103 | 1 | 12.57 | 0.01257 |
| 1 mG | 0.1 | 10-4 | 79.55 | 0.0796 | 1 | 10-3 |
| 1 G | 100 | 0.1 | 7.96x104 | 79.58 | 103 | 1 |
1 mG (milliGauss) = 100 nT (nanoTesla)
1 nT = 10 uG (microGauss) or 0.01 mG
100 microTeslas = 1 Gauss
1 microTesla = 10 mG
1 milliTesla = 10 Gauss 1 Tesla = 10,000 Gauss
1 nT = 1000 pT (picoTeslas) = 0.01 mG (10 microGauss) strongest brainwave is 1,000 times less
1 pT = 1000 fT (femtoTesla)
1 nT = 1,000,000 fT The best resolution of a SQUID (Super Quantum Interference Device) is 1,000,000 times less
http://www.magnetsales.com/Design/Calc_filles/ConversionMag.asp
MAGNETIC UNITS CONVERSION CALCULATOR
Magnetic Fields - A Relative Comparison
LOW LEVEL MAGNETIC FIELDS
Smallest value in a magnetically shielded room 10^-10 Gauss (0.1 nanoGauss)
Galactic magnetic field 10 microGauss Gauss
Gauss Solar Wind 50 microGauss
Interstellar molecular cloud 1 milligauss
Interstellar Space 10^-6 Gauss (1 microGauss)
SQUID 1.0 fT (femtoTesla)
(0.1 nanoGauss)
Human Eye Magnetic Field 0.1 pT (picoTeslas)
Human Brain Magnetic Field 0.1 - 1.0 pT (picoTeslas)
( 0.01 - 0.1 microGauss)
Human Heart Magnetic Field 50^-12 Tesla (5 microGauss)
Hypothesized & Observed Animal Sensitivies to Magnetic Fields
Honeybees 0.25 mG
Homing Pigeons 0.1 mG
Sharks & Whales 0.5 mG
Lowest level to cause reaction in Electromagnetically Sensitive Patients 0.1 - 0.2 mG
Swedish Safety standard 1.0 mG (proposed US EPA standard)
Indoor EMF levels (when good wiring practices followed) 0.1 - 1.2 mG
New Swiss Standard 2.5 mG ELF 0.25 mG VLF
Cancer researchers concerned with recent powerline issues are coming up with many reports on oncological effects of very low-level 1 mG ELF electromagnetic fields
Leukemia studies which link low level EMF fields 2 - 4 mG
A study (Ahlbom & Feychting, 1993) reported that at 2 mG and above, exposed children were 2.7 times as likely to develop cancer as unexposed children, and at 3 mG and above, the odds rose to 3.8 times as likely!
Computer Monitors - VDTs should produce magnetic fields of no more than 2 mG at a distance of 30 cm (about 1 ft) from the front surface of the monitor and 50 cm (about 1 ft 8 in) from the sides and back of the monitor.
The TCO'92 standard has become a de facto standard in the VDT industry worldwide. A 1999 standard, promulgated by the Swedish TCO (known as the TCO'99 standard), provides for international and environmental labeling of personal computers. Many computer monitors marketed in the U.S. are certified as compliant with TCO'99 and are thereby assured to produce low magnetic fields.
Indoor EMF levels with poor wiring practice 3 - 20 mG
Hotspots near breaker boxes, transformers 20 - 2000 mG
Directly beneath high voltage lines 2 - 250 mG
Amount to affect CRT computer monitor 10 mG
STRONGER EMF FIELDS (please note that the DC Magnetic Fields listed are not generally attributed as having negative health effects - and in fact, a number of alternative health experts actually recommend using magnets for healing and fitness)
Earth DC Magnetic Field (natural) 330 mG(equator) - 670 mG (poles)
Earth DC Magnetic Fields (affected by building structure) 200 mG - 800 mG
Recommended Limit for Pacemakers 1000 mG (1 Gauss)
Refrigerator Magnet (thin label type) 10 Gauss
Magnetic Field which could erase magnetic data 10 Gauss
Average Bar Magnet (DC) 100 Gauss
Independent research finds a change in blood behavior 500 Gauss
Strongest Inexpensive Ferrite Magnets 1000 Gauss
High magnetic field levels exceeding 100 Gauss (100,000 mG) may cause a temporary visual flickering sensation called magnetophosphenes which disappears when the field is removed.
Gauss required to affect / erase magnetic tape 2000 - 3000 Gauss
Magnets used in Biomagnetic Therapy (DC) 300 - 3000 Gauss
High Powered Neodymium N42 - N45 Magnets (DC) 7500 - 9200 Gauss
Junkyard Electromagnet (but over a large area to lift cars) 10000 Gauss
Medical MRI 2000 - 30000 Gauss
50000 Gauss SAFETY LIMIT
High Level Laboratory Superconducting Electromagnet 100,000 - 130,000 Gauss
Strongest Sustained Magnetic Field in a Lab 450,000 Gauss
Strongest Magnetic Spike artificially produced (4 - 8 microseconds) 10,000,000 Gauss +
Magnetic Field Instantly Lethal to Organic Life 10^9 Gauss
Surface of a Neutron Star 10^12 - 10^13 Gauss
Surface of a Magnetar 10^15 Gauss
Highest Theoretical Magnetic Field 10^49 - 10^53 Gauss
EMF MEASURING INSTRUMENT RANGES
Typical Range for inexpensive EMF meter 1 - 10 mG
Range for Quality EMF meter 0.1 - 200 mG
Sensitive High Quality Reference Meter 0.01 - 2000 mG
Commerical High Field Gaussmeter 1 mG - 20 kiloGauss
ICNIRP Guidelines for EMF Exposure International Commission on Non-Ionizing Radiation Protection (ICNIRP) is an organization of 15,000 scientists from 40 nations who specialize in radiation protection.
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Exposure (60 Hz) |
Electric field |
Magnetic field |
Occupational |
8.3 kV/m |
4.2 G (4,200 mG) |
International Commission on Non-Ionizing Radiation Protection (ICNIRP) is an organization of 15,000 scientists from 40 nations who specialize in radiation protection. |
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The National Radiological Protection Board (NRPB) says the UK should adopt international exposure standards. The NRPB has recommended for many years that nobody should be exposed to a level higher than 1,600 microTeslas. (16 mG)
But in a consultation document on restricting people's exposure, it now recommends the UK should adopt the guidelines of the International Committee on Non-Ionizing Radiation Protection (Icnirp).
The commission's recommended level is far lower, at 100 microTeslas. (1 mG)
ACGIH Occupational Threshold Limit Values for 60-Hz EMF American Conference of Governmental Industrial Hygienists (ACGIH) is a professional organization that facilitates the exchange of technical information about worker health protection. It is not a government regulatory agency.
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Electric field
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Magnetic field
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Occupational exposure should not exceed for longer than 2 hours Exposure limit for workers as suggested by the ACGIH
Prudence dictates the use of protective Exposure Limit for workers as suggested by the IRPA/INIRC German Limit
Montana has adopted this exposure limit Recommended 1996 as maximum for "workers" and their working environments by the NCRP, but not yet official. Aaronia "E2" recommendation Aaronia "E1" recommendation
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25 kV/m 20 kV/m
15 kV/m 5 kV/m
1 kV/m
100 V/m
10 V/m
1 V/m |
10 G (10,000 mG) 1 G (1,000 mG)
10 mG
1.0 mG
0.1 mG |
American Conference of Governmental Industrial Hygienists (ACGIH) is a professional organization that facilitates the exchange of technical information about worker health protection. It is not a government regulatory agency. |
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Electric Field Levels & Safety
Under the midspan of a 230 kV and 500 kV transmission line, the electric field strength is 2 kV/m and 7 kV/m, respectively, three feet above the ground; more than enough to illuminate a hand-held fluorescent tube. Up to 10 kV/m
ICNIRP exposure guidelines 5 kV/m Public Exposure 10 kV/m Occupational Exposure Limit
State Transmission Line Standards and Guidelines
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Electric Field |
Magnetic Field |
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State |
On R.O.W.* |
Edge R.O.W. |
On R.O.W. |
Edge R.O.W. |
Florida |
8 kV/m a |
2 kV/m |
- |
150 mG a (max. load) |
Minnesota |
8 kV/m |
- |
- |
- |
Montana |
7 kV/m |
1 kV/m e |
- |
- |
New Jersey |
- |
3 kV/m |
- |
- |
New York |
11.8 kV/m |
1.6 kV/m |
- |
200 mG (max. load) |
Oregon |
9 kV/m |
- |
- |
- |
*R.O.W. = right-of-way (or in the Florida standard, certain additional areas adjoining the right-of-way). |
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As an interesting note, sharks can detect fields down to 1 microvolt/per meter squared.
RF Levels & Safety
OSHA 1910 Subpart G 1910.97 Occupational health and environmental control Non-ionizing radiation
The exposure limit in this standard (10 mW/sq. cm.) is expressed in voluntary language and has been ruled unenforceable for Federal OSHA enforcement. The standard does specify the design of an RF warning sign.
For PCS antennas, the 1992 ANSI/IEEE exposure standard for the general public is 1.2 mW/cm-sq
For cellular phones, the ANSI/IEEE exposure standard for the general public is 0.57 mW/cm-sq
ICNIRP standard is 0.40 mW/cm-sq for cellular phone frequencies and 0.90 mW/cm-sq for PCS phone frequencies
NCRP guideline is 0.57 mW/cm-sq for cellular phone frequencies and 1.00 mW/cm-sq for PCS phone frequencies
SAR for cell phones - SAR stands for Specific Absorption Rate, which is the unit of measurement for the amount of RF energy absorbed by the body when using a mobile phone. Energy absorption from RF fields in tissues is measured as a SAR within a given tissue mass
The unit of SAR is watts per kilogram ( W/kg )
RESOURCE LINKS FOR LOOKING UP THE SAR RATINGS OF VARIOUS CELL PHONES
http://www.mmfai.org/public/sar.cfm
North American Standard 1.6 Watts per Kg averaged over 1 gram of body tissue
European Standard 2.0 Watts per Kg average over 10 grams of body tissue
A typical 802.11b wireless network card will transmit at around 30 milliwatts (a few 100mW and 200mW cards out there) and operates in the 2.4 GHz frequency band. Current FCC regulations limit power output to 1 Watt EIRP (Effective Isotropic Radiated Power) for 802.11b (2.4GHz) devices
A study conducted in the Unites States found that, in large cities , the average background RF levels were about 50 µ W/m 2 . About 1% of people living in large cities are exposed to RF fields exceeding 10 mW/m 2 . Higher RF field levels can occur in areas located close to transmitter sites or radar systems.
The average GSM mobile handset has a power output of around 600 milliwatts
Compare this with microwave ovens, which can emit 500 to 700 Watts
RF fields between 10 MHz and 10 GHz penetrate exposed tissues and produce heating due to energy absorption in these tissues. The depth of penetration of the RF field into the tissue depends on the frequency of the field and is greater for lower frequencies.
SAR is the basic dosimetric quantity for RF fields between about 1 MHz and 10 GHz. A SAR of at least 4 W/kg is needed to produce adverse health effects in people exposed to RF fields in this frequency range. Such energies are found tens of meters away from powerful FM antennas at the top of high towers, which makes these areas inaccessible.
RF fields above 10 GHz are absorbed at the skin surface, with very little of the energy penetrating into the underlying tissues.
For adverse health effects, such as eye cataracts and skin burns, to occur from exposure to RF fields above 10 GHz, power densities above 1000 W/m 2 are needed. Such densities are not found in everyday life. They do exist in very close proximity to powerful radars. Current exposure standards preclude human presence in this areas.
RADIATION LEVELS & SAFETY
Rem ( R oentgen E quivalent M an) is the unit of Dose (actually absorbed taking biological effects into account)
Rad (Roentgen Absorbed Dose) is simply the actual amount of radiation absorbed
Rem = Rads x Quality Factor (QF)
where the Quality Factor depends on the type of radiation. Heavy particles as alphas have a QF of 20, neutrons have a QF of 3-10 depending on the energy of the neutrons. Betas and gammas have a QF of 1.
The amount of ionising radiation, or 'dose', received by a person is measured in terms of the energy absorbed in the body tissue, and is expressed in gray . One gray (Gy) is one joule deposited per kilogram of mass.
Equal exposure to different types of radiation expressed as gray do not however necessarily produce equal biological effects. One gray of alpha radiation, for example, will have a greater effect than one gray of beta radiation. When we talk about radiation effects, we therefore express the radiation as effective dose, in a unit called the sievert (Sv).
1 Rem = .01 Sieverts
A former unit of (radio)activity is the Curie - 1 Bq is 27 x 10 -12 curies.
Title 10 Code of Federal Regulations Part 20 (10CFR20) is the NRC regulation governing radiation protection at a nuclear power plant. This regulation imposes requirements on such important items as annual allowed radiation exposure, radiation protection methods, radioactive releases, and records.
Adult workers may receive a whole body dose 5 Rem per year; minors are restricted to 0.5 Rem per year; pregnant women are restricted to 0.5 Rem during the term of the pregnancy (for protection of the embryo). For comparison, actual physical effects (minor blood changes) from radiation exposure are not expected until a person receives 25 Rem in a short period of time. Higher eye and extremity doses are allowed because these have less effect than on that part of the body containing blood-forming organs.
However there is no scientific evidence of risk at doses below about 50 millisieverts in a short time or about 100 millisieverts per year. At lower doses and dose rates, up to at least 10 millisieverts per year, the evidence suggests that beneficial effects are as likely as adverse ones.
High radiation areas are those where a person could receive more than 100 millirem in an hour.
At a nuclear plant, areas containing radioactive materials may be classified according to radiation level, contamination level, and airborne radioactivity level. Unrestricted areas are those where a person could expect to receive less than 500 millirem in a year.
Background radiation levels are typically around 300 millirem per year. In some areas of the world, background levels can reach as high as 15,000 millirem
Naturally occurring background radiation is the main source of exposure for most people. Levels typically range from about 1.5 to 3.5 millisievert per year but can be more than 50 mSv/yr. The highest known level of background radiation affecting a substantial population is in Kerala and Madras States in India where some 140,000 people receive doses which average over 15 millisievert per year from gamma radiation in addition to a similar dose from radon. Comparable levels occur in Brazil and Sudan, with average exposures up to about 40 mSv/yr to many people.
Several places are known in Iran, India and Europe where natural background radiation gives an annual dose of more than 50 mSv and up to 260 mSv (at Ramsar in Iran). Lifetime doses from natural radiation range up to several thousand millisievert. However, there is no evidence of increased cancers or other health problems arising from these high natural levels.
The ICRP recommends that the maximum permissible dose for occupational exposure should be 20 millisievert per year averaged over five years (ie 100 millisievert in 5 years) with a maximum of 50 millisievert in any one year. For public exposure, 1 millisievert per year averaged over five years is the limit. In both categories, the figures are over and above background levels, and exclude medical exposure
Radioactivity of some natural and other materials
| 1 adult human (100 Bq/kg) | 7000 Bq |
| 1 kg of coffee | 1000 Bq |
| 1 kg superphosphate fertiliser | 5000 Bq |
| The air in a 100 sq metre Australian home (radon) | 3000 Bq |
| The air in many 100 sq metre European homes (radon) | 30 000 Bq |
| 1 household smoke detector (with americium) | 30 000 Bq |
| Radioisotope for medical diagnosis | 70 million Bq |
| Radioisotope source for medical therapy | 100 000 000 million Bq |
| 1 kg 50-year old vitrified high-level nuclear waste | 10 000 000 million Bq |
| 1 luminous Exit sign (1970s) | 1 000 000 million Bq |
| 1 kg uranium | 25 million Bq |
| 1 kg uranium ore (Canadian, 15%) | 25 million Bq |
| 1 kg uranium ore (Australian, 0.3%) | 500 000 Bq |
| 1 kg low level radioactive waste | 1 million Bq |
| 1 kg of coal ash | 2000 Bq |
| 1 kg of granite | 1000 Bq |
Radiation levels and their effects
The following table gives an indication of the likely effects of a range of whole body radiation doses and dose rates to individuals:
10,000 mSv (10 sieverts) as a short-term and whole-body dose would cause immediate illness, such as nausea and decreased white blood cell count, and subsequent death within a few weeks.
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1,000 mSv (1 sievert) in a short term dose is about the threshold for causing immediate radiation sickness in a person of average physical attributes, but would be unlikely to cause death. Above 1000 mSv, severity of illness increases with dose.
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Above about 100 mSv , the probability of cancer (rather than the severity of illness) increases with dose. The estimated risk of fatal cancer is 5 of every 100 persons exposed to a dose of 1000 mSv (ie. if the normal incidence of fatal cancer were 25%, this dose would increase it to 30%).
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50 mSv is, conservatively, the lowest dose at which there is any evidence of cancer being caused in adults. It is also the highest dose which is allowed by regulation in any one year of occupational exposure. Dose rates greater than 50 mSv/yr arise from natural background levels in several parts of the world but do not cause any discernible harm to local populations.
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20 mSv/yr averaged over 5 years is the limit for radiological personnel such as employees in the nuclear industry, uranium or mineral sands miners and hospital workers (who are all closely monitored).
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10 mSv/yr is the maximum actual dose rate received by any Australian uranium miner.
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3-5 mSv/yr is the typical dose rate (above background) received by uranium miners in Australia and Canada.
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3 mSv/yr (approx) is the typical background radiation from natural sources in North America, including an average of almost 2 mSv/yr from radon in air.
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2 mSv/yr (approx) is the typical background radiation from natural sources, including an average of 0.7 mSv/yr from radon in air. This is close to the minimum dose received by all humans anywhere on Earth . |
0.3-0.6 mSv/yr is a typical range of dose rates from artificial sources of radiation, mostly medical.
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| 0.05 mSv/yr , a very small fraction of natural background radiation, is the design target for maximum radiation at the perimeter fence of a nuclear electricity generating station. In practice the actual dose is less. |
http://www.philrutherford.com/radiation_software.html
RADIATION SOFTWARE LINK
http://lhcb-elec.web.cern.ch/lhcb-elec/html/radiation_hardness.htm
RADIATION HARDNESS OF ELECTRONIC CIRCUITRY
NOISE LEVELS OSHA Safety Limits
90 dB 8 hours
92 dB 6 hours
95 dB 4 hours
97 dB 3 hours
100 dB 2 hours
102 dB 1.5 hours
105 dB 1 hour
110 dB 0.5 hours
115 dB 0.25 hours or less
Impulsive / Explosive noise not to exceed 140 dB
Electromagnetic Frequency Graphic
http://hps.org/ Health Physics Society
