June 2002


EMF


Electric and Magnetic Fields 

Associated with the 

Use of Electric Power 

Questions &Answers 

prepared by the 

National Institute of Environmental Health Sciences 

National Institutes of Health 

sponsored by the 

NIEHS/DOE EMF RAPID Program Electric and Magnetic Fields Research and Public Information Dissemination Program 
1

2

3

4

5

6

7

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

EMF Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Reviews basic terms about electric and magnetic 

fields. 

Evaluating Potential Health Effects . . . . . . . . . . . . . . . . . .10 

Explains how scientific studies are conducted and 

evaluated to assess possible health effects. 

Results of EMF Research . . . . . . . . . . . . . . . . . . . . . . . . . .16 

Summarizes results of EMF-related research including 

epidemiological, clinical, and laboratory studies. 

Your EMF Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 

Discusses typical magnetic exposures in homes and 

workplaces and identifies common EMF sources. 

EMF Exposure Standards . . . . . . . . . . . . . . . . . . . . . . . . . 46 

Describes standards and guidelines established by 

state, national, and international safety 

organizations for some EMF sources and exposures. 

National and International EMF Reviews . . . . . . . . . . . . . 50 

Presents the findings and recommendations of 

major EMF research reviews including the EMF 

RAPID Program. 

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 

Selected references on EMF topics. 

June 2002 http://www.niehs.nih.gov/emfrapid 
Introduction 

Since the mid-twentieth century, electricity has been an essential part of our lives. 

Electricity powers our appliances, office equipment, and countless other devices tha

we use to make life safer, easier, and more interesting. Use of electric power is 

something we take for granted. However, some have wondered whether the electri

and magnetic fields (EMF) produced through the generation, transmission, and use 

of electric power [power-frequency EMF, 50 or 60 hertz (Hz)] might adversely affec

our health. Numerous research studies and scientific reviews have been conducted 

to address this question. 

Unfortunately, initial studies of the health effects of EMF did not provide 

straightforward answers. The study of the possible health effects of EMF has been 

particularly complex and results have been reviewed by expert scientific panels in 

the United States and other countries. This booklet summarizes the results of these 

reviews. Although questions remain about the possibility of health effects related t

EMF, recent reviews have substantially reduced the level of concern. 

The largest evaluation to date was led by two U.S. government institutions, the 

National Institute of Environmental Health Sciences (NIEHS) of the National Institute

of Health and the Department of Energy (DOE), with input from a wide range of 

public and private agencies. This evaluation, known as the Electric and Magnetic 

Fields Research and Public Information Dissemination (EMF RAPID) Program, was a 

six-year project with the goal of providing scientific evidence to determine whether 

exposure to power-frequency EMF involves a potential risk to human health. 

2 http://www.niehs.nih.gov/emfrapid June 200
In 1999, at the conclusion of the EMF RAPID Program, the NIEHS reported to 

the U.S. Congress that the overall scientific evidence for human health risk from 

EMF exposure is weak. No consistent pattern of biological effects from exposure 

to EMF had emerged from laboratory studies with animals or with cells. However, 

epidemiological studies (studies of disease incidence in human populations) had 

shown a fairly consistent pattern that associated potential EMF exposure with a 

small increased risk for leukemia in children and chronic lymphocytic leukemia in 

adults. Since 1999, several other assessments have been completed that support an 

association between childhood leukemia and exposure to power-frequency EMF. 

These more recent reviews, however, do not support a link between EMF 

exposures and adult leukemias. For both childhood and adult leukemias, 

interpretation of the epidemiological findings has been difficult due to the absence 

of supporting laboratory evidence or a scientific explanation linking EMF exposures 

with leukemia. 

EMF exposures are complex and exist in the home and workplace as a result of all 

types of electrical equipment and building wiring as well as a result of nearby 

power lines. This booklet explains the basic principles of electric and magnetic 

fields, provides an overview of the results of major research studies, and 

summarizes conclusions of the expert review panels to help you reach your own 

conclusions about EMF-related health concerns. 

June 2002 http://www.niehs.nih.gov/emfrapid 
1EMF Basics 

This chapter reviews terms you need to know to have a basic understanding o

electric and magnetic fields (EMF), compares EMF with other forms o

electromagnetic energy, and briefly discusses how such fields may affect us. 

Q What are electric and magnetic fields? 

A Electric and magnetic fields (EMF) are invisible lines of force that surround any 

electrical device. Power lines, electrical wiring, and electrical equipment all produc

EMF. There are many other sources of EMF as well (see pages 33–35). The focus o

this booklet is on power-frequency EMF—that is, EMF associated with the 

generation, transmission, and use of electric power. 

Electric fields are produced 

Electrical Terms Familiar Comparisons 

Voltage. Electrical pressure, the potential 

to do work. Measured in volts (V) 

or in kilovolts (kV) (1kV = 1000 volts). 

Hose connected to an open faucet 

but with the nozzle turned off. 

Lamp plugged in 

but turned off: 

Current. The movement of electric 

charge (e.g., electrons). Measured in 

amperes (A). 

120V Switch 

off 

Switch 

on 

Lamp plugged in 

and turned on: 

120V 

1A 

Water pressure in hose. 

Nozzle closed 

Hose connected to an open faucet 

and with the nozzle turned on. 

Moving water in hose. 

Nozzle open 

by voltage and increase in 

strength as the voltage 

increases. The electric field 

strength is measured in 

units of volts per meter 

(V/m). Magnetic fields 

result from the flow of 

current through wires or 

electrical devices and 

increase in strength as the 

current increases. Magnetic 

fields are measured in units 

of gauss (G) or tesla (T). 

Most electrical equipment 

has to be turned on, i.e., 

current must be flowing, 

for a magnetic field to be 

produced. Electric fields ar

often present even when 

the equipment is switched 

off, as long as it remains 

Voltage produces an electric field and current produces a magnetic field.		 connected to the source of 

electric power. Brief bursts 

4 http://www.niehs.nih.gov/emfrapid June 200
when electrical devices are 

turned on or off. 

Electric fields are shielded 

or weakened by materials 

that conduct electricity— 

even materials that 

conduct poorly, including 

trees, buildings, and 

human skin. Magnetic 

fields, however, pass 

through most materials 

and are therefore more 

difficult to shield. Both 

electric fields and magnetic 

fields decrease rapidly as 

the distance from the 

source increases. 

Even though electrical 

equipment, appliances, and 

power lines produce both 

electric and magnetic fields, 

most recent research has 

focused on potential health 

effects of magnetic field 

exposure. This is because 

some epidemiological 

studies have reported an 

increased cancer risk 

associated with estimates of 

magnetic field exposure 

(see pages 19 and 20 for a 

summary of these studies). 

No similar associations 

have been reported for 

electric fields; many of the 

studies examining 

biological effects of electric 

fields were essentially 

negative. 

g

• Produced by voltage. • Produced by current. 

• Measured in volts per meter (V/m) 

or in kilovolts per meter (kV/m). 

• Easily shielded (weakened) by 

conducting objects such as trees and 

buildings. 

• Strength decreases rapidly with 

increasing distance from the source. 

Lamp plugged in but turned off. 

Voltage produces an electric field. 

Lamp plugged in and turned on. Cur

now produces a magnetic field also. 

• Measured in gauss (G) or tesla (

• Not easily shielded (weakened) 

most material. 

• Strength decreases rapidly with 

increasing distance from the sou

An appliance that is plugged in and therefore connected to a source of electricit

electric field even when the appliance is turned off. To produce a magnetic f

appliance must be plugged in and turned on so that the current is flowing. 

Magnetic Field Strength Decreases with Distance 

4 ft (122 cm) 

1 mG 

2 ft (61 cm) 

7

mG 

20 mG 

6 in

(15 cm) 

90

mG 

1 ft (30 cm) 

Magnetic field measured in milliga

Source: EMF in Your Environment, E

You cannot see a magnetic field, but this illustration represents how the streng

magnetic field can diminish just 1–2 feet (30–61 centimeters) from the sou

magnetic field is a 60-Hz power-frequency field. 

June 2002 http://www.niehs.nih.gov/emfrapid 
frequency, and amplitude (strength). The graphic below shows the waveform of an 

alternating electric or magnetic field. The direction of the field alternates from one 

polarity to the opposite and back to the first polarity in a period of time called one 

cycle. Wavelength describes the distance between a peak on the wave and the next 

peak of the same polarity. The frequency of the field, measured in hertz (Hz), 

describes the number of cycles that occur in one second. Electricity in North America 

alternates through 60 cycles per second, or 60 Hz. In many other parts of the world, 

the frequency of electric power is 50 Hz. 

Frequency and Wavelength 

Electromagnetic 

waveform 

1 cycle Frequency is measured in hertz (Hz). 

1 Hz = 1 cycle per second. 

Examples: 

Source Frequency Wavelength 

Power line (North America) 60 Hz 3100 miles (5000 km) 

Power line (Europe and most other locations) 50 Hz 3750 miles (6000 km) 

Q How is the term EMF used in this booklet? 

A The term “EMF” usually refers to electric and magnetic fields at extremely low

frequencies such as those associated with the use of electric power. The term EMF 

can be used in a much broader sense as well, encompassing electromagnetic fields 

with low or high frequencies (see page 8). 

Measuring EMF: Common Terms 

Electric fields 

Electric field strength is measured in volts per meter (V/m) or in kilovolts per meter (kV/m). 1 kV = 1000 V 

Magnetic fields 

Magnetic fields are measured in units of gauss (G) or tesla (T). Gauss is the unit most commonly used 

the United States. Tesla is the internationally accepted scientific term. 1 T = 10,000 G 

Since most environmental EMF exposures involve magnetic fields that are only a fraction of a tesla or 

gauss, these are commonly measured in units of microtesla (μT) or milligauss (mG). A milligauss is 1/1,00

of a gauss. A microtesla is 1/1,000,000 of a tesla. 1 G = 1,000 mG; 1 T = 1,000,000 μT 

To convert a measurement from microtesla (μT) to milligauss (mG), multiply by 10. 

1 μT = 10 mG; 0.1 μT = 1 mG 

6 http://www.niehs.nih.gov/emfrapid June 200
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power-frequency (50 or 60 Hz) fields. In the ELF range, electric and magnetic fields 

are not coupled or interrelated in the same way that they are at higher frequencies. 

So, it is more useful to refer to them as “electric and magnetic fields” rather than 

“electromagnetic fields.” In the popular press, however, you will see both terms used, 

abbreviated as EMF. 

This booklet focuses on extremely low frequency EMF, primarily power-frequency 

fields of 50 or 60 Hz, produced by the generation, transmission, and use of electricity. 

How are power-frequency EMF different from other 

types of electromagnetic energy? 

X-rays, visible light, microwaves, radio waves, and EMF are all forms of 

electromagnetic energy. One property that distinguishes different forms of 

electromagnetic energy is the frequency, expressed in hertz (Hz). Power-frequency 

EMF, 50 or 60 Hz, carries very little energy, has no ionizing effects, and usually has 

no thermal effects (see page 8). Just as various chemicals affect our bodies in 

different ways, various forms of electromagnetic energy can have very different 

biological effects (see “Results of EMF Research” on page 16). 

Some types of equipment or operations simultaneously produce electromagnetic 

energy of different frequencies. Welding operations, for example, can produce 

electromagnetic energy in the ultraviolet, visible, infrared, and radio-frequency 

ranges, in addition to power-frequency EMF. Microwave ovens produce 60-Hz 

fields of several hundred milligauss, but they also create microwave energy inside 

the oven that is at a much higher frequency (about 2.45 billion Hz). We are 

shielded from the higher frequency fields inside the oven by its casing, but we are 

not shielded from the 60-Hz fields. 

Cellular telephones communicate by emitting high-frequency electric and magnetic 

fields similar to those used for radio and television broadcasts. These radiofrequency and microwave fields are quite different from the extremely low 

frequency EMF produced by power lines and most appliances. 

How are alternating current sources of EMF different 

from direct current sources? 

Some equipment can run on either alternating current (AC) or direct current 

(DC). In most parts of the United States, if the equipment is plugged into a 

household wall socket, it is using AC electric current that reverses direction in the 

electrical wiring—or alternates—60 times per second, or at 60 hertz (Hz). If the 

equipment uses batteries, then electric current flows in one direction only. This 

June 2002 http://www.niehs.nih.gov/emfrapid 
X-rays, about 1 billion billion Hz, 

can penetrate the body and 

damage internal organs and 

tissues by damaging important 

molecules such as DNA. This 

process is called “ionization.” 

Power-frequency EMF, 50 or 60 Hz, 

carries very little energy, has no 

ionizing effects and usually 

no thermal effects. It 

can, however, cause 

very weak electric 

currents to flow 

in the body. 

Gamma rays 

X-rays 

Ultraviolet 

radiation 

Very low 

frequency (VLF) 

3000–30,000 Hz 

Extremely low 

frequency (ELF) 

3–3000 Hz 

Direct current 

1022— 

1020— 

1018— 

1016— 

1014— 

1012— 

1010— 

108— 

106— 

104— 

102— 

0— 

Ionizing radiation

800–900 MHz 

& 

1800–1900 MHz 

15–30 kHz 

& 

50–90 Hz 

Visible 

light 

Infrared 

radiation 

Microwaves 

Radiowaves 

60 Hz 

Microwaves, several billion Hz, 

can have “thermal” or heating 

effects on body tissues. 

Cell phone 

Computer 

The wavy line at the right illustrates the concept that the higher the frequency, the more 

rapidly the field varies. The fields do not vary at 0 Hz (direct current) and vary trillions of 

times per second near the top of the spectrum. Note that 104 means 10 x 10 x 10 x 10 or 

10,000 Hz. 1 kilohertz (kHz) = 1,000 Hz. 1 megahertz (MHz) = 1,000,000 Hz. 

8 http://www.niehs.nih.gov/emfrapid June 200
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A



part of its normal operation. 

What happens when I am exposed to EMF? 

In most practical situations, DC electric power does not induce electric currents in 

humans. Strong DC magnetic fields are present in some industrial environments, 

can induce significant currents when a person moves, and may be of concern for 

other reasons, such as potential effects on implanted medical devices (see page 47 

for more information on pacemakers and other medical devices). 

AC electric power produces electric and magnetic fields that create weak electric 

currents in humans. These are called “induced currents.” Much of the research on 

how EMF may affect human health has focused on AC-induced currents. 

Electric fields 

A person standing directly under a high-voltage transmission line may feel a mild 

shock when touching something that conducts electricity. These sensations are 

caused by the strong electric fields from the high-voltage electricity in the lines. 

They occur only at close range because the electric fields rapidly become weaker as 

the distance from the line increases. Electric fields may be shielded and further 

weakened by buildings, trees, and other objects that conduct electricity. 

Magnetic fields 

Alternating magnetic fields produced by AC electricity can induce the flow of weak 

electric currents in the body. However, such currents are estimated to be smaller 

than the measured electric currents produced naturally by the brain, nerves, and 

heart. 

Doesn’t the earth produce EMF? 

Yes. The earth produces EMF, mainly in the form of static fields, similar to the 

fields generated by DC electricity. Electric fields are produced by air turbulence and 

other atmospheric activity. The earth’s magnetic field of about 500 mG is thought 

to be produced by electric currents flowing deep within the earth’s core. Because 

these fields are static rather than alternating, they do not induce currents in 

stationary objects as do fields associated with alternating current. Such static fields 

can induce currents in moving and rotating objects. 

June 2002 http://www.niehs.nih.gov/emfrapid 
Evaluating Effects 

2Evaluating Potential Health Effects 

This chapter explains how scientific studies are conducted and evaluated 

to assess potential health effects. 

Q How do we evaluate whether EMF exposures cause 

health effects? 

A 
Animal experiments, laboratory studies of cells, clinical studies, computer simulations, 


and human population (epidemiological) studies all provide valuable information. 

When evaluating evidence that certain exposures cause disease, scientists consider 

results from studies in various disciplines. No single study or type of study is definitive. 

Laboratory studies 

Laboratory studies with cells and 

animals can provide evidence to 

help determine if an agent such as 

EMF causes disease. Cellular 

studies can increase our 

understanding of the biological 

mechanisms by which disease 

occurs. Experiments with animals 

provide a means to observe effects 

of specific agents under carefully 

controlled conditions. Neither 

cellular nor animal studies, 

however, can recreate the complex 

nature of the whole human 

organism and its environment. 

Therefore, we must use caution in 

applying the results of cellular or 

animal studies directly to humans 

or concluding that a lack of an 

effect in laboratory studies proves 

that an agent is safe. Even with 

Laboratory studies and human studies provide pieces of the puzzle, but no single these limitations, cellular and 

study can give us the whole picture. animal studies have proven very 

10 http://www.niehs.nih.gov/emfrapid June 2002 
Evaluating Effects 

useful over the years for identifying and understanding the toxicity of numerous 

chemicals and physical agents. 

Very specific laboratory conditions are needed for researchers to be able to detect 

EMF effects, and experimental exposures are not easily comparable to human 

exposures. In most cases, it is not clear how EMF actually produces the effects 

observed in some experiments. Without understanding how the effects occur, it is 

difficult to evaluate how laboratory results relate to human health effects. 

Some laboratory studies have reported that EMF exposure can produce biological 

effects, including changes in functions of cells and tissues and subtle changes in 

hormone levels in animals. It is important to distinguish between a biological effect 

and a health effect. Many biological effects are within the normal range of variation 

and are not necessarily harmful. For example, bright light has a biological effect on 

our eyes, causing the pupils to constrict, which is a normal response. 

Clinical studies 

In clinical studies, researchers use sensitive instruments to monitor human physiology 

during controlled exposure to environmental agents. In EMF studies, volunteers are 

exposed to electric or magnetic fields at higher levels than those commonly 

encountered in everyday life. Researchers measure heart rate, brain activity, hormonal 

levels, and other factors in exposed and unexposed groups to look for differences 

resulting from EMF exposure. 

Epidemiology 

A valuable tool to identify 

human health risks is to study 

a human population that has 

experienced the exposure. 

This type of research is called 

epidemiology. 

The epidemiologist observes 

and compares groups of 

people who have had or have 

not had certain diseases and 

exposures to see if the risk of 

disease is different between 

the exposed and unexposed 

groups. The epidemiologist 

does not control the exposure 

and cannot experimentally 

control all the factors that 

might affect the risk of 

disease. 

Most researchers agree that epidemiology—the study of patterns and possible causes 

of diseases—is one of the most valuable tools to identify human health risks. 

June 2002 http://www.niehs.nih.gov/emfrapid 11 
Evaluating Effects 

Q



A



How do we evaluate the results of epidemiological 

studies of EMF? 

Many factors need to be considered when determining whether an agent 

causes disease. An exposure that an epidemiological study associates with 

increased risk of a certain disease is not always the actual cause of the disease. 

To judge whether an agent actually causes a health effect, several issues are 

considered. 

Strength of association 

The stronger the association between an exposure and disease, the more confident 

we can be that the disease is due to the exposure being studied. With cigarette 

smoking and lung cancer, the association is very strong—20 times the normal risk. 

In the studies that suggest a relationship between EMF and certain rare cancers, 

the association is much weaker (see page 19). 

Dose-response 

Epidemiological data are more convincing if disease rates increase as exposure 

levels increase. Such dose-response relationships have appeared in only a few 

EMF studies. 

Consistency 

Consistency requires that an association found in one study appears in other 

studies involving different study populations and methods. Associations found 

consistently are more likely to be causal. With regard to EMF, results from different 

studies sometimes disagree in important ways, such as what type of cancer is 

associated with EMF exposure. Because of this inconsistency, scientists cannot be 

sure whether the increased risks are due to EMF or other factors. 

Biological plausibility 

When associations are weak in an epidemiological study, results of laboratory 

studies are even more important to support the association. Many scientists remain 

skeptical about an association between EMF exposure and cancer because laboratory 

studies thus far have not shown any consistent evidence of adverse health effects, 

nor have results of experimental studies revealed a plausible biological explanation 

for such an association. 

Reliability of exposure information 

Another important consideration with EMF epidemiological studies is how the 

exposure information was obtained. Did the researchers simply estimate people’s 

EMF exposures based on their job titles or how their houses were wired, or did 

they actually conduct EMF measurements? What did they measure (electric fields, 

magnetic fields, or both)? How often were the EMF measurements made and at 

12 http://www.niehs.nih.gov/emfrapid June 2002 
Evaluating Effects 

what time? In how many different places were the fields measured? More recent 

studies have included measurements of magnetic field exposure. Magnetic fields 

measured at the time a study is conducted can only estimate exposures that 

occurred in previous years (at the time a disease process may have begun). Lack of 

comprehensive exposure information makes it more difficult to interpret the results 

of a study, particularly considering that everyone in the industrialized world has 

been exposed to EMF. 

Confounding 

Epidemiological studies show relationships or correlations between disease and 

other factors such as diet, environmental conditions, and heredity. When a disease 

is correlated with some factor, it does not necessarily mean that the correlated 

factor causes the disease. It could mean that the factor occurs together with some 

other factor, not measured in the study, that actually causes the disease. This is 

called confounding. 

For example, a study might show that alcohol consumption is correlated with 

lung cancer. This could occur if the study group consists of people who drink and 

also smoke tobacco, as often happens. In this example, alcohol use is correlated 

with lung cancer, but cigarette smoking is a confounding factor and the true cause 

of the disease. 

Statistical significance 

Researchers use statistical methods to determine the likelihood that the association 

between exposure and disease is due simply to chance. For a result to be 

considered “statistically significant,” the association must be stronger than would be 

expected to occur by chance alone. 

Meta-analysis 

One way researchers try to get more information from epidemiological studies is 

to conduct a meta-analysis. A meta-analysis combines the summary statistics of 

many studies to explore their differences and, if appropriate, calculates an overall 

summary risk estimate. The main challenge faced by researchers performing 

meta-analyses is that populations, measurements, evaluation techniques, 

participation rates, and potential confounding factors vary in the original studies. 

These differences in the studies make it difficult to combine the results in a 

meaningful way. 

Pooled analysis 

Pooled analysis combines the original data from several studies and conducts a new 

analysis on the primary data. It requires access to the original data from individual 

studies and can only include diseases or factors included in all the studies, but it 

has the advantage that the same parameters can be applied to all studies. As with 

meta-analysis, pooled analysis is still subject to the limitations of the experimental 

June 2002 http://www.niehs.nih.gov/emfrapid 13 
Evaluating Effects 

design of the original studies (for example, evaluation techniques, participation


rates, etc.). Pooled analysis differs from meta-analysis, which combines the


summary statistics from different studies, not their original data.


Q How do we characterize EMF exposure? 

No one knows which aspect of EMF exposure, if any, affects human health. Because A of this uncertainty, in addition to the field strength, we must ask how long an 

exposure lasts, how it varies, and at what time of day or night it occurs. House 

wiring, for example, is often a significant source of EMF exposure for an individual, 

but the magnetic fields produced by the wiring depend on the amount of current 

flowing. As heating, lighting, and appliance use varies during the day, magnetic field 

exposure will also vary. 

For many studies, researchers describe EMF exposures by estimating the average 

field strength. Some scientists believe that average exposure may not be the best 

measurement of EMF exposure and that other parameters, such as peak exposure 

or time of exposure, may be important. 

Q What is the average field strength? 

A 
In EMF studies, the information reported most often has been a person’s EMF
 


exposure averaged over time (average field strength). With cancer-causing
 

chemicals, a person’s average exposure over many years can be a good way to
 

predict his or her chances of getting the disease. 
 

There are different ways to calculate average magnetic field exposures. One method 

involves having a person wear a small monitor that takes many measurements over 

a work shift, a day, or longer. Then the average of those measurements is calculated. 

Another method involves placing a monitor that takes many measurements in a 

residence over a 24-hour or 48-hour period. Sometimes averages are calculated for 

people with the same occupation, people working in similar environments, or 

people using several brands of the same type or similar types of equipment. 

Q How is EMF exposure measured in epidemiological
 

studies?


A
 Epidemiologists study patterns and possible causes of diseases in human

populations. These studies are usually observational rather than experimental. 

This means that the researcher observes 

Association and compares groups of people who have 

In epidemiology, a positive association between an exposure (such as had certain diseases and exposures and 

EMF) and a disease is not necessarily proof that the exposure caused looks for possible “associations.” The the disease. However, the more often the exposure and disease epidemiologist must find a way to occur together, the stronger the association, and the stronger is the estimate the exposure that people had at possibility that the exposure may increase the risk of the disease. an earlier time. 

14 http://www.niehs.nih.gov/emfrapid June 2002 
Evaluating Effects 

Some exposure estimates for residential studies have been based on designation of 

households in terms of “wire codes.” In other studies, measurements have been 

made in homes, assuming that EMF levels at the time of the measurement are 

similar to levels at some time in the past. Some studies involved “spot 

measurements.” Exposure levels change as a person moves around in his or her 

environment, so spot measurements taken at specific locations only approximate 

the complex variations in exposure a person experiences. Other studies measured 

magnetic fields over a 24-hour or 48-hour period. Exposure levels for some 

occupational studies are measured by having certain employees wear personal 

monitors. The data taken from these monitors are sometimes used to estimate 

typical exposure levels for employees with certain job titles. Researchers can then 

estimate exposures using only an employee’s job title and avoid measuring 

exposures of all employees. 

Methods to Estimate EMF Exposure 

Wire Codes 

A classification of homes based on characteristics of power lines outside the home (thickness of the wires, 

wire configuration, etc.) and their distance from the home. This information is used to code the homes 

into groups with higher and lower predicted magnetic field levels. 

Spot Measurement 

An instantaneous or very short-term (e.g., 30-second) measurement taken at a designated location. 

Time-Weighted Average 

A weighted average of exposure measurements taken over a period of time that takes into account the 

time interval between measurements. When the measurements are taken with a monitor at a fixed 

sampling rate, the time-weighted average equals the arithmetic mean of the measurements. 

Personal Monitor 

An instrument that can be worn on the body for measuring exposure over time. 

Calculated Historical Fields 

An estimate based on a theoretical calculation of the magnetic field emitted by power lines using historical 

electrical loads on those lines. 

June 2002 http://www.niehs.nih.gov/emfrapid 15 
EMF Research 

3Results of EMF Research 

This chapter summarizes the results of EMF research worldwide, including 

epidemiological studies of children and adults, clinical studies of how 

humans react to typical EMF exposures, and laboratory research with 

animals and cells. 

Q Is there a link between EMF exposure and childhood 

leukemia? 

A Despite more than two decades of research to determine whether elevated EMF

exposure, principally to magnetic fields, is related to an increased risk of childhood 

leukemia, there is still no definitive answer. Much progress has been made, 

however, with some lines of research leading to reasonably clear answers and 

others remaining unresolved. The best available evidence at this time leads to the 

following answers to specific questions about the link between EMF exposure and 

childhood leukemia: 

Is there an association between power line configurations (wire codes) and 

childhood leukemia? No. 

Is there an association between measured fields and childhood leukemia? Yes, but 

the association is weak, and it is not clear whether it represents a causeand-effect relationship. 

Q What is the epidemiological evidence for evaluating a 

link between EMF exposure and childhood leukemia? 

A The initial studies, starting with the pioneering research of Dr. Nancy Wertheimer 

and Ed Leeper in 1979 in Denver, Colorado, focused on power line configurations 

near homes. Power lines were systematically evaluated and coded for their 

presumed ability to produce elevated magnetic fields in homes and classified into 

groups with higher and lower predicted magnetic field levels (see discussion of wire 

codes on page 15). Although the first study and two that followed in Denver and 

Los Angeles showed an association between wire codes indicative of elevated 

magnetic fields and childhood leukemia, larger, more recent studies in the central 

part of the United States and in several provinces of Canada did not find such an 

16 http://www.niehs.nih.gov/emfrapid June 2002 
EMF Research 

association. In fact, combining the National Cancer Institute Study evidence from all the studies, we can In 1997, after eight years of work, Dr. Martha Linet and colleagues at the conclude with some confidence that National Cancer Institute (NCI) reported the results of their study of wire codes are not associated with a childhood acute lymphoblastic leukemia (ALL). The case-control study measurable increase in the risk of involved more than 1,000 children living in 9 eastern and midwestern childhood leukemia. U.S. states and is the largest epidemiological study of childhood 

leukemia to date in the United States. To help resolve the question of The other approach to assessing EMF wire code versus measured magnetic fields, the NCI researchers carried exposure in homes focused on the out both types of exposure assessment. Overall, Linet reported little measurements of magnetic fields. evidence that living in homes with higher measured magnetic-field levels Unlike wire codes, which are only was a disease risk and found no evidence that living in a home with a 

applicable in North America due to the high wire code configuration increased the risk of ALL in children. 

nature of the electric power distribution 

system, measured fields have been 

studied in relation to childhood United Kingdom Childhood Cancer Study leukemia in research conducted around 

the world, including Sweden, England, In December 1999, Sir Richard Doll and colleagues in the United 

Germany, New Zealand, and Taiwan. Kingdom announced that the largest study of childhood cancer ever

undertaken—involving nearly 4,000 children with cancer in England, Large, detailed studies have recently Wales, and Scotland—found no evidence of excess risk of childhood been completed in the United States, leukemia or other cancers from exposure to power-frequency magnetic Canada, and the United Kingdom that fields. It should be noted, however, that because most power lines in provide the most evidence for making the United Kingdom are underground, the EMF exposures of these an evaluation. These studies have children were mostly lower than 0.2 microtesla or 2 milligauss. 

produced variable findings, some 

reporting small associations, others 

finding no associations. 

After reviewing all the data, the U.S. National Institute of Environmental Health 

Sciences (NIEHS) concluded in 1999 that the evidence was weak, but that it was 

still sufficient to warrant limited concern. The NIEHS rationale was that no 

individual epidemiological study provided convincing evidence linking magnetic 

field exposure with childhood leukemia, but the overall pattern of results for some 

methods of measuring exposure suggested a weak association between increasing 

exposure to EMF and increasing risk of childhood leukemia. The small number of 

cases in these studies made it impossible to firmly demonstrate this association. 

However, the fact that similar results had been observed in studies of different 

populations using a variety of study designs supported this observation. 

A major challenge has been to determine whether the most highly elevated, but 

rarely encountered, levels of magnetic fields are associated with an increased risk of 

leukemia. Early reports focused on the risk associated with exposures above 2 or 3 

milligauss, but the more recent studies have been large enough to also provide 

some information on levels above 3 or 4 milligauss. It is estimated that 4.5% of 

homes in the United States have magnetic fields above 3 milligauss, and 2.5% of 

homes have levels above 4 milligauss. 

June 2002 http://www.niehs.nih.gov/emfrapid 17 
EMF Research 

What is Cancer? 

Cancer 

“Cancer” is a term used to describe at least 200 different diseases, all involving uncontrolled cell growth. 

The frequency of cancer is measured by the incidence—the number of new cases diagnosed each year. 

Incidence is usually described as the number of new cases diagnosed per 100,000 people per year. 

The incidence of cancer in adults in the United States is 382 per 100,000 per year, and childhood cancers 

account for about 1% of all cancers. The factors that influence risk differ among the forms of cancer. 

Known risk factors such as smoking, diet, and alcohol contribute to specific types of cancer. (For example, 

smoking is a known risk factor for lung cancer, bladder cancer, and oral cancer.) For many other cancers, 

the causes are unknown. 

Leukemia 

Leukemia describes a variety of cancers that arise in the bone marrow where blood cells are formed. The 

leukemias represent less than 4% of all cancer cases in adults but are the most common form of cancer 

in children. For children age 4 and under, the incidence of childhood leukemia is approximately 6 per 

100,000 per year, and it decreases with age to about 2 per 100,000 per year for children 10 and older. In 

the United States, the incidence of adult leukemia is about 10 cases per 100,000 people per year. Little is 

known about what causes leukemia, although genetic factors play a role. The only known causes are 

ionizing radiation, benzene, and other chemicals and drugs that suppress bone marrow function, and a 

human T-cell leukemia virus. 

Brain Cancer 

Cancer of the central nervous system (the brain and spinal cord) is uncommon, with incidence in the 

United States now at about 6 cases in 100,000 people per year. The causes of the disease are largely 

unknown, although a number of studies have reported an association with certain occupational chemical 

exposures. Ionizing radiation to the scalp is a known risk factor for brain cancer. Factors associated with 

an increased risk for other types of cancer—such as smoking, diet, and excessive alcohol use—have not 

been found to be associated with brain cancer. 

To determine what the integrated information from all the studies says about 

magnetic fields and childhood leukemia, two groups have conducted pooled 

analyses in which the original data from relevant studies were integrated and 

analyzed. One report (Greenland et al., 2000) combined 12 relevant studies with 

magnetic field measurements, and the other considered 9 such studies (Ahlbom et 

al., 2000). The details of the two pooled analyses are different, but their findings 

are similar. There is weak evidence for an association (relative risk of 

approximately 2) at exposures above 3 mG. However, few individuals had high 

exposures in these studies; therefore, even combining all studies, there is 

uncertainty about the strength of the association. 

The following table summarizes the results for the epidemiological studies of EMF 

exposure and childhood leukemia analyzed in the pooled analysis by Greenland et 

al. (2000). The focus of the summary review was the magnetic fields that occurred 

three months prior to diagnosis. The results were derived from either calculated 

historical fields or multiple measurements of magnetic fields. The North American 

18 http://www.niehs.nih.gov/emfrapid June 2002 
EMF Research 

Residential Exposure to Magnetic Fields and Childhood Leukemia 

Magnetic field category (mG) 

>1 – ≤2 mG >2 – ≤3 mG >3 mG 

First author Estimate 95% CL Estimate 95% CL Estimate 95% CL 

Coghill 0.54 0.17, 1.74 No controls No controls 

Dockerty 0.65 0.26, 1.63 2.83 0.29, 27.9 No controls 

Feychting 0.63 0.08, 4.77 0.90 0.12, 7.00 4.44 1.67, 11.7 

Linet 1.07 0.82, 1.39 1.01 0.64, 1.59 1.51 0.92, 2.49 

London 0.96 0.54, 1.73 0.75 0.22, 2.53 1.53 0.67, 3.50 

McBride 0.89 0.62, 1.29 1.27 0.74, 2.20 1.42 0.63, 3.21 

Michaelis 1.45 0.78, 2.72 1.06 0.27, 4.16 2.48 0.79, 7.81 

Olsen 0.67 0.07, 6.42 No cases 2.00 0.40, 9.93 

Savitz 1.61 0.64, 4.11 1.29 0.27, 6.26 3.87 0.87, 17.3 

Tomenius 0.57 0.33, 0.99 0.88 0.33, 2.36 1.41 0.38, 5.29 

Tynes 1.06 0.25, 4.53 No cases No cases 

Verkasalo 1.11 0.14, 9.07 No cases 2.00 0.23, 17.7 

Study summary 0.95 0.80, 1.12 1.06 0.79, 1.42 1.69* 1.25, 2.29 

1 – <2 mG 2 – <4 mG ≥4 mG 

**United Kingdom 0.84 0.57, 1.24 0.98 0.50, 1.93 1.00 0.30, 3.37 

95% CL = 95% confidence limits. 

Source: Greenland et al., 2000. 

* Mantel-Haenszel analysis (p = 0.01). Maximum-likelihood summaries differed by less than 1% from these 

summaries; based on 2,656 cases and 7,084 controls. Adjusting for age, sex, and other variables had little effect on 

summary results. 

** These data are from a recent United Kingdom study not included in the Greenland analysis but included in another 

pooled analysis (Ahlbom et al. 2000). The United Kingdom study included 1,073 cases and 2,224 controls. 

For this table, the column headed “estimate” describes the relative risk. Relative risk is the ratio of the risk of childhood 

leukemia for those in a magnetic field exposure group compared to persons with exposure levels of 1.0 mG or less. For 

example, Coghill estimated that children with exposures between 1 and 2 mG have 0.54 times the risk of children whose 

exposures were less than 1 mG. London's study estimates that children whose exposures were greater than 3 mG have 

1.53 times the risk of children whose exposures were less than 1 mG. The column headed “95% CL” (confidence limits) 

describes how much random variation is in the estimate of relative risk. The estimate may be off by some amount due to 

random variation, and the width of the confidence limits gives some notion of that variation. For example, in Coghill's 

estimate of 0.54 for the relative risk, values as low as 0.17 or as high as 1.74 would not be statistically significantly 

different from the value of 0.54. Note there is a wide range of estimates of relative risk across the studies and wide 

confidence limits for many studies. In light of these findings, the pooling of results can be extremely helpful to calculate 

an overall estimate, much better than can be obtained from any study taken alone. 

studies (Linet, London, McBride, Savitz) were 60 Hz; all other studies were 50 Hz. 

Results from the recent study from the United Kingdom (see page 17) are also 

included in the table. This study was included in the analysis by Ahlbom et al. 

(2000). The relative risk estimates from the individual studies show little or no 

association of magnetic fields with childhood leukemia. The study summary for the 

pooled analysis by Greenland et al. (2000) shows a weak association between 

childhood leukemia and magnetic field exposures greater 3 mG. 

June 2002 http://www.niehs.nih.gov/emfrapid 19 
EMF Research 

Q Is there a link between EMF exposure and childhood 

brain cancer or other forms of cancer in children? 

A Although the earliest studies suggested an association between EMF exposure and all 

forms of childhood cancer, those initial findings have not been confirmed by other 

studies. At present, the available series of studies indicates no association between 

EMF exposure and childhood cancers other than leukemia. Far fewer of these studies 

have been conducted than studies of childhood leukemia. 

Q Is there a link between residential EMF exposure and 

cancer in adults? 

A
The few studies that have been conducted to address EMF and adult cancer do not


provide strong evidence for an association. Thus, a link has not been established 

between residential EMF exposure and adult cancers, including leukemia, brain 

cancer, and breast cancer (see table below). 

Residential Exposure to Magnetic Fields and Adult Cancer 

Results (odds ratios)



First author Location Type of exposure data Leukemia CNS tumors All cancers



Coleman United Kingdom Calculated historical fields 0.92 NA NA 

Feychting and Ahlbom Sweden Calculated & spot measurements 1.5* 0.7 NA 

Li Taiwan Calculated historical fields 1.4* 1.1 NA 

Li Taiwan Calculated historical fields 1.1 (breast cancer) 

McDowall United Kingdom Calculated historical fields 1.43 NA 1.03 

Severson Seattle Wire codes & spot measurements 0.75 NA NA 

Wrensch San Francisco Wire codes & spot measurements NA 0.9 NA 

Youngson United Kingdom Calculated historical fields 1.88 NA NA 

CNS = central nervous system.



*The number is statistically significant (greater than expected by chance). 
 

Study results are listed as “odds ratios” (OR). An odds ratio of 1.00 means there was no increase or decrease in risk. In other words, the odds
 


that the people in the study who had the disease (in this case, cancer) and were exposed to a particular agent (in this case, EMF) are the
 


same as for the people in the study who did not have the disease. An odds ratio greater than 1 may occur simply by chance, unless it is
 


statistically significant.



20 http://www.niehs.nih.gov/emfrapid June 2002 
EMF Research 

Q Have clusters of cancer or other adverse health effects 

been linked to EMF exposure? 

A An unusually large number of cancers, miscarriages, or other adverse health effects

that occur in one area or over one period of time is called a “cluster.” Sometimes 

clusters provide an early warning of a health hazard. But most of the time the 

reason for the cluster is not known. There have been no proven instances of cancer 

clusters linked with EMF exposure. 

xxx 

x x 

x ? 

x ? x 

? x 

x 

x 

x x 

The definition of a “cluster” depends on 

how large an area is included. Cancer cases 

(x’s in illustration) in a city, neighborhood, 

or workplace may occur in ways that 

suggest a cluster due to a common 

environmental cause. Often these patterns 

turn out to be due to chance. Delineation 

of a cluster is subjective—where do you 

draw the circles? 

Q If EMF does cause or promote cancer, shouldn’t cancer 

rates have increased along with the increased use of 

electricity? 

A Not necessarily. Although the 

use of electricity has increased 

greatly over the years, EMF 

exposures may not have 

increased. Changes in building 

wiring codes and in the design 

of electrical appliances have in 

some cases resulted in lower 

magnetic field levels. Rates for 

various types of cancer have 

shown both increases and 

decreases through the years, due 

in part to improved prevention, 

diagnosis, reporting, and 

treatment. 

June 2002 http://www.niehs.nih.gov/emfrapid 21 
EMF Research 

Q



A



Is there a link between EMF exposure in electrical 

occupations and cancer? 

For almost as long as we have been concerned with residential exposure to EMF and 

childhood cancers, researchers have been studying workplace exposure to EMF and adult 

cancers, focusing on leukemia and brain cancer. This research began with surveys of job 

titles and cancer risks, but has progressed to include very large, detailed studies of the 

health of workers, especially electric utility workers, in the United States, Canada, France, 

England, and several Northern European countries. Some studies have found evidence 

that suggests a link between EMF exposure and both leukemia and brain cancer, whereas 

other studies of similar size and quality have not found such associations. 

California 

A 1993 study of 36,000 California electric utility workers reported no 

strong, consistent evidence of an association between magnetic fields and 

any type of cancer. 

Canada/France 

A 1994 study of more than 200,000 utility workers in 3 utility companies 

in Canada and France reported no significant association between all 

leukemias combined and cumulative exposure to magnetic fields. There 

was a slight, but not statistically significant, increase in brain cancer. The 

researchers concluded that the study did not provide clear-cut evidence 

that magnetic field exposures caused leukemia or brain cancer. 

North Carolina 

Results of a 1995 study involving more than 138,000 utility workers at 

5 electric utilities in the United States did not support an association 

between occupational magnetic field exposure and leukemia, but 

suggested a link to brain cancer. 

Denmark 

In 1997 a study of workers employed in all Danish utility companies 

reported a small, but statistically significant, excess risk for all cancers 

combined and for lung cancer. No excess risk was observed for leukemia, 

brain cancers, or breast cancer. 

United Kingdom 

A 1997 study among electrical workers in the United Kingdom did not find 

an excess risk for brain cancer. An extension of this work reported in 2001 

also found no increased risk for brain cancer. 

Efforts have also been made to pool the findings across several of the above studies 

to produce more accurate estimates of the association between EMF and cancer 

(Kheifets et al., 1999). The combined summary statistics across studies provide 

insufficient evidence for an association between EMF exposure in the workplace 

and either leukemia or brain cancer. 

22 http://www.niehs.nih.gov/emfrapid June 2002 
EMF Research 

Q Have studies of workers in other industries suggested 

a link between EMF exposure and cancer? 

A One of the largest studies to report an association between cancer 

and magnetic field exposure in a broad range of industries was


conducted in Sweden (1993). The study included an assessment


of EMF exposure in 1,015 different workplaces and involved


more than 1,600 people in 169 different occupations. An


association was reported between estimated EMF exposure and


increased risk for chronic lymphocytic leukemia. An association


was also reported between exposure to magnetic fields and brain


cancer, but there was no dose-response relationship.
 

Another Swedish study (1994) found an excess risk of lymphocytic


leukemia among railway engine drivers and conductors. However,
 

the total cancer incidence (all tumors included) for this group of


workers was lower than in the general Swedish population. A


study of Norwegian railway workers found no evidence for an


association between EMF exposure and leukemia or brain cancer.
 

Although both positive and negative effects of EMF exposure have


been reported, the majority of studies show no effects.


A 

Q Is there a link between EMF exposure and breast 

cancer? 

Researchers have been interested in the possibility that EMF exposure might cause 

breast cancer, in part because breast cancer is such a common disease in adult women. 

Early studies identified a few electrical workers with male breast cancer, a very rare 

disease. A link between EMF exposure and alterations in the hormone melatonin was 

considered a possible hypothesis (see page 24). This idea provided motivation to 

conduct research addressing a possible link between EMF exposure and breast cancer. 

Overall, the published epidemiological studies have not shown such an association. 

Q What have we learned from clinical studies? 


A Laboratory studies with human volunteers have attempted to answer questions

such as, 


Does EMF exposure alter normal brain and heart function? 
 

Does EMF exposure at night affect sleep patterns? 
 

Does EMF exposure affect the immune system? 
 

Does EMF exposure affect hormones?



The following kinds of biological effects have been reported. Keep in mind that a 

biological effect is simply a measurable change in some biological response. It may 

or may not have any bearing on health. 

June 2002 http://www.niehs.nih.gov/emfrapid 23 
EMF Research 

Heart rate 

An inconsistent effect on heart rate by EMF exposure has been reported. When 

observed, the biological response is small (on average, a slowing of about three to 

five beats per minute), and the response does not persist once exposure has ended. 

Two laboratories, one in the United States and one in Australia, have reported effects 

of EMF on heart rate variability. Exposures used in these experiments were relatively 

high (about 300 mG), and lower exposures failed to produce the effect. Effects have 

not been observed consistently in repeated experiments. 

Sleep electrophysiology 

A laboratory report suggested that overnight exposure to 60-Hz magnetic fields may 

disrupt brain electrical activity (EEG) during night sleep. In this study subjects were 

exposed to either continuous or intermittent magnetic fields of 283 mG. Individuals 

exposed to the intermittent magnetic fields showed alterations in traditional EEG 

sleep parameters indicative of a pattern of poor and disrupted sleep. Several studies 

have reported no effect with continuous exposure. 

Hormones, immune system, and blood chemistry 

Several clinical studies with human volunteers have evaluated the effects of powerfrequency EMF exposure on hormones, the immune system, and blood chemistry. 

These studies provide little evidence for any consistent effect. 

Melatonin 

The hormone melatonin is secreted mainly at night and primarily by the pineal 

gland, a small gland attached to the brain. Some laboratory experiments with 

cells and animals have shown that melatonin can slow the growth of cancer cells, 

including breast cancer cells. Suppressed nocturnal melatonin levels have been 

observed in some studies of laboratory animals exposed to both electric and 

magnetic fields. These observations led to the hypothesis that EMF exposure might 

reduce melatonin and thereby weaken one of the body’s defenses against cancer. 

Many clinical studies with human volunteers have now examined whether 

various levels and types of magnetic field exposure affect blood levels of 

melatonin. Exposure of human volunteers at night to power-frequency EMF 

under controlled laboratory conditions has no apparent effect on melatonin. Some 

studies of people exposed to EMF at work or at home do report evidence for a 

small suppression of melatonin. It is not clear whether the decreases in melatonin 

reported under environmental conditions are related to the presence of EMF 

exposure or to other factors. 

24 http://www.niehs.nih.gov/emfrapid June 2002 
EMF Research 

Q



A



Q



A



What effects of EMF have been reported in laboratory 

studies of cells? 

Over the years, scientists have conducted more than 1,000 laboratory studies to 

investigate potential biological effects of EMF exposure. Most have been in vitro 

studies; that is, studies carried out on cells isolated from animals and plants, or on 

cell components such as cell membranes. Other studies involved animals, mainly 

rats and mice. In general, these studies do not demonstrate a consistent effect of 

EMF exposure. 

Most in vitro studies have used magnetic fields of 1,000 mG (100 μT) or higher, 

exposures that far exceed daily human exposures. In most incidences, when one 

laboratory has reported effects of EMF exposure on cells, other laboratories have not 

been able to reproduce the findings. For such research results to be widely accepted 

by scientists as valid, they must be replicated—that is, scientists in other laboratories 

should be able to repeat the experiment and get similar results. Cellular studies have 

investigated potential EMF effects on cell proliferation and differentiation, gene 

expression, enzyme activity, melatonin, and DNA. Scientists reviewing the EMF 

research literature find overall that the cellular studies provide little convincing 

evidence of EMF effects at environmental levels. 

Have effects of EMF been reported in laboratory 

studies in animals? 

Researchers have published more than 30 detailed reports on both long-term and 

short-term studies of EMF exposures in laboratory animals (bioassays). Long-term 

animal bioassays constitute an important group of studies in EMF research. Such 

studies have a proven record for predicting the carcinogenicity of chemicals, physical 

agents, and other suspected cancer-causing agents. In the EMF studies, large groups 

of mice or rats were continuously exposed to EMF for two years or longer and were 

then evaluated for cancer. The U.S. National Toxicology Program (http://ntpserver.niehs.nih.gov/) has an extensive historical database for hundreds of different 

chemical and physical agents evaluated using this model. EMF long-term bioassays 

examined leukemia, brain cancer, and breast cancer—the diseases some 

epidemiological studies have associated with EMF exposure (see pages 16–23). 

Several different approaches have been used to evaluate effects of EMF exposure in 

animal bioassays. To investigate whether EMF could promote cancer after genetic 

damage had occurred, some long-term studies used cancer initiators such as 

ultraviolet light, radiation, or certain chemicals that are known to cause genetic 

damage. Researchers compared groups of animals treated with cancer initiators to 

groups treated with cancer initiators and then exposed to EMF, to see if EMF 

exposure promoted the cancer growth (initiation-promotion model). Other studies 

tested the cancer promotion potential of EMF using mice that were predisposed to 

cancer because they had defects in the genes that control cancer. 

June 2002 http://www.niehs.nih.gov/emfrapid 25 
EMF Research 

Animal Leukemia Studies: Long-Term, Continuous Exposure Studies, Two or More Years in Length 

First author Sex/species Exposure/animal numbers Results 

Babbitt (U.S.) Female mice 14,000 mG, 190 or 380 mice per group. No effect 

Some groups treated with ionizing radiation. 

Boorman (U.S.) Male and female rats 20 to 10,000 mG, 100 per group No effect 

McCormick (U.S.) Male and female mice 20 to 10,000 mG, 100 per group No effect 

Mandeville (Canada) Female rats 20 to 20,000 mG, 50 per group No effect 

In utero exposure 

Yasui (Japan) Male and female rats 5,000 to 50,000 mG, 50 per group No effect 

10 milligauss (mG) = 1 microtesla (μT) = 0.001 millitesla (mT) 

Leukemia 

Fifteen animal leukemia studies have been completed and reported. Most tested for 

effects of exposure to power-frequency (60-Hz) magnetic fields using rodents. 

Results of these studies were largely negative. The Babbitt study evaluated the 

subtypes of leukemia. The data provide no support for the reported epidemiology 

findings of leukemia from EMF exposure. Many scientists feel that the lack of 

effects seen in these laboratory leukemia studies significantly weakens the case for 

EMF as a cause of leukemia. 

Breast cancer 

Researchers in the Ukraine, Germany, Sweden, and the United States have used 

initiation-promotion models to investigate whether EMF exposure promotes breast 

cancer in rats. 

The results of these studies are mixed; while the German studies showed some 

effects, the Swedish and U.S. studies showed none. Studies in Germany reported 

effects on the numbers of tumors and tumor volume. A National Toxicology 

Program long-term bioassay performed without the use of other cancer-initiating 

substances showed no effects of EMF exposure on the development of mammary 

tumors in rats and mice. 

The explanation for the observed difference among these studies is not readily 

apparent. Within the limits of the experimental rodent model of mammary 

carcinogenesis, no conclusions are possible regarding a promoting effect of EMF on 

chemically induced mammary cancer. 

Other cancers 

Tests of EMF effects on skin cancer, liver cancer, and brain cancer have been 

conducted using both initiation-promotion models and non-initiated long-term 

bioassays. All are negative. 

Three positive studies were reported for a co-promotion model of skin cancer in 

mice. The mice were exposed to EMF plus cancer-causing chemicals after cancers 

26 http://www.niehs.nih.gov/emfrapid June 2002 
EMF Research 

had already been initiated. The same research team as well as an independent 

laboratory were unable to reproduce these results in subsequent experiments. 

Non-cancer effects 

Many animal studies have investigated whether EMF can cause health problems 

other than cancer. Researchers have examined many endpoints, including birth 

defects, immune system function, reproduction, behavior, and learning. Overall, 

animal studies do not support EMF effects on non-cancer endpoints. 

Q Can EMF exposure damage DNA? 

A
Studies have attempted to determine whether EMF has genotoxic potential; that is,


whether EMF exposure can alter the genetic material of living organisms. This 

question is important because genotoxic agents often also cause cancer or birth 

defects. Studies of genotoxicity have included tests on bacteria, fruit flies, and some 

tests on rats and mice. Nearly 100 studies on EMF genotoxicity have been reported. 

Most evidence suggests that EMF exposure is not genotoxic. Based on experiments 

with cells, some researchers have suggested that EMF exposure may inhibit the cell’s 

ability to repair normal DNA damage, but this idea remains speculative because of 

the lack of genotoxicity observed in EMF animal studies. 

June 2002 http://www.niehs.nih.gov/emfrapid 27 
Your EMF Environment 

4Your EMF Environment 

This chapter discusses typical magnetic field exposures in home and work 

environments and identifies common EMF sources and field intensities 

associated with these sources. 

Q How do we define EMF exposure? 

A Scientists are still uncertain about the best way to define “exposure” because

experiments have yet to show which aspect of the field, if any, may be relevant to 

reported biological effects. Important aspects of exposure could be the highest 

intensity, the average intensity, or the amount of time spent above a certain 

baseline level. The most widely used measure of EMF exposure has been the timeweighted average magnetic field level (see discussion on page 15). 

Q How is EMF exposure measured? 


A Several kinds of personal exposure meters are now available. These automatically

record the magnetic field as it varies over time. To determine a person’s EMF 


exposure, the personal exposure meter is usually worn at the waist or is placed as 

close as possible to the person during the course of a work shift or day. 

EMF can also be measured using survey meters, sometimes called “gaussmeters.” 

These measure the EMF levels in a given location at a given time. Such 

measurements do not necessarily reflect personal EMF exposure because they are 

not always taken at the distance from the EMF source that the person would 

typically be from the source. Measurements are not always made in a location for 

the same amount of time that a person spends there. Such “spot measurements” 

also fail to capture variations of the field over time, which can be significant. 

28 http://www.niehs.nih.gov/emfrapid June 2002 
Your EMF Environment 

Q What are some typical EMF exposures? 

A The figure below is an example of data collected with a personal exposure meter. 

20 

16 

12 

8 

4 

0 

Magnetic Field (mG) 

6 pm Midnight 6 am Noon 6 pm 

Work Around 

house 

Going 

to work Work Lunch out 

Going 

home 

Sleeping (no 

electric blanket) 

Personal Magnetic Field Exposure 

Mean magnetic field 

exposure during 

this 24-hour period 

was 0.5 mG. 

In the above example, the magnetic field was measured every 1.5 seconds over a 

period of 24 hours. For this person, exposure at home was very low. The occasional 

spikes (short exposure to high fields) occurred when the person drove or walked 

under power lines or over underground power lines or was close to appliances in 

the home or office. 

Several studies have used personal exposure meters to measure field exposure in 

different environments. These studies tend to show that appliances and building 

wiring contribute to the magnetic field exposure that most people receive while at 

home. People living close to high voltage power lines that carry a lot of current tend 

to have higher overall field exposures. As shown on page 32, there is considerable 

variation among houses. 

Q What are typical EMF exposures for people living in 

the United States? 

A
Most people in the United States are exposed to magnetic fields that average less


than 2 milligauss (mG), although individual exposures vary. 

The following table shows the estimated average magnetic field exposure of the 

U.S. population, according to a study commissioned by the U.S. government as part 

June 2002 http://www.niehs.nih.gov/emfrapid 29 
Your EMF Environment 

of the EMF Research and Public Information Dissemination (EMF RAPID) Program 

(see page 50). This study measured magnetic field exposure of about 1,000 people 

of all ages randomly selected among the U.S. population. Participants wore or 

carried with them a small personal exposure meter and kept a diary of their 

activities both at home and away from home. Magnetic field values were 

automatically recorded twice a second for 24 hours. The study reported that 

exposure to magnetic fields is similar in different regions of the country and similar 

for both men and women. 

Estimated Average Magnetic Field Exposure of the U.S. Population 

Average 24-hour Population 95% confidence People exposed* 

field (mG) exposed (%) interval (%) (millions) 

> 0.5 76.3 73.8–78.9 197–211 

> 1 43.6 40.9–46.5 109–124 

> 2 14.3 11.8–17.3 31.5–46.2 

> 3 6.3 4.7–8.5 12.5–22.7 

> 4 3.6 2.5–5.2 6.7–13.9 

> 5 2.42 1.65–3.55 4.4–9.5 

> 7.5 0.58 0.29–1.16 0.77–3.1 

> 10 0.46 0.20–1.05 0.53–2.8 

> 15 0.17 0.035–0.83 0.09–2.2 

*Based on a population of 267 million. This table summarizes some of the results of a study that sampled about 1,000 people 

in the United States. In the first row, for example, we find that 76.3% of the sample population had a 24-hour average 

exposure of greater than 0.5 mG. Assuming that the sample was random, we can use statistics to say that we are 95% 

confident that the percentage of the overall U.S. population exposed to greater than 0.5 mG is between 73.8% and 78.9%. 

Source: Zaffanella, 1993. 

The following table shows average magnetic fields experienced during different 

types of activities. In general, magnetic fields are greater at work than at home. 

Estimated Average Magnetic Field Exposure of the U.S. Population 

for Various Activities 

Average Population exposed (%) 

field (mG) Home Bed Work School Travel 

> 0.5 69 48 81 63 87 

> 1 38 30 49 25 48 

> 2 14 14 20 3.5 13 

> 3 7.8 7.2 13 1.6 4.1 

> 4 4.7 4.7 8.0 < 1 1.5 

> 5 3.5 3.7 4.6 1.0 

> 7.5 1.2 1.6 2.5 0.5 

> 10 0.9 0.8 1.3 < 0.2 

> 15 0.1 0.1 0.9 

Source: Zaffanella, 1993. 

30 http://www.niehs.nih.gov/emfrapid June 2002 
Your EMF Environment 

Q What levels of EMF are found in common environments? 

A Magnetic field exposures can vary greatly from site to site for any type of 

environment. The data shown in the following table are median measurements 

taken at four different sites for each environment category. 

EMF Exposures in Common Environments 

Magnetic fields measured in milligauss (mG) 

Median* Top 5th 

Environment exposure percentile 

OFFICE BUILDING 

Support staff 0.6 3.7 

Professional 0.5 2.6 

Maintenance 0.6 3.8 

Visitor 0.6 2.1 

SCHOOL 

Teacher 0.6 3.3 

Student 0.5 2.9 

Custodian 1.0 4.9 

Administrative staff 1.3 6.9 

HOSPITAL 

Patient 0.6 3.6 

Medical staff 0.8 5.6 

Visitor 0.6 2.4 

Maintenance 0.6 5.9 

Median* Top 5th 

Environment exposure percentile 

MACHINE SHOP 

Machinist 

Welder 

Engineer 

Assembler 

Office staff 

GROCERY STORE 

Cashier 

Butcher 

Office staff 

Customer 

0.4 6.0 

1.1 24.6 

1.0 5.1 

0.5 6.4 

0.7 4.7 

2.7 11.9 

2.4 12.8 

2.1 7.1 

1.1 7.7 

*The median of four measurements. For this table, the 

median is the average of the two middle measurements. 

Source: National Institute for Occupational Safety and 

Health. 

Q What EMF field levels are encountered in the home? 

A
Electric fields

Electric fields in the home, on average, range from 0 to 10 volts per meter. They can 

be hundreds, thousands, or even millions of times weaker than those encountered 

outdoors near power lines. Electric fields directly beneath power lines may vary from 

a few volts per meter for some overhead distribution lines to several thousands of 

volts per meter for extra high voltage power lines. Electric fields from power lines 

rapidly become weaker with distance and can be greatly reduced by walls and roofs 

of buildings. 

Magnetic fields 

Magnetic fields are not blocked by most materials. Magnetic fields encountered in 

homes vary greatly. Magnetic fields rapidly become weaker with distance from 

the source. 

June 2002 http://www.niehs.nih.gov/emfrapid 31 
25% 

50% 

15% 

5% 

1% 

Your EMF Environment 

The chart on the left summarizes data from a study 

Magnetic Field Measured in 992 Homes 

25% 50% 

Source: Zaffanella, 1993 

6.6 mG 

2.9 mG 

2.1 mG 

1.1 mG 

0.6 mG 

All-room mean 

magnetic fields 

% of homes that exceeded 

magnetic fields on the left 

by the Electric Power Research Institute (EPRI) in 

which spot measurements of magnetic fields were 

made in the center of rooms in 992 homes 

throughout the United States. Half of the houses 

studied had magnetic field measurements of 0.6 

mG or less, when the average of measurements 

from all the rooms in the house was calculated 

(the all-room mean magnetic field). The all-room 

mean magnetic field for all houses studied was 0.9 

mG. The measurements were made away from 

electrical appliances and reflect primarily the 

fields from household wiring and outside 

power lines. 

If you are comparing the information in this chart 

with measurements in your own home, keep in 

mind that this chart shows averages of 

measurements taken throughout the homes, not 

the single highest measurement found in the home. 

Q What are EMF levels close to electrical appliances? 

A
Magnetic fields close to electrical appliances are often much stronger than those


from other sources, including magnetic fields directly under power lines. Appliance 

fields decrease in strength with distance more quickly than do power line fields. 

The following table, based on data gathered in 1992, lists the EMF levels generated 

by common electrical appliances. Magnetic field strength (magnitude) does not 

depend on how large, complex, powerful, or noisy the appliance is. Magnetic fields 

near large appliances are often weaker than those near small devices. Appliances in 

your home may have been redesigned since the data in the table were collected, 

and the EMF they produce may differ considerably from the levels shown here. 

Electric Blankets 

Source: Center for Devices and Radiological Health, 

U.S. Food and Drug Administration. 

Measurements taken 5 cm from the blanket surface. 

Conventional PTC 

Low-Magnetic Field 

5-cm peak 

5-cm average 

39.4 

21.8 

2.7 0.9 

45 

40 

35 

30 

25 

20 

15 

10 

5 

0 

Values in

milligauss (mG) 

The graph shows magnetic fields produced by electric 

blankets, including conventional 110-V electric 

blankets as well as the PTC (positive temperature 

coefficient) low-magnetic-field blankets. The fields 

were measured at a distance of about 2 inches from 

the blanket’s surface, roughly the distance from the 

blanket to the user’s internal organs. Because of the 

wiring, magnetic field strengths vary from point to 

point on the blanket. The graph reflects this and gives 

both the peak and the average measurement. 

32 http://www.niehs.nih.gov/emfrapid June 2002 
Sources of Magnetic Fields (mG)* 

Your EMF Environment 

Distance from source Distance from source 

6” 1’ 2’ 4’ 6” 1’ 2’ 4’ 

Office Sources Workshop Sources 

AIR CLEANERS BATTERY CHARGERS 

Lowest 110 20 3 – Lowest 3 2 – – 

Median 180 35 5 1 Median 30 3 – – 

Highest 250 50 8 2 Highest 50 4 – – 

COPY MACHINES DRILLS 

Lowest 4 2 1 – Lowest 100 20 3 – 

Median 90 20 7 1 Median 150 30 4 – 

Highest 200 40 13 4 Highest 200 40 6 – 

FAX MACHINES POWER SAWS 

Lowest 4 – – – Lowest 50 9 1 – 

Median 6 – – – Median 200 40 5 – 

Highest 9 2 – – Highest 1000 300 40 4 

FLUORESCENT LIGHTS ELECTRIC SCREWDRIVERS (while charging) 

Lowest 20 – – – Lowest – – – – 

Median 40 6 2 – Median – – – – 

Highest 100 30 8 4 Highest – – – – 

ELECTRIC PENCIL SHARPENERS 

Lowest 20 8 5 – Distance from source 

Median 200 70 20 2 1’ 2’ 4’ 

Highest 300 90 30 30 Living/Family Room Sources 

VIDEO DISPLAY TERMINALS (see page 48) CEILING FANS 

(PCs with color monitors)** Lowest – – – 

Lowest 7 2 1 – Median 3 – – 

Median 14 5 2 – Highest 50 6 1 

Highest 20 6 3 – WINDOW AIR CONDITIONERS 

Bathroom Sources Lowest 

Median 

– 

3 

– 

1 

– 

– HAIR DRYERS Highest 20 6 4 

Lowest 

Median 

1 

300 

– 

1 

– 

– 

– 

– COLOR TELEVISIONS** 

Highest 700 70 10 1 Lowest 

Median 

– 

7 

– 

2 

– 

– ELECTRIC SHAVERS 

Lowest 4 – – – Highest 20 8 4 

Median 100 20 – – 

Highest 600 100 10 1 

Continued 

June 2002 http://www.niehs.nih.gov/emfrapid 33 
Your EMF Environment 

Sources of Magnetic Fields (mG)* 

Distance from source Distance from source 

6” 1’ 2’ 4’ 6” 1’ 2’ 4’ 

Kitchen Sources Kitchen Sources 

BLENDERS ELECTRIC OVENS 

Lowest 30 5 – – Lowest 4 1 – – 

Median 70 10 2 – Median 9 4 – – 

Highest 100 20 3 – Highest 20 5 1 – 

CAN OPENERS ELECTRIC RANGES 

Lowest 500 40 3 – Lowest 20 – – – 

Median 600 150 20 2 Median 30 8 2 – 

Highest 1500 300 30 4 Highest 200 30 9 6 

COFFEE MAKERS REFRIGERATORS 

Lowest 4 – – – Lowest – – – – 

Median 7 – – – Median 2 2 1 – 

Highest 10 1 – – Highest 40 20 10 10 

DISHWASHERS TOASTERS 

Lowest 10 6 2 – Lowest 5 – – – 

Median 20 10 4 – Median 10 3 – – 

Highest 100 30 7 1 Highest 20 7 – – 

FOOD PROCESSORS 

Lowest 20 5 – – Bedroom Sources 

Median 

Highest 

30 

130 

6 

20 

2 

3 

– 

– DIGITAL CLOCK**** 

GARBAGE DISPOSALS 

Lowest 60 

Median 80 

8 

10 

1 

2 

– 

– 

Lowest 

Median 

High 

– 

1 

8 

– 

– 

2 

– 

– 

1 

Highest 100 20 3 – ANALOG CLOCKS 

MICROWAVE OVENS*** (conventional clockface)**** 

Lowest 100 1 1 – Lowest 1 – – 

Median 200 4 10 2 Median 15 2 – 

Highest 300 200 30 20 Highest 30 5 3 

MIXERS BABY MONITOR (unit nearest child) 

Lowest 30 5 – – Lowest 4 – – – 

Median 100 10 1 – Median 6 1 – – 

Highest 600 100 10 – Highest 15 2 – – 

Continued 

34 http://www.niehs.nih.gov/emfrapid June 2002 
Sources of Magnetic Fields (mG)* 

Your EMF Environment 

Distance from source Distance from source 


6” 1’ 2’ 4’ 6” 1’ 2’ 4’ 


Laundry/Utility Sources 	 Laundry/Utility Sources 

ELECTRIC CLOTHES DRYERS 	 PORTABLE HEATERS 

Lowest 2 – – – Lowest 5 1 – – 

Median 3 2 – – Median 100 20 4 – 

Highest 10 3 – – Highest 150 40 8 1 

WASHING MACHINES 	 VACUUM CLEANERS 

Lowest 4 1 – – Lowest 100 20 4 – 

Median 20 7 1 – Median 300 60 10 1 

Highest 100 30 6 – Highest 700 200 50 10 

IRONS 	 SEWING MACHINES 

Lowest 6 1 – – Home sewing machines can produce magnetic fields 

Median 8 1 – – of 12 mG at chest level and 5 mG at head level. 

Highest 20 3 – – Magnetic fields as high as 35 mG at chest level and 

215 mG at knee level have been measured from 

industrial sewing machine models (Sobel, 1994). 

Source: EMF In Your Environment, U.S. Environmental Protection Agency, 1992. 

* 	Dash (–) means that the magnetic field at this distance from the operating appliance could not be distinguished 

from background measurements taken before the appliance had been turned on. 

** Some appliances produce both 60-Hz and higher frequency fields. For example, televisions and computer screens 

produce fields at 10,000-30,000 Hz (10-30 kHz) as well as 60-Hz fields. 

*** 	Microwave ovens produce 60-Hz fields of several hundred milligauss, but they also create microwave energy 

inside the appliance that is at a much higher frequency (about 2.45 billion hertz). We are shielded from the higher 

frequency fields but not from the 60-Hz fields. 

**** 	Most digital clocks have low magnetic fields. In some analog clocks, however, higher magnetic fields are produced 

by the motor that drives the hands. In the above table, the clocks are electrically powered using alternating current, 

as are all the appliances described in these tables. 

Q What EMF levels are found near power lines? 

A Power transmission lines bring power from a generating station to an electrical

substation. Power distribution lines bring power from the substation to your home. 

Transmission and distribution lines can be either overhead or underground. Overhead 

lines produce both electric fields and magnetic fields. Underground lines do not 

produce electric fields above ground but may produce magnetic fields above ground. 

Power transmission lines 

Typical EMF levels for transmission lines are shown in the chart on page 37. At a 

distance of 300 feet and at times of average electricity demand, the magnetic fields 

from many lines can be similar to typical background levels found in most homes. 

The distance at which the magnetic field from the line becomes indistinguishable 

from typical background levels differs for different types of lines. 

June 2002 http://www.niehs.nih.gov/emfrapid 35 
Your EMF Environment 

Q



A



Q



A



Power distribution lines 

Typical voltage for power distribution lines in North America ranges from 4 to 24 

kilovolts (kV). Electric field levels directly beneath overhead distribution lines may 

vary from a few volts per meter to 100 or 200 volts per meter. Magnetic fields 

directly beneath overhead distribution lines typically range from 10 to 20 mG for 

main feeders and less than 10 mG for laterals. Such levels are also typical directly 

above underground lines. Peak EMF levels, however, can vary considerably 

depending on the amount of current carried by the line. Peak magnetic field levels as 

high as 70 mG have been measured directly below overhead distribution lines and as 

high as 40 mG above underground lines. 

How strong is the EMF from electric power substations? 

In general, the strongest EMF around the outside of a substation comes from the 

power lines entering and leaving the substation. The strength of the EMF from 

equipment within the substations, such as transformers, reactors, and capacitor 

banks, decreases rapidly with increasing distance. Beyond the substation fence or 

wall, the EMF produced by the substation equipment is typically indistinguishable 

from background levels. 

Do electrical workers have higher EMF exposure than 

other workers? 

Most of the information we have about occupational EMF exposure comes from 

studies of electric utility workers. It is therefore difficult to compare electrical 

workers’ EMF exposures with those of other workers because there is less 

information about EMF exposures in work environments other than electric utilities. 

Early studies did not include actual measurements of EMF exposure on the job but 

used job titles as an estimate of EMF exposure among electrical workers. Recent 

studies, however, have included extensive EMF exposure assessments. 

A report published in 1994 provides some information about estimated EMF 

exposures of workers in Los Angeles in a number of electrical jobs in electric 

utilities and other industries. Electrical workers had higher average EMF exposures 

(9.6 mG) than did workers in other jobs (1.7 mG). For this study, the category 

“electrical workers” included electrical engineering technicians, electrical engineers, 

electricians, power line workers, power station operators, telephone line workers, 

TV repairers, and welders. 

36 http://www.niehs.nih.gov/emfrapid June 2002 
Your EMF Environment 

Typical EMF Levels for Power Transmission Lines* 

Electric fields from power lines are relatively 

stable because line voltage doesn’t change 

very much. Magnetic fields on most lines 

fluctuate greatly as current changes in 

response to changing loads. Magnetic fields 

must be described statistically in terms of 

averages, maximums, etc. The magnetic fields 

above are means calculated for 321 power 

lines for 1990 annual mean loads. During peak 

loads (about 1% of the time), magnetic fields 

are about twice as strong as the mean levels 

above. The graph on the left is an example of 

how the magnetic field varied during one week 

for one 500-kV transmission line. 

*These are typical EMFs at 1 m (3.3 ft) above ground for various distances from power lines in the Pacific 

Northwest. They are for general information. For information about a specific line, contact the utility that 

operates the line. 

Source: Bonneville Power Administration, 1994. 

Magnetic Field from a 500-kV Transmission 

Line Measured on the Right-of-Way 

Every 5 Minutes for 1 Week 70 

60 

50 

40 

30 

20 

10 

0 

Thurs Fri Sat Sun Mon Tue Wed Thur 

Milligauss 

For This 1-Week Period: 

Mean field = 38.6 mG 

Minimum field = 22.4 mG 

Maximum field = 62.7 mG 

Electric Field (kV/m) 1.0 0.5 0.07 0.01 0.003 

Mean Magnetic Field (mG) 29.7 6.5 1.7 0.4 0.2 

Electric Field (kV/m) 2.0 1.5 0.3 0.05 0.01 

Mean Magnetic Field (mG) 57.5 19.5 7.1 1.8 0.8 

Electric Field (kV/m) 7.0 3.0 1.0 0.3 0.1 

Mean Magnetic Field (mG) 86.7 29.4 12.6 3.2 1.4 

115 kV 

230 kV 

500 kV 

Approx. Edge 

of Right-of-Way 15 m 

(50 ft) 

30 m 

(100 ft) 

61 m 

(200 ft) 

91 m 

(300 ft) 

Approx. Edge 

of Right-of-Way 15 m 

(50 ft) 

30 m 

(100 ft) 

61 m 

(200 ft) 

91 m 

(300 ft) 

Approx. Edge 

of Right-of-Way 

20 m 

(65 ft) 

30 m 

(100 ft) 

61 m 

(200 ft) 

91 m 

(300 ft) 

June 2002 http://www.niehs.nih.gov/emfrapid 37 
Your EMF Environment 

Q What are possible EMF exposures in the workplace? 

A The figures below are examples of magnetic field exposures determined with

exposure meters worn by four workers in different occupations. These 

measurements demonstrate how EMF exposures vary among individual workers. 

They do not necessarily represent typical EMF exposures for workers in these 

occupations. 

Magnetic Field Exposures of Workers (mG) 

50 

40 

30 

20 

10 

0 

8:30 am 9:00 am 9:30 am 10:00 am 10:30 am 11:00 am 11:30 am 12:12 pm 

7:00 am 9:00 am 11:00 am 1:00 pm 3:00 pm 5:00 pm 

50 

40 

30 

20 

10 

0 

Maintenance mechanic 

The mechanic repaired a compressor at 9:45 am and 11:10 am. 

The government worker was at the copy machine at 8:00 am, at the 

computer from 11:00 am to 1:00 pm and also from 2:30 pm to 4:30 pm. 

Government office worker 

Mean: 1.0 

Geometric 

mean: 0.7* 

Mean: 9.1 

Geometric 

mean: 7.0* 

*The geometric mean is calculated by squaring the values, adding the squares, and then taking the square root of the sum.

 Source: National Institute for Occupational Safety and Health and U.S. Department of Energy. 

50 

40 

30 

20 

10 

0 

7:00 am 9:00 am 11:00 am 1:00 pm 3:00 pm 

7:00 am 8:00 am 9:00 am 10:00 am 11:00 am 12:00 am 1:00 pm 

50 

40 

30 

20 

10 

0 

Sewing machine operator in garment factory 

The sewing machine operator worked all day, took a 1-hour lunch 

break at 11:15 am, and took 10-minute breaks at 8:55 am and 2:55 pm. 

The electrician repaired a large air-conditioning motor at 9:10 am 

and at 11:45 am. 

Electrician 

Mean: 32.0 

Geometric 

mean: 24.0* 

Mean: 0.9 

Geometric 

mean: 0.7* 

mG mG mG mG 

38 http://www.niehs.nih.gov/emfrapid June 2002 
Your EMF Environment 

The tables below and on page 41 can give you a general idea about magnetic field 

levels for different jobs and around various kinds of electrical equipment. It is 

important to remember that EMF levels depend on the actual equipment used in 

EMF Measurements During a Workday 

ELF magnetic fields 

measured in mG 

Median for Range for 90% 

Industry and occupation occupation* of workers** 

ELECTRICAL WORKERS IN VARIOUS INDUSTRIES 

Electrical engineers 1.7 0.5–12.0 


Construction electricians 3.1 1.6–12.1 


TV repairers 4.3 0.6–8.6 


Welders 9.5 1.4–66.1 


ELECTRIC UTILITIES 

Clerical workers without computers 0.5 0.2–2.0 

Clerical workers with computers 1.2 0.5–4.5 

Line workers 2.5 0.5–34.8 

Electricians 5.4 0.8–34.0 

Distribution substation operators 7.2 1.1–36.2 

Workers off the job (home, travel, etc.) 0.9 0.3–3.7 

TELECOMMUNICATIONS 

Install, maintenance, & repair technicians 1.5 0.7–3.2 

Central office technicians 2.1 0.5–8.2 

Cable splicers 3.2 0.7–15.0 

AUTO TRANSMISSION MANUFACTURE 

Assemblers 0.7 0.2–4.9 


Machinists 1.9 0.6–27.6 


HOSPITALS 

Nurses 1.1 0.5–2.1 


X-ray technicians 1.5 1.0–2.2 


SELECTED OCCUPATIONS FROM ALL ECONOMIC SECTORS 

Construction machine operators 0.5 0.1–1.2 

Motor vehicle drivers 1.1 0.4–2.7 

School teachers 1.3 0.6–3.2 

Auto mechanics 2.3 0.6–8.7 

Retail sales 2.3 1.0–5.5 

Sheet metal workers 3.9 0.3–48.4 

Sewing machine operators 6.8 0.9–32.0 

Forestry and logging jobs 7.6 0.6–95.5*** 

Source: National Institute for Occupational Safety and Health. 

ELF (extremely low frequency)—frequencies 3–3,000 Hz. 

* The median is the middle measurement in a sample arranged by size. These personal exposure 

measurements reflect the median magnitude of the magnetic field produced by the various EMF 

sources and the amount of time the worker spent in the fields. 

** This range is between the 5th and 95th percentiles of the workday averages for an occupation. 

*** Chain saw engines produce strong magnetic fields that are not pure 60-Hz fields. 

June 2002 http://www.niehs.nih.gov/emfrapid 39 
Your EMF Environment 

the workplace. Different brands or models of the same type of equipment can have 

different magnetic field strengths. It is also important to keep in mind that the 

strength of a magnetic field decreases quickly with distance. 

If you have questions or want more information about your EMF exposure at 

work, your plant safety officer, industrial hygienist, or other local safety official can 

be a good source of information. The National Institute for Occupational Safety and 

Health (NIOSH) is asked occasionally to conduct health hazard evaluations in 

workplaces where EMF is a suspected cause for concern. For further technical 

assistance contact NIOSH at 800-356-4674. 

Q What are some typical sources of EMF in the workplace? 

A Exposure assessment studies so far have shown that most people’s EMF exposure 

at work comes from electrical appliances and tools and from the building’s power 

supply. People who work near 

transformers, electrical closets, 

circuit boxes, or other highcurrent electrical equipment may 

have 60-Hz magnetic field 

exposures of hundreds of 

milligauss or more. In offices, 

magnetic field levels are often 

similar to those found at home, 

typically 0.5 to 4.0 mG. However, 

these levels can increase 

dramatically near certain types of 

equipment. 

40 http://www.niehs.nih.gov/emfrapid June 2002 
 

EMF Spot Measurements 

Your EMF Environment 

ELF magnetic fields 

Industry and sources (mG) Other frequencies Comments 

ELECTRICAL EQUIPMENT USED IN MACHINE MANUFACTURING 

Electric resistance heater 6,000–14,000 VLF 


Induction heater 10–460 High VLF 


Hand-held grinder 3,000 – Tool exposures measured at operator's chest. 


Grinder 110 – Tool exposures measured at operator's chest. 


Lathe, drill press, etc. 1–4 – Tool exposures measured at operator's chest. 


ALUMINUM REFINING 

Aluminum pot rooms 3.4–30 Very high static field Highly-rectified DC current (with an ELF ripple) 

refines aluminum. 

Rectification room 300–3,300 High static field 

STEEL FOUNDRY 

Ladle refinery 

Furnace active 170–1,300 High ULF from the ladle's big Highest ELF field was at the chair of control room operator. 

magnetic stirrer 

Furnace inactive 0.6–3.7 High ULF from the ladle's big Highest ELF field was at the chair of control room operator. 

magnetic stirrer 

Electrogalvanizing unit 2–1,100 High VLF 

TELEVISION BROADCASTING 

Video cameras 7.2–24.0 VLF 

(studio and minicams) 

Video tape degaussers 160–3,300 – Measured 1 ft away. 

Light control centers 10–300 – Walk-through survey. 

Studio and newsrooms 2–5 – Walk-through survey. 

HOSPITALS 

Intensive care unit 0.1–220 VLF Measured at nurse’s chest. 

Post-anesthesia care unit 0.1–24 VLF 

Magnetic resonance imaging (MRI) 0.5–280 Very high static field, VLF and RF Measured at technician's work locations. 

TRANSPORTATION 

Cars, minivans, and trucks 0.1–125 Most frequencies less than 60 Hz Steel-belted tires are the principal ELF source for 

gas/diesel vehicles. 

Bus (diesel powered) 0.5–146 Most frequencies less than 60 Hz 

Electric cars 0.1–81 Some elevated static fields 

Chargers for electric cars 4–63 – Measured 2 ft from charger. 

Electric buses 0.1–88 – Measured at waist. Fields at ankles 2-5 times higher. 

Electric train passenger cars 0.1–330 25 & 60 Hz power on U.S. trains Measured at waist. Fields at ankles 2-5 times higher. 

Airliner 0.8–24.2 400 Hz power on airliners Measured at waist. 

GOVERNMENT OFFICES 

Desk work locations 0.1–7 – Peaks due to laser printers. 


Desks near power center 18–50 – 


Power cables in floor 15–170 – 


Building power supplies 25–1,800 – 


Can opener 3,000 – Appliance fields measured 6 in. away. 


Desktop cooling fan 1,000 – Appliance fields measured 6 in. away. 


Other office appliances 10–200 – 


Source: National Institute for Occupational Safety and Health, 2001. 


ULF (ultra low frequency)—frequencies above 0, below 3 Hz. 


ELF (extremely low frequency)—frequencies 3–3,000 Hz. 


VLF (very low frequency)—frequencies 3,000–30,000 Hz (3–30 kilohertz). 


June 2002 http://www.niehs.nih.gov/emfrapid 41 
Your EMF Environment 

Q What EMF exposure occurs during travel? 


A Inside a car or bus, the main sources of magnetic field exposure are those you pass

by (or under) as you drive, such as power lines. Car batteries involve direct 


current (DC) rather than alternating current (AC). Alternators can create EMF, 

but at frequencies other than 60 Hz. The rotation of steel-belted tires is also a 

source of EMF. 

Most trains in the United States are diesel powered. Some electrically powered 

trains operate on AC, such as the passenger trains between Washington, D.C. and 

New Haven, Connecticut. Measurements taken on these trains using personal 

exposure monitors have suggested that average 60-Hz magnetic field exposures for 

passengers and conductors may exceed 50 mG. A U.S. government-sponsored 

exposure assessment study of electric rail systems found average 60-Hz magnetic 

field levels in train operator compartments that ranged from 0.4 mG (Boston high 

speed trolley) to 31.1 mG (North Jersey transit). The graph on the next page shows 

average and maximum magnetic field measurements in operator compartments of 

several electric rail systems. It illustrates that 60 Hz is one of several 

electromagnetic frequencies to which train operators are exposed. 

Workers who maintain the tracks on electric rail lines, primarily in the 

northeastern United States, also have elevated magnetic field exposures at both 

25 Hz and 60 Hz. Measurements taken by the National Institute for Occupational 

Safety and Health show that typical average daily exposures range from 3 to 

18 mG, depending on how often trains pass the work site. 

Rapid transit and light rail systems in the United States, such as the Washington 

D.C. Metro and the San Francisco Bay Area Rapid Transit, run on DC electricity. 

These DC-powered trains contain equipment that produces AC fields. For example, 

areas of strong AC magnetic fields have been measured on the Washington Metro 

close to the floor, during braking and acceleration, presumably near equipment 

located underneath the subway cars. 

42 http://www.niehs.nih.gov/emfrapid June 2002 
Your EMF Environment 

Magnetic Field Measurements in Train Operators’ Compartments 

Magnetic field measured in milligauss (mG). 

Source: U.S. Department of Transportation, 1993 

mG 

300 

200 

100 

0 

Amtrak Northeast Corridor 

Nonelectrical Rail 

5–2560 Hz 

5–45 Hz 

50–60 Hz 

65–300 Hz 

305–2560 Hz 

North Jersey Transit Long Branch 

Amtrak Northeast Corridor (60 Hz) 

Amtrak Northeast Corridor (25 Hz) 

mG 

60 

50 

40 

30 

20 

10 

0 

305–2560 Hz 

65–300 Hz 

50–60 Hz 

5–45 Hz 

5–2560 Hz 

Boston Trolley Bus 

Boston High Speed Trolley 

Washington D.C. Metrorail (all cars) 

Boston Subway 

These graphs illustrate that 60 Hz is one of several electromagnetic frequencies to which train operators are exposed. 

The maximum exposure is the top of the blue (upper) portion of the bar; the average exposure is the top of the red 

(lower) portion. 

A 

Q How can I find out how strong the EMF is where I live 

and work? 

The tables throughout this chapter can give you a general idea about magnetic field 

levels at home, for different jobs, and around various kinds of electrical equipment. 

For specific information about EMF from a particular power line, contact the utility 

that operates the line. Some will perform home EMF measurements. 

You can take your own EMF measurements with a magnetic field meter. For a spot 

measurement to provide a useful estimate of your EMF exposure, it should be 

taken at a time of day and location when and where you are typically near the 

equipment. Keep in mind that the strength of a magnetic field drops off quickly 

with distance. 

Independent technicians will conduct EMF measurements for a fee. Search the 

Internet under “EMF meters” or “EMF measurement.” You should investigate the 

experience and qualifications of commercial firms, since governments do not 

standardize EMF measurements or certify measurement contractors. 

June 2002 http://www.niehs.nih.gov/emfrapid 43 
Your EMF Environment 

Q



A



Q



A



At work, your plant safety officer, industrial hygienist, or other local safety official 

can be a good source of information. The National Institute for Occupational Safety 

and Health (NIOSH) sometimes conducts health hazard evaluations in workplaces 

where EMF is a suspected cause for concern. For further technical assistance, 

contact NIOSH at 800-356-4674. 

How much do computers contribute to my EMF 

exposure? 

Personal computers themselves produce very little EMF. However, the video 

display terminal (VDT) or monitor provides some magnetic field exposure unless it 

is of the new flat-panel design. 

Conventional VDTs containing 

cathode ray tubes use magnetic 

fields to produce the image on the 

screen, and some emission of those 

magnetic fields is unavoidable. 

Unlike most other appliances which 

produce predominantly 60-Hz 

magnetic fields, VDTs emit magnetic 

fields in both the extremely low 

frequency (ELF) and very low 

frequency (VLF) frequency ranges 

(see page 8). Many newer VDTs 

have been designed to minimize 

magnetic field emissions, and those 

identified as “TCO’99 compliant” 

meet a standard for low emissions 

(see page 48). 

What can be done to limit EMF exposure? 

Personal exposure to EMF depends on three things: the strength of the magnetic 

field sources in your environment, your distance from those sources, and the time 

you spend in the field. 

If you are concerned about EMF exposure, your first step should be to find out 

where the major EMF sources are and move away from them or limit the time you 

spend near them. Magnetic fields from appliances decrease dramatically about an 

arm’s length away from the source. In many cases, rearranging a bed, a chair, or a 

work area to increase your distance from an electrical panel or some other EMF 

source can reduce your EMF exposure. 

44 http://www.niehs.nih.gov/emfrapid June 2002 
Your EMF Environment 

Another way to reduce EMF exposure is to use equipment designed to have 

relatively low EMF emissions. Sometimes electrical wiring in a house or a building 

can be the source of strong magnetic field exposure. Incorrect wiring is a common 

source of higher-than-usual magnetic fields. Wiring problems are also worth 

correcting for safety reasons. 

In its 1999 report to Congress, the National Institute of Environmental Health 

Sciences suggested that the power industry continue its current practice of siting 

power lines to reduce EMF exposures. 

There are more costly actions, such as burying power lines, moving out of a home, 

or restricting the use of office space that may reduce exposures. Because scientists 

are still debating whether EMF is a hazard to health, it is not clear that the costs of 

such measures are warranted. Some EMF reduction measures may create other 

problems. For instance, compacting power lines reduces EMF but increases the 

danger of accidental electrocution for line workers. 

We are not sure which aspects of the magnetic field exposure, if any, to reduce. 

Future research may reveal that EMF reduction measures based on today’s limited 

understanding are inadequate or irrelevant. No action should be taken to reduce 

EMF exposure if it increases the risk of a known safety hazard. 

June 2002 http://www.niehs.nih.gov/emfrapid 45 
Exposure Standards 

5EMF Exposure Standards 

This chapter describes standards and guidelines established by state, national, 

and international safety organizations for some EMF sources and exposures. 

Q Are there exposure standards for 60-Hz EMF? 


A In the United States, there are no federal standards limiting occupational or

residential exposure to 60-Hz EMF. 


At least six states have set standards for transmission line electric fields; two of 

these also have standards for magnetic fields (see table below). In most cases, the 

maximum fields permitted by each state are the maximum fields that existing lines 

produce at maximum load-carrying conditions. Some states further limit electric 

field strength at road crossings to ensure that electric current induced into large 

metal objects such as trucks and buses does not represent an electric shock hazard. 

State Transmission Line Standards and Guidelines 

Electric Field Magnetic Field 

State On R.O.W.* Edge R.O.W. On R.O.W. Edge R.O.W. 

Florida 8 kV/ma 2 kV/m — 150 mGa (max. load) 

10 kV/mb 200 mGb (max. load) 

250 mGc (max. load) 

Minnesota 8 kV/m — — — 

Montana 7 kV/md 1 kV/me 

New Jersey — 3 kV/m 

New York 11.8 kV/m 1.6 kV/m — 200 mG (max. load) 

11.0 kV/mf 

7.0 kV/md 

Oregon 9 kV/m — — — 

*R.O.W. = right-of-way (or in the Florida standard, certain additional areas adjoining the right-of-way). kV/m = kilovolt 

per meter. One kilovolt = 1,000 volts. aFor lines of 69-230 kV. bFor 500 kV lines. c

For 500 kV lines on certain existing 

R.O.W. dMaximum for highway crossings. eMay be waived by the landowner. f

Maximum for private road crossings. 

Two organizations have developed voluntary occupational exposure guidelines for 

EMF exposure. These guidelines are intended to prevent effects, such as induced 

currents in cells or nerve stimulation, which are known to occur at high magnitudes, 

much higher (more than 1,000 times higher) than EMF levels found typically in 

46 http://www.niehs.nih.gov/emfrapid June 2002 
Exposure Standards 

occupational and residential environments. These guidelines are summarized in the 

tables on the right. 

The International Commission		 ICNIRP Guidelines for EMF Exposure 

on Non-Ionizing Radiation 

Protection (ICNIRP) 

concluded that available data 

regarding potential long-term 

effects, such as increased risk 

of cancer, are insufficient to 

provide a basis for setting 

exposure restrictions. 

The American Conference 

Exposure (60 Hz) Electric field Magnetic field 

Occupational 8.3 kV/m 4.2 G (4,200 mG) 

General Public 4.2 kV/m 0.833 G (833 mG) 

International Commission on Non-Ionizing Radiation Protection (ICNIRP) is an organization of
 


15,000 scientists from 40 nations who specialize in radiation protection.
 


Source: ICNIRP, 1998.
 


ACGIH Occupational Threshold Limit Values for 60-Hz EMF 

of Governmental Industrial Electric field Magnetic field 

Hygienists (ACGIH) Occupational exposure should not exceed 25 kV/m 10 G (10,000 mG) publishes “Threshold Limit Prudence dictates the use of protective 15 kV/m – Values” (TLVs) for various clothing above physical agents. The TLVs Exposure of workers with cardiac 1 kV/m 1 G (1,000 mG) for 60-Hz EMF shown in pacemakers should not exceed the table are identified as 

American Conference of Governmental Industrial Hygienists (ACGIH) is a professional guides to control exposure; organization that facilitates the exchange of technical information about worker health

they are not intended to		 protection. It is not a government regulatory agency.
 


Source: ACGIH, 2001. 
 demarcate safe and



dangerous levels.



Q Does EMF affect people with pacemakers or other 

medical devices? 

A According to the U.S. Food and Drug Administration (FDA), interference from

EMF can affect various medical devices including cardiac pacemakers and 

implantable defibrillators. Most current research in this area focuses on higher 


frequency sources such as cellular phones, citizens band radios, wireless computer 


links, microwave signals, radio and television transmitters, and paging transmitters. 


Sources such as welding equipment, power lines at electric generating plants, and



rail transportation equipment can produce lower frequency EMF strong enough to



interfere with some models of pacemakers and defibrillators. The occupational



exposure guidelines developed by ACGIH state that workers with cardiac



pacemakers should not be exposed to a 60-Hz magnetic field greater than 1 gauss



(1,000 mG) or a 60-Hz electric field greater than 1 kilovolt per meter (1,000 V/m)



(see ACGIH guidelines above). Workers who are concerned about EMF exposure
 


effects on pacemakers, implantable defibrillators, or other implanted electronic



medical devices should consult their doctors or industrial hygienists.



June 2002 http://www.niehs.nih.gov/emfrapid 47 
Exposure Standards 

Q



A



Nonelectronic metallic medical implants (such as artificial joints, pins, nails, screws, 

and plates) can be affected by high magnetic fields such as those from magnetic 

resonance imaging (MRI) devices and aluminum refining equipment, but are 

generally unaffected by the lower fields from most other sources. 

The FDA MedWatch program is collecting information about medical device 

problems thought to be associated with exposure to or interference from EMF. 

Anyone experiencing a problem that might be due to such interference is 

encouraged to call and report it (800-332-1088). 

What about products advertised as producing low or 

reduced magnetic fields? 

Virtually all electrical appliances and devices emit electric and magnetic fields. The 

strengths of the fields vary appreciably both between types of devices and among 

manufacturers and models of the same type of device. Some appliance manufacturers 

are designing new models that, in general, have lower EMF than older models. As a 

result, the words “low field” or “reduced field” may be relative to older models and 

not necessarily relative to other manufacturers or devices. At this time, there are no 

domestic or international standards or guidelines limiting the EMF emissions of 

appliances. 

The U.S. government has set no standards for magnetic fields from computer 

monitors or video display terminals (VDTs). The Swedish Confederation of 

Professional Employees (TCO) established in 1992 a standard recommending strict 

limits on the EMF emissions of computer monitors. The 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. 

Beware of advertisements claiming that the federal government has certified that the 

advertised equipment produces little or no EMF. The federal government has no such 

general certification program for the emissions of low-frequency EMF. The U.S. Food 

and Drug Administration’s Center for Devices and Radiological Health (CDRH) does 

certify medical equipment and equipment producing high levels of ionizing radiation 

or microwave radiation. Information about certain devices as well as general 

information about EMF is available from the CDRH at 888-463-6332. 

48 http://www.niehs.nih.gov/emfrapid June 2002 
Exposure Standards 

A 

Q Are cellular telephones and towers sources of EMF 

exposure? 

Cellular telephones and towers involve radio-frequency and microwave-frequency 

electromagnetic fields (see page 8). These are in a much higher frequency range 

than are the power-frequency electric and magnetic fields associated with the 

transmission and use of electricity. 

The U.S. Federal Communications Commission (FCC) licenses communications 

systems that use radio-frequency and microwave electromagnetic fields and 

ensures that licensed facilities comply with exposure standards. Public information 

on this topic is published on two FCC Internet sites: http://www.fcc.gov/oet/info/ 

documents/bulletins/#56 and http://www.fcc.gov/oet/rfsafety/ 

The U.S. Food and Drug Administration also provides information about cellular 

telephones on its web site (http://www.fda.gov/cdrh/ocd/mobilphone.html). 

June 2002 http://www.niehs.nih.gov/emfrapid 49 
EMF Reviews 

6National and International EMF Reviews 

This chapter presents the findings and recommendations of major 

EMF research reviews, including the U.S. government’s EMF RAPID 

Program. 

Q What have national and international agencies 


concluded about the impact of EMF exposure on 


human health? 


A Since 1995, two major U.S. reports have concluded that limited evidence exists for 

an association between EMF exposure and increased leukemia risk, but that when 

all the scientific evidence is considered, the link between EMF exposure and cancer 

is weak. The World Health Organization in 1997 reached a similar conclusion. 

The two reports were the U.S. National Academy of Sciences report in 1996 and, in 

1999, the National Institute of Environmental Health Sciences report to the U.S. 

Congress at the end of the U.S. EMF Research and Public Information 

Dissemination (RAPID) Program. 

The U.S. EMF RAPID Program 

Initiated by the U.S. Congress and established by law in 1992, the 

U.S. EMF Research and Public Information Dissemination (EMF 

RAPID) Program set out to study whether exposure to electric and 

magnetic fields produced by the generation, transmission, or use of 

electric power posed a risk to human health. For more information 

about the EMF RAPID Program, visit the web site (http://www.niehs.nih.gov/ 

emfrapid). 

The U.S. Department of Energy (DOE) administered the overall EMF RAPID 

Program, but health effects research and risk assessment were supervised by the 

National Institute of Environmental Health Sciences (NIEHS), a branch of the U.S. 

National Institutes of Health (NIH). Together, DOE and NIEHS oversaw more than 

100 cellular and animal studies, as well as engineering and exposure assessment 

studies. Although the EMF RAPID Program did not fund any additional 

epidemiological studies, an analysis of the many studies already conducted was an 

important part of its final report. 

50 http://www.niehs.nih.gov/emfrapid June 2002 
EMF Reviews 

The electric power industry contributed about half, or $22.5 million, of the $45 

million eventually spent on EMF research over the course of the EMF RAPID 

Program. The NIEHS received $30.1 million from this program for research, public 

outreach, administration, and the health assessment evaluation of extremely low 

frequency (ELF) EMF. The DOE received approximately $15 million from this 

program for engineering and EMF mitigation research. The NIEHS contributed an 

additional $14.5 million for support of extramural and intramural research 

including long-term toxicity and 

EMF RAPID Program carcinogenicity studies conducted by 

Interagency Committee the National Toxicology Program. 

• National Institute of Environmental Health Sciences An interagency committee was • Department of Energy established by the President of the • Department of Defense United States to provide oversight • Department of Transportation and program management support • Environmental Protection Agency 

• Federal Energy Regulatory Commission for the EMF RAPID Program. The

• National Institute of Standards and Technology	 	 interagency committee included 

• Occupational Safety and Health Administration		 representatives from NIEHS, DOE, 

• Rural Electrification Administration		 and seven other federal agencies with 

EMF-related responsibilities. 

The EMF RAPID Program also received advice from a National EMF Advisory 

Committee (NEMFAC), which included representatives from citizen groups, labor, 

utilities, the National Academy of Sciences, and other groups. They met regularly with 

DOE and NIEHS staff to express their views. NEMFAC meetings were open to the 

public. The EMF RAPID Program sponsored citizen participation in some scientific 

meetings as well. A broad group of citizens reviewed all major public 

information materials produced for the program. 

NIEHS Working Group Report 1998 

In preparation for the EMF RAPID Program’s goal of reporting to the 

U.S. Congress on possible health effects from exposure to EMF from 

power lines, the NIEHS convened an expert working group in June 

1998. Over 9 days, about 30 scientists conducted a complete review of 

EMF studies, including those sponsored by the EMF RAPID Program 

and others. Their conclusions offered guidance to the NIEHS as it 

prepared its report to Congress. 

Using criteria developed by the International Agency for Research on 

Cancer, a majority of the members of the working group concluded that 

exposure to power-frequency EMF is a possible human carcinogen. 

The majority called their opinion “a conservative public health decision based on 

limited evidence for an increased occurrence of childhood leukemias and an increased 

occurrence of chronic lymphocytic leukemia (CLL) in occupational settings.” For these 

June 2002 http://www.niehs.nih.gov/emfrapid 51 
EMF Reviews 

diseases, the working group reported that animal and cellular studies neither confirm 

nor deny the epidemiological studies’ suggestion of a disease risk. This report is 

available on the NIEHS EMF RAPID web site (http://www.niehs.nih.gov/emfrapid). 

NIEHS Report to Congress at Conclusion of EMF RAPID Program 

In June 1999, the NIEHS reported to the U.S. Congress that scientific 

evidence for an EMF-cancer link is weak. 

The following are excerpts from the 1999 NIEHS report: 

The NIEHS believes that the probability that ELF-EMF exposure is truly a 

health hazard is currently small. The weak epidemiological associations and 

lack of any laboratory support for these associations provide only marginal, 

scientific support that exposure to this agent is causing any degree of harm. 

The scientific evidence suggesting that extremely low frequency EMF 

exposures pose any health risk is weak. The strongest evidence for health 

effects comes from associations observed in human populations with two 

forms of cancer: childhood leukemia and chronic lymphocytic leukemia in 

occupationally exposed adults. While the support from individual studies 

is weak, the epidemiological studies demonstrate, for some methods of 

measuring exposure, a fairly consistent pattern of a small, increased risk 

with increasing exposure that is somewhat weaker for chronic 

lymphocytic leukemia than for childhood leukemia. In contrast, the 

mechanistic studies and the animal toxicology literature fail to demonstrate any 

consistent pattern across studies, although sporadic findings of biological effects 

(including increased cancers in animals) have been reported. No indication of 

increased leukemias in experimental animals has been observed. 

The full report is available on the NIEHS EMF RAPID web site 

(http://www.niehs.nih.gov/emfrapid). 

No regulatory action was recommended or taken based on the NIEHS report. The NIEHS 

director, Dr. Kenneth Olden, told the Congress that, in his opinion, the conclusion of the 

NIEHS report was not sufficient to warrant aggressive regulatory action. 

The NIEHS did not recommend adopting EMF standards for electric appliances or 

burying electric power lines. Instead, it recommended providing public information 

about practical ways to reduce EMF exposure. The NIEHS also suggested that 

power companies and utilities “continue siting power lines to reduce exposures 

and . . . explore ways to reduce the creation of magnetic fields around transmission 

and distribution lines without creating new hazards.” The NIEHS encouraged 

manufacturers to reduce magnetic fields at a minimal cost, but noted that the risks 

do not warrant expensive redesign of electrical appliances. 

The NIEHS also encouraged individuals who are concerned about EMF in their homes 

to check to see if their homes are properly wired and grounded, since incorrect wiring 

or other code violations are a common source of higher-than-usual magnetic fields. 

52 http://www.niehs.nih.gov/emfrapid June 2002 
EMF Reviews 

National Academy of Sciences Report 

In October 1996, a National Research Council committee of the National Academy 

of Sciences (NAS) released its evaluation of research on potential associations 

between EMF exposure and cancer, reproduction, development, learning, and 

behavior. The report concluded: 

Based on a comprehensive evaluation of published studies relating to the effects of 

power-frequency electric and magnetic fields on cells, tissues, and organisms 

(including humans), the conclusion of the committee is that the current body of 

evidence does not show that exposure to these fields presents a human-health 

hazard. Specifically, no conclusive and consistent evidence shows that exposures to 

residential electric and magnetic fields produce cancer, adverse neurobehavioral 

effects, or reproductive and developmental effects. 

The NAS report focused primarily on the association of childhood leukemia with 

the proximity of the child’s home to power lines. The NAS panel found that 

although a link between EMF exposure and increased risk for childhood leukemia 

was observed in studies that had estimated EMF exposure using the wire code 

method (distance of home from power line), such a link was not found in studies 

that had included actual measurements of magnetic fields at the time of the study. 

The panel called for more research to pinpoint the unexplained factors causing 

small increases in childhood leukemia in houses close to power lines. 

World Health Organization International EMF Project 

The World Health Organization (WHO) International EMF Project, with 

headquarters in Geneva, Switzerland, was launched at a 1996 meeting with 

representatives of 23 countries attending. It was intended to respond to growing 

concerns in many member states over possible EMF health effects and to address the 

conflict between such concerns and technological and economic progress. In its 

advisory role, the WHO International EMF Project is now reviewing laboratory and 

epidemiological evidence, identifying gaps in scientific knowledge, developing an 

agenda for future research, and 

developing risk communication booklets 

and other public information. The WHO 

International EMF Project is funded with 

contributions from governments and 

institutions and is expected to provide an 

overall EMF health risk assessment. 

Additional information about this program 

can be found on the WHO EMF web site 

(http://www.who.int/peh-emf). 

As part of this project, in 1997 a working 

group of 45 scientists from around the 

world surveyed the evidence for adverse 

June 2002 http://www.niehs.nih.gov/emfrapid 53 
EMF Reviews 

EMF health effects. They reported that, “taken together, the findings of all 

published studies are suggestive of an association between childhood leukemia and 

estimates of ELF (extremely low frequency or power-frequency) magnetic fields.” 

Much like the 1996 U.S. NAS report, the WHO report noted that living in homes near 

power lines was associated with an approximate 1.5-fold excess risk of childhood 

leukemia. But unlike the NAS panel, WHO scientists had seen the results of the 1997 U.S. 

National Cancer Institute study of EMF and childhood leukemia (see page 17). This work 

showed even more strongly the inconsistency between results of studies that used a wire 

code to estimate EMF exposure and studies that actually measured magnetic fields. 

Regarding health effects other than cancer, the WHO scientists reported that the 

epidemiological studies “do not provide sufficient evidence to support an 

association between extremely-low-frequency magnetic-field exposure and adult 

cancers, pregnancy outcome, or neurobehavioural disorders.” 

World Health Organization International Agency for Research on Cancer 

The WHO International Agency for Research on Cancer (IARC) produces a 

monograph series that reviews the scientific evidence regarding potential 

carcinogenicity associated with exposure to environmental agents. An international 

scientific panel of 21 experts from 10 countries met in June 2001 to review the 

scientific evidence regarding the potential carcinogenicity of static and ELF 

(extremely low frequency or power-frequency) EMF. The panel categorized its 

conclusions for carcinogenicity based on the IARC classification system—a system 

that evaluates the strength of evidence from epidemiological, laboratory (human 

and cellular), and mechanistic studies. The panel classified power-frequency EMF 

as “possibly carcinogenic to humans” based on a fairly consistent statistical 

association between a doubling of risk of childhood leukemia and magnetic field 

exposure above 0.4 microtesla (0.4 μT, 4 milligauss or 4 mG). 

In contrast, they found no consistent evidence that childhood EMF exposures are 

associated with other types of cancer or that adult EMF exposures are associated with 

increased risk for any kind of cancer. The IARC panel reported that no consistent 

carcinogenic effects of EMF exposure have been observed in experimental animals and 

that there is currently no scientific explanation for the observed association between 

childhood leukemia and EMF exposure. Further information can be obtained at the 

IARC web sites (http://www.iarc.fr and http://monographs.iarc.fr). 

International Commission on Non-Ionizing Radiation Protection 

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) issued 

exposure guidelines to guard against known adverse effects such as stimulation of 

nerves and muscles at very high EMF levels, as well as shocks and burns caused by 

touching objects that conduct electricity (see page 47). In April 1998, ICNIRP revised 

its exposure guidelines and characterized as “unconvincing” the evidence for an 

association between everyday power-frequency EMF and cancer. 

54 http://www.niehs.nih.gov/emfrapid June 2002 
EMF Reviews 

European Union 

In 1996, a European Union (EU) advisory panel provided an overview of the state 

of science and standards among EU countries. With respect to power-frequency 

EMF, the panel members said that there is no clear evidence that exposure to EMF 

results in an increased risk of cancer. 

Australia—Radiation Advisory Committee Report to Parliament 

In 1997, Australia’s Radiation Advisory Committee briefly reviewed the EMF 

scientific literature and advised the Australian Parliament that, overall, there is 

insufficient evidence to come to a firm conclusion regarding possible health effects 

from exposure to power-frequency magnetic fields. 

The committee also reported that “the weight of opinion as expressed in the U.S. 

National Academy of Sciences report, and the negative results from the National 

Cancer Institute study (Linet et al., 1997) would seem to shift the balance of probability 

more towards there being no identifiable health effects” (see pages 17 and 53). 

Canada—Health Canada Report 

In December 1998, a working group of public health officers at Health Canada, the 

federal agency that manages Canada’s health care system, issued a review of the 

scientific literature regarding power-frequency EMF health effects. They found the 

evidence to be insufficient to conclude that EMF causes a risk of cancer. 

The report concluded that while EMF effects may be observed in biological systems 

in a laboratory, no adverse health effects have been demonstrated at the levels to 

which humans and animals are typically exposed. 

As for epidemiology, 25 years of study results are inconsistent and inconclusive, the 

panel said, and a plausible EMF-cancer mechanism is missing. Health Canada 

pledged to continue monitoring EMF research and to reassess this position as new 

information becomes available. 

Germany—Ordinance 26 

On January 1, 1997, Germany became the first nation to adopt a national rule 

on EMF exposure for the general public. Ordinance 26 applies only to facilities 

such as overhead and underground transmission and distribution lines, 

transformers, switchgear and overhead lines for electric-powered trains. Both 

electric (5 kV/m) and magnetic field exposure limits (1 Gauss) are high enough 

that they are unlikely to be encountered in ordinary daily life. The ordinance 

also requires that precautionary measures be taken on a case-by-case basis 

when electric facilities are sited or upgraded near homes, hospital, schools, 

day care centers, and playgrounds. 

June 2002 http://www.niehs.nih.gov/emfrapid 55 
EMF Reviews 

Q
 

A



Great Britain—National Radiological Protection Board Report 

The National Radiological Protection Board (NRPB) in Great Britain advises the 

government of the United Kingdom regarding standards of protection for exposure 

to non-ionizing radiation. The NRPB’s advisory group on non-ionizing radiation 

periodically reviews new developments in EMF research and reports its findings. 

Results of the advisory group’s latest review were published in 2001. The report 

reviewed residential and occupational epidemiological studies, as well as cellular, 

animal, and human volunteer studies that had been published. 

The advisory group noted that there is “some epidemiological evidence that 

prolonged exposure to higher levels of power frequency magnetic fields is associated 

with a small risk of leukaemia in children.” Specifically, the NRPB advisory group’s 

analysis suggests “that relatively heavy average exposures of 0.4 μT [4 mG] or more 

are associated with a doubling of the risk of leukaemia in children under 15 years of 

age.” The group pointed out, however, that laboratory experiments have provided 

“no good evidence that extremely low frequency electromagnetic fields are capable 

of producing cancer.” 

Scandinavia—EMF Developments 

In October 1995, a group of Swedish researchers and government officials published 

a report about EMF exposure in the workplace. This “Criteria Group” reviewed EMF 

scientific literature and, using the IARC classification system, ranked occupational 

EMF exposure as “possibly carcinogenic to humans.” They also endorsed the 

Swedish government’s 1994 policy statement that public exposure limits to EMFs 

were not needed, but that people might simply want to use caution with EMFs. 

In 1996, five Swedish government agencies further explained their precautionary 

advice about EMF. EMF exposure should be reduced, they said, but only when 

practical, without great inconvenience or cost. 

Health experts in Norway, Denmark, and Finland generally agreed in reviews 

published in the 1990s that if an EMF health risk exists, it is small. They 

acknowledged that a link between residential magnetic fields and childhood 

leukemia cannot be confirmed or denied. In 1994, several Norwegian government 

ministries also recommended increasing the distance between residences and 

electrical facilities, if it could be done at low cost and with little inconvenience. 

What other U.S. organizations have reported on EMF? 

American Medical Association 

In 1995, the American Medical Association advised physicians that no scientifically 

documented health risk had been associated with “usually occurring” EMF, based on 

a review of EMF epidemiological, laboratory studies, and major literature reviews. 

American Cancer Society 

In 1996, the American Cancer Society released a review of 20 years of EMF 

epidemiological research including occupational studies and residential studies of 

56 http://www.niehs.nih.gov/emfrapid June 2002 
EMF Reviews 

adult and childhood cancer. The society noted that some data support a possible 

relationship of magnetic field exposure with leukemia and brain cancer, but further 

research may not be justified if studies continue to find uncertain results. Of 

particular interest is the summary of results from eight studies of risk from use of 

household appliances with relatively high magnetic fields, such as electric blankets 

and electric razors. The summary suggested that there is no persuasive evidence for 

increased risk with more frequent or longer use of these appliances. 

American Physical Society 

The American Physical Society (APS) represents thousands of U.S. physicists. 

Responding to the NIEHS Working Group’s conclusion that EMF is a possible 

human carcinogen, the APS executive board voted in 1998 to reaffirm its 1995 

opinion that there is “no consistent, significant link between cancer and power 

line fields.” 

California’s Department of Health Services 

In 1996, California’s Department of Health Services (DHS) began an ambitious fiveyear effort to assess possible EMF public health risk and offer guidance to school 

administrators and other decision-makers. The California Electric and Magnetic Fields 

(EMF) Program is a research, education, and technical assistance program concerned 

with the possible health effects of EMF from power lines, appliances, and other uses of 

electricity. The program’s goal is to find a rational and fair approach to dealing with 

the potential risks, if any, of exposure to EMF. This is done through research, policy 

analysis, and education. The web site has educational materials on EMF and related 

health issues for individuals, schools, government agencies, and professional 

organizations (http://www.dhs.ca.gov/ps/deodc/ehib/emf). 

Q What can we conclude about EMF at this time? 

A Electricity is a beneficial part of our daily lives, but whenever electricity is

generated, transmitted, or used, electric and magnetic fields are created. Over the 

past 25 years, research has addressed the question of whether exposure to powerfrequency EMF might adversely affect human health. For most health outcomes, 

there is no evidence that EMF exposures have adverse effects. There is some 

evidence from epidemiology studies that exposure to power-frequency EMF is 

associated with an increased risk for childhood leukemia. This association is 

difficult to interpret in the absence of reproducible laboratory evidence or a 

scientific explanation that links magnetic fields with childhood leukemia. 

EMF exposures are complex and come from multiple sources in the home and 

workplace in addition to power lines. Although scientists are still debating whether 

EMF is a hazard to health, the NIEHS recommends continued education on ways of 

reducing exposures. This booklet has identified some EMF sources and some simple 

steps you can take to limit your exposure. For your own safety, it is important that 

any steps you take to reduce your exposures do not increase other obvious hazards 

such as those from electrocution or fire. At the current time in the United States, 

there are no federal standards for occupational or residential exposure to 60-Hz EMF. 

June 2002 http://www.niehs.nih.gov/emfrapid 57 
References 

7References 

Selected references on EMF topics. 

Basic Science 

Kovetz A. Electromagnetic Theory. New York: Oxford University Press (2000). 

Vanderlinde J. Classical Electromagnetic Theory. New York: Wiley (1993). 

EMF Levels and Exposures 

Dietrich FM & Jacobs WL. Survey and Assessment of Electric and Magnetic (EMF) 

Public Exposure in the Transportation Environment. Report of the U. S. Department of 

Transportation. NTIS Document PB99-130908. Arlington, VA: National Technical 

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Kaune WT. Assessing human exposure to power-frequency electric and magnetic fields. 

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