EMFs In The Workplace
Everyone in our modern society is exposed to the electric and magnetic fields (EMFs)
that surround all electric devices. Recently, scientific studies have raised questions
about the possible health effects of EMFs. This fact sheet answers frequently asked
questions about EMFs in the workplace. You can use this information to help identify
EMF sources at work and to take simple steps for reducing exposures. However, you
cannot use this information to judge the safety of your exposures, since the scientific
evidence does not yet show whether EMF exposures are hazardous.
What are EMFs?
EMFs are invisible lines of force created whenever electricity is generated or used.
EMFs are produced by power lines, electric wiring, and electric equipment and
appliances. The frequency of EMFs is measured in hertz (Hz, or cycles per second).
People are exposed to both electric and magnetic fields, but scientists are most
concerned about magnetic fields. This fact sheet deals only with magnetic fields that
have frequencies near 60 Hz the frequency of electric power in North America.
Static magnetic field
around a bar magnet.
What do we know about workplace
exposures to EMFs?
Workers may be exposed to high magnetic fields if they work near electrical systems
that use large amounts of electric power (for example, large electric motors,
generators, or the power supply or electric cables of a building). High magnetic fields
are also found near power saws, drills, copy machines, electric pencil sharpeners, and
other small electric appliances. The strength of the magnetic field depends on
equipment design and current flow not on equipment size, complexity, or voltage.
Though some electric equipment produces EMFs of other frequencies, most health
research has considered only frequencies near 60 Hz.
These electric heaters for metal parts expose workers to magnetic fields
that are 10,000 times greater than the average magnetic fields found outside
the workplace.
What are some typical EMF
exposures on the job?
The EMF exposures for many jobs have not been measured, but the following table
shows average exposures to magnetic fields for typical workers who use electric
equipment. Exposures during a work shift vary with the strength of the magnetic field,
the worker s distance from the EMF source, and the time the worker spends in the
field. For comparison, the table also lists worker exposures off the job.
Average magnetic field
exposures for various types
of workers
(in milligauss)*
Average daily exposures
Type of worker Median** Range
Workers on the job:
Clerical workers without
computers 0.5 0.2 - 2.0
Clerical workers with
computers 1.2 0.5 - 4.5
Machinists 1.9 0.6 - 27.6
Electric line workers 2.5 0.5 - 34.8
Electricians 5.4 0.8 - 34.0
Welders 8.2 1.7 - 96.0
Workers off the job
(home, travel, etc.) 0.9 0.3 - 3.7
*Magnetic fields are often measured in gauss or milligauss (one thousandth of a gauss
= 1 milligauss).
**The median is the middle measurement: half the workers have average daily
exposures above this point and half below.
Do EMFs cause cancer
or other health effects?
Studies have shown that some workers exposed to high magnetic fields have increased
cancer rates. But such associations do not necessarily show that EMF exposures cause
cancer (any more than the springtime association of robins and daffodils shows that one
causes the other). Scientists have looked carefully at all the EMF evidence, but they
disagree about the health effects of EMFs except to say that better information is
needed.
What DO studies show
about the health effects
of
EMFs in workers?
No increased leukemia has been reported overall in studies of welders, yet they are
among the occupations with the highest EMF exposures.
Have limits been
set for worker
exposures to EMFs?
Because of the scientific uncertainty, no Federal limits for worker exposures to EMFs
have been recommended or established in the United States. Two private organizations
have developed guidelines to protect workers from the known effects of extremely high
exposures (that is, those more than 1,000 times the exposures typically found in
occupational environments). However, these guidelines do not address the possible
health effects of the low EMF exposures usually found on the job.
Should workers and
employers try to
reduce exposures to EMFs?
The National Institute for Occupational Safety and Health (NIOSH) and other
government agencies do not consider EMFs a proven health hazard. Because some
studies have associated high magnetic field exposures with increased cancer risks, the
government will continue studying EMFs. While research continues, concerned
workers and employers might consider the following simple, inexpensive measures for
reducing EMF exposures:
- Inform workers and employers about possible hazards of magnetic fields.
- Increase the worker's distance from the EMF source. Since magnetic fields
often drop off dramatically within about 3 feet of the source, workers can stand
back from electrical equipment, and work stations can be moved out of the 3-ft
range of stronger EMF sources.
- Use low-EMF designs wherever possible (for the layout of office power
supplies, for example).
- Reduce EMF exposure times. No action should be taken to reduce EMF
exposure if it increases the risk of a known safety or health hazard such as
electrocution.
EMF exposures depend on the worker's distance from the source.
What is NIOSH doing
about EMF exposures?
NIOSH has been evaluating the possible health effects of EMFs since 1991. NIOSH
scientists have measured the fields in workplaces where employees are concerned about
their EMF exposures; they are also studying the biological effects of EMFs. In
addition, NIOSH scientists work cooperatively with researchers in universities and
other Federal agencies to share their study results. These cooperative efforts have
increased recently under the National EMF Research and Public Information
Dissemination (RAPID) program.