OSHA Hazard Information Bulletins
February 7, 1990
| MEMORANDUM FOR: |
REGIONAL ADMINISTRATORS |
| THRU: |
LEO CAREY
Director
Directorate of Field Programs |
| FROM: |
Barry J. White
Director
Directorate of Technical Support |
| SUBJECT: |
Hazard Information Bulletin - The Effects of Exposure to
Extremely Low Frequency (ELF) Electromagnetic Radiation |
The purpose of this bulletin is to present a review of health effects data
associated with extremely low frequency (ELF) electromagnetic (em) radiation
exposure as found in current publications. Findings addressed in this
bulletin do not reflect any Occupational Safety and Health Administration
(OSHA) position on em hazards.
Recently, public and employee concerns have been expressed about ELF
exposure as a result of media coverage over the last few years. An example
of such coverage is the detailed evaluation of em publications published by
Savitz in 1987. Savitz's analysis deals with potential adverse effects of
ELF fields, but it is probably equally applicable to the entire em
field-cancer case study literature(1). The issue of ELF bioeffects is very
controversial with few safety and health organizations having adopted
exposure limits. ELF radiation, a part of the em spectrum, discussed in this
bulletin is confined to the nonionizing frequency range up to 300 gigahertz
(GHz). Of particular interest is the 50 to 60 Hz range which is associated
with electrical power distribution, and equipment utilizing alternating
current.
ELF radiation is comprised of both electric and magnetic fields and occur
naturally in the environment(2). The generation of em radiation is often
unintentional as in the case of motors and fluorescent light or deliberate
for a specific application such as television equipment. Irradiation of
biological systems with em energy under certain conditions leads to
temperature elevations when the rate of energy absorption exceeds the rate of
energy dissipation(3). Biological changes that occur during ELF exposure
(which is not readily absorbed, and therefore does not normally cause
significant temperature elevation) have not been well documented.
The human body contains free electric charges (largely in ion-rich fluids
such as blood and lymph) that move in response to forces exerted by charges
on and current flowing in nearby conductors, such as power lines and the
wiring of appliances (see figures 1 and 2). The processes that produce these
body currents are called electric and magnetic induction. In electric
induction, charges on a power line or appliances attract or repel free
charges within the body. Since body fluids are good conductors of
electricity, charges in the body move to its surface under the influence of
this electric force. The nature of magnetic fields are greater near the
periphery of the body and smaller at the center of the body. Because
magnetic fields have only recently become a human health concern, data on the
detailed distribution of magnetically induced currents in human and animals
are quite sparse compared to the information available on electric induction.
Human exposure to em radiation from natural sources is often considered
small by comparison to that of industrial sources. Recently some research has
shown a potential risk of cancer due to exposure to em radiation. For
example in one of many conflicting research efforts, higher incidents of
cancer were observed among children who lived in the vicinity of high voltage
electric power lines. These lines surrounded by fields of extremely low
frequency electromagnetic energy were statistically linked to clusters of
cancer among children. Research also indicates that em radiation can have
varying effects on the human body dependent upon wavelength, intensity, and
length of exposure.
As a result of our review of existing publications on em radiation, we have
concluded that most research on occupational exposure to em radiation has
been conducted using small laboratory animals. Controlled research studies
on human exposure was also conducted. Most of the studies on human exposure
to em radiation suffer from limitations: (1) Exposure for therapeutic
purposes, namely partial body irradiation at high-intensities for relatively
short periods of time is not representative of occupational exposure
conditions. (2) Differences in methodologies used in different states make a
comparison difficult if not impossible. (3) Errors in estimating field
strength to which personnel were exposed due to the lack of adequate
instrumentation. Nevertheless these studies show that the chief organs
formerly thought to be at risk from exposure to em radiation, the skin, eyes,
and ears, may not be the only ones effected. The roll em radiation plays in
causing cancer is not yet defined.
For your information, an article by Slesin indicated that a 1988,
epidemiological study by Dr. Marjorie Speers and others, showed the potential
risk of brain tumors among workers exposed to electromagnetic fields(5).
This work seems to support earlier studies conducted by Dr. Samuel Milham,
Jr. (Washington State Department of Social and Health Services in Olympia)
and Dr. Ruey Lin (National Taiwan University in Taipei)(6) Another example is
a June, 1988, Seattle, Washington, court case in which an electronic
technician diagnosed with leukemia filed a suit against his employer claiming
that his condition was a result of exposure to electromagnetic radiation(7).
A third example is presented in a research conducted by Doctors Harry Brown
and Swaraj Chattopadhyay (Rutgers University) concluding that exposure to
nonionizing radiation can play a role in cancer.
On the other hand, in 1987, the Hazard Evaluation and Technical Assistance
Branch of the National Institute for Occupation Safety and Health (NIOSH)
conducted a field investigation into possible health hazards at an
acceleration laboratory(9). NIOSH's report addressed both radio frequency
(rf) and static magnetic fields. The report at its conclusion indicates that
evidence that rf radiation alone can produce cancer was weak but it might act
as a cancer promoter in animals.
As you can see, there is no consensus on the potential hazard of exposure to
em radiation. Additional human exposure research should help in
understanding the transmission, and interaction mechanism of em radiation
with the exposed worker as well as, how to detect and quantify this field,
and how to protect workers from em radiation effects. Most experts agree
that more research on human exposures to this type of radiation is needed.
In conclusion, it is clear that further epidemiological studies and research
into biological effects of em radiation and magnetic field (including
chemical reaction in the body) is needed to fully understand and determine
all health effects resulting from exposure cases. Cases involving exposure
to em radiation should be considered on a case by case basis taking into
consideration the circumstances surrounding it. It is premature to enforce
specific guidelines for exposure to ELF radiation. However, a program which
addresses ELF hazards identification and training is encouraged.
For your information, we are attaching a bibliography of the health effect
publications on em radiation published since 1980. Please distribute this
bulletin to area offices, state plan states and consultation projects.
__________
FOOTNOTE(1)Savitz, D.A. and Calle, E.E., Journal of Occupational Medicine 29
"Leukemia and Occupational Exposure to Electromagnetic Fields: Review of
Epidemiologic Surveys," pages 47-51, 1987.
FOOTNOTE(2)National Council on Radiation Protection and Measurements, Radio
frequency Electromagnetic Fields, Properties, Qualities and Units,
Biophysical Interaction and Measurement, page 19, March, 1989.
FOOTNOTE(3)Suess, M.J., Copenhagen: World Health Organization Regional
Office for Europe: Non-ionizing Radiation Protection, page 104, 1982.
FOOTNOTE(4)Brown, H. D and Chattopadhyay, S.K., Cancer Biochemistry
Biophysics, "Electromagnetic - Field Exposure and Cancer," page 297, May,
1988.
FOOTNOTE(5)Slesin, Louis. Microwave News: "A Report on Nonionizing
Radiation," Page 1, July / August, 1988.
FOOTNOTE(6)and(7)Siesin, Louis. Microwave News: "Support for Radio Operator
Cancer Risk," page 2, January / February, 1989.
FOOTNOTE(8)Brown, H.D and Chattopadhyay, S.K., Cancer Biochemistry
Biophysics, "Electromagnetic - Field Exposure and Cancer," page 297, May,
1988.
FOOTNOTE(9)National Institute For Occupational Safety and Health (NIOSH),
Cincinnati Ohio, Health Hazard Evaluation Report number HETA 87-329, page 5,
1989.
Attachments:
Alternating Current:
Figure 1: A schematic representation of the pattern of currents induced in
the body of a person standing under a transmission line by the alternating
magnetic field set up by the current flowing in that line. A 60 Hz magnetic
field with a flux density of one gauss will induce currents in the periphery
of the body with a current density of about 100 nanoAmps per square
centimeter. The current density at the center of the body is zero. (From:
Biological Effects of Power Frequency Electric and Magnetic Fields. U.S.
Congress Report No. OTA-BP-E-53)
Figure 2: A schematic representation of the surface charges and internal
currents that are electrically induced by the charges on an overhead
powerline in a person under the line whose feet are well-grounded. The total
current induced to flow from each foot to ground is about 8 microamps per
kV/m of applied field (1 microamp is 1 millionth of an ampere). The density
of electrically-induced current is the amount of current that passes through
a body cross-section perpendicular to the direction of current flow. The
current density induced by a 1 kV/m vertical electric field is about 30
nanoamps per square centimeter averaged over the entire volume of the body.
One nanoamp is 1 billionth of an ampere. (From: Biological Effects of Power
Frequency Electric and Magnetic Fields. U.S. Congress Report No. OTA-BP-E-53)
Bibliography
AU - Author TI - Title SI - Source NIOSH Computerized Index Number SO -
Source
AU - Servanties B TI - Damase criteria for determining microwave exposure.
SI - TOXBIB/89/213413 SO - Health Phys; vol 56, iss 5, 1989, p781-786 (ref:
15)
AU - Kolmodin-Hedman B AU - Hansson Mild K AU - Hasbers M AU - Jonsson E AU
- Andersson M-C AU - Eriksson A TI - Health Problems Among Operators of
Plastic Welding Machines and Exposure to Radio frequency Electromagnetic
Fields SI - NIOSH/00181953 SO - International Archives of Occupational and
Environmental Health, Vol. 60,No.4, pages 243-247, 16 references, 1988
AU - Knave B AU - Floderus B TI - Exposure to Low-Frequency Electromagnetic
Fields A Health Hazard SI - NIOSH/00181593 SO - Scandinavian Journal of Work,
Environment and Health, Vol. 14, Supplement 1, pages 46-48, 11 references,
1988
AU - Aldrich TE AU - Easterly CE TI - Electromagnetic Fields and Public
Health SI - NIOSH/00179613 - SO - Environmental Health Perspectives, Vol. 75,
pages 159-171, 13 references, 1987
AU - Anonymous TI - Guidelines on Limits of Exposure to Radiofrequency
Electromagnetic Fields in the Frequency Range from 100 KHz to 300 GHz SI -
NIOSH /00179608 SO - Health Physics, Vol. 54, No. 1, Pages 115-123, 34
references, 1988
AU - Bowman JD AU - Garabrant DH AU - Sobel E AU - Peters JM TI - Exposures
to Extremely Low Frequency (ELF) Electromagnetic Fields in Occupations with
Elevated Leukemia Rates SI - NIOSH/00180633 SO - Applied Industrial HYgiene,
Vol. 3, No. 6, pages 189-194, 38 references, 1988
AU - Castillo M AU - Quencer PM TI - Sublethal Exposure to Microwave Radar
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259, No. 3, pages 355, 3 references, 1988
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the Health Physics Society, Boston, Massachusetts, USA, July 4-8, 1988.
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Occupational Hazards From Non-ionizing Electromagnetic Radiation SI - The
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Occupational Safety and Health Series No. 53.,1985
AU - Kolmodin-Hedman B AU - Mild KH AU - Hagberg M AU - Jonsson E AU -
Andersson M-c AU - Eriksson A TI - Health Problems Among Operators of Plastic
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Technology Assessment Washington, D.C 20510-8025 May, 1989
AU - PAZ JD AU - Milliken R AU - Ingram WT AU - Frank A AU - Atkin A TI -
Potential Ocular Damage From Microwave Exposure During Electrosurgery:
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TI - Case-control study of Childhood Cancer and Exposure to 60-Hz Magnetic
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