Unlike ionizing radiation, nonionizing radiation does not have enough photon energy
to remove an electron from an atom. However, it can still be hazardous. For example:
Extremely low-frequency electric and magnetic fields (EMFs) surround electrical
machinery, home appliances, electric wiring, and high-voltage electrical transmission
lines and transformers. (Figure 11)
A good deal of public and government attention has been focused in recent years
on the possible health effects of EMFs. The public is exposed to these fields through
the generation, transmission, and use of electric power. The National Institute
of Environmental Health Sciences (NIEHS), a branch of the National Institutes of
Health (NIH), has compiled information on this issue. (You can get more information
on this and other issues from the NIEHS Web site http://www.niehs.nih.gov/emfrapid)
High-voltage power transmission and distribution lines have been a major focus of
concern. Alternating-current (AC) electricity, with a frequency of 60 cycles per
second, falls into the extremely low frequency range on the electromagnetic spectrum
and thus has far too little energy to cause ionization.
However, AC electric and magnetic fields can induce electric currents in conducting
materials, including human and animal tissue. (Direct-current fields, such as the
Earth's magnetic field, do not have this effect). The electric current induced in
our bodies may have potential biological and health effects.
Evidence of health effects from EMF is inconclusive, although some studies have
indicated a possible link between EMFs and childhood leukemia and other forms of
cancer. The information available, however, is not sufficient to establish a cause-effect
relationship.
Some studies have reported the possibility of increased cancer risks, especially
leukemia and brain cancer, for electrical workers and others whose jobs require
them to be around electrical equipment. Additional risk factors, however, such as
exposure to cancer-initiating agents, may also be involved.
Some researchers have looked at possible associations between EMF exposure and breast
cancer, miscarriages, depression, suicides, Alzheimer's disease, and Amyotrophic
Lateral Sclerosis (ALS, or Lou Gehrig's Disease), but the general scientific consensus
is that the evidence is not yet conclusive.
In June of 1998, a special review panel convened by the NIEHS reviewed EMF health
studies. A majority of the panel found "limited evidence that residential exposure
to extremely low frequency magnetic fields may increase the risk of childhood leukemia."
A majority also found limited evidence that workplace exposure to EMFs may cause
chronic lymphocytic leukemia in adults.
According to NIEHS, "the probability that 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 NIEHS did conclude, however, in
its 1999 Report to Congress, that extremely-low-frequency EMF exposure cannot be
recognized as entirely safe because of weak scientific evidence that exposure may
pose a leukemia hazard; the associations reported for childhood leukemia and adult
chronic lymphocytic leukemia cannot be dismissed easily as random or negative findings.
On the positive side, the NIEHS panel found "strong evidence" that exposure to electric
and magnetic fields can speed the healing of broken bones.
How can individuals reduce exposure? People concerned about their own exposure can
take several steps to reduce it. Except in certain cases, most people's greatest
exposure to EMFs may come from sources inside the home, rather than from power lines
outside it. The NIEHS suggests avoiding standing too close to computers, microwave
ovens, televisions, or other devices that may emit EMFs. People can reduce exposure
to EMFs by turning off devices such as electric blankets when they are not in use
and by not keeping devices such as electric alarm clocks too close to the bed. Adults
can discourage children from playing near high power lines or electrical transformers.
The distance from a source of EMFs is important because the intensity of EMFs decreases
proportionally to the square of the distance to their source. So doubling your distance
from a source will reduce exposure to one-quarter of its previous level. There are
no federal health standards governing public exposure to EMFs. A few states, however,
have set standards for transmission line electric and magnetic fields.
Radio-Frequency (RF)
and Cellular Phones
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Figure 12. Use of Cellular Phones Has Become
Part of Many People's Daily Lives
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As hand-held cellular telephones become increasingly popular, people are understandably
concerned about potential health effects from exposure to high-frequency radio waves.
(Figure 12)
The radio waves used by analog and digital cellular phones are much higher frequency
than the electric and magnetic fields produced by power lines, so their biological
effects are different from the possible effects of EMFs.
Studies have shown that intense exposure to this type of nonionizing radiation can
cause heat-related effects such as cataracts, skin burns, deep burns, heat exhaustion,
and heat stroke, as well as electrical shock.
As a result of the studies, the United States and other countries have established
standards to protect workers and the public from the known effects of excess exposure
to the radio waves used in telecommunications. The antennas of cell-phone base stations
and personal cell phones must comply with these standards.
Most epidemiological studies have found no significant correlation between exposure
to radio frequency (RF) radiation and an increased risk of cancer. One animal study
at the University of Adelaide in Australia, showed that mice genetically predisposed
to a type of cancer developed twice as many cancers when exposed to cell phone radiation.
This study is being repeated at the University of Adelaide and other research laboratories
to verify the finding.
The Food and Drug Administration (FDA), responsible for protecting the public from
radiation exposure from consumer products, said that "the available science does
not allow us to conclude that mobile phones are absolutely safe, or that they are
unsafe. However, the available evidence does not demonstrate any adverse health
effects associated with the use of mobile phones."
December 2, 2002
