MICROWAVES used in microwave ovens oscillate at 2450 million cycles per second
(MHz). On the
frequency spectrum
, that region is located at the lower end of the radar band, slightly above the
frequencies used for UHF (ultra-high frequencies) TV channels, and safely
within the
NON-ionizing region.
However, it is important to note: Although microwaves do not carry enough
energy to be
ionizing,
they can be dangerous.
For example, if the lens of the eye were exposed to excessive heat from
microwaves, its circulatory system would be unable to provide sufficient
cooling, and it would cook like the white of an egg. Also, the stomach,
intestines, and bladder are especially sensitive to thermal damage from high
levels of microwaves. Similarly, the testes are very sensitive to changes in
temperature, because sperm can be formed only at temperatures lower than that
of the body itself. Therefore, accidental exposure to high levels of microwave
energy can alter or kill sperm, producing temporary sterility.
The effects of long term exposure to low levels of microwaves, and their
significance to human health, will become clear only after large numbers of
people who are being exposed to microwaves are studied for many years. Studies
are being done with animals, but it is difficult to translate the effects of
microwaves on animals to possible effects on humans. With animals, for example,
researchers find it difficult to simulate the conditions under which people use
microwave ovens. Because no one can say with certainty what levels of exposure
are save, the course of wisdom is, as one U.S. Government spokesman pointed
out, to avoid "exposure to any unneeded radiation.
Inasmuch as the significance for humans of repeated exposure to low levels of
microwave radiation is still unclear, there is enough evidence to warrant
certain commonsense precautions:
If microwaves can cook a piece of beef, these waves will also have the same
effect on human tissue if it is exposed to high enough intensities for a long
enough period of time. Certain body organs are particularly sensitive to this
thermal
effect. "Thermal" means heat. Thus, it is the heat produced by a hot stove
that causes the careless cook to utter a sudden unsavory expletive. Likewise,
it is the heat generated by the microwaves that creates the hazard in this case.
What Are Safe Levels of Exposure?
No one really knows for sure. Several American laboratories have found that low
level exposure to microwaves can cause cumulative effects to the eyes,
resulting in cataracts. Research also reports a reduction in personnel
efficiency, and even a possible link to cancer. As painstaking experimentation
continues, one thing is certain: There is a
non-thermal
effect from microwaves that many people are exposed to on a daily basis. What
degree of danger does this non-thermal effect represent? The answer to that
question has to do with the controversial difference between a simple
biological
effect
, and a serious biological
hazard.
For example, a reduction in the ability to perform certain tasks may be the
effect, but at what point does that effect constitute a hazard?
How Far Away Is Safe?
One pertinent characteristic of microwaves is that they disperse and dissipate
very quickly in the atmosphere. Under Federal guidelines set by the Department
of Health and Human Services (DHHS), the maximum allowable leakage from a
microwave oven [after the sale] is 5 milliwatts [or 5 thousandths of a watt]
per square centimeter [or within the area the size of an aspirin tablet], as
measured at about 2 inches from the oven surface. However, as you move away
from the oven, the level of exposure to any energy that may be leaking
decreases dramatically. This may be likened to the difference between holding
your hand just inches above a burning candle, and then moving it 10 or 12
inches away. To illustrate: Let's say you are standing just 2 inches away from
an operating microwave where you are being zapped by 5 milliwatts of microwave
radiation. Then, you wisely step back to a distance of 20 inches, or roughly an
arm's length away. Your level of exposure would drop by a factor of 100 [the
square of the distance] to an infinitesimal .05 milliwatts. When you consider
that the typical cooking power of a microwave oven is in the range 600 to 700
watts, and even higher in some models, .05 milliwatts is clearly a tiny amount.
Unsettling Reports
Yet, the question remains: Is exposure to low levels of microwave radiation
dangerous to humans? Soviet research has yielded some rather unsettling
reports. Rather than concentrating on the effects of high-intensity levels,
scientists in the U.S.S.R have focused their efforts on the effects of
prolonged or repeated exposure to low levels of microwaves. Their studies show
that long-term exposure to low levels of microwave energy could result in
unpleasant effects that are not attributable to the thermal (heating) effect
alone. So, the U.S.S.R and other European countries have set their own strict
guidelines for microwave safety, concluding that Western safety standards are
simply not safe. For instance, Russian workers are required to wear special
goggles any time they are temporarily exposed to a microwave radiation level of
1 milliwatt per square centimeter. Remember, the U.S. Federal Standard is 5
milliwatts per square centimeter. (It should be noted that some manufacturers
have voluntarily established their own, more stringent, standards. For example,
Amana, Menumaster, Caloric, Modern Maid, and Sharp have lowered the maximum
allowable leakage from 5 mw/cm
2
to 4 mw/cm
2
.)
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