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11 Surprising Facts and Myths About Microwave Ovens

 A fixture in office break rooms, convenience stores and homes for decades, the microwave oven has been

heating frozen foods, leftovers and even more elaborate meals for decades. In fact, some hip urban restaurants

employ the familiar device to cook all their meals, from apps to entrees. Not only does this save energy and allow

the r estaurants to cope with small square footages in space-constrained districts, but it also offers a new retro-

novelty, giving a wow factor to those who aren't familiar with the appliance's true versatility.

Yet Google "are microwave ovens safe," and you'll get a barrage of hits from concerned mothers and others who

are worried that the handy device might have a dark, even dangerous side. Of course, the prevailing consensus

among scientists, public health experts, government agencies and the general public is that microwave ovens are

overwhelmingly safe when used as directed. However, it's also true that there may be some legitimate questions

about the safety of certain aspects of the technology, beyond the paranoia of the tin-foil hat crowd.

Let's take a closer look at some myths, facts and misconceptions about microwave ovens, which are estimated to

be used in at least 90% of American homes .

1. Microwave Ovens Were Discovered Accidentally

Status: Fact 

 Apparently no one thought of cooking food with microwaves until the 1940s, when a self-taught engineer named

Percy Spencer was building radar equipment in a lab for Raytheon, and noticed that a chocolate bar he had in his

pocket started to melt. He had been building magnetrons, and realized that microwaves can be directed at food to

heat it up rapidly. He tested his idea by popping popcorn and exploding an egg. Not long after we were all happily

scarfing down TV dinners.

2. There Is Dissent Over How Microwaves Actually Heat Food

Status: Fact 

Microwave radiation is a form of non-ionizing radiation (meaning it can't directly break up atoms or molecules) that

lies between common radio and infrared frequencies. So it is not thought to damage DNA of living things, the way

X and gamma rays do. Still, microwaves can obviously cause heating effects, and can harm or kill at high

energies. That's why microwave ovens on the market must operate at or below strict limits set by the federal

government.

Most microwave ovens hit food with microwaves at a frequency of 2.45 gigahertz (GHz) (a wavelength of 12.24

centimetres (4.82 in)). The prevailing belief is that molecules in the food, particularly water, absorb energy fromthe waves through dielectric heating. That is, since water molecules are polar, having a positive end and negative

end, they begin to rotate rapidly as the alternating electric field passes through. That rotation is thought to add

heat to the food.

However, there are some scientists who have dissented with this view, suggesting that other interactions between

the particles may be responsible for the heating.

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3. Microwave Ovens Cook Food from the

Inside Outside

Status: Myth 

 Although many people believe this to be the case,

microwaves actually work on the outer layers of food, heating

it by exciting the water molecules there. The inner parts of 

food are warmed as heat transfers from the outer layers

inward. This is why a microwave can only cook a big hunk of 

meat to a depth of about one inch inward.

4. Metals Get Dangerously Hot in

Microwaves

Status: Myth 

Metals reflect microwaves, whereas plastic, glass and ceramics allow them to pass through. That means metals

don't appreciably heat up in a microwave oven. However, thin pieces of metal, such as foils or the tines of a fork,

can act as antenna, and the waves can arc off them, forming dramatic sparks.

5. Microwave Ovens are Energy Efficient Ways to Cook

Status: Fact 

 A complete analysis of cooking efficiency depends on a number of factors, including what you are trying to prepar 

and the cost -- and greenness -- of your local supply of electricity, gas or other fuel. Typically though, a microwave

uses less energy to heat food than conventional ovens or ranges, because it works faster and more of the energy

is focused directly on the food, versus heating containers or surrounding air. In fact, Energy Star calculated that

cooking or re-heating small portions of food in the microwave saves as much as 80% of the energy needed for an

oven.

Don't get too excited, however. Consumer advocate Michael Bluejay pointed out to Earth Talk that even for 

someone who bakes three hours a week, using the cheapest cooking method would save only an estimated

$2.06/month compared to the most expensive method. "Focusing on cooking methods is not the way to save

electricity [at home]," says Bluejay. "You should look at heating, cooling, lighting and laundry instead."

6. You Can't Heat Oils in a Microwave

Status: Fact 

Oils such as olive oil do not heat well in microwaves because their molecules lack the polarity found in water. It's

also true that frozen butter is hard to thaw in a microwave, because the bulk of the substance is oil, and the

portion of water present is in the form of ice, which keeps the molecules locked up in crystal form, making

oscillation more difficult.

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7. Heating Plastics in a Microwave Can Be

Dangerous

Status: Fact 

The safest course of action is to avoid putting any plastics in

the microwave. When the Milwaukee Journal Sentinel  tested

plastics labeled microwave-safe and advertised for infants,

even those were found to release "toxic doses" of Bisphenol A

when heated in a microwave. "The amounts detected were at

levels that scientists have found cause neurological and

developmental damage in laboratory animals," the paper 

reports.

In fact, the term "microwave safe" is not regulated by the

government, so it has no verifiable meaning. According to the Journal Sentinel 's testing, BPA "is present in frozen

food trays, microwaveable soup containers and plastic baby food packaging." It is often found in plastics marked

No. 7, but may also be present in some plastics labeled with Nos. 1, 2 and 5 as well, according to the report.

Better to stick to glass or ceramics.

8. Boiling a Cup of Water in a Microwave Can Cause It to Explode

Status: Fact 

One potential danger of microwave ovens is getting scalded by over heated water . What can happen is that when

plain water is heated in a microwave in a clean ceramic or glass container for too long, it can prevent bubbles

from forming, which normally cool it down. The water can become superheated, past its boiling point. So when it is

disturbed, say by moving it or dropping something in it, the heat releases violently, erupting boiling water out of the

cup.

To avoid this risk heat water only the minimum amount of time needed. Or place a wooden spoon or stick in it (you

should be fine with a metal spoon too, as we discussed above. Don't use a metal fork though, which could spark.)

9. Microwave Cooking Can Be Unsafe Because It Doesn't Heat Evenly

Status: Fact 

 As we learned from Jim Gaffigan, microwaves don't always heat food evenly, sometimes leaving cold pockets

next to hot pockets. If you're working with raw meat, this can be dangerous, since it could leave harmful bacteria.

The Center for Science in the Public Interest has warned that consumers should follow heating instructions

carefully, including the standing time needed for additional cooking (in other words don't try to cool it off before yo

touch it).

10. Microwaves Leak Unsafe Levels of 

Electromagnetic Radiation

Status: Myth (at least most of the time) 

For decades scientists and consumers have been debating

over the possible effects of non-ionizing electromagnetic

radiation on living tissue. Since we can't very well grow

people in controlled lab experiments, it's very difficult to sort

out the various risks we might get from fields emitted frompower lines, cell phones, airplane flights, computers, clock

radios, and of course microwave ovens. We know strong

fields raise cancer rates and other problems, but what about

the cumulative effect of small exposure, or effects on

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children?

No one knows, although we can take heart that the FDA limits the amount of microwaves that can leak from an

oven throughout its lifetime to 5 milliwatts (mW) of microwave radiation per square centimeter, at approximately 2

inches from the oven surface. According to the agency, "This limit is far below the level known to harm people." It's

also true that microwave energy decreases dramatically as you move away from the source of radiation. A

measurement made 20 inches from an oven would be approximately one one-hundredth of value measured at 2

inches. The federal standard also requires all ovens to have two independent interlock systems that stop the

production of microwaves the moment the latch is released or the door opened.

In an interview with TDG, mechanical engineer Mark Connelly, the deputy technical director of Consumer Reports

said that the vast majority of microwave ovens his group has tested have shown "very little leakage of radiation."

Connelly echoed the advice of the FDA, which is that if people are concerned, they can simply step away from a

microwave oven when in use.

 Asked if people should avoid looking into a working microwave, since the eyes are known to be the most sensitive

to that form of radiation, and are known to develop cataracts at high field strengths, Connelly said he didn't think it

mattered, "since the window is shielded, and there shouldn't be leakage through that."

"If you are concerned, then go out and spend $20 on a testing kit to reassure yourself that there isn't any radiationleaking from your microwave," Connelly added. He said his testing of consumer-grade kits has shown them to be

reasonably reliable, despite some press accounts to the contrary. "Microwaves can wear over time, with gaskets

wearing or trouble developing in the door. So I think it's prudent to spend a little money to test them," he said.

11. Microwaves Alter Food in Undesirable, Possibly Unsafe, Ways

Status: Undetermined but Unlikely 

It's a fact of life that any type of cooking changes the chemistry of food. It can reduce the levels of some nutrients,

ust as it can increase the levels of others (e.g. lycopenes), or make them more or less available to the body for 

use. (Raw food anyone?) The prevailing view is that microwaves do not alter foods in ways that are any more

deleterious or harmful than other types of cooking. In fact, some have argued that the faster cooking time may

actually preserve more nutrients versus other methods.

Still, we know sufficiently little about nutrition and the cumulative effects of food science that some aren't so

convinced (of course, there is also the threat of any harmful substances present getting released upon cooking,

such as the diacetyl blamed for "popcorn lung.") In a recent article E Magazine pointed out that popular holistic

health expert Dr. Andrew Weil has written, "There may be dangers associated with microwaving food... there is a

question as to whether microwaving alters protein chemistry in ways that might be harmful." According to the

magazine, Dr. Fumio Watanabe of Japan's Kochi Women's University found that heating samples for six minutes

degenerated 30 to 40% of the milk's vitamin B12. This kind of breakdown took about 25 minutes of boiling with

conventional heat. In a 1992 Stanford Medical School study often cited by microwave opponents, researchersreported a "marked decrease" in immune-boosting factors in microwaved human breast milk. In the late 1980s

Swiss scientists reported decreases in hemoglobin and white blood cells in rats that had eaten microwaved food.

It's also much reported on the Internet that microwaving human blood renders it unsafe for transfusion -- though

medical professionals point out that rapidly heating blood via any method can have the same negative result.

The conclusion made by government agencies and mainstream organizations is that microwaved food is safe, as

well as convenient. There's a limited number of studies that may suggest otherwise, but given the lack of large-

scale or compelling evidence it's hard to feel that tossing our your microwave is a particularly smart step.

Everyone interviewed for this piece pointed to other issues as more pressing, from ubiquitous exposure to cell

phones to more serious threats from radon, or bigger energy users like heating and cooling. That doesn't meanmicrowaves aren't worth thinking about, however.

 And what are microwaves good for?

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