OT Fwd: Radiation Emissions From Microwave Ovens

[Guest guest]

[Note: Today, many quite unfounded scares about modern

technology are being disseminated, either directly by the

ruling persons (by their mass media above all) or by some

puppets of theirs who pretend they're " against " them, or

both. The reasons for this are political - the persons in

power would prefer to have the world regress to " them good

old days " when there were no such big challenges to those

persons by " ordinary people " as there are today. The article

I'm forwarding here is by a governmental " radiation protec-

tion " agency (one in Australia). Experience shows that such

agencies today always tend to overstate dangers from radia-

tion - ionizing or non-ionizing such - and never tend to

underestimate them. - Quite another matter are vaccinations.

These really are harmful, and the same ruling persons, out

of the same political motives of wanting terror against

ordinary people, are very busy too trying to convince every-

body how " useful " and " harmless " they are. - Rolf M.]

Article by: Australian Radiation Protection and Nuclear

Safety Agency,

at http://www.arpansa.gov.au/is_mwave.htm

Radiation Emissions From Microwave Ovens

Introduction

Microwave ovens use microwave radiation to cook food, either

in the home or in commercial or other premises. There is no

evidence to suggest that microwave ovens when used according

to the manufacturer's instructions, and maintained in good

working order will be a radiation hazard. Some features of

microwave ovens and precautions in their use are described

below.

The Australian Radiation Protection and Nuclear Safety

Agency monitors potential radiation hazards arising from

consumer products and equipment used in industry and

evaluates possible public radiation health risks arising from

their use.

What are Microwaves?

Microwaves, like visible light, are a part of the

electromagnetic radiation spectrum. They are extremely high

frequency radio waves. As the frequency of radiation

increases, its wavelength decreases, so very high frequencies

correspond to very short wavelengths; hence the name

microwaves. Infrared radiation, ultraviolet light and X-rays

are also electromagnetic radiations, but have even shorter

wavelengths than microwaves.

Microwaves may either be reflected, transmitted or absorbed

by matter in their path. Metallic materials totally reflect

microwaves. Most non-metallic materials such as glass and

plastics are partially transparent to microwaves. Material

containing moisture, such as food and even people, absorbs

microwave energy. If energy is absorbed at a rate greater

than the rate at which the material looses energy (ie. rate

of cooling), its temperature will increase.

What are Microwaves used for?

Some of the more common uses of microwaves include satellite

communications, mobile phones, radar, air and sea

navigational aids. Other applications include industrial

heating and therapeutic diathermy treatment.

The use of microwave ovens in industrial, commercial,

domestic and other premises has increased substantially over

recent decades. This brochure refers only to domestic-type

microwave ovens intended for use in the home or workplace

staff rooms.

How do Microwave Ovens work?

In the microwave oven, an electronic device called a

magnetron is used to produce the microwaves. These microwaves

have a frequency of 2,450 MHz1 . The microwaves then pass

into the enclosed metal oven cavity where they are reflected

around the oven walls and absorbed in food or drink placed

in the oven. Uneven absorption may caused localised " hot

spots " .

The microwaves penetrate the food or liquid and agitate the

water molecules within. This causes molecular friction, which

produces heat and results in a rapid rise in temperature.

Cooking time is usually much shorter than in a conventional

oven. The rate of heating depends on the moisture content,

shape, volume and mass of food present. Uneven heating can

occur in some foods where the outside may be only warm while

the inside may be close to boiling (jam filled donuts or meat

pies are examples). In other foods, some parts will be

cooked, while others are not. Some parts of frozen food may

remain frozen if insufficient time is allowed for the heating

process.

The oven walls and most non-metallic cooking utensils are not

directly heated by microwaves because they do not absorb

microwave energy. However, the inside of the oven will feel

warm due to the presence of the hot food and heat from the

electrical circuits.

What are the health issues of Microwave exposure?

Exposure to sufficiently high levels of microwaves will cause

heating. In the case of human tissue, excessive heating could

have serious health effects such as deep tissue burns and

hyperthermia. The purpose of Australian Standards is to avoid

all known adverse health effects by limiting exposures to

levels below those at which heating occurs.

Extensive research has provided no substantiated evidence

that microwave exposure, at any level, either causes or

promotes cancer.

How safe are Microwave Ovens?

Microwaves generated in microwave ovens cease to exist once

the electrical power to the magnetron is turned off (like

visible light from light globes). They do not remain in the

food when the power is turned off. Neither can they make the

food or the oven radioactive. Therefore, food cooked in a

microwave oven is not a radiation hazard.

All microwave ovens have at least two safety interlock

switches which stop the generation of microwaves immediately

the door is opened. The design of modern microwave ovens is

such that the microwaves should be contained within the

oven, but it is still possible for some leakage to occur

around the doors of certain microwave ovens. Generally, the

required design of oven doors should restrict this leakage

to a level well below that recommended by the Australian/

New Zealand Standard AS/NZS60335.2.25:2002 Household and

similar electrical appliances – Safety Part 2.25: Particular

requirements - Microwave ovens.

The Standard specifies a test to assess the level of

microwave leakage and states that 'The microwave leakage at

any point 50 millimetres or more from the external surface of

the appliance shall not exceed 50 watts per square metre'.

This Standard applies to ovens designed for domestic

applications, even if used in a workplace. The recommended

limit is conservative and includes significant safety

factors, so that even leakage levels appreciably above the

limit will have no known effect on human health.

Surveys by organisations providing testing services have

shown that microwave oven leakage levels in excess of the

recommended limits are rare and an oven in good condition

and used correctly is safe. If an oven appears damaged, it

should not be used until a suitably experienced technician

has tested the oven and checked that the leakage does not

exceed the recommended limit. Routine testing of microwave

oven leakage is not considered necessary.

Cardiac Pacemakers

Even when very close to a microwave oven, modern pacemakers

are not likely to be susceptible to interference where

leakage levels are within the recommended limits. Persons

with pacemakers should obtain and rely on their own medical

advice in this respect. Additional advice is available from

the Therapeutic Goods Administration.

Cooking Containers and Foils

Plastic containers considered suitable for holding foods at

room temperature may not necessarily be suitable for use in

a microwave oven. The high cooking temperatures may cause the

plastic's chemistry to break down and thereby contaminate

food in the container. Since it is difficult to determine the

composition of plastic from its appearance, it is recommended

that plastic containers or films not be used in a microwave

oven unless specifically designated for such use. Any

questions about such products should be directed to the

manufacturer.

Most ceramics, glass-ceramics, some plastics and papers are

satisfactory for microwave oven use. Dishes with metallic

glazes should not be used. If fast food foil containers and

aluminium foil are used, the oven manufacturer's directions

should be carefully followed. Do not let fast food foil

containers or aluminium foil touch the sides of the oven as

this may cause sparking.

Inspection by the user

A microwave oven should only be used if an inspection

confirms all of the following points.

The surface of the door is not damaged.

The door fits squarely and securely and opens and closes

smoothly.

The door hinges are in good condition.

The oven is clean and in particular the door edges and

interior surrounds are not covered with food or burnt

material.

No corrosion is evident on the door, the door hinges or the

oven interior.

Precautions for radiation safety in the use of Microwave

Ovens

Follow the oven manufacturer's instructions on recommended

operating procedures and safety precautions.

Never tamper with or inactivate the interlocking devices.

Never use the oven without the trays provided by the

manufacturer unless specifically allowed in the

manufacturer's instructions.

Never operate the oven without a load (ie. an absorbing

material such as food or water) in the oven cavity unless

specifically allowed in the manufacturer's instructions.

Never rest heavy objects such as food containers on the door

while it is open.

Clean the oven cavity, the door and seals with water and a

mild detergent at regular intervals (do not use abrasive

cleaning pads).

Supervise children using microwave ovens

Other precautions for the safe use of Microwave Ovens

It is sometimes possible to super-heat some liquids or foods

beyond their natural boiling point. Such super heated liquids

may boil suddenly and violently when jolted or stirred after

removal from the oven - it is therefore a good idea to take

precautions such as covering the food or liquid or allowing

it cool before removal from the oven.

When thawing frozen foods in the microwave oven it is

important to thaw the food thoroughly before cooking.

Do not use microwave ovens for sterilising baby bottles or

other food utensils.

Ensure that all food prepared in a microwave oven is stirred

and/or left to stand for a few minutes before consuming. In

particular, care must be exercised when heating a baby's

bottle. Even though the glass bottle may be cool to the

touch, the milk could be very hot. Cases have been reported

where babies have received severe burns from drinking liquids

taken directly from a microwave oven. To avoid problems do

not heat baby's liquids in a microwave oven. If there are no

alternative means, thoroughly shake the bottle to mix the

contents and test it's temperature against the skin after

heating.

Use only cooking containers designated as suitable for

microwave cooking.

MHz is an abbreviation for Megahertz; 1 MHz is one million

cycles of electromagnetic wave oscillations per second.