Microwave Oven Radiation

Microwave ovens use pulses (50 or 60 per second) of electromagnetic waves from a magnetron to make molecules in the food vibrate, producing heat.

Microwave energy penetrates food quite effectively, heating it to a depth of about 1.5 inches.

For the technically minded, this is how it works

    • Certain types of molecules in our food are polarised, that is they have an electrical charge, positive at one end of the molecule, negative on the other. Water, and substances that mix or dissolve in water are polarised. Most solids and oils are not.
    • When the microwave energy is applied, polarised molecules try to align themselves with the electric field, but it is oscillating at 2,450,000,000 times per second (in domestic microwave ovens) so the polarized molecules constantly rotate at this rate (dipole rotation). No surprise, this warms them up, and rubbing shoulders with neighbouring molecules (which may not be polarized) warms up the neighbours too.

As long as there is moisture in the food, the overall temperature of the food will not exceed the boiling point of water (100º C).

Can Microwave Action damage the food?

Can Microwave EMF Affect Your Health?Heat has beneficial and damaging effects on food. But is microwaved food worse for you than conventionally cooked food?

There is very little hard, scientific evidence that this is so, although there is plenty of internet legend about this topic.

For example, it is claimed that if you water a plant with microwaved water, the plant will die – apparently based on a science experiment conducted by a schoolgirl using just two plants, in which one plant was watered with microwaved water – and died.

This claim is repeated so often on the internet that it can be hard to believe that it is not a verified, scientific fact. It is not, and the claim has been convincingly refuted several times, including here.

As with any method of cooking, there are pros and cons of microwaving. With some foods, more of certain nutrients may be lost by microwaving than by using other cooking methods.

But the converse is also true: some foods fare better when cooked in a microwave oven, than using some conventional methods.

And whichever method you use, it is important to cook the food enough (to destroy pathogens and parasites) but not too much.

Nutrient Losses and Molecular Changes

Microwave cooking does not raise the temperature of the food much above 100ºC, and microwave cooking times are generally shorter, so nutrient losses can be minimal.

For example, when cooking vegetables, it is possible to microwave them in very little water, which also helps to minimise nutrient loss and shorten cooking time. (Actually, nutrient loss is least when steaming vegetables – that is the ideal way to cook them!)

If any foods would be susceptible to damage by microwave heating, it would most likely be proteins.

Their complex molecular structures can be changed when heated, so beneficial protein molecules in food can become less useful. But scientists believe that microwaves don’t damage proteins, heat does.

If you’ve ever tried to microwave a steak, you will know that it can be very hard to eat the result! But this is not because of denatured proteins. It’s because the juices in the meat have been extracted.

All Microwave Ovens Leak Microwave Radiation

Microwave ovenSo far we’ve looked at what happens inside the microwave oven. Now what about outside?

Microwave ovens emit two kinds of EM radiation – microwaves (which leak past the seals and through the screen) and low-frequency radiation (50/60 Hz), which is emitted primarily by the electrical transformer used to power the magnetron, and cannot be shielded by the casing of the oven.

Although the microwave radiation is screened by the frame of the oven, including the meshed glass door, practically all microwave ovens leak microwave radiation, even when they are brand new, and in perfect working order.

This can be confirmed by anyone who has a radio-frequency EMF meter.

When living on a large property, I could stand in the garden with my radio-frequency EMF meter and detect the moment the microwave oven inside the kitchen (about 120 feet away) was switched on or off. This is normal for microwave ovens.

Statutory Limit for Microwave Radiation Leakage

In the US – and most of Europe – the law permits EMF radiation leakage from microwave ovens up to  5 mW/cm2 (or about 137 V/m) at a distance of 5 cm (2 inches).

This is not enough to COOK you, so it is deemed by the government to be acceptable.

Hopefully, your microwave oven does not come close to this legal limit, which is already over a thousand times times higher than the level which many authorities would consider to be safe for long-term exposure!

Nevertheless, it is a very bad idea to watch the microwave oven at work by peering in the glass door while it defrosts the Sunday roast or cooks the family meal. (At that distance,  the microwave EMF could be even higher than the US legal limit).

Not all countries agree with this 5 mW/cm2 standard. Russia’s limit is .01 mW/cm2 (five hundred times smaller).

So keep your distance while the microwave is busy. The field strength at 1 metre (3 feet) is over fifty times smaller than at 5cm (2″). For greater safety, keep a distance of 1.5 metres (5 feet) away.

Faulty Microwave Radiation Leakage

Preparing to Use the Microwave OvenA microwave oven can become very unsafe if the door is not latching properly or if any of the structure is damaged.

In such conditions, the screening of the microwaves might be ineffective and radiation many times stronger than the legal limit could be emitted.

If the door switch is working correctly, a microwave oven is completely safe once the door has been opened. The magnetron stops instantly and there is no residual microwave energy left in the food or the oven, only heat.

 Low-frequency Radiation from Microwave Ovens

Many people worry about leaking microwaves but almost no-one is aware of the low-frequency EMF emitted by a typical microwave oven, which is often intense and extensive. (e.g. 40 mG at 60 cm).  See our EMF Table for comparison with other appliances.

Even if microwave ovens emitted no microwave energy, this level of low-frequency EMF would cause the microwave oven to rank high on any list of low-frequency EMF sources.

Another reason to keep well away from a working microwave 😎

General Recommendations for Safe Use of Microwave Ovens

Here are our general microwaving recommendations

  1. Be careful not to overcook. Once the moisture content of foods has been lost (by evaporation), the temperature of the remaining food can rise rapidly. This which would cause unhealthy damage to food molecules – no matter what cooking method you employed.
  2. Keep at least 1.5 meters (5 feet) away from your microwave oven while it is in use.
  3. Where you have a choice, and time permits, rather use conventional cooking methods, to reduce your exposure to microwave and low-frequency EMF.

The real problem with using a microwave oven is not what it does to the food – or you when you eat the food – but what the leaked radiation might do to you. So follow these guidelines to stay safe.

The obvious solution would be for manufacturers to design a microwave oven which does not leak any microwave radiation! This must be too difficult a problem for microwave engineers to solve currently. But one day they will – and that will be a good time to replace your current microwave.

The rest of this page has nothing to do with electromagnetic radiation. It’s just a collection of interesting facts and opinions (mine) about using microwave ovens.

Using a Microwave to Defrost and Reheat Food

Microwave a frozen pizzaThere is no known reason to avoid defrosting food in the microwave. It doesn’t harm the food, or you when you eat it. And if you come home late from work, it does help to be able to quickly defrost something, and get supper on the go!

Reheating food is another primary use for the microwave oven in many households. It is very convenient and quick.

It is important to ensure that the reheated food is steaming hot, to ensure the destruction of all bacteria – especially since some microwave ovens do not always distribute the heat evenly throughout the food.

Should You Microwave Milk?

Milk is certainly susceptible to heat, as anyone knows who ever left a milk pan on the stove. There does not seem to be any evidence that microwaved milk is more damaged than milk heated conventionally, or that milk products are more susceptible to microwave damage than other foods.

Should you Microwave Baby Food?

Microwaving Babies BottleA very common notion is that microwave ovens should not be used for heating baby’s bottle or food. This is partly because one study has found that beneficial immune system helpers in mother’s milk may be more rapidly destroyed by microwaving, than by conventional methods of warming.

There is no other scientifically validated reason known to us why baby food should be damaged by microwaving, any more than any other food. But I confess that in our household we never microwaved our baby’s food, so I would quite understand if you felt the same!

Should You Microwave Food in Plastic Containers?

Cooking food in plastic containers in the microwave oven is not recommended because toxic plastic molecules from the container can leach into the food. Some plastic containers can reach temperatures far higher than the food they contain.

This applies to plastic containers not designed for microwaving food, including margarine tubs and yoghurt containers. In fact, it is best to assume that any plastic container is not suitable, unless the manufacturer has labelled it as microwave safe.

Microwave Causes Exploding Water – Myth or True?

This video has nothing to do with microwave radiation, but it might be interesting to you if you use a microwave oven.


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