Is Induction Cooking Safe?
October 2010: Are you old enough to remember the introduction of microwave ovens? That amazing invention that has revolutionized our way of food preparation using high frequency radio waves? Well, now we have medium frequency radio waves for induction cooking. Like microwave ovens, induction stove tops cook rapidly and save energy. They are used in commercial kitchens and they are now being introduced into the home. But are they safe to use?
The principle of induction cooking
Beneath each cooking zone of the induction hob there is a coil through which a medium-frequency alternating current (20 – 100 kHz) flows. This creates a strong magnetic field of the same frequency which passes unobstructed through the ceramic cover and penetrates the pan sitting on the cooking zone. The magnetic field creates a circular current in the electrically conductive base of the pan (eddy current). This principle is called induction. The base of the pan is made of a material in which the heat-loss of the eddy current is as high as possible at the frequency being used. This happens in ferromagnetic materials. In these materials the alternating field is forced into the outer layer of the pan base (skin effect), which increases the resistance of the material to the current and produces intense heat. The alternating magnetic field within the base of the pan also repeatedly magnetises and demagnetises the material, and this creates additional heat (hysteresis loss).
The induction coil and the pan standing on the cooking zone form a capacitor. When the induction coil is switched on, the PAN is charged electrically. If the pan is touched by a person, a small current (leakage current) may flow through that person’s body. You might not get burned if the temperature is low, but you will absorb the radiation from the magnetic field directly from the pot and pan. Yikes.
Once again, this product has not been tested on humans so we don’t know the effect that it will have on our body. The public will be the human test subjects for this new method of cooking. One study could be found and it involved a 2 hour exposure showing it did not damage DNA. Does that make you feel safe? We have no idea what the stray currents will do to our body, let alone the 20 – 100 thousand frequency field effect will have on our food.
The Swiss government decided to do their own tests on this method of cooking and found out that unless you use the product as suggested – it’s not going to pass the ICNIRP guidelines! The current standard for induction hobs stipulates that the unit must comply with the reference value recommended by the ICNIRP (International Commission on Non-Ionising Radiation Protection) of 6.25 microtesla (µT) at a distance of 30 cm when one cooking zone is operated with a suitable pan which is large enough and centred on the cooking zone.
However, in everyday use, who places the pans directly over the element? The effect on the stray fields of several cooking elements used at the same time or unsuitable pans being used or the pans not being centred on the cooking zone was therefore also investigated. Smart thinking!
The magnetic fields were measured between 1 cm and 30 cm away from the edge of the glass ceramic cooking field since it is not always possible to keep at least 30 cm away from the hob in practice. This applies particularly to pregnant women, children and people of small stature. In almost all real world circumstances the user would exceed the ICNIRP guidelines! And we all know how high those ICNIRP guidelines are!!!!!!
There is a good explanation of the induction cooking method on the Swiss Federal Office of Public Health. Pay careful attention to the graphs showing ICNIRP and real world use.
In light of this helpful information from our Swiss friends – stay away from this stove! And warn your friends too!