Rumor: home hair dryer is a killer with high radiation. The cumulative radiation of three consecutive times of using a household hair dryer is equal to the radiation of one X-ray in the hospital. Moreover, hair dryers mainly blow hair and act on the head at close range for a long time. It has just been verified on the Internet that compared with mobile phones that often work near the head, hair dryers are indeed more lethal.
Truth: for the radiation problem of various household appliances, the first thing to say is a few basic knowledge: as long as the voltage is connected at both ends of the appliance, there will be an electric field; As long as there is current flowing in the electric appliance, there will be a magnetic field around the current; And the voltage and current in the electric appliance are often variable. The changing electric field will produce a magnetic field, and the changing magnetic field will also produce an electric field. Therefore, no matter how large or small household appliances, whether they are computers, televisions, microwave ovens, or “household appliances” such as flashlights, as long as they are connected with electricity, they will radiate electromagnetic fields more or less when used.
Hair dryers, as one of them, are no exception. Every time you enjoy the gentle warm air after washing your hair, you may not think that the power consumption per second of this small electric appliance is actually very large, and the power can reach 1000 watts, which is even higher than the working power of a giant like a refrigerator. As a high-power electrical appliance, it is not surprising that the electromagnetic field intensity emitted by the hair dryer when working exceeds these “key suspected objects of radiation” compared with a mobile phone that relies on a small battery to work at milliwatt level power, or a microwave oven that shields radiation with the door closed tightly.
However, the higher intensity of the electromagnetic field radiated by the hair dryer does not mean that it is harmful to human health. This radiation and that radiation are different and very different.
different from taking x-rays
First, compare with X-ray. X-ray is a kind of ionizing radiation, and the electromagnetic field emitted by household appliances is non ionizing radiation. X-ray radiation is similar to nuclear radiation. It can break the molecular bonds of cells in the human body and may cause cancer. It must not be underestimated. It is very important to control the dose in use. Non ionizing radiation has no such ability. The unit that measures the intensity of X-ray radiation is the roentgen, which indicates the number of charges received by the body per unit mass, while the intensity of radiation from household appliances is usually the intensity of electromagnetic fields. It can be seen that there is no conversion between the radiation of the hair dryer and the radiation of the X-ray film, so there is no comparison. It is estimated that “the cumulative amount of radiation from using a household hair dryer for three consecutive times is equal to the amount of radiation from an X-ray in the hospital”. To put it another way, even if we want to compare the effects on the human body, we can’t compare them because of the different effects.
different from mobile phones, computers and microwave ovens
To be more specific, although the radiation emitted by electrical appliances belongs to non ionizing radiation, and most of it belongs to the radio wave band of electromagnetic waves, the electromagnetic fields emitted by different electrical appliances have different frequencies. For the hair dryer, 50Hz alternating current is used. Accordingly, the frequency of electromagnetic wave generated around the hair dryer is also about 50Hz. The frequency of the electromagnetic wave emitted by the mobile phone for communication is in the range of 0.8ghz to 2GHz (different communication systems will differ, and 1GHz is 109 Hz). The microwave in the microwave oven is also about this frequency, while the circuit in the computer CPU operates at a frequency of several GHz, and the frequency of the electromagnetic field radiated is also about this range. Just looking at the quantity, the radiation frequency of the hair dryer is much lower than those of these brothers.
The different frequencies make the mechanism of their influence on human body different. After being absorbed by the human body, radio-frequency electromagnetic fields (that is, mobile phones, microwave ovens, computer cases, etc.) will be converted into the energy of fast-moving molecules in the body. Friction will occur between fast-moving molecules and the temperature will rise. Microwave ovens use this thermal effect to heat food. Compared with the ionization effect of x-ray just mentioned, this thermal effect is dwarfed. It requires relatively large electromagnetic field energy (such as the electromagnetic field strength inside the microwave oven) to really pose a threat to the human body. However, the scientific community dare not underestimate this thermal effect. When you heat food in the microwave oven, you sometimes find that the inside of the food is hot, but the surface is still cold. If the electromagnetic field affects the internal tissues of the human body in this way, it is also terrible. Therefore, corresponding intensity standards have been formulated for the electromagnetic field in this frequency band. Generally, the radiation intensity around mobile phones, computers and microwave ovens is far below the critical value of the safety standards.
Low frequency electromagnetic fields (that is, hair dryers) do not have the heating effect of radio frequency electromagnetic fields. The possible threats to human health mainly lie in that low frequency electric fields and low frequency magnetic fields will generate or induce currents in the human body. If the currents are large enough, they can stimulate nerves and muscles. However, to generate such stimulation, the energy of the electromagnetic field itself must be large enough. Taking various factors into consideration, the International Commission for non ionizing radiation protection (ICNIRP) has formulated the maximum safety value of radio waves of various frequencies including radio frequency electromagnetic fields and low-frequency electromagnetic fields: [1]
Is hair dryer a killer of high radiation?
Among them, the results of the frequency band radiated by the hair dryer and the frequency band radiated by mobile phones, computers and microwave ovens are as follows:
It can be seen that the intensity required for electromagnetic fields of different frequencies to cause harm to people is very different. The frequency of the hair dryer is very different from that of the mobile phone microwave oven. It is too simple and rude to directly take the radiation value of the hair dryer and the mobile phone. Due to the lack of relevant knowledge, such words will appear in the report: “according to a data from Shanghai Environmental Radiation Research and monitoring center, the radiation value of an ordinary household 1000W hair dryer is 350 milligauss (equal to 35 μ T）。” [2] In fact, 35 μ T is far below the safe maximum magnetic induction strength, so there is no need to panic.
Conclusion: the rumor has been cracked. The working power of the hair dryer is relatively large, and it can radiate relatively strong electromagnetic fields. However, the radiation of the hair dryer belongs to the low-frequency electromagnetic field, and the intensity of harm to the human body is much greater than the radiation intensity of the hair dryer. It is more alarmist to describe hair dryers as high radiation killers.
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