question: Why are certain frequencies more harmful than others? For instance, radio waves vs. x-rays?
comment: The difference is ionizing radiation vs nonionizing radiation. Ionizing radiation have enough energy to when it hit a molecule to detach electrons from atoms and the result is that molecules can change. Nonionizing radiation do not have enough energy so the only thing it can do when it hit you is to heat you up. The process is per particle that hit you so if we talk about electromagnetic radiation a single photons need to have enough energy do detach a electron. So the radiation need to be UV light or higher energy for it to be ionizing and radio waves have less energy that that so the only thing that it can do to damage you is by heating you up.
passages: On the other hand, radiation from other parts of the electromagnetic spectrum, such as ultraviolet light and gamma rays, are known to cause significant harm in some circumstances. For more information on the health effects due to specific electromagnetic phenomena and parts of the electromagnetic spectrum, see the following articles:
  
  BULLET::::- Static electric fields: see Electric shock
  
  BULLET::::- Static magnetic fields: see MRI#Safety
  
  BULLET::::- Extremely low frequency (ELF): see Power lines#Health concerns
  
  BULLET::::- Radio frequency (RF): see Electromagnetic radiation and health
  
  BULLET::::- Mobile telephony: see Mobile phone radiation and health
  
  BULLET::::- Light: see Laser safety
   Section::::Types of non-ionizing electromagnetic radiation.:Very low frequency (VLF).
  
  Very low frequency or VLF is the radio frequencies (RF) in the range of 3 to 30 kHz. Since there is not much bandwidth in this band of the radio spectrum, only the very simplest signals are used, such as for radio navigation. Also known as the myriameter band or myriameter wave as the wavelengths range from ten to one myriameter (an obsolete metric unit equal to 10 kilometers).
  
  Section::::Types of non-ionizing electromagnetic radiation.:Extremely low frequency (ELF).
   Radio spectrum pollution
  
  Radio spectrum pollution is the straying of waves in the radio and electromagnetic spectrums outside their allocations that cause problems for some activities. It is of particular concern to radio astronomers.
   In electromagnetic therapy and electromagnetic radiation and health research, electromagnetic spectrum frequencies between 0 and 100 hertz are considered extremely low-frequency fields. A common source of exposure of the public to ELF fields is 60 Hz electric and magnetic fields from high-voltage electric power transmission lines and secondary distribution lines, such as those supplying electricity to residential neighborhoods.
  
  Section::::Possible health effects.
   Radio frequency (RF) energy at power density levels of 1-10 mW/cm or higher can cause measurable heating of tissues. Typical RF energy levels encountered by the general public are well below the level needed to cause significant heating, but certain workplace environments near high power RF sources may exceed safe exposure limits. A measure of the heating effect is the specific absorption rate or SAR, which has units of watts per kilogram (W/kg). The IEEE and many national governments have established safety limits for exposure to various frequencies of electromagnetic energy based on SAR, mainly based on ICNIRP Guidelines, which guard against thermal damage.
   Electromagnetic radiation composed of photons that carry minimum-ionization energy, or more, (which includes the entire spectrum with shorter wavelengths), is therefore termed ionizing radiation. (Many other kinds of ionizing radiation are made of non-EM particles). Electromagnetic-type ionizing radiation extends from the extreme ultraviolet to all higher frequencies and shorter wavelengths, which means that all X-rays and gamma rays qualify. These are capable of the most severe types of molecular damage, which can happen in biology to any type of biomolecule, including mutation and cancer, and often at great depths below the skin, since the higher end of the X-ray spectrum, and all of the gamma ray spectrum, penetrate matter.
   Section::::Biological and environmental effects.
   Since 1962, the microwave auditory effect or tinnitus has been shown from radio frequency exposure at levels below significant heating. Studies during the 1960s in Europe and Russia claimed to show effects on humans, especially the nervous system, from low energy RF radiation; the studies were disputed at the time.
  
  Section::::Effects by frequency.:Millimeter waves.
  
  Recent technology advances in the developments of millimeter wave scanners for airport security and WiGig for personal area networks have opened the 60 GHz and above microwave band to SAR exposure regulations. Previously, microwave applications in these bands were for point-to-point satellite communication with minimal human exposure.
   There are publications which support the existence of complex biological and neurological effects of weaker "non-thermal" electromagnetic fields (see Bioelectromagnetics), including weak ELF electromagnetic fields and modulated RF and microwave fields. Fundamental mechanisms of the interaction between biological material and electromagnetic fields at non-thermal levels are not fully understood.
  
  Section::::Effects by frequency.
  
  While the most acute exposures to harmful levels of electromagnetic radiation are immediately realized as burns, the health effects due to chronic or occupational exposure may not manifest effects for months or years.
  
  Section::::Effects by frequency.:Extremely-low frequency.
   BULLET::::2. The portion where the wavelength is smaller than the body. Heating via induced currents can occur. In addition there are claims of other adverse biological effects. Such effects are not well understood and even largely denied. (MW and higher-frequency RF).
  
  BULLET::::3. The portion where the wavelength is much larger than the body, and heating via induced currents seldom occurs (lower-frequency RF, power frequencies, static fields).
  
  The above effects have only been shown to be due to heating effects. At low power levels where there is no heating affect, the risk of cancer is not significant.
   As lower frequencies penetrate deeper into the tissue, and as there are fewer nerve endings in deeper-located parts of the body, the effects of the radio frequency waves (and the damage caused) may not be immediately noticeable. The lower frequencies at high power densities present a significant risk.
   At higher frequencies (visible and beyond), the effects of individual photons begin to become important, as these now have enough energy individually to directly or indirectly damage biological molecules. All UV frequences have been classed as Group 1 carcinogens by the World Health Organization. Ultraviolet radiation from sun exposure is the primary cause of skin cancer.
   Thus, at UV frequencies and higher (and probably somewhat also in the visible range), electromagnetic radiation does more damage to biological systems than simple heating predicts. This is most obvious in the "far" (or "extreme") ultraviolet. UV, with X-ray and gamma radiation, are referred to as ionizing radiation due to the ability of photons of this radiation to produce ions and free radicals in materials (including living tissue). Since such radiation can severely damage life at energy levels that produce little heating, it is considered far more dangerous (in terms of damage-produced per unit of energy, or power) than the rest of the electromagnetic spectrum.
   Section::::Non-ionizing radiation.:Very low frequency.
  
  Very low frequency (VLF) refers to a frequency range of 30 Hz to 3 kHz which corresponds to wavelengths of 100,000 to 10,000 meters respectively. Since there is not much bandwidth in this range of the radio spectrum, only the very simplest signals can be transmitted, such as for radio navigation. Also known as the myriameter band or myriameter wave as the wavelengths range from ten to one myriameter (an obsolete metric unit equal to 10 kilometers).
  
  Section::::Non-ionizing radiation.:Extremely low frequency.
   Non-ionizing radiation in certain conditions also can cause damage to living organisms, such as burns. In 2011, the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) released a statement adding radio frequency electromagnetic fields (including microwave and millimeter waves) to their list of things which are possibly carcinogenic to humans.
  
  RWTH Aachen University's EMF-Portal web site presents one of the biggest database about the effects of Electromagnetic radiation. As of 12 July 2019 it has 28,547 publications and 6,369 summaries of individual scientific studies on the effects of electromagnetic fields..
  
  Section::::See also.
   Stochastic effects do not have a threshold of irradiation, are coincidental, and cannot be avoided. They can be divided into somatic and genetic effects. Among the somatic effects, secondary cancer is the most important. It develops because radiation causes DNA mutations directly and indirectly. Direct effects are those caused by ionizing particles and rays themselves, while the indirect effects are those that are caused by free radicals, generated especially in water radiolysis and oxygen radiolysis. The genetic effects confer the predisposition of radiosensitivity to the offspring. The process is not well understood yet.
  
  Section::::Cell damage classification.:Target structures.
   Section::::Regions.
  
  The types of electromagnetic radiation are broadly classified into the following classes (regions, bands or types):
  
  BULLET::::1. Gamma radiation
  
  BULLET::::2. X-ray radiation
  
  BULLET::::3. Ultraviolet radiation
  
  BULLET::::4. Visible radiation
  
  BULLET::::5. Infrared radiation
  
  BULLET::::6. Terahertz radiation
  
  BULLET::::7. Microwave radiation
  
  BULLET::::8. Radio waves
  
  This classification goes in the increasing order of wavelength, which is characteristic of the type of radiation.
   Not all types of electromagnetic radiation are carcinogenic. Low-energy waves on the electromagnetic spectrum including radio waves, microwaves, infrared radiation and visible light are thought not to be, because they have insufficient energy to break chemical bonds. Evidence for carcinogenic effects of non-ionizing radiation is generally inconclusive, though there are some documented cases of radar technicians with prolonged high exposure experiencing significantly higher cancer incidence.
   Section::::Possible health effects.:Leukemia.
   UV is the longest wavelength radiation whose photons are energetic enough to ionize atoms, separating electrons from them, and thus causing chemical reactions. Short wavelength UV and the shorter wavelength radiation above it (X-rays and gamma rays) are called "ionizing radiation", and exposure to them can damage living tissue, making them a health hazard. UV can also cause many substances to glow with visible light; this is called "fluorescence".
   The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 10 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications. The limit for long wavelengths is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length. Gamma rays, X-rays, and high ultraviolet are classified as "ionizing radiation" as their photons have enough energy to ionize atoms, causing chemical reactions.
   The U.S. Food and Drug Administration (FDA), and U.S. Federal Communications Commission (FCC) set limits for the amounts of RF energy exposure permitted in a standard work-day.
  
  Section::::History.
   There have been some concerns over the possible ecological impact of ELF signals. In 1984 a federal judge halted construction, requiring more environmental and health studies. This judgment was overruled by a federal appeals court on the basis that the US Navy claimed to have spent over $25 million studying the effects of the electromagnetic fields, with results indicating that they were similar to the effect produced by standard power distribution lines. The judgment was not accepted by everyone and, during the time that ELF was in use, some Wisconsin politicians such as Democrat Senators Herb Kohl, Russ Feingold and Congressman Dave Obey called for its closure. Similar concerns have, in the past, been raised about electromagnetic radiation and health.
   Section::::Applications.
  
  Section::::Applications.:Scientific research.
  
  This band is commonly used in radio astronomy and remote sensing. Ground-based radio astronomy is limited to high altitude sites such as Kitt Peak and Atacama Large Millimeter Array (ALMA) due to atmospheric absorption issues.
   Another way to manage RFI is to establish a radio quiet zone (RQZ). RQZ is a well-defined area surrounding receivers that has special regulations to reduce RFI in favor of radio astronomy observations within the zone. The regulations may include special management of spectrum and power flux or power flux-density limitations. The controls within the zone may cover elements other than radio transmitters or radio devices. These include aircraft controls and control of unintentional radiators such as industrial, scientific and medical devices, vehicles, and power lines. The first RQZ for radio astronomy is United States National Radio Quiet Zone (NRQZ), established in 1958.
  