An Introduction to Non-Ionizing Radiation

We interact with several types of radiation in our daily life and on certain occasions. Even though all radiation carries some common properties but there are still several differences between them due to different characteristics and effects. Based on the characteristics and applications, radiation is divided into two main categories: ionizing and non-ionizing radiation. A brief introduction to both types of radiation is provided here. Similarities and differences in radiation are discussed in detail to justify why nonionizing radiation is different than ionizing radiation. Very little has been explored; nonionizing radiation needs more attention. Therefore, more emphasis is put on nonionizing radiation, its properties, classification, wavelength, and energy range, and why nonionizing radiation plays an important role in our lives, which are reported here. 

We encounter radiation in our daily life. Emission or transmission of energy in the form of waves or particles is known as radiation. There are two types of radiation – ionizing and non-ionizing. The types and interactions of non-ionizing radiation with a medium, materials, or body tissue are discussed in this chapter. Non-ionizing radiation has less energy than ionizing radiation; it does not possess enough energy to produce ions or ionize body tissues and cells. Non-ionizing radiation includes Static fields, ultrasound, and a part of the electromagnetic spectrum. Sunlight, mobile phones, the earth’s magnetic field and electrical appliances are some of the common sources of nonionizing radiation. Although these radiations have low energy, they have many useful applications, especially in medicine. Non-ionizing radiations originate from various natural and manmade sources. It has always been present and is all around us. These radiations cannot destroy human tissues by ionizing body atoms, instead, they can destroy body cells by excitations, heating, vibration, phonons generation, and chemical changes because of the relatively low energy of the particles of nonionizing radiation. Non-ionizing radiation has many beneficial applications, including uses in agriculture, medicine, industry, and research. As the use of nonionizing radiation increases, so does the potential for health hazards. In this chapter, we will look at non-ionizing radiation, the way it interacts with matter, and some of the potential biological health effects produced by various types of non-ionizing radiation.

Electromagnetic radiation is a form of energy that comprises electric and magnetic waves. It propagates in free space and contains neither mass nor charge but carries energy as a photon packet. The energy associated with electromagnetic radiation is directly proportional to the frequency from extremely low frequencies to visible light and above. The highly low-frequency electromagnetic field is generated by the electrical devices and power systems, while the radio and microwave signal radiates by the mobile tower, microwave oven, heater, radar, etc. The extremely high-frequency radiation emitted from medical devices, radioactive decay, nuclear weapons, etc. Therefore, environmental exposure to electromagnetic radiation increases gradually due to increasing electricity demands, advanced technologies, mobile communications, etc. However, exposure to electromagnetic radiation has an adverse biological effect depending on the current intensity, strength of the magnetic field, and duration of exposure. This book chapter introduces electrostatics and magneto-statics, the formation of electromagnetic fields and waves, frequency spectrum, source of radiations, and their exposure limits.

Ultraviolet (UV) radiation is used in several devices for various applications. These applications include medical, research and industrial uses. Some of these applications are fundamental tools for our modern era. These applications range from visualization of DNA to eradication of dangerous diseases and microorganisms in the air and water. While UV radiation is not energetic enough to be considered ionizing radiation and is treated as less hazardous, it is the form of non-ionizing radiation that is closest to the ionization region. UV radiation does have the ability to break chemical bonds and can pose significant hazards to humans. These hazards may include discomfort, temporary loss of sight or impairment, permanent loss of sight, or cancer. To mitigate the hazards from UV exposures, the hazards must be assessed, and administrative controls and engineering controls should be utilized. Federal regulations and guidance regarding UV hazard assessment and mitigation for the end-users of UV devices are not currently robust, but the American Conference of Governmental Industrial Hygienists (ACGIH) has provided some useful information for assessment.

Electromagnetic radiation with a wavelength between 380 nm and 760 nm is called visible light. Electromagnetic radiation within the mentioned wavelength range is called visible because we can see the world around us with the help of this radiation. A misconception usually exists that light is visible and exists in multiple colors. Light is not visible; it gives the feeling and sensation of various colors. For example, light with a wavelength of 450 nm gives the sensation of blue color, and light with a wavelength of 530 nm gives the sensation of green color; hence, we simply call it blue and green light. Light is very useful in our daily lives in many areas other than just seeing the world around us. Despite the enormous benefits of visible light, there are also some harms and hazards associated with this part of electromagnetic waves. Along with the basic understanding of daily life phenomena based on light and several benefits of light, this chapter also reports harms and hazards accompanied by visible light that we should be aware of and should protect ourselves from. Several examples of the hazards of visible light are provided in this chapter

A laser is an intense and amplified beam of light that is used in many applications. The use of lasers in medicine, astronomy, industries, defense, information technology, and oceanography is common and known to many people. The use of lasers in eye treatment, especially the technique of LASIK in eye surgery, shows the successful use of lasers in many fields. However, along with so many outstanding benefits, the intense beam of visible or invisible light also brings many complications while handling laser beams. Several harms and damages are associated with the use of laser beams. Skin injuries and eye defects are common complications caused by laser beams. If proper shielding and safety protocols are not followed, a laser can bring many harms ranging from minor skin irritations to blindness of the eyes. This chapter reports the benefits as well as harms and hazards associated with the use of laser beams. A detailed description of the harms associated with various classes of lasers is provided here. For the safe use of a laser beam, it is important to follow the established rules and regulations. A detailed description and discussion of the hazards associated with the use of laser beams, rules to be followed while using a laser beam, and laser emergency protocols are reported here. 

 Infrared radiation falls on the electromagnetic spectrum between microwaves and red visible light with a wavelength of ~750 nm-1 mm. Infrared radiation is emitted from materials as heat and can be used for medical, industrial, and military purposes. Infrared can be used to reduce swelling, increase tissue repair in sports injuries and help treat patients with cardiovascular disease. The industrial sector uses infrared tomography to image inside buildings, electrical equipment, and fuel processing plants. There are few known harms when it comes to infrared radiation effects. Infrared radiation can cause skin damage, eye damage, and greenhouse effects. Not much research is known on the appropriate dosage or the body's response to doses of infrared radiation. There are a few preventative ways to reduce the harm caused by infrared radiation. People can follow the three cardinal rules of radiation and the ALARA principle. They can also wear personal protection equipment when working or around infrared radiation sources. People can also learn and try to help the planet by reducing their carbon footprint to stop global warming from getting worse.

Radiofrequency and microwave radiation are part of the electromagnetic spectrum. They occupy the lower end of the spectrum with respect to frequency and are on the higher end with respect to wavelength. They have lower energy than the rest of the forms of electromagnetic energy on the spectrum, and as a result, they do not have enough energy to ionize the materials they irradiate. Radiofrequency and microwave radiation have been used in many applications, including communications and the use of radar to be able to predict weather patterns, medicine in both diagnostic and therapeutic uses, and industry. A major development in recent years has been the development of the 5G mobile network, which uses millimeter waves to transmit data to and from mobile phones that operate in the radiofrequency region. However, the rise of the 5G mobile network has many concerns that high exposures to these levels of radiation can be harmful to humans. This has been a point of discussion in the past and has led to decades of research into the potential health effects of radiofrequency and microwave radiation on humans. Even with a large amount of research that has been done, the health effects of radiofrequency and microwave radiation are still a highly debated subject. The IARC classifies radiofrequency electromagnetic energy coming off from mobile phones as a Group 2B substance, which means that it is not clear whether it causes cancer. Overall, radiofrequency and microwave radiation can be harmful, but research shows that it is mainly in the really high levels of exposure. Oftentimes, the public does not come close to approaching the limits established from the regulatory exposure limits set forth by various regulatory bodies around the world.

Modern life is strongly associated with new technologies such as telecommunication and wireless devices. These new technologies strongly affect the way people communicate, learn, train, think and solve their problems. Today, modern cell phones not only send and receive phone calls, but they also allow people to send and receive short messages, and e-mails, share photos and videos, write, edit and share documents, play games, listen to music, watch movies, surf the Internet, find an address using GPS (Global Positioning Systems) and use a wide range of applications. Given this consideration, excessive use of smartphones is associated with growing global concerns over the health effects of radiofrequency electromagnetic fields (RF-EMF) generated by these devices. As discussed by WHO, considering the very large number of people who use mobile phones, even a small increase in the risk of adverse health effects, either cancer or other health effects, could have key public health implications. WHO believes that research about these health effects is mostly focused on potential adverse effects of mobile phones, not their base stations, because the RF-EMF levels of mobile phones are 3 orders of magnitude higher than those of base stations. Therefore, in this chapter, due to the greater likelihood of adverse health effects of handsets, we mainly focused on reviewing the current scientific evidence on health risks associated with mobile phones. However, the health effects of RF-EMF exposure on people living in the proximity of mobile base stations are also reviewed. 

Ultrasound is very safe when used at the diagnostic frequency and intensities. However, a temperature rise of 1.5 – 2.5 °C or more above the normal temperature of the human body exposed to ultrasound for longer than 1 hour may cause thermal induced effects. For most diagnostic ultrasounds, the Mechanical Index should not exceed 1.9. The Mechanical Index should not exceed 0.23 when performing an ultrasound on the eyes. Using diagnostic ultrasound with Mechanical Index above, these limits may cause cavitation in tissues. This chapter mostly covers the possible hazards and harms associated with ultrasound. For the benefits and uses of ultrasound in our lives, you may read chapter 13 of our previously published book: An introduction to Medical Physics, edited by Muhammad Maqbool.

Nonionizing radiation cannot ionize the human body tissues due to its low energy; however, its thermal, mechanical, chemical, vibrational, and several other effects can create complications. To avoid hazards and complications from nonionizing radiation, it is mandatory to establish and follow proper rules and regulations while dealing with such radiation. This chapter reports an overview of various rules and regulations regarding the uses and limits of nonionizing radiation, provided by various organizations. 

The applications of Nonionizing radiation (NIR) has increased in recent years. Safety authorities and the public were concerned about the use of devices that emit NIR. Questions about acute or chronic effects have subsequently become more important. According to many studies and experiments carried out, EMF does not affect the functioning of a living organism, provided that those certain established acceptable standards are not exceeded. It comprises lower quantum energies and, therefore, has different biological effects and interactions with matter. It displays its unique personality, although it shares the same wave characteristics as ionizing radiation. We can describe this in terms of its frequency, energy, and wavelength. It is longer, less frequent, and lazier compared to ‘IR’, but it can still inflict a good deal of damage. This Chapter will cover the effect of NIR interaction with matter, risk management, and safety associated with its application.