Radiation, Their Effects and Precautions: Most of us have heard of radiation, but can you explain what it is? The ironic part is that even though so many of us are unaware of radiation (because our senses can’t detect it), it is all around us. Microwaves, radios, and even bananas all expose us to radiation. But the danger isn’t found in substance; it is the type of radiation and length of our exposure to it that we should be worried about.

The word radiation comes from the Latin word radiation, “ray of light.” Radiation is a process where energy travels through space as high particles or waves from the atoms of radioactive material. Know that there are two sources of radiation- natural and artificial. Natural radiation comes from the Sun, from the element radon in the air, Earth’s rocks/soil and outer space. Man-made radiation is radiation artificially created by people! It is usually used in communications, industry, research and medicine, and can be found in nuclear weapons and nuclear power plants. Approximately half of all cancer patients receive radiation therapy during their lifetimes. Radiation therapy uses high amounts of energy to kill cancerous cells by damaging their \({\rm{DNA}}\), affecting normal cells. 

In this article, we will study radiation and its effects on human health and precautions to deal with radiation exposure.

Definition of Radiation

Radiation is the energy from a source that travels through space or other mediums. Light, heat, radio waves, microwaves are all forms of radiation.

General Classification of Radiation

There are four classifications of radiation-

1. Particle Radiation: Harmful rays such as alpha rays \(\left( \alpha \right)\), beta rays \(\left( \beta \right)\), and neutron rays.
2. Gravitational Radiation:  Radiation that takes the form of ripples in the curvature of space-time called gravitational waves.
3. Acoustic radiation: Infrastructure design determinants like sound waves(ultrasound, audible sound, infrasound) and seismic waves.
4. Electromagnetic radiation: Containing electric field and magnetic field mutually perpendicular to each other and the direction of propagation such as Gamma,\({\rm{X}}\)-rays, \({\rm{U}}{\rm{.V}}{\rm{.}}\) rays etc.

Types of Radiation

It is known that radiation is energy emitted by a source, which travels through a medium, such as air, and is absorbed by matter. Based on the energy of the radiation, they are classified into two types as follows:

1. Ionizing Radiation
2. Non-ionizing Radiation

Ionizing Radiation

Radiation with enough energy that produces ions in the matter at the molecular level upon the interaction is called ionising radiation. It has the potential to remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionised. If a human body is an interacting matter, it can result in significant damage, including damage to \({\rm{DNA}}\) and denaturation of proteins. This statement does not say that non-ionising radiation can’t cause injury to humans, but the injury is generally limited to heat damage, i.e. burns. One interesting thing is that the visible spectrum is the divide between ionising and non-ionising radiation. This sentence makes sense clinically when we think of \({\rm{U}}{\rm{.V}}{\rm{.}}\) radiation causing skin cancer.

Types of Ionising Radiation

Ionizing Radiation is emitted due to unstable atoms that either has excess energy or mass or both. To attain a stable state, they release the extra mass or energy in the form of radiation. Given below are the different types of ionising radiation along with a few of their characteristics:

1. Alpha \(\left( \alpha \right)\) rays
2. Beta \(\left( \beta \right)\) rays
3. Gamma \((\gamma )\) rays
4. \({\rm{X}}\)-rays

Alpha Rays \(\left( \alpha \right)\), Beta Rays \(\left( \beta \right)\) and Gamma Rays \((\gamma )\)

Earnest Rutherford performed experiments and proved that when a sample of a radioactive substance (Uranium salt) is put in a box made of lead and allowed to emit radiations through a small hole only, three kinds of radiations are emitted-

1. Radiations that deviate towards the negative plate are called \(\alpha \)-rays.
2. Radiations that deviate towards positive plates are called \(\beta \) particles.
3. Radiations that are undeflected are called \(\gamma \)-rays.

Gamma rays are also emitted after \(\alpha \) decay or \(\beta \) decay as follows:

When a nucleus emits \(\alpha \) or \(\beta \) particle, the daughter nucleus may be left in an excited state of higher energy. Therefore, the daughter nucleus de-excites to the ground state by emitting one or more photons. Since the nuclear energy level gaps are of the order of MeV, the emitted photon is of extremely high energy and short wavelength. I.e. \(\gamma \) ray.

Example:  Successive emission of \(\gamma \) rays of energy \(1.17{\rm{ MeV}}\) and \(1.33{\rm{ MeV}}\) from the deexcitation of \(_{28}{\rm{N}}{{\rm{i}}^{60}}\) nucleus formed from \({\beta ^ – }\) decay of \(_{27}{\rm{C}}{{\rm{O}}^{60}}\)

Gamma rays are electromagnetic radiations of the shortest wavelength.   Their wavelength range is from \(0.01{{\rm{A}}^0}\) to \(0.1{{\rm{A}}^0}\), and the frequency range is \(3 \times {10^{22}}\;{\rm{Hz}}\) to \(3 \times {10^{19}}\;{\rm{Hz}}\).  

Sources of Gamma rays: Gamma rays are emitted by radioactive decay and cosmic rays.

Properties of \(\left( \alpha \right)\), \(\left( \beta \right)\), and \((\gamma )\) Rays

Features	\(\alpha \)-particles	\(\beta \)-particles	\(\gamma \)-rays
1. Identity	Helium nucleus or doubly ionised helium atom \(\left( {_2{\rm{H}}{{\rm{e}}^4}} \right)\)	Fast-moving electron (\({ – {\beta ^0}}\) or \({{\beta ^ – }}\))	Photons (E.M. waves)
2. Charge	\( + 2{{\rm{e}}^{ – {\rm{e}}}}\)	\( – {\rm{e}}\)	Zero
3. Mass \(4{{\rm{m}}_{\rm{p}}}\) (\({{\rm{m}}_{\rm{p}}} = \) mass of proton \( = 1.87 \times {10^{–27}}\)	\(4{{\rm{m}}_{\rm{p}}}\)	\({{\rm{m}}_{\rm{e}}}\)	Massless
4. Speed	\( \approx {10^7}\;{\rm{m}}/{\rm{s}}\)	\(1\% \) to \(99\% \) of speed of light	Speed of light
5. Range of kinetic energy	\(4{\rm{ MeV}}\) to \(9{\rm{ MeV}}\)	All possible values between a certain minimum to \(1.2{\rm{ MeV}}\)	Between a minimum value to \(2.23{\rm{ MeV}}\)
6. Penetration power \(\left( {\gamma ,{\rm{ }}\beta ,{\rm{ }}\alpha } \right)\)	\(1\)(Stopped by a paper)	\(100\)(\(100\) times of α)	\(10,000\)(\(100\) times of \(\beta \) upto  \(30{\rm{ cm}}\) of iron (or \({\rm{Pb}}\)) sheet
7. Ionisation power \(\left( {\alpha > \beta > \gamma } \right)\)	\(10,000\)	\(100\)	\(1\)
8. Effect of electric or magnetic field	Deflected	Deflected	Not deflected
9. Energy spectrum	Line and discrete	Continuous	Line and discrete
10. Mutual interaction with matter	Produces heat	Produces heat	Produces, photoelectric effect, Compton effect, pair production
11. Equation of decay	\(_Z{X^A}\xrightarrow{{\alpha – {\text{decay}}}}_{Z – 2}{Y^{A – 4}} + _2H{e^4}\) \(_Z{X^A}\xrightarrow{{{n_\alpha }}}_{Z’}{Y^{A’}} \Rightarrow {n_\alpha } = \frac{{A’ – A}}{4}\)	\(_Z{X^A} \to _{Z + 1}{Y^A} + _{ – 1}{e^0}+ \overline v \) \(_Z{X^A}\xrightarrow{{{n\beta }}}_{Z’}{X^A} \Rightarrow {n_\beta } = \left( {2{n_\alpha } – Z + Z’} \right)\)	\({}_Z{X^A} \to {}_Z{X^a} + \gamma \)

X-rays

Scientist Wilhelm Rontgen discovered \({\rm{x}}\)-rays. Hence, they are also called Rontgen rays. Their wavelength range is from \(0.1{{\rm{A}}^0}\) to \(100{{\rm{A}}^0}\), and their frequency range is \(3 \times {10^{19}}\;{\rm{Hz}}\) to \(5 \times {10^{17}}\;{\rm{Hz}}\).

Sources of X-rays

When a suitable metal target suddenly stops fast-moving electrons, \({\rm{X}}\)-rays are produced.  The sources of \({\rm{X}}\)-rays are Rontgen’s gas-filled tube, Coolidge’s tube and fast electrons stopped by the solid target.

Wilhelm Rontgen observed that when the pressure inside a discharge tube is kept low at \({10^{–3}}\,{\rm{mm}}\) of \({\rm{Hg}}\) and voltage is high at \(25{\rm{ kV}}\), the anode emits some unknown radiations (\({\rm{X}}\)-rays). Since an unknown quantity is represented by \({\rm{X}}\), these rays were called \({\rm{X}}\)-rays.

Properties of X-rays

1. They affect photographic plates.
2. They produce the photoelectric effect.
3. They cause fluorescence and phosphorescence.
4. They are highly penetrating rays and can pass through soft materials like flesh, thin metal sheets, wood etc.
5. They have high ionising power.

Uses of X-rays

They are used

1. in the detection of dislocation and fractures of bones.
2. In the detection of foreign objects like bullets, pins, coins etc., in a human body.
3. In the determination of defects in castings, rubber tyres, welding etc.
4. In the study of the crystal structure.
5. To kill the tumours in the body.

Non – Ionising Radiation

Radiation that has insufficient energy to cause ionisation is non-ionising radiation. These radiations contradict ionising radiation like Gamma rays, \({\rm{X}}\)-rays and Alpha particles, which are on the other end of the spectrum and are unstable and reactive. Non-ionising radiation produces heat, which is helpful in cooking food in a microwave oven. Humans and other organisms see some types of non-ionising radiation, such as visible light and infrared light. Following are the types of non-ionising radiation:

1. Ultraviolet Radiation
2. Visible light
3. Infrared
4. Microwave
5. Radio waves
6. Very Low Frequency (VLF)
7. Extremely Low Frequency (ELF)
8. Thermal Radiation
9. Black-body Radiation

UV-rays

Radiations lying beyond the violet band of the visible spectrum are called \({\rm{UV}}\)-rays.  Their wavelength range is from \(100{{\rm{A}}^0}\) to \(4000{{\rm{A}}^0}\), and the frequency range is: \(5 \times {10^{17}}\;{\rm{Hz}}\) to \(8 \times {10^{14}}\;{\rm{Hz}}\).  

Sources of UV-rays

Sun is the natural source of \({\rm{U}}{\rm{.V}}{\rm{.}}\) rays.  Artificial sources are discharge tubes, mercury vapour lamps, Arc lamps etc.

Figure – Mercury vapour lamp

Detectors of UV-rays: photoelectric tube and the photographic plate

Properties of UV-rays

1. They affect photographic plates.
2. They produce the photoelectric effect.
3. They cause fluorescence and phosphorescence.
4. They cause decomposition in organic acids.  
5. The ordinary glass absorbs them; therefore, \({\rm{U}}{\rm{.V}}{\rm{.}}\) rays are used in the study of \({\rm{U}}{\rm{.V}}{\rm{.}}\) radiations, quartz, fluorite prisms are used.
6. Glass is opaque to \({\rm{U}}{\rm{.V}}{\rm{.}}\) radiation; hence welders use protective goggles made of glass.

Visible Light

The part of the E.M. spectrum to which the human eye is sensitive is visible light. Their wavelength ranges from \(4000{{\rm{A}}^0}\) to \(8000{{\rm{A}}^0}\)^, and the frequency is \(8 \times {10^{14}}\;{\rm{Hz}}\) to \(4 \times {10^{14}}\;{\rm{Hz}}\). The eye interprets this wavelength bandwidth as different colours.

Sources of Visible Light

Sun is the natural source of visible rays. Electric bulb, candle etc. are the artificial sources of visible light.

Fig – Electric bulb of different colours

Properties of Visible Light

1. They affect photographic plates.   
2. They produce the photoelectric effect.       
3. They cause fluorescence and phosphorescence.  
4. They produce chemical effects.  

Uses of Visible Light

Most of the information we get through our vision, by seeing through our eyes are possible because of visible light.  The microscope needs visible light.

Infrared Rays

Radiations lying beyond the red band of the visible spectrum are called \({\rm{IR}}\)-rays. Their wavelength ranges from \(8000{{\rm{A}}^0}\) to \(4000\mu {\rm{m}}\). The frequency range is \(4 \times {10^{14}}\;{\rm{Hz}}\) to \({10^{11}}\;{\rm{Hz}}\).

Sources of Infrared (IR) Rays

All hot bodies like Sun, human body, candle etc. emit \({\rm{IR}}\)-rays, of which the Sun is a natural source. Nernst filament, Infrared LED, pointolite lamp etc. are artificial sources.

Figure – Pointolite lamp and Nernst filament lamp

Detectors of Infrared Rays

1. Thermocouple and thermopile.
2. Bolometer and photo conducting cell.

Properties of Infrared Rays

1. They affect photographic plates.
2. They produce the photoelectric effect.  
3. They produce a heat sensation when they fall on the skin.
4. They dilate the blood vessel.
5. They are less scattered compared to visible light, and they can also pass through smoke and thick fog.
6. They undergo reflection, refraction, interference, polarisation.

Microwaves

These are the electromagnetic \(\left( {{\rm{EM}}} \right)\) radiations with a wavelength range \(4000\mu {\rm{m}}\) to \({10^{ – 2}}\;{\rm{m}}\) and frequency range \({10^{11}}\;{\rm{Hz}}\) to \({10^9}\;{\rm{Hz}}\).

Sources of Microwaves

The sources of microwaves are the Magnetron valve, Klystron valve and Gunn diode.

Fig – Klystron valve

Fig – Gunn diode

Uses of Microwaves

1. For radar communication and satellite communication.
2. To reduce cooking time considerably in a microwave oven.
3. To study the molecular and atomic structure.

Radio Waves

These are the electromagnetic \(\left( {{\rm{EM}}} \right)\) radiations with wavelength range from \({10^{ – 2}}{\rm{m}}\) to \({10^5}\;{\rm{m}}\) and frequency range \({10^9}\;{\rm{Hz}}\) to \({\rm{few Hz}}\).

Sources of Radio Waves

\({\rm{L}} – {\rm{C}}\) oscillator is the best source of radio waves.

Fig – Production of Radio waves

Types of Radio Waves

1. The frequency range from \(530\,{\rm{kHz}}\) to \(1710\,{\rm{kHz}}\) is for an amplitude-modulated band.   

2. The frequency range from \(1710\,{\rm{kHz}}\) to \(54\,{\rm{MHz}}\) is for a short-wave band.

3. The frequency range from \(54\,{\rm{MHz}}\) to \(890\,{\rm{MHz}}\) is for television waves.

4. The frequency range from \(88\,{\rm{MHz}}\) to \(108\,{\rm{MHz}}\) is for frequency modulated band, used in commercial FM radio.

Uses of Radio Waves

They are used for radio, TV, navigation and far communication purposes.

Black Body Radiation

A perfect black body is one which absorbs all the heat radiations of whatever wavelength, incident on it. It neither transmits nor reflects any of the incident radiation and therefore appears black coloured, whatever the incident radiation colour is.

Practically, no natural object possesses strictly the properties of a perfectly black body. But platinum black and lamp-black are a good approximation of the black body. They absorb about \(99\%\) of the incident radiation. Fery designed the most basic and commonly used black body. It consists of an enclosure with a very small opening that is painted black from the inside. The opening acts as a perfect black body.

Any radiation that falls on the opening goes inside and has very little chance of escaping the enclosure before getting absorbed through multiple reflections. The cone opposite to the opening ensures that no radiation is reflected directly.

Thermal Radiation

The electromagnetic radiation produced by the thermal motion of particles in matter is called thermal radiation. This \({\rm{EM}}\) radiation lies in the invisible region of the spectrum known as the Infrared region. Everybody with a temperature above absolute zero(\(0\) kelvin) emits Thermal Radiation. The motion of the constituent particles inside the body causes thermal radiation. At absolute zero, this motion is completely suspended. Therefore a body at absolute zero emits no radiation, and everything above absolute zero temperature does emit radiation. Thermal radiation is responsible for the shine or glow of hot objects, E.g. red hot iron. At that temperature, most of the thermal energy emitted falls in the red band of the spectrum. At higher temperature, it starts emitting a different colour.

Radiation Effects

Following are the different effects that radiation has on the human body:

Biological Effects of Radiation

Biological Effects of Radiation can be divided into two groups according to how the responses (symptoms or effects) relate to dose (or amount of radiation received)

1. Stochastic Effects
2. Deterministic Effects

Stochastic Effects

Those effects that have a probability of occurring with increased dose are called Stochastic Effects. Their severity is unchanged. E.g., skin cancer. The chance of suffering from skin cancer increases with increasing exposure to the Sun. Stochastic effects are either present or not present as a light switch. These effects develop due to the mutation effect of low dose radiation; the threshold dose is not known accurately. Different Cancer’s appear above different dose ranges, The severity of the effect does not depend on the dose, but the frequency of the appearance of the (probabilistic) effect in the exposed population group is dose-dependent (in most cases) linearly increasing with the dose.

Deterministic Effects

Those effects that increase in severity with increased dose are called Deterministic effects. E.g., sunburn. The more we’re exposed to the Sun, and the higher the ‘dose’ of sunlight we receive, the more severe the sunburn. These effects develop due to cell killing by high dose radiation. They appear above a given threshold or prescribed dose, which is considerably higher than doses from natural radiation or occupational exposure at normal operation; the severity of the effect depends on the dose; at a given high dose, the effect is observed in a severe form in all exposed cells, at higher doses the effect can’t increase

Acute Radiation Syndrome (ARS)

Acute radiation syndrome is the most notable deterministic effect of ionising radiation. Signs and symptoms of \({\rm{ARS}}\) are collectively highly characteristic of \({\rm{ARS}}\).

Many symptoms appear in phases during hours to weeks after exposure in different phases-

1.  Prodromal phase,
2. Latent phase,
3. Manifest illness
4. Recovery (or death)

 Extent and severity of symptoms of \({\rm{ARS}}\) are determined by –

1. The total radiation dose received
2. How rapidly dose delivered (dose rate)
3. How does distributed in the body (whole or partial body irradiation)

Carcinogenic Effects

Carcinogenic (cancer) effects have been known practically since the discovery of radioactivity by Henry Becquerel. The first case of radiation-induced cancer was described in \(1902\). The epidemiological test was made from over \(575\) cancers and leukaemias for the \(80,000\) plus survivors irradiated at Hiroshima and Nagasaki in Japan and about \(2,000\) cancers of the thyroid in children in the Chernobyl region in Ukraine. The actual available data doesn’t enable us to show a risk of cancer at greater than \(0,\,1{\rm{ Gy}}\) dose by acute irradiation. Nevertheless, the risk of cancer and the related risk remains linear for doses below \(0,\,1{\rm{ Gy}}\).

Genetic Effects

Genetic effects due to heredity might result in lesions of chromosomes in the germinal lineage (ovule and spermatozoid), prone to lead to anomalies in close or distant descendants of the irradiated individual. Nadson and Philipov \((1925)\) discovered the mutagenic action of radiation and was demonstrated by Muller from \(1927\) onwards in a fly. It has not been possible to find any data showing a genetic effect in man; the risk is evaluated from the data obtained from animals.

Genetic radiation damage leads to an increase of chromosome aberrations in human spermatogonia following radiation exposure of testes. Inheritance of radiation damage in the human population (including A-bomb survivors) has not been detected yet.

Precautionary Measures to Prevent Radiation Damage

The preliminary objective of radiation protection is to protect people and the environment against the harmful effects of ionising radiation. This objective is achieved through a process called risk assessment that involves

1. Identifying the radiation hazard
2. estimating the optimal size of the risk and
3. Assessing the importance in comparison with other risks.

The risk assessment results should be recorded properly and used as the basis for making final decisions about how to manage the risk. Finally, every risk assessment needs to be reviewed and updated from time to time when new work practices or equipment are introduced.

Summary

Radiation damages our intestines and stomach, blood vessels, and bone marrow, which makes blood cells. Damage to the bone marrow increases the number of white blood cells (WBC’s) in the body that battle the disease. As a result, internal bleeding or infections kill many people who die from radiation sickness. The Centre for Disease Control and Prevention (CDC) may recommend staying inside your home during a radiation emergency rather than evacuating. That is because your home walls will absorb some harmful radiation.

FAQs on Radiation, Their Effects, and Precautions

Q.1. How does radiation lower the immune system?
Ans: Radiation therapies can irritate the skin, causing small breaks that could allow the entry of bacteria and germs into our body. Radiation can weaken our immune system if directed to the bones, particularly the bones in our pelvis region, where the marrow functions as a factory for blood cells.

Q.2. Which materials can block radiation?
Ans: Lead \(\left( {{\rm{Pb}}} \right)\), antimony \(\left( {{\rm{Sb}}} \right)\), tin \(\left( {{\rm{Sb}}} \right)\), bismuth \(\left( {{\rm{Bi}}} \right)\), tungsten \(\left( {{\rm{W}}} \right)\) etc. are the materials which can block radiation.

Q.3. What are the effects of radiation poisoning?
Ans: A very high level of radiation exposure within a short period of time can cause symptoms such as vomiting and nausea within hours, leading to death in a few days or weeks. This problem is called acute radiation syndrome, commonly referred to as “radiation sickness.”

Q.4. How much time does it take to recover from radiation therapy?
Ans: Most of the side effects and symptoms go away within a couple of weeks to two or three months after treatment is complete. But after the treatment, some side effects may continue because it takes time for healthy energetic cells to recover from the radiation therapy effects. Late side effects can occur months or years after treatment.

Q.5. What is the most common side effect of radiation treatment?
Ans: Fatigue physical, emotional and mental can cause exhaustion. This tiredness is not induced by overactivity and is not necessarily overcome by rest, but many people would recommend rest to alleviate tiredness. Fatigue is the most found acute side effect of radiation therapy.