Biological Effects of Radiation

Radiation is energy which travels in the form of waves or high-speed particles. Radiation can occur naturally or be man-made. There are two types:

Non-ionizing radiation, which includes radio waves, cell phones, microwaves, infrared radiation and visible light

Ionizing radiation, which includes ultraviolet radiation, radon, x-rays, and gamma rays

Sources of radiation exposure:

Background radiation is all around us all the time. Most of it forms naturally from minerals. These radioactive minerals are in the ground, soil, water, and even our bodies. Background radiation can also come from outer space and the sun.

 Other sources are man-made, such as x-rays, radiation therapy to treat cancer, and electrical power lines.

Radiation is one of the best-investigated hazardous agents.Biological effects of radiation are typically divided into two categories. 

1️⃣The first category consists of exposure to high doses of radiation over short periods of time producing acute or short term effects. 

2️⃣The second category represents exposure to low doses of radiation over an extended period of time producing chronic or long term effects.

High doses tend to kill cells, while low doses tend to damage or change them. 

High doses can kill so many cells that tissues and organs are damaged. This in turn may cause a rapid whole body response often called the *Acute Radiation Syndrome (ARS).*

 The effects of low doses of radiation occur at the level of the cell, and the results may not be observed for many years.

Acute RadiationSyndrome (ARS)

ARS is having three types syndrome,

1. Haematopoietic Syndrome

2. Gastrointestinal Syndrome

3. Central Nervous System syndrome

As the dose increases above 1.5Gy these three systems manifest it depending on the dose levels.  

 Acute  Effect

A single accidental exposure to a high dose of radiation during a short period of time is referred to as an acute exposure and may produce biological effects within a short period after exposure. The signs and symptoms of the ARS are nausea, vomiting, fatigue and loss of appetite.

🌐Skin damage

🌐Nausea and vomiting

🌐Malaise and fatigue

🌐Increased temperature

🌐Blood changes

🌐Bone marrow damage

🌐Damage to cells lining the small intestine

🌐Damage to blood vessels in the brain

🌐Hematopoietic  orBlood forming organs  are   most sensitive                                  

🌀Gastrointestinal system   is  very sensitive

🌀Central Nervous System with brain and muscles are least sensitive

Effects of Low Doses of Radiation:

There are three general categories of effects resulting from exposure to low doses of radiation. These are:

1️⃣Genetic -      The effect is suffered by the offspring of the individual exposed (mutations).

2️⃣Somatic -    The effect is primarily suffered by the     individual exposed. Since cancer is the Primary result, it is sometimes called the Carcinogenic Effect.

3️⃣In utero effect-the effect, suffered by a developing embryo/fetus, is seen after birth. However, this is actually a special case of the somatic effect, since the embryo/foetus is the one exposed to the radiation.

Risks of prenatal radiation exposure:

1. Mortality : This depends on when the exposure occurs. 

2. Malformations:Malformations may be caused in organs developing at the time of the exposure. 

3. Severe Mental Retardation:The developing human brain is very vulnerable to radiation damage between the 8th and 15th weeks of pregnancy. 

4. Reduced Intelligence 

5.Childhood Cancer. 

Effect of radiation on DNA

Direct action can lead to either DNA damage or DNA mutations. 

DNA damage includes changes to the chemical structure of the DNA molecule . 

DNA mutations involve changes to the sequence of base pairs .If DNA damage is not repaired, it can lead to mutations. Mutations can prevent genes from making correct proteins. This can be very harmful to an organism.

Ionizing radiation can also affect important molecules other than DNA. For example, it can break the bonds holding water molecules together. This creates hydrogen (H+) and hydroxyls (OH-) ions. These are called free radicals. 

Free radicals are highly reactive. They easily combine with other ions inside cells. For example, hydroxyl ions (OH-) can react with hydrogen atoms inside a DNA molecule to form hydrogen peroxide (H2O2). This can cause DNA damage. 

Over time, damage from free radicals can build up. It is believed that free radical damage contributes to aging and diseases like cancer, Alzheimer’s and Parkinson’s disease.