Biological Effects of Ionizing Radiation:

Radiation is energy that comes from a source and travels through some material or through space. The different types of radiation are electromagnetic spectrum, radiations from ground, cosmic and internal. The biological effects of ionizing radiation will be their on health of human being that must be sudied and try to minimize them and handle them effectively for quality life on earth.

Sources of Radiations Exposed to Human beings:

  1. Medical Exposures – Treatment of Tinea capitis, X-ray treatment of ankylosing spondylitis, Prenatal diagnostic X-ray, X-ray therapy of enlarged thymus gland, thorotrast ( radioactive contrast material used in angiography), Treatment of Neoplastic diseases.
  2. Occupational Exposures – Radium dial painters, Uranium miners, Nuclear dockyard workerrs, Participants in a nuclear weapons test, Industrial photography workers, Radioisotope production workers, Civil aviation and astronautic workers, Scientific researcher, diagnostic and therapeutic radiation medical personnel.
  3. Atomic- Bomb Detonation Exposures – Survivors, offspring of survivors.

Types of Radiations:

Radiations are of two types as follows:

A) Ionizing (α, β, γ and X-rays)

B) Non Ionizing (visible, infrared, radio waves)


Ionizing Radiation:

The most improtant form of radiation injury is ionizing radiation which has three types of the effects on cells

i) Somatic effects which cause acute cell killing .

ii) Genetic damage by mutation and therfore, passes genetic deffects to the next progeny of cells.

iii) Malignant transformation off cells.

Biological effects of Ionizing radiation on major organs:

  1. Skin: Radiation dermatitis, Cancer
  2. Lungs: Interstition pulmonary fibrosis
  3. Kidney: Radiation nephritis
  4. Heart:  Mycardial fibrosis, Constrictive pericarditis
  5. Gastrointestinal tract: Strictures of small bowel and Oesophagus
  6. Haematopoietic tissue: Pancytopenia due to  bone marrow depression
  7. Gonads: Testicular atrophy in male and destruction of ovaries
  8.  Eyes: Cataract

The Biological effects of ionizing raditaion include:

Prompt effects:

High doses delivered to the whole body of healthly adult with short period of the time can produce effects such as blood component changes, fatigue, diarrhea, nausea and death.

Blood count changes 50 rem
Vomiting100 rem
Mortality150 rem
LD 50/60 (with minimal supportive care)320-360 rem
LD 50/60 (with medical treatment)480-540 rem
100 % Mortality800 rem

Delayed Effects:

Effects such as cataracat formation and cancer induction thta may appear month or years after a radiation exposure.

Stochastic Effects:

It refers to random and unpredictable effects usually following chronic exposure to low dose radiation. Example Hereditary ands Carcinogenesis.


The effects are non random and have a highly predictable response of radiation of radiations. Example radiations induced lung fibrosis and cataract.

Biological Effects of Ionizing Radiation is begin with the consequencw of radiation interaction with the atoms forming cells. As a result, radiation effects on humans can be seen. They are two mechanisms by which radiation ultimately affects cells.

  1. Direct Effects – radiation interact with the atoms of the DNA molecules and cellular components and ability of chromosomes to replicate will loss, if the alterating due to radiation is significant then direct cell damage will take place.
  2. Indirect Effects – when cell exposed to radiation, probability of radiation interacting with DNA will be less, most of cellular contant is water so more chance of interaction with water. Radiation interact with water form radicals of hydrogen and hydroxyls.  As, we know that radical are unstable and more reactive they react other components of cells or form H2O2 a toxic substance to tissues.
Biological Effects of Ionizing Radiation

Sensitivity towards Radiation:

The rapidly dividing cell are more sensitive to radiation like white blood cells. Reproductive cells and gastrointestinal cells are less  sensitive and least are nerve and muscle cells. Similarly, sensitivity of organs will also be differes among them as blood forming organs are more sensitive because their rapid regeneration rate.

Whole-body sensitivity depends on following Factors:

  1. Total Dose exposed
  2. Type of cells exposed
  3. Type of Radiation
  4. Age of Individual
  5. Part of body exposed
  6. General state of health
  7. Tissue volume exposed
  8. Time interval over which dose is received

Biological effects of Ionizing radiation are typically divided into two categories:

The first category consists of exposure to high doses of radiation over short periods of time producing Acute Radiation Syndrome (ARS). Summary of biological effects of Ionizing radiation in High Dose.

The initial signs and symptoms of the acute radiation syndrome are nausea, vomiting, fatigue, and loss of appetite. Below about 150 rad, these symptoms, which are no different from those produced by a common viral infection, may be the only outward indication of radiation exposure.

The Second category represents exposure to low doses of radiation over an extended period of time producing Chronic Radiation Syndrome (CRS).

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

Genetic  –     The effect is suffered by the offspring of the individual exposed.

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

In-Utero – Some mistakenly consider this to be a genetic consequence of radiation exposure, because 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/fetus is the one exposed to the radiation.

For more information of pharma topics – Pharma Educator