Radiation Effect On Human Body

Radiation

Energy that emitted from a source is referred as Radiation. Radiation is energy that travels through spaces. It can be defined as energy released in form of particles. It is in the form of waves or moving subatomic particles and rays. We can differentiate Radiation in two types.

a) Ionizing Radiation b) Non-Ionizing Radiation

Ionizing Radiation

The Radiation which has very high energy is called Ionizing Radiation.it is dangerous and leaves bad impact on human body. Alpha, Beta, X-Ray are some examples of Ionization radiation.it has high energy and displace electron from there orbit. Creating charge atom and create D.N.A damage, outright cell death. Ionization Radiation is Radiation with enough energy so that during an interaction with an atom it can remove tightly bound electron from orbit. Causing the atom to become charged or ionized.

A long-term somatic effect is the damage to cells that are continually reproducing. These cells are the most sensitive to radiation because any changes made in the parent cell's chromosome structure will be transmitted to its daughters. Also, radiation can affect the delicate chemistry of the cell causing changes in the rate of cell division or even the destruction of that cell. We have already dealt with mutations in the reproductive cells. In these, damage affects future generations. However, a mutation in a somatic cell has consequences only for the individual. If the mutation in the somatic cell increases the rate of its reproduction in an uncontrolled manner, then the number of daughter cells may increase in large numbers in that area. When this occurs, it often happens that the daughter cells divide before reaching their mature state. The result then is an ever increasing number of cells that have no beneficial function to the body, yet are absorbing body nutrition at an increasing rate. The tissue could now be called a tumour. If the cells remain in their place of origin and do not directly invade surrounding tissues, the tumour is said to be benign. If the tumour invades neighbouring tissues and causes distant secondary growths (called metastases), it is malignant. Cancer is a malignant tumour. Whether it is fatal or not depends on the tissue in which it is located, how rapidly it grows, and how soon it is detected.

Non-Ionizing radiation

The type of Radiation is low energy Radiation no ion charge are produce in this Radiation. UV rays, Microwaves, Radiofrequency waves are some examples of Non-Ionizing Radiation. These rays are not directly harmful impact our lives. Depend heavily on these for survival. Non-Ionizing Radiation originates from various sources naturally originated or man –made this Radiation refer to any type of electromagnetic Radiation that does not carry enough energy per quantum to ionize atom or molecule that is to completely remove an electron from an atom or molecule. These are low energy Radiation not enough energy to pull electron from orbit but can excite the electron

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Ionizing radiation interacts with molecules of the living cells by process called ionization . there ionization process result in the formation of electrically charged ions , which can effect large chemical molecules in cells and cause biological damage

Radiation Causes Ionization of ATOMS which may affect MOLECULES which may affect CELLS which may affect TISSUES which may affect ORGANS which may affect THE WHOLE BODY

Effect of radiation on cells :

Ionizing radiation induces direct DNA damage and indirect damage through the radiolysis of water. This damage is either eliminated or fixed in the cell as a mutation or chromosomal rearrangement by DNA repair processes. After release by cell cycle checkpoint control mechanisms, an irradiated surviving cell (blue) may proliferate, passing on the legacy of radiation to its progeny (diagram A), potentially initiating the carcinogenic process. The irradiated cell (blue) can also communicate with nonirradiated neighboring cells (cyan) by cell-to-cell gap junction communication and
or secretion of soluble factors eliciting nontargeted apoptosis (black) or micronucleation (red) in cells that have never been exposed to radiation (diagram B)

Ionizing radiation has two modes of action when causing damage to a cell: directly and indirectly. The type is determined by where in the cell, the radiation hits and how much energy it carries. Direct action causes damage directly to the cell, for example by disrupting a protein or breaking the DNA strand. This is usually caused by high energy radiation, which passes through the nucleus or organelles. Here the energy interacts with an electron in the molecule and knocks it away, which disrupts the molecules’ structure and thus disables it to function . For particle radiation this disruption can also be mechanical, when the particles collide with the molecule (Nias, 1998, Saha, 2013). Indirect action has the same result as direct, but it acts on water – the most abundant molecule in cells – rather than the biomolecule itself. When water is irradiated it causes a cascade of reactions which leads to the formation of free radicals (Nias, 1998, Saha, 2013).

Direct and indirect action on DNA, exemplified by the oxidation of guanosine to 8-hydroxy-guanine. In direct action, radiation causes damage to the DNA directly, whereas in indirect action, the damage is done by radicals formed by radiation to water.

Types of DNA damage that can be produced by radiation, (Nias, 1998, Cooke et al., 2003, Evans et al., 2004, Griffiths et al., 2008, Gordenin, 2012, Saha, 2013). 

Radiation Effects High Doses (Acute) Vs Low Doses (Chronic)

Biological effects of 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 or short term effects. The 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).

1- High Dose Effects (Acute)

erythema (reddening like sunburn), dry desquamation (peeling), and moist desquamation (blistering). Skin effects are more likely to occur with exposure to low energy gamma, X-ray, or beta radiation. Most of the energy of the radiation is deposited in the skin surface. The dose required for erythema to occur is relatively high, in excess of 300 rad. Blistering requires a dose in excess of 1,200 rad.

SKIN EFFECTS AFTER A SINGLE EXPOSURE (Wagner et al., 1994)

Hair loss, also called epilation, is similar to skin effects and can occur after acute doses of about 500 rad.

Sterility can be temporary or permanent in males, depending upon the dose. In females, it is usually permanent, but it requires a higher dose. To produce permanent sterility, a dose in excess of 400 rad is required to the reproductive organs. For Males : 1.0 Gy leads to a temporary reduction in the number of spermatozoa ? 1.5 Gy leads to temporary sterility ? 2.0 Gy results in temporary sterility (for several years) ? 5.0 to 6.0 Gy (acute) can produce permanent sterility , For Females dose of 0.65 to 1.50 Gy will lead to a reduced fertility ? greater than 6.0 Gy produces sterility The “sterility” dose is smaller for older women who have fewer primary oocytes

Cataracts (a clouding of the lens of the eye) appear to have a threshold of about 200 rad. Neutrons are especially effective in producing

Deterministic Effects

Deterministic effects may occur at a variety of doses and at a variety of times after (and perhaps during) irradiation. Twenty symptoms and conditions are discussed below. In addition, five radiation syndromes plus the prodromal syndrome are discussed in the following chapter. The syndromes are collections of symptoms and conditions that have been seen in individual human beings or animals that can result in death.

 Doses required to produce deterministic effects (Mettler and Moseley 1985 pp. 172- 176)

Exposure Levels at Which Health Effects Appear in Healthy Adults (NCRP 1989)

Equal-weight aggregate of elicited percentiles of LD50 at 100 Gy/hr versus NUREG/CR-4214, Rev. 2 values assuming minimal medical treatment. Reproduced from Table 4.1 from Haskin et al. 1997. 

Radiation Linear Energy Transfer

he biological consequence for a given absorbed dose varies with radiation linear energy transfer (LET). This is expressed as the relative biological effectiveness (RBE) of a given radiation relative to x-rays.

Death as a Result of Deterministic Health Effects of Radiation

As a health outcome, death may be the result of any of five acute radiation syndromes. These are

? the bone marrow or hematopoietic syndrome

? the gastrointestinal (GI) syndrome

? the cerebrovascular syndrome

? the pulmonary syndrome, and

? the cutaneous syndrome.

Each of these syndromes is preceded by prodromal symptoms (Hall 2000).

Effects of Acute Exposure on Ovarian Function (USNRC 1989)

Effects of Fractionated Testicular Irradiation on Sperm Count (USNRC 1989)

Stochastic Effects

Carcinogenesis and heritable ill-health are the main stochastic effects of concern.

Stochastic effect is those effect which occur when a person receives a high dose of radiation. These effects have an increase probability of occurrence with increase dose. There is no threshold dose below which is creatively certain that a stochastic effect cannot occur. Severity does not depend on magnitude of absorbed doses these effects occur by chance usually without threshold level of dose have no level of radiation dose effect arises from injury to one or a few cells. Malignant disease and heritable effect for which the probability of effect occur. Occurrence of stochastic effect is probabilistic in nature and is proportional to dose received. Stochastic effect is of two types

a) somatic stochastic effect b) Genetic effect

Somatic stochastic effect These effects of radiation limited to expose individual and they are distinguished from genetic effect. These effects are harming that expose individuals suffer during their lifetime.

Genetic or heriditary effect The ionizing radiation damage the genetic material in reproductive cell and by the result of which these effects are transmits from generation to generation. Radiation induced material to an individual gene and D.N.A that can contribute to the birth of defective descendants.

ICRP-26 defined ‘stochastic effects’, where ‘stochastic’ was used to mean ‘of a random or statistical nature’. For an effect to be called stochastic, the probability of it occurring, but not its severity, was regarded as a function of dose without threshold. It recommended that RP aim at limiting the probability of the stochastic effects to an acceptable level, and an LNT dose–response relationship was assumed. Since ICRP-26, there have been no changes to the name or definition of stochastic effects, and only ‘cancer’ and ‘hereditary effects’ (replacing ‘heritable effects’ used from ICRP-9) have been assigned to this category. Since ICRP-41 , stochastic effects have been supposed to result from injury to a single cell or small number of cells. ICRP-103 stated that RP aims to reduce risks of stochastic effects to the extent reasonably achievable, and that stochastic effects are either cancer development in exposed individuals owing to mutation of somatic cells or heritable disease in their offspring owing to mutation of reproductive cells.

Radiation carcinogenesis is characterized by a latent period, an interval of time between irradiation and the onset of clinical symptoms. Latent periods are shorter for higher doses. The Life Span Study (LSS) cohort of Japanese nuclear bomb survivors has shown latent periods of 2 to 10 years for leukemia, and 10 or more years for solid tumors

2- Effects of Exposure to Low Doses of Radiation

With any exposure to radiation, there is some risk The approximate risks for the three principal effects of exposure to low levels of radiation are:

Genetic - Risks from 1 rem of radiation exposure to the reproductive organs are approximately 50 to 1,000 times less than the spontaneous risk for various anomalies. Somatic - For radiation induced cancers, the risk estimate is small compared to the normal incidence of about 1 in 4 chances of developing any type of cancer. However, not all cancers are associated with exposure to radiation. The risk of dying from radiation induced cancer is about one half the risk of getting the cancer.

In-Utero - Spontaneous risks of fetal abnormalities are about 5 to 30 times greater than the risk of exposure to 1 rem of radiation. However, the risk of childhood cancer from exposure

Inutero is about the same as the risk to adults exposed to radiation. By far, medical practice is the largest source of in-utero radiation exposure.

HEREDITARY EFFECTS IN HUMANS

The descendants of those Japanese who were exposed during the nuclear bombing of Nagasaki and Hiroshima in 1945 are the largest group of irradiated humans available for study. Until now, hereditary effects such as leukaemia and mental retardation have only been seen in those children who were heavily irradiated while still in their mother's womb. Children conceived and born after the explosion have shown no change in the natural mutation rate. However, although these negative results are encouraging, the numbers involved (30,000 children born to irradiated parents) are too small for proper statistical analyses. Also, some mutations may take several generations to show themselves. 

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EFFECTS OF AN ACUTE DOSE OF 4 - 6 GRAY

Conclusion

Radiation is all around us in many different forms and it may be Ionizing or Non-Ionizing Radiation.it is very necessary to dealing with Radiation and its effect all the Radiation workers and their patient have to avoid the maximum doses of Radiation. Ionizing Radiation exposure to cell can affect the cell or change in cell D.N.A and change the nature of cell and sometimes it can kill the cell.it may cause immediate effect or not become apparent for long time. Radiation cause Biological effect and cause many diseases which may leads to death. Hence, there is an urgent need to take precautionary steps to avoid Biological Effect of Radiation.

Long-term somatic effects of radiation exposure are cancers and cataracts. For Nuclear Energy Workers, the risk of fatal cancer is 4% per 1000 mSv. This risk was estimated from data at high doses and high dose rates, and by then using a reduction factor of 2 to allow for the fact that the risk at low doses and low dose rates is less. Acute exposures are those delivered in a short time, i.e., within a day. Chronic exposures are those delivered over a long period of time, i.e., weeks and months. Short-term somatic effects are caused by acute high exposures. Acute doses below 250 mGy are unlikely to have any observable effects. Acute doses of about 3 to 5 Gy have a 50% chance of killing you some weeks after the exposure, if you receive no medical treatment. Radiation injury is treated by conserving and augmenting the blood constituents and by assisting the body's anti-bacterial mechanisms. Localised doses cause much less damage than whole-body doses of the same size. 

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