1. Sanitary-and-hygienic, ecological and social consequences of radiative and nuclear failures. Anti-radiation and social protection of the population which treats to action of an ionizing radiation Dr. Igor M. Leskiv, MD Department of Oncology & Radiology

2. What are the biological effects of ionizing radiation?
One characteristic of ionizing radiation on human body is that the energy absorbed is low but the biological effects are serious. For example after receiving a lethal dose of 10 Gy, the body temperature will only increase by 0.02 oC but the dose may lead to death of all the exposed entities.
The second characteristic is the latent biological effects of radiation. Acute biological effects can occur within several hours to several days while the long term effects usually appear several years after the exposure.

3. Characteristic of effects
Type of effects
Characteristic of effects
Occurring time
Object
Effects on organs
Deterministic Effects
Acute Effects
Somatic Effects
Skin damage
Damage of reproductive system
Damage of blood forming system
Damage of digestive system
Damage of central nervous system
Latent Effects
Cataract
Damage of immunization system
Cancer
Stochastic Effects
Genetic Effects
Heredity effects
The biological effects of ionizing radiation can be classified according to the characteristics of effects, occurring times and the object that shows the effects.

4. The effects of critical organs
Different organs have different sensitivity to ionizing radiation. For example, gonad and bone marrows are more sensitive organs, but the bones are less sensitive
Deterministic effects and stochastic effects
From the biological effects of radiation on human body, radiation effects are generally divided into two categories: "Deterministic effects" and "Stochastic effects".
Threshold for deterministic effects (Sv)
Effects
One single absorption (Sv)
Prolong absorption (Sv-year)
testis
permanent infertility 2
ovary
> 0.2
Lens of
eyes
milky of lens cataract
> 0.1
> 0.15
Bone
marrow
Blood forming deficiency
0.5
> 0.4

5. Acute effects: There are three types of acute effects of radiation:
According to the time for the effects to occur, the biological effects of radiation can be divided into two categories: a) acute effects and b) latent effects
Acute effects: There are three types of acute effects of radiation:
1. Haematopoietic syndrome 2. Gastrointestinal syndrome 3. Central Nervous syndrome
Latent effects: Latent effects of radiation refer to those which occur 6 months after the exposure. It consists of two categories: somatic effects and genetic effects. The former refers to the effects occur on the exposed individuals (e.g. cataracts, radiation sickness, cancers, etc.) while the latter occurs in their future generations because of mutations of the genetic cells.

6. An acute radiation dose is defined as a large dose (10 rad or greater, to the whole body) delivered during a short period of time (on the order of a few days at the most). If large enough, it may result in effects which are observable within a period of hours to weeks
Acute doses can cause a pattern of clearly identifiable symptoms (syndromes). These conditions are referred to in general as Acute Radiation Syndrome. Radiation sickness symptoms are apparent following acute doses >100 rad. Acute whole body doses of >450 rad may result in a statistical expectation that 50% of the population exposed will die within 60 days without medical attention.
As in most illnesses, the specific symptoms, the therapy that a doctor might prescribe, and the prospects for recovery vary from one person to another and are generally dependent on the age and general health of the individual.

7. Acute effects:
Blood-forming organ (Bone marrow) syndrome (>100 rad) is characterized by damage to cells that divide at the most rapid pace (such as bone marrow, the spleen and lymphatic tissue). Symptoms include internal bleeding, fatigue, bacterial infections, and fever.
Gastrointestinal tract syndrome (>1000 rad) is characterized by damage to cells that divide less rapidly (such as the linings of the stomach and intestines). Symptoms include nausea, vomiting, diarrhea, dehydration, electrolytic imbalance, loss of digestion ability, bleeding ulcers, and the symptoms of blood-forming organ syndrome.

8. Acute effects:
Central nervous system syndrome (>5000 rad) is characterized by damage to cells that do not reproduce such as nerve cells. Symptoms include loss of coordination, confusion, coma, convulsions, shock, and the symptoms of the blood forming organ and gastrointestinal tract syndromes. Scientists now have evidence that death under these conditions is not caused by actual radiation damage to the nervous system, but rather from complications caused by internal bleeding, and fluid and pressure build-up on the brain Other effects from an acute dose include:
200 to 300 rad to the skin can result in the reddening of the skin (erythema), similar to a mild sunburn and may result in hair loss due to damage to hair follicles to 200 rad to the ovaries can result in prolonged or permanent suppression of menstruation in about fifty percent (50%) of women rad to the ovaries or testicles can result in permanent sterilization. 50 rad to the thyroid gland can result in benign (non cancerous) tumors.

9. According to the subjects on which the effects occur, the biological effects of radiation are classified into: "Somatic effects" and "Genetic effects".
Somatic effects: This is the biological effects that occur on the exposed individuals.
Prompt somatic effects are those that occur soon after an acute dose (typically 10 rad or greater to the whole body in a short period of time). One example of a prompt effect is the temporary hair loss which occurs about three weeks after a dose of 400 rad to the scalp. New hair is expected to grow within two months after the dose, although the color and texture may be different.
Delayed somatic effects are those that may occur years after radiation doses are received. Among the delayed effects thus far observed have been an increased potential for the development of cancer and cataracts. Since some forms of cancer are among the most probable delayed effects, the established dose limits were formulated with this risk in mind. These limits are set such that the calculated risk of cancer in radiation workers is an increase of a very small fraction of the normal cancer risk. (More on risk in a moment)

10. Genetic effects or heritable effects : Genetic effects refer to biological changes on the descendants of the exposed individuals due to mutation of their genetic cells.
When genetic cells are irradiated, the chromosomes or DNA of the cells may be affected which may lead to genetic mutations, chromosome aberrations or changes in the number of chromosomes in the cells. As a result, the probability of genetic changes will increase, bringing detrimental effects to the descendants of the exposed persons.
Genetic effect appear in the future generations of the exposed person as a result of radiation damage to the reproductive cells. Genetic effects are abnormalities that may occur in the future generations of exposed individuals. They have been extensively studied in plants and animals, but risks for genetic effects in humans are seen to be considerably smaller than the risks for somatic effects. Therefore, the limits used to protect the exposed person from harm are equally effective to protect future generations from harm

11. Sensitivity of body organs to radiation
Gonad: The probability of cancer induction in this organ is comparatively low. The main concern is the genetic effects due to irradiation of this organ and the probability is proportional to the absorbed dose.
Red bone marrow: The effect on bone marrow plays an important role in the induction of leukemia. Based on statistical data from radiotherapy patients and atomic bomb survivors in Japan, the induction of leukemia has a maximum at several years after the irradiation and will return to the normal incident level after about 25 years.
Bone: The radiosensitive cells in bone are endosteal cells and epithelial cells on the bone surfaces. The sensitivity of bone is less than that of the breast, red bone marrow, lung and thyroid.
Lung: Cancer of the lung has been observed in miners exposed to high concentration of radon and its decay products. External irradiation can also induce lung cancer and the risk is about the same as that for the development of leukemia.
Thyroid: Radiation can induce thyroid cancer. However, the mortality of this type of cancer is much lower than that of leukemia primarily because of the success in the treatment of thyroid cancer.

12. Sensitivity of body organs to radiation
Breast: During reproductive life, the female breast may be one of the more radiosensitive tissues of the human body. The risk for breast cancer is about one half of that of leukemia.
Skin: The effects on skin depend on absorbed dose and the area of irradiation. Major effects are erythema and ulceration of the skin. The probability of induction of skin cancer is less than the above organs.
Lens: The effects of radiation on the eyes are causing cataract, which is the opacity of the lens. The lens is 5 to 10 times more sensitive to neutrons than to x-ray. Thresholds exist with lower values for children than those for the adults.
Fetus: Effects depend on the stage of pregnancy at the time of exposure. At the early stage of pregnancy when the cells are still not differentiated, it usually causes death of the embryo. It is generally believed that exposure of fetus at the first 3 weeks of pregnancy should not cause any deterministic and stochastic effect to the embryo. Later stage irradiation of the fetus may leads to malformation of body organs and increase in cancer risk of the child.

13. The local radiation damages are divided into early and late ones
The local radiation damages are divided into early and late ones. Damages developed in the process of radiation therapeutics or within 3 months after its completion belong to early ones. Damages, which appear at any period after the expiry of 3 month after radiation therapeutics belong to late radiation damages. The early damages are observed mainly in those cases, when the total radiation dose exceeds the tolerance of irradiated tissues by 30-50% . If the total dose does not exceed the tolerance of tissues or exceeds its slightly, the radiation damages can develop during the remote periods, especially under the unfavorable additional circumstances (the action of mechanical or chemical trauma on irradiation field, insolation etc.). The disturbances of vital activity of skin in these conditions result in arising of radiation necrosis and then ulcer.

14. The radiation ulcers are characterized by their stability and quite often require the surgical treatment - skin transplantation on the surface of granulations or dissection of injured area with the following plasty.

16. The treatment of local radiation damages must be complex
The treatment of local radiation damages must be complex. It consists of generally roborant therapeutics and local application of anti-inflammatory and resorptive medicinal preparations. At the unsuccessful long-term conservative treatment apply the surgical interference. The strict clinic-dissymmetric and radiobiological substantiation and flexible planning of the process of radiation therapy allow avoiding the severe complications in most cases. But, taking into consideration the long period of rehabilitation, the radiation therapeutist together with physicians of corresponding specialties must observe the patients for a long time, realizing the measures, directed on prevention and treatment of possible consequences. The cost of radiation curing of the tumors must not be too high. After the rehabilitation period the patient can be in usual for him living home or working conditions, but he has to follow the doctor’s recommendations and recurrently examination.