Radiation Hygiene Butyrskaia Irina Borisovna IMPORTANCE All living

Radiation Hygiene Butyrskaia Irina Borisovna

IMPORTANCE All living and nonliving on the Earth is exposed cosmic irradiation and natural radionuclides from the Earth crust, rocks, soil, water, air, food, and inside themselves. Natural radiation background been composed during millions of years is added by radiation occurring due to human activity. The last one is provided artificially (sources of ionizing radiation for scientific, industrial, medical, military, and consumptive purposes, rapid development of nuclear energy production), or due to antropogenic destroyment of the Earth crust

The experience of eliminating accidents at nuclear power plants suggests that doctors of any specialties should know the basics of radiation hygiene, since they can significantly affect the consequences of emergency situations. Explosion at Fukushima NPP

Definitions Ionizing radiation (IR) - any radiation, with the exception of visible light and ultraviolet radiation, the interaction of which with the environment leads to its ionization, i. e. to the formation of ions of both signs. Radiation safety of the population - the state of protection of present and future generations of people from the harmful effects of their health by IR. Radiation hygiene - a branch of hygiene that studies the effect of IR on human health and develops measures to reduce its adverse effects.

Natural and artificial radioactivity Radioactivity – spontaneous transformation of elements nuclei to others accompanying with emission of ionizing radiation. Types of ionizing radiations: wavy (electromagnetic waves) – Ro (X-rays) and γ-rays, and corposcular (particles) – α, β, neutrons. Substances containing radioactive nuclides are named radioactive. Natural radioactivity is provided by definite radionuclides containing in soil, water, and air: U-238, Ra-228, Th-232, C-14, K-40, Rn 222. Artificial radioactivity occurs in decomposition of natural radionuclides. Main artificial radionuclides: Sr-90, Cs-137, I-131 etc.

Almost all artificial radioactive isotopes belong to β- or β- and γ-emitters, but natural radionuclides are α-emitters. The most potentially dangerous fragments are Sr-90 and Cs-137 because of their active participation in the biological cycle and long period of half-life.

Qualities of radiation Type of radiation Penetrating ability Ionizing power, Protection in tissues pairs per mm 3 Alpha-particles 0. 15 mm 6000 Clothes, paper Beta-particles 1 cm 6 Aluminum Neutrons 10 m 400 Paraffin, polymer materials, heavy water Gamma-rays 1 -10 m 0, 1 Lead, concrete X-rays 0. 3 - 5 m 0, 1 Lead, concrete

Radiation background Natural radiation background (NRB) arises from sources: (a) Cosmic rays. Their impact is about 35 mrad a year. 25 -40%% (b) Objects of environment (soil, air, water and foodstuff) The radiation due to artificial radionuclides scattered in the biosphere is an artificial background radiation, which in the whole of the Earth adds only 1– 3% to the NRB. The measure of the RB is the exposition dose rate. The global level of RB is 0. 01 -0. 05 m. R / hr. (10 -50 mk. R/hr), in the Crimea: 10 -20 mk. R/hr natural radiation = 100 – 200 m. BER a year

Units 1. Unit of radioactivity: Becquerel (SI) – substance activity with 1 nucleus decay per a second. Extra-system unit - curie - 4 х1010 decays per a sec. 2. Unit of exposition dose. Coulomb/kg – dose forming ions with charge 1 C in 1 kg of air. Extra-system unit - roentgen – dose forming 2, 08 х109 pairs of ions in 1 cm 3 of air. 1 R ≈ 0, 0098 Zv 3. Unit of exposition dose rate: C/kg x sec (extra-system R/hr, m. R/min, mk. R/sec) 4. Unit of absorbed dose. Gray (Gy) – dose that passes energy of ionizing radiation 1 J to mass of 1 kg. Extra-system unit – Rad - 100 ergs to 1 g of substance. 1 Gy = 100 rad. 5. Unit of equivalent dose Siewert (Sv) – biological effect of absorbed dose 1 Gy. Extra-system unit - BER – biological effect of absorbed dose 1 rad. 1 Sv = 100 BER 1 BER = 10 m. Sv

Maximum permissible dose MPD The dose that must not cause any pathological changes in the staff during the period of work (a) For personal - 5 BER/year (50 m. Sv), 100 m. BER/week (b) For living or working near the source of radiation – 0, 5 BER/year (5 m. Sv) (c) Total natural radiation per a year for population – 0. 1 BER/year (1 m. Sv)

Mechanism of radiation impact There are two mechanisms of radiation impact (a) Indirect action: formation of free radicals (H ion, OH- ion, later hydrogen peroxide (H 2 O 2) and hydroperoxide (HO 2) (b) Direct action: thе damage of cellular nuclei (genetic shifts)

The critical organs groups: According to Bergonie-Tribondeau Law, cells are more sensitive to radiation if reproduce more rapidly, mitosis is more prolonged, and less differentiated. They distinguish 3 groups of critical organs/tissues: 1 group - the most sensitive tissues to ionizing radiation – red bone marrow, sexual glands, small bowel epithelium 2 group – moderately sensitive tissues to ionizing radiation - internal organs 3 group - the minimally sensitive tissues to ionizing radiation - bones, cartilages, muscles, nervous tissue

Biological effects of radiation SOMATIC (non-stochastic, threshold) Immediate 1. Radiation disease 2. Radiation burns Postponed 1. Leukaemia 2. Shortening of life SOMATIC EFFECTS: A dose 400 - 500 R is fatal in ~50% of cases, and 600 -700 - in 100%. A dose 25 -50 R cause WBC affection. The postponed effects take time to develop: the latent period may vary from a few weeks to years.

Biological effects of radiation PROBABILISTIC (stochastic, non-threshold) 1. mutagenic 2. cancerogenic 3. teratogenic 4. immunodepressive GENETIC EFFECTS: genetic effects would be manifested in future generation. Genetic effects result from chromosomes damage - chromosome mutations and point mutations. Chromosome mutation is associated with infertility. Point mutations affect the genes.

Providing radiation safety Radiation monitoring should include: Periodic monitoring of the exposure dose rate at workplaces, in adjacent premises, in the territory and in the sanitary protection zone of the facility; · Monitoring the protective properties of stationary fences; Monitoring the protective properties of non-stationary and personal protective equipment; Dosimetric control of staff; Individual dosimetric control of persons belonging to category B, periodical participating in special x-ray examinations (surgeons, anesthesiologists, etc. ), to limit radiation exposure; Control of radiation exposure of patients.

Effective doses of patients irradiation in X-ray examination Chest X-ray – 0, 15 m. Sv Chest X-ray-scopy – 1, 8 m. Sv Chest fluorography - 0, 8 m. Sv Urography – 0, 6 m. Sv Bowel X-ray-scopy – 2, 6 m. Sv Teeth X-ray – 0, 03 m. Sv KT of the chest – 7 m. Sv Mammography – 0, 7 m. Sv

Types of ionizing radiation sources: closed and opened 1. Closed sources – no corpuscles, rays only. 2. Opened sources – produce particles (ά, β, and neutrons) and rays (X, γ)

Protection from closed and opened sources of radiation 1) protection by doze (observation of MPD) 2) protection by the distance (distance between workers and sources ) 3) protection by time (restriction of work time with ionizing radiation) 4) protection by screens (using radioprotective materials)

The protective methods from opened sources of radiation: Additionally one should provide Pressurization of sources Automatization of work Special systems of ventilation and sewerage Special planning premises (isolation, separated room for work, rest , and patients, using nonabsorbable materials) Special premises (storages) for radioactive substances and radioactive wastes Individual protective measures (masks, gloves, suits, dosimeters)

Personal protective methods

Periodic radiometric control of radiopollution of the air, water, and solid material is carried out by radiometers. Workers must wear biodosimeters which show accumulated dose of radiation. dosimeters

Methods of radioactive waste neutralization Methods that are used in the processing of waste can be divided into two categories. The first one is the exposition in time - storing waste until all or almost all of the RSs disintegrate. Usually, if there is a mixture of radioactive elements in the waste, the maximum exposure time is determined by the isotope having the longest halflife, and the period itself is assumed to be 10 halflives (for example, for I-131 - 82 days). The second category is the dilution of waste to negligible levels of activity those do not pose a danger to public health.

Removal of radioactive waste The radioactive waste disposal facility is an enterprise that provides centralized collection, disposal (transportation) and burial of radioactive waste. Such items are arranged for the burial of waste of a large industrial area, city, region. At sites where work is being done with radioactive substances, liquid and solid rad. waste is usually collected in special receivers - containers. Dosimetrists of the receiving service of the disposal point check the pressurization and strength of the packages, the intensity of gamma radiation and neutron radiation from them, contamination by radioactive substances. The radiation dose rate from a container with rad. waste should not exceed 10 m. Ber/h at a distance of 1 meter.

Nutrition in intensive radioactive burden Up to 94% of radionuclides come from food, 5% from water and 1% from air. With increased radioactive burden, the following is recommended: increased amount of proteins in the diet, especially sulfur-containing ones (strontium-137 is removed from the bones, internal organs, and blood); increased amount of vegetable fat, animal fat 10%; from the group of carbohydrates: increase cellulose, pectin substances; antioxidant vitamins: A, E, C (remove free radicals), 2 -3 times more than the daily requirement; mineral substances: calcium - prevents the accumulation of strontium in the bones (found in dairy products, legumes, meat); selenium (contained in bananas, plums).

Ecological and medical consequences of Chernobyl accident Radiation accident - loss of control of sources of IR, caused by equipment malfunction, improper actions of workers (personnel), natural disasters or other reasons that led to exposure of people above the standards or radioactive contamination of the environment. The accident at the Chernobyl nuclear power plant occurred on April 26, 1986. The thermal explosion at the power unit led to the release into the atmosphere of 50 tons of evaporated nuclear fuel, creating in the surrounding atmosphere a huge reservoir of long-lived radionuclides: uranium, plutonium, cesium, strontium.

In the initial period of the accident, the dominant doseforming factor was internal exposure to I-131 short-lived radionuclides with a half-life of 8 days, concentrating mainly in the thyroid. Then, external and internal exposure to Cs 137 radionuclides, with a halflife of 33 years, which are evenly distributed in the muscles when they are ingested with water and local food (milk, meat, potatoes, mushrooms, berries), become the leading ones.

After the passage of the cloud resulting from the accident at the reactor, the gamma radiation dose rates causing external exposure of people correlate with the amount of precipitation. Thus, in the area of Kiev after the Chernobyl accident at the beginning of May 1986, dose rate levels reached 500 -800 μR / hour. By the end of 1987, the gamma background decreased by 10 times. Radioactive contamination of soil, vegetation, food, water bodies, various objects in the territory was caused by radionuclides with an average half-life: strontium-89, barium-140, ruthenium 106, cerium-141, 144, zirconium-95, and then long-lived cesium radionuclides 137, 134, strontium-90.

According to the Association of Chernobyl Doctors, among those affected by the Chernobyl disaster, the incidence and prevalence of the main classes of diseases, especially the nervous system and mental disorders, disorders of the endocrine, digestive, respiratory and cardiovascular systems, as well as oncological pathology, continue to increase. The most critical contingents to the effects of ionizing radiation are: persons who have undergone acute radiation sickness; participants in the aftermath of the Chernobyl accident of 1986 -1987, including for a long time (5 years or more) working in the Chernobyl Exclusion Zone; children, including irradiated intrauterinely.

According to epidemiological studies, an increase in the incidence of thyroid cancer among emergency responders, evacuated population and residents of radioactively contaminated territories has been observed in affected countries. Due to increase of kids age, the peak of thyroid cancer has moved from the early childhood age group to the adolescent and young age groups. An increase in the frequency of leukemia is observed in liquidators irradiated in the first days after the accident. An almost fourfold increase in the prevalence of mental disorders among staff working from 1986 -1987 was noted.