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Prophylaxis harmful action of lasers
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PROPHYLAXIS HARMFUL ACTION OF LASERS
1. Hygienic measures
2. Planning and technical measures
3. Medical-preventive measures
4. Individual means of protection
THEME № 18. RADIATION HYGIENE AND ECOLOGY
Radiation as adverse physical professional factor.
Radioactive radiation is widely applied in the atomic power station, in industry, in medicine for medical and diagnostic procedures, so it can give negative action on many working. Besides that, in connection with wide radiactive pollution biosphere, especially after failures on atomic power stations, increased level of radioactivity may have negative influence on the health of the population.
Feature of the action of this factor on organism is presence pathological changes even at very small levels of influence that demands especially strict observance hygienic requirements, norms of radiating safety (NRS) and careful survey working.
Concept “Radio-activity”.
Radio-activity – it is ability some substances to spontaneous disintegration (transformation nucleus of atoms of one elements into others) with allocation energy as particles or radiation.
In hygiene all sources of radiation share on CLOSED and OPEN:
- CLOSED source - in environment acts only radiation (example - x-ray tube);
- OPEN source - in environment can act both radiation and particles (example - radioactive isotopes).
Characteristic kinds of ionization radiation:
1. Corpuscular radiation:
- Alpha - radiation – it is a stream of alpha particles (nucleus of helium) - basically from natural isotopes. Ionization ability - forming 6000 ions in 1 mm3 of air, penetrating ability – run in air 11mm, in body 1/6 mm - penetrates only into a superficial layer of skin. Protection is enough by clothes, by aluminium foil. The basic danger - at internal hit in an organism with water, food;
- Betta - radiation – it is a stream of betta-particles (electrones or positrons). Ionization ability - 6 pairs in 1mm3, penetrating ability - up to 1m in air, in body - up to 1sm. For protection can use any materials, except lead (formation braking x-ray radiation).
- Neutron radiation - a stream of neutrons. Ionization - 400 ions in 1mm3, run in air - hundreds meters, in body - up to 10 m. Protection against fast neutrons - substances with a small serial number (hydrogen) - water, paraffin, polymer materials, slow neutrons are absorbed by borum, cadmium.
2. Electromagnetic radiation:
X-ray and gamma - radiation. Ionization 0, 1 ions in 1mm3, run in air hundred meters, in body - some meters (depends on rigidity of radiation - from length of a wave). Gamma – radiation is more rigid. Protection - materials with high density - lead, concrete.
Basic units of radio-activity.
1. Unit of radio-activity of isotope: Bekkerel (System Iternational - SI) - activity of substance with 1 nuclear disintegration for 1 sec. Old unit - Kuri - 4 х 1010 disintegrations for 1 sec.
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2. Unit of exposition doze. Used for the characteristic doze of ionization in air - for gamma and x-ray radiation. Kulon / kg (SI) - a doze forming in 1 kg of air ions by a charge 1 kulon. Old unit - Roentgen - a doze forming in 1sm3 of air 3 х 109 pairs of ions.
3. Unit of power exposition doze. Unit of a doze referred to a time unit – Roentgen / hour, milliR/mines, microR/sec
4. Unit of absorbed doze. Grey (Gy) -absorbed doze in 1 Joule of energy on 1 kg of substance. Old unit - Rad - 100 erg absorbed energy on 1g substance. 1 Gy = 100 Rad.
5. Unit of equivalent doze. Zivert (Zv) - biological effect of the absorbed doze in 1Gy. BER - the biological effect of the absorbed doze 1 Rad. 1 Zv = 100 BER.
ACTION RADIATION ON ORGANISM
Basic stages development radiation injuries:
1. Formation ionized and excited atoms and molecules which cooperate among themselves and various molecular systems, forming biologically active substances, also it is possible breaks of intermolecular connections (initial or starting processes);
2. Action formed biologically active substances (free radicals, ions etc. ) on biological structures of a cells in organism - destruction biosubstances and formation new substances unusual for an organism;
3. Violation by formed biologically active substances metabolism of biological systems with changes appropriate functions.
Major biological reactions in organism at action radiation.
All consequences action of radiation on organism conditionally can be divided on SOMATIC effects and REMOVAL effects.
Somatic - effects at the irradiated organism, removal effects – appeared after long time or at future generations.
Radiating effects divide on:
STOCHASTIC (probable) effects – it is no threshold of harmful action, have probable character - estimated on possible risk - cancerogenic, mutagen action, hereditary effects. It is difficult to investigate it in experimental research, it is impossible to establish threshold (limit) of harmful action precisely. These effects basically are shown at action of small dozes (when the professional and natural irradiation for life does not exceed 100 BER).
NOT STOCHASTIC (threshold) effects - the weight of defeat depends on doze and it is possible to establish threshold (limit) of harmful action and to determine safe levels influence of radiation. All norms of radiation are based on the prevention of these effects.
To not stochastic effects concern:
1. Sharp beam sickness – it is at dozes of irradiation at once more than 100 BER (100-200 - easy degree; 200-300 - average; 300-500 - heavy and from above 500 BER - the heaviest). Dozes 500-600 BER at a unitary irradiation - are absolutely fatal.
2. Chronic beam sickness – it may be at long time irradiation in a doze less than 100 BER.
3. Beam burns on the skin - reaction of 1 degree - at doze up to 500 BER; 2 degree - up to 800; 3 - up to 1200; 4 - above 1200 BER.
4. Beam cataract - at doze of radiation more than 30 BER per one year.
Researches showed, that somatic effects do not arise at observance established hygienic specifications, however because there are not threshold of stochastic and hereditary effects hygienic specifications can not guarantee it absence. The main principle of norms of radiating safety (NRS) is the decreasing a doze of radiation as more, as possible.
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