Prevention of Harmful Effect of Lasers

· Hygienic measures

· Planning and technical measures

· Medical-preventive measures

· Individual means of protection.

Recommendations for Practical Classes on the Theme

Key Questions:

Methods of prevention of harmful effect of noise:

-What is noise, its classification and units of measurement;

-Devices for measurement of level and spectrum of noise;

-Effect of noise on a human organism, MPL of noise for different premises and criteria of their development;

Methods of prevention of harmful effect of vibration:

-What is vibration, its classification and units of measurement;

-Devices for vibration measurement;

-Effect of vibration on a human organism, norms of vibration;

-Methods of prevention of harmful effect of vibration.

Methods of prevention of harmful effect of EMF, ultrasound, infrasound, laser irradiation on the man.

Hygienic characteristics of EMF, ultrasound, infrasound, laser irradiation;

Effect of electromagnetic field, ultrasound, infrasound, laser on organism.

Devices for measurement of EMF, ultrasound, infrasound, laser irradiation.

Methods of prevention of harmful effect of these factors.

Self Test

1. In a workshop of a machine-building factory, where women work, a periodic (up to 2 times per hour) hand moving of processed details takes place. What limiting norm of elevation and moving cargoes by women should be recommended to the authorities in accordance with standards authorized by Ministry of Health of Ukraine?

*A. 10 kg

B. 20 kg

C. 15 kg

D. 7 kg

E. 5 kg

 

2. What are the basic methods of research of vibration effect on a person?

*A. evaluation of a skin temperature

B. a corrector test

C. capillaroscopy

D. investigation of vibration sensitivity

E. evaluation of pain sensitivity

 

3. Which of the following is a correct definition of noise?

*A. It is a chaotic combination of sounds of different frequency and intensity.

B. These are mechanical fluctuations of solid bodies.

C. These are sounds irritating CNS of the man.

Problem Solving

1. In the bar department of a foundry shop a high-frequency heating is applied for drying bars. In the shop 10 drying chambers work simultaneously. A range of working frequencies is 30-48 MHz. What primary pathological changes can occur at work in the given conditions?

2. In one of the premises of the chemical enterprise the constant disturbance of microclimate (temperature rate, ventilation) takes place. Identify measures which should be recommended to maintain the industrial microclimate in the given premise in accordance with hygienic requirements?

3. The noise level on a workplace makes up 121 dB. What psycophysiological effect is most probable in the workers?

Standard Answers:

1. Asthenovegetative syndrome.

2. To equip the premise with a conditioner.

3. Risk of an acoustic trauma.

 

Theme No 19.

Radiation Hygiene and Ecology

Radiation as an Adverse Physical Occupational Factor

Ionizing radiation is widely applied in the atomic power station, industry, medicine for medical and diagnostic procedures, so it can have a negative effect on many workers. Besides, in connection with great radioactive pollution of biosphere, especially after accident on the atomic power station, an increased level of radioactivity may have a negative effect on health of population.

A feature of effect of this factor on organism is the presence of pathological changes even at small levels of action that demands especially strict observance of hygienic requirements, norms of radiation safety (NRS) and careful medical examination of staff.

Concept of Radioactivity

Radioactivity is the property of some atomic nuclei of spontaneously emitting gamma rays or subatomic particles (alpha and beta rays).

 

In hygiene all sources of radiation are subdivided into closed and open.

At closed source only ionizing radiation gets into the environment, e.g. x-ray tube.

At open source both radiation and particles can get into the environment, e.g. radioactive isotopes.

Characteristics of Types of Ionizing Radiation

The following are distinguished:

v Corpuscular radiation, including:

Ø Alpha-radiation is a stream of alpha particles (nuclei of helium) basically from natural isotopes. The ionization ability is the formation of 6,000 ions per 1 mm3 of air, the penetrating ability is a particle track equal to 11 mm in the air and 1/6 mm in the body, so it penetrates only into a superficial layer of the skin. Protection by clothes, aluminum foil is sufficient. The basic danger appears at internal entry into organism with water and food;

Ø Beta-radiation is a stream of beta-particles (electrons or positrons). The ionization ability is 6 pairs per 1 mm3, penetrating ability - up to 1 m in the air, 1cm in the body. Any materials, except for lead can be used for protection (formation of braking x-ray radiation).

Ø Neutron radiation is a stream of neutrons. Ionization is 400 ions per 1 mm3, particle track in the air - hundreds meters, in the body - up to 10 m. The protection against fast neutrons is substances with a small serial number (hydrogen), e.g. water, paraffin, polymer materials; slow neutrons are absorbed by boron, cadmium.

v Electromagnetic radiation including:

Ø X-ray and gamma-radiation. Ionization is 0.1 ions per 1 mm3, particle track in the air is hundreds meters, in the body - some meters (depends on intensity of radiation, length of waves). Gamma–radiation is more severe. Materials with high density, e.g. lead, concrete may serve as protection.

Basic Units of Radioactivity

· Unit of isotope radioactivity: becquerel - a SI unit of measurement of radioactivity, equal to 1 disintegration per second; 1 Bq = 0.027 x 10-9 Ci. Curie (Ci) is an old unit equal to 4 х 1010 disintegrations per sec.

· Unit of exposure dose. It is used for characteristics of ionization dose in the air - for gamma and x-ray radiation. Coulomb/kg (SI) - a dose producing in 1 kg of air ions with electrical charge of 1 coulomb. An old unit - Roentgen - a dose producing in 1cm3 of air 3 х 109 pairs of ions.

· Units of intensity of exposure dose. Unit of a dose correlated to a time unit – R/hour, mR/min, µR/sec.

· Unit of absorbed dose.Grey (Gy) –anabsorbed dose of 1 Joule energy per 1 kg substance.An old unit - Rad - the unit for the dose absorbed from ionizing radiation, equivalent to 100 ergs per gram of tissue; 100 rad = 1 Gy.

· Unit of equivalent dose. In International System of units (SI) as a unit of equivalent dose sievert (Sv) = 1 Gy. Q is accepted – it is a dose of ionizing radiation of any kind producing the same biological effect as a dose of x-ray or gamma-radiations of 1 Gy in view of a quality coefficient (1 Sv = 100 ber).

Effect of Ionizing Radiation on Organism

The basic stages of development of radiation damages are:

· The formation of ionized and excited atoms and molecules which interact with each other and various molecular systems, forming biologically active substances; the breaks of intermolecular links are also possible due to radiation effect (the initial or starting processes);

· The effect of newly formed biologically active substances (free radicals, ions, etc.) on biological structures of a cell in organism causing the destruction of biosubstances and formation of new substances unusual for organism;

· Metabolism imbalance in biological systems with changes of appropriate functions on a background of neurohumoral reactions.

The Major Biological Reactions of Organism to Radiation Effect

All consequences of radiation effect on organism can be conditionally divided into

somatic and inherited.

The somatic effects occur in the irradiated organism, the inherited ones – in posterity.

 

All radiation effects are subdivided into the following:

Stochastic (probable) effects arenonthreshold ones, which are estimated by probable risk of occurrence of radiation damage, i.e. cancerogenic, mutagenic, hereditary effects. It is difficult to investigate them in experimental research, as it is impossible to establish precisely a threshold of harmful effect. These effects are basically manifested at action of small doses (when the occupational and natural irradiation for the whole life does not exceed 100 rem).

Nonstochastic (threshold) effects - the severity of damage depends on dose and it is possible to establish a threshold of damaging effect, i.e. to determine the safe levels of radiation effect. All norms of radiation are based on prevention of these effects.

To nonstochastic effects the following refer:

· Acute radiation sickness. It occurs at single radiation doses of more than 100 rem (100-200 rem – a mild degree; 200-300 – a moderate degree; 300-500 – a severe degree and over 500 rem - the severest). Doses of 500-600 rem at a single irradiation are absolutely lethal.

· Chronic radiation sickness. It may occur at prolonged irradiation in a dose of less than 100 rem.

· Radiation burns of skin. The reaction of I degree occurs at a dose up to 500 rem; II degree - up to 800 rem; III degree - up to 1200 rem; IV degree - over 1200 rem.

· Irradiation cataract occurs at a dose of radiation over 30 rem per year.

The researches proved that the somatic effects do not occur at observance of established hygienic standards; however the latter cannot guarantee the absence of these effects as there is no threshold of stochastic and hereditary effects. The main principle of norms of radiation safety (NRS) is decreasing a dose of radiation as much as possible.