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Theme № 17. Hygiene of work at action physical professional harmfull factors (noise, vibration, Electric-Magnetic fields).
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THEME № 17. HYGIENE OF WORK AT ACTION PHYSICAL PROFESSIONAL HARMFULL FACTORS (NOISE, VIBRATION, ELECTRIC-MAGNETIC FIELDS).
Concept about harmful professional factors physical nature
On working can operate many physical PHF: adverse microclimatic factors; not optimum illumination or surplus of its components, laser radiation, noise, vibration, electromagnetic fields (EMF), high or low pressure, radioactive radiation.
NOISE.
By the data the WHO, noise - universal problem for mankind, one of main physical factor of pollution of environmental and industrial environment.
CONCEPT " NOISE":
- In physics noise - the chaotic sound fluctuations, which are not having regularity;
- In hygiene noise - any sounds, preventing recognition useful sound signals, violation the rest, rendering negative action on organism of the person and lowering his serviceability.
NOISE - inordinate sound oscillations in a frequency range, heard by the man (20 - 20000 Hertz), acting at the man in operating time, rest or dream.
CLASSIFICATIONS NOISE
By SOURCES: household, transport, industrial, building, agricultural
By DURATION:
- stable - fluctuation level of noise no more than 5 dB
- unstable - fluctuation level of noise more than 5 dB
- impulsive - intermittent noise
By FREQUENCY:
1) Heard sounds (16 - 20000 Hertz):
- low-frequency - up to 400 Hz
- middle - 400 - 1000 Hz
- high-frequency - more than 1000 Hz
2) Infra sound - frequency up to 20 Hz. It can be the expressed action on internal bodies since frequency of sound can coincide with frequency fluctuations of internal bodies - is most dangerous frequency 8 Hz - violations of alpha - rhythm of a brain; 1-3 Hz - violations of breath etc.;
3) Ultrasound - more than 20000 Hz. It can be mechanical and chemical action – cavitation (making cavities in interstitial tissues), destruction molecules, it ionization; thermal action - heating fabrics (used in physiotherapy, at the big levels - local defeat of peripheral nervous and blood system, violation CNS etc. ).
Units of measurement level of noise.
Action of noise depends not only on frequency, but also from a level.
In acoustics loud of sound is sound pressure in Nuton / m2 (difference between atmospheric and sound pressure).
Unit of sound in hygiene is logarithmic unit - Bell, it shows excess of sound pressure above a sound threshold: 0 - 14 Bell, or 0 - 140 deciBell (dB):
Available sound pressure
1 dB = 20 lg ---------------------------------------------
Sound threshold
Sound threshold = threshold of recognition - 2 х 10-5 Nuton/m2 = 0 dB
Painful sound threshold 14 Bell = 140 dB.
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SON - comparative unity volume different on frequency sounds
Abroad unit of sound it is FON (sound with frequency 1000 Gz at a level 1 dB).
Action noise on organism.
SPECIFIC action: Violation function acoustic analyzer owing to a long angio (vessel) spasmes, in result - degenerate changes in the nervous terminations and neuritis acoustical nerve (professional deafness)
NOISE ILLNESS
3 STAGES NOISE ILLNESS at audiomethria (estimation level of hearing):
- Acoustical adaptation – at action of noise acoustical threshold grows on 10-15 dB, but through 1-3 min. comes to norm (physiologic phenomenon);
- Acoustical exhaustion - decrease of hearingon 15-20 dB during hours or days after finishing noise;
- Progressing deafness - gradual complete hearing loss in connection with organic changes at the center of audition in CNS (noise at the level more 80 dB quickly causes decrease of hearing and development deafness at the experience till 5 years).
NONSPECIFIC action of noise: Excitation brain, hypothalamus and a spinal cord, quickly develops braking of CNS, then - exhaustion nervous cells - irritability, emotional unstability, decrease attention, memory, serviceability, through vegetative nervous system change functions different systems and bodies.
As a result of long action intensive noise develops NOISE ILLNESS - the general disease with defeat of an ear, CNS and other systems.
Struggle against noise on manufacture and in the occupied places.
1. Administrative - legislative measures.
2. Architectural - planning (functional zones in cities, sanitary - protective breaks, transport highways).
3. Hygienic:
а) preventive sanitary control - normalization noise - establishment MPL:
MAXIMAL PERMISSIBLE LEVELS of NOISE IN VARIOUS PREMISES
View of premise MPL, dB test of harmful activity _______________________________________________________
Inhabited rooms 30 conservation dream at night
Wards in hospitals 25 support treatment - protective
regimen in hospital
Educational rooms 50 conservation perception of the
information
Industrial premises 65* - 85 prophylaxis noise illness
_______________________________________________________
The note: * - for high-frequency noise
b) Current sanitary control - the control noise levels and restriction it.
4. Medical-preventive - preliminary and current survey workers at noisy manufactures.
5. Technological: decreasing noise linings, coverings of walls, automatization etc.
6. Individual: headphones, are higher 100 dB - flannel helmets.
Vibration.
Vibration it is oscillations elastic bodies with frequency more than 1 Hz.
It is characterized by amplitude, frequency, direction.
CLASSIFICATION VIBRATION: GENERAL, LOCAL
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BY FREQUENCY: Low-frequency, Middle-frequency, High-frequency
BY DIRECTION: Horizontal, Vertical
Local vibration of small intensity gives a positive effect (vibrating massage); at the general vibration of high intensity - changes CNS, through vegetative nervous system - changes of internal bodies.
Local vibration causes long angiospasmes and mechanical trauma periphery nerves in hand fingers – violations throfics in fabrics, polyneuritis, arthrosis - VIBRATION ILLNESS.
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