Physical hazards

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Physical hazards
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Sources of Noise

• Noise can be a problem both in community and
  industry. Sources of community noise are mainly
  transportation, hobbies (amplified music),
  recreational (radios, TV, etc,) and air
  conditioners. Examples of industrial noise are
  textile industries, factories, airplanes
  industries etc

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Noise

• Definition Unwanted sound (the most simple).
• Another definition is Wrong Sound, in the wrong
  place, at the wrong time.

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Physics of sound

• 1. Wave each complete cycle of compression and
  rarifaction.
• 2. Frequency number of times per second that a
  complete vibration occurs.
• 3. Intensity a measure of maximum distance an
  air molecule moves from its normal position
  during its vibration.
• 4. Pitch that ear hears is a function of
  frequency
• 5. Loudnessrelated to intensity
• 6. Wave Length depends on frequency. It is
  equal to speed of sound divided by frequencies
  and different intensities

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Unit of Measuring Sound

• A dyne is 1/1000,000th of atmospheric pressure.
  Least audible quantity of intensity which human
  ear can appreciate is 0.002 dyne/cm2 or microbar
  while the highest appreciated is 200 dyne/cm2.
• Decibel (dB)
• It is a unit of comparison. A ratio between two
  sound pressures and it does no have an absolute
  value. The decibel is a logarithmic ratio
  between a certain pressure in microbar and the
  reference value.
• Sound pressure level in dB k 10 g P1 where K
  is a constant for correction
  P2

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• Physiology Human ear is sensitive between 16
  C.P.S. (Hz) and 20,000 Hz. Below 16 Hz
  vibrations are infra-audible and those above
  20,000 Hz are ultra-sonic. Many animals e.g.,
  dogs and cats can hear sounds infra-audible to
  the human ear. Human ear has a maximum
  sensitivity between 1000 and 4000 C.P.S. i.e.
  least amount of sound intensity will be necessary
  for hearing at these frequencies. As we grow
  older the upper limit of sensitivity decreases.
  Some adults are not able to detect 12,000 cycles
  tones or even 10,000 cycles. Below 16 cycles,
  one will feel rather than hear the sound since
  the vibrations will be within feeling ability.

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Sources of noise

• Noise can be a problem both in community and
  industry. Sources of community noise are mainly
  transportation, hobbies (amplified music),
  recreational (radios, TV, etc,) and air
  conditioners. Examples of industrial noise are
  textile industries, factories, airplanes
  industries etc.

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Harmful effects of noise

• Physiological
• Annoyance The major factor causing it is the
  difficulty in communication and the inability to
  hear speech in loud noise.
• Dissatisfaction personality changes, loss of
  coordination and aggressiveness.

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• Performance
• Physical work usually not affected.
• Two factors are important in this respect namely
  nature of work and sensitivity of individual to
  noise
• Mental work usually affected specially the
  quality of the work e.g., more faults are met
  with typists
• Sensitive individuals to noise usually affected
  in both quantity and quality of work.
• Non-sensitive individuals usually not affected
  but they may be malingers.

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• Accidents Absenteeism
• Usually increase on the basis that annoyance
  visual disturbances and difficulty in hearing
  warning signals are important predisposing
  causes.

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Harmful effects of noise

• Physiological (Non-auditory) Effects
• Pain in the ears
• Increase secretion of adrenaline, nor-adrenaline
  and cortisone, this may be the cause of increased
  incidence of duodenal ulcer in animals.
• Chest feeling associated with nausea, vomiting.
• Rise of both intracranial and diastolic blood
  pressures.
• Interference with sleep
• Giddiness, nausea and fatigue
• Visual disturbance narrowing of pupils
  affection of colour perception reduction of
  night vision

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Harmful effects of noise

• Auditory Effects
• The most important
• a) Air-conduction deafness
• Usually occurs as a result of explosion or
  sudden intense noise and may result in rupture of
  eardrums and in severe cases dislodgment of the
  ossicles. This kind of deafness is reversible by
  healing of the tympanic membrane. It involves
  usually a loss of 5 to 10 dB in auditory ability.

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• b) Nerve conduction deafness
• Usually met with among workers continuously
  exposed to more than 85 dB for long periods.
• Two types were notified
• 1. Transient auditory fatigue
• Suppression of hearing acuity noticed for the
  higher frequencies being centered about 4000
  C.P.S. (Hz). Recovery begins on cessation of
  exposure. This type is due to reversible
  biochemical changes in the nerve endings of the
  auditory nerve. This is also referred to as
  Temporary Threshold Shift (T.T.S.).

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Harmful effects of noise

• 2. Permanent Hearing Loss
• In susceptible individuals, continuous exposure
  to noise causes permanent impairment of hearing
  first noted around 4000 C.P.S. and later on,
  involves other frequencies.

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Harmful effects of noise

• Complaints
• Tinnitus
• Inability to follow conversation in a group
• Inability to hear telephone
• Inability to hear high pitched feminine voice
• Hears his own voice less clearly and he speaks
  with a loud voice to hear his own words.

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Factors responsible for hearing loss

• Kind of noise continuous or intermittent
• In open or in closed space (closed more harmful)
• Intensity of noise at different frequencies.
  Audible comfortable range between 20-60 dB.
  Discomfort occurs between 60-85 dB. Above gt85 dB
  noise is harmful.
• Duration of exposure.
• Age of individual.

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Diagnosis of Industrial Deafness

• History of exposure to noise
• Characteristic audiogram
• Loss of hearing, particularly between 2000 and
  6000 Hz. A V-shape depression, the center of
  which is around 4000 C.P.S. acoustic notch.
  This is to differentiate it from presbycusis due
  to old age and other functional and organic
  causes of deafness.

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Control and Prevention

• 1. At the source
• Substitution of noisy process by a less noisy
  one
• Segregation
• Isolation to minimize the number of exposed
  workers
• Enclosure
• Technical devices
• Suspension using rubber, springs or padding the
  points of friction.
• Mufflers.

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Control and prevention

• At the working environment
• Using sound-absorbing materials that prevent
  reflection of sound waves. Covering the floor
  and walls by rubber, tile, bagasse, etc.

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Control and prevention

• a. Pre-placement medical examination
• Periodic audiometric examination
• Every 2 years to discover the cases as early as
  possible.
• Health education
• Personal protective equipments Use of ? ear
  plugs ?ear muffs
• Legislation

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Abnormal Air Temperature

• Man is a homeotherm i.e. his blood temperature
  is constant (37 0.5C) whatever the
  environmental air temperature would be. This is
  in contrast to some other animals, particularly
  reptiles. To keep this body temperature
  constant, heat gained by the body from metabolism
  (M) must equal heat loss from the body surfaces
  by convection (C), radiation (R) and insensible
  perspiration i.e., Evaporation (E).
• ( M C RE )

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• Comfortable thermal environment conditions are
  those under which a person can maintain normal
  balance between production and loss of heart at
  normal body temperature and without sweating.
  This comfort zone temperature has been evaluated
  to be between 25 - 28C

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• The effect of temperature on human body depends
  on many factors
• 1. Air temperature ? which can be measured by
  the ordinary dry bulb thermometer.
• 2. Air velocity ? which is usually measured by
  anemometers or Kata thermometer. Kata therometer
  is an alcohol thermometer with a glass bulb 4 cm
  long and 1.8 cm in deg. to 95 deg. F. Before
  taking the reading, the bulb is immersed in hot
  water to warm it slightly above 130 deg. F and
  then the thermometer suspended in air. The time
  in seconds required for the temperature to fall
  from 100 deg. to 95 deg. is noted with a
  stopwatch. The length of time depends on the
  cooling power of the air.

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• 3. Mean radiant temperature ? measured by globe
  thermometer. The globe thermometer consists of a
  hollow copper bulb 6 inches (15 in diameter and
  is coated on the outside with black paint which
  absorbs the radiant heat from the surrounding
  objects. A specially calibrated mercury
  thermometer is inserted, with its bulb at the
  center of temperature and that of the ordinary
  dry bulb is a measure of the heat.

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• 4. Relative humidity, which is the percentage of
  moisture present in the air complete saturation
  being taken as 100. The greater the relative
  humidity the nearer the air to saturation.
• Dry and wet bulb hygrometer is the most widely
  used for measuring humidity. The instrument
  consists of two similar thermometers a dry bulb
  and wet bulb thermometers that are mounted side
  by side on stand. The dry bulb measures the air
  temperature

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• Air temperature
• Velocity
• Effective temp
• Corrected effective temp

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• Clinical effects of abnormal temperature

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Effects of Cold Stress

• Injury to cold may be general or local
• - General cold injury (hypothermia) is
  characterized by numbness, loss of sensation,
  muscular weakness, desire for sleep, coma and
  death.
• - Local cold injury a) above freezing.
  Immersion or trench foot. After exposure for 12
  hours. b) below freezing. Frostbite, tissues
  freeze and ice crystals form in between the
  cells.
• Management is done by warming the effected part
  using water at 44C for 20 minutes. Intake of
  hot fluids promotes general rewarming.

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Prevention of ill-effects of Heat

• 1. Health education.
• 2. Balanced diet.
• 3. High fluid and salt intake.
• 4. Avoid Excessive physical fatigue.
• 5. First-aid provisions.
• 6. Heat Stroke management centers in concerning
  hospitals.
• 7. Pre-placement and periodic medical
  examinations for workers in hot environment.
  Daily exposure hours must be cut down for those
  workers.
• 8. Clothing worn should be light, white, porous,
  loose and better if make of asbestos.
• 9. Protective goggles, shields and helmets are
  helpful.

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• 4. Heat Exhaustion occurs among persons
  exposed in mildly hot environment which results
  in diminution of blood supply to the brain as a
  result of vaso-dilatation of peripheral blood
  vessels of exposed parts. However body
  temperature is normal yet the main warning signs
  and symptoms include moist skin, low B.P, high
  pulse, dilated pupils, headache, giddiness, loss
  of power of concentration, loss of appetite,
  nausea, personality changes, irritability,
  liability to sleep and confusion. Removal to a
  cool atmosphere and cool water to drink will soon
  restore patient to normal.

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• 7. Heat Stroke It is one of the main health
  problems during Haj. Case fatality ratio reaches
  40. It is attributed to failure of heat
  regulating mechanism. It is characterized by
  very high body temperature that may rise to 44C
  and profound disturbances including delirium,
  convulsions and partial or complete loss of
  consciousness. The skin is dry and hot, high
  pulse, normal or high B.P and keep breathing.
  Death is often sudden and may e due to
  hyperpotassemia, due to release of potassium from
  red blood cells that have been injured by the
  heat.
• Treatment consists of cooling the body in the
  Makkah Heat Regulating Apparatus at 4-20C.
  This apparatus is available in all Makkah, Mena
  and Arafat hospitals especially during Haj. The
  old trend of rapid cooling in ice water baths is
  stopped now, because this provokes reflex
  shivering which in turn increases body heat
  gained, metabolism and consequently body
  temperature.

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Clinical effect of temp

• Sun burn
• Prickly heat
• Heat exhaustion
• Heat hyperpyrexia
• Heat stroke
• Heat syncope
• Heat cramps

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