Transcript physical health hazards(1)

Physical hazards
Sources of Noise:
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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
Noise
• Definition: Unwanted sound (the most
simple).
• Another definition is “Wrong Sound, in the
wrong place, at the wrong time.”
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. Loudness:related to intensity
• 6. Wave Length: depends on frequency. It is equal to
speed of sound divided by frequencies and different
intensities
Unit of Measuring Sound:
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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
• Physiology: Human ear is sensitive between 16 C.P.S.
(Hz) and 20,000 Hz. Below 16 Hz vibrations are infraaudible and those above 20,000 Hz are ultra-sonic.
Many animals e.g., dogs and cats can hear sounds infraaudible 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.
Sources of noise
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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.
Harmful effects of noise
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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:
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Physical work usually not affected.
Two factors are important in this respect
namely; nature of work and sensitivity of
individual to noise:
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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.
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
Harmful effects of noise
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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.
• b) Nerve conduction deafness:
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Usually met with among workers continuously
exposed to more than 85 dB for long periods.
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Two types were notified:
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1. Transient auditory fatigue:
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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.).
Harmful effects of noise
• 2. Permanent Hearing Loss:
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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
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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.
Factors responsible for hearing
loss:
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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
>85 dB noise is harmful.
Duration of exposure.
Age of individual.
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.
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.
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….
Control and prevention
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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
Abnormal Air Temperature
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Man is a homeotherm i.e. his blood
temperature is constant (37 ± 0.5°C) 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 + R+E )
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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 - 28°C
• 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.
• 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.
• 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.
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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
• Clinical effects of abnormal
temperature
Effects of Cold Stress:
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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.
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Management is done by warming the effected part
using water at 44°C for 20 minutes. Intake of hot fluids
promotes general rewarming.
Prevention of ill-effects of Heat:
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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.
• 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.
• 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 44°C 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 4-20°C. 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.
Clinical effect of temp
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Sun burn
Prickly heat
Heat exhaustion
Heat hyperpyrexia
Heat stroke
Heat syncope
Heat cramps