Title: ERGONOMICS: Environmental Issues
1ERGONOMICSEnvironmental Issues
2Environmental Factors Worksite Considerations
- The assessment of the working environment needs
to include - The immediate workplace
- The physical relationship between the work
situation and the operator - Impact of temperature, humidity, altitude, noise,
illumination and vibration
3Some Points to Consider
- What effect, if any, do sub-optimal environmental
conditions have on the standard of performance of
the worker? - Is an individuals selective attention and
concentration disturbed? - Is the operator at risk for injury?
- Do environmental disturbances affect the
emotional state of the worker
4What seems to be the problem(s)?
- NOISE
- VIBRATION
- LIGHTING
- AMBIENT CONDITIONS
5What are some of the key environmental
considerations
?
6What factors are likely to affect the
performance of the operator
?
7How would you go about improving the work
site
?
8Operators PERCEPTION is an important
consideration
- Active process of looking for meaning in the
environment in which we live. - Involves receiving and interpreting sensory
information and is unique to each individual. - Depends on cultural background, user experience,
personal disposition and interest in the
particular task.
9There are 4 main ENVIRONMENTAL CONSIDERATIONS
- NOISE
- VIBRATION
- LIGHTING
- AMBIENT CONDITIONS
10NOISE
11The Structure of the Ear A review!
- External ear auricle which collects sound waves
and transmits them via the external acoustic
meatus (auditory canal) to the tympanic membrane
(eardrum).
12The Structure of the Ear A review!
- Middle ear made up of the tympanic cavity in the
temporal bone and contains three auditory
ossicles (bones) the malleus (hammer), the incus
(anvil) and the stapes (stirrup).
13The Structure of the Ear A review!
- Inner ear this is made up of the bony labyrinth
which consists of the Cochlea (the main organ of
hearing), Vestibular Apparatus and the Membranous
Labyrinth.
14Creating Sounds The Basics
- An initial disturbance from a vibrating object
will force surrounding air molecules to move. - Molecules are squeezed closer together then
pulled apart resulting in compression and
refraction. - Sound is propagated through an elastic medium
such as air or fluid. - Rapid oscillations in air pressure within the
ear. - Sound is thus propagated by a pressure wave
moving outward from a vibrating body.
15Sound defined
- a complex scramble of many
- frequencies that is highly
- likely to have a disturbing
- effect on the listener
16Loebs (1986) identified 3 distinct but related
meanings of noise
- 1. Sound which varies randomly in intensity and
frequency. - 2. Sound which interferes with the reception of
another sound (masking). - 3. Sound which the individual does not want to
hear.
17Noise leads to two key changes
- Distraction
- makes it difficult to maintain concentration
when there is more than one source of auditory
information - Arousal
- loud noise is arousing, but whether it has an
affect on performance is debatable
18Negative Affects of Noise
- Damage to hearing
- Disturbance of sleep
- Poor performance of required task due to
increases in muscular tension, accelerated heart
rate - Impaired alertness
- Increased fatigue, tiredness and irritability
- Hypertension, Heart Rate
19Damage to hearing
- Intensive noise causes a portion of the organ of
Corti to be separated from the basilar membrane. - Metabolic theory suggests the depletion of key
enzymes and metabolites in the hair cells
20- Sound Intensity
- Is perceived as loudness which is generally
measured in decibels (dB) - Frequency
- Pitch of the sound measured in Hertz (Hz)
21Normal response of the human ear
Note that this is a logarithmic scale
22Protection against Noise
- Design it out before it becomes a factor.
- Reduce it at source.
- Insulate sound.
- Personal ear protection should be worn where
exposure exceeds 85 db.
23Two Noise Rating Scales
24Actual Sound (Noise Perception Rating Scale)
- 1. Quiet2. Conscious Awareness3. Loud4. Excessi
vely Load5. Unbearable
25Personal Response (Annoyance Scale)
- 1. Relaxing
- 2. Not Disturbing
- 3. Disturbing
- 4. Annoying
- 5. Highly Irritating
26Hearing Sensitive Jobs
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27VIBRATION
28Vibration
- Defined simply as a movementwhich a body makes
about a fixed point (Oborne, 1995).
29 Whole Body Vibration (WBV)
- most commonly associated with motor vehicle
drivers - can occur in a number of different environments
30Vibration
- The effects of vibration are often only
considered in one axis (Z). - Need to consider the speed and intensity of the
vibration. - UNIT Hertz (Hz) cycles.s-1
31Physiological outcomes from vibration frequencies
- (Hz) Tactile sensation 0.1
105Giddiness and instability 0.1
103 Motion sickness 0.2 1Vibrating hand
tool diseases 75 - 100Major body resonances 3,
4-7.5, 11Respiration difficulties 4 -
8Abdominal pain 4 - 14Muscle tone 10 -
20Lumbosacral pain 7.5 - 20Head
sensations 9 - 20Disturbances of vision 1 -
95Speech difficulties 7.5 20Urge to
defecate urinate 10 20
32Vibration
- Resonance occurs when the vibrational frequency
of an external force matches an organs natural
frequency - Pope et al., (1996) state that spinal resonance
occurs at 4 - 5 Hz - Coerman (1968) reported that vibrations between
2.5 5 Hz generate strong resonance in the
vertebrae of the neck and lumbar regions
33Vibration Terms
- Daily vibration exposure
- The 8-hour energy equivalent vibration total
value for a worker in meters per second squared
(m/s²), including all hand-arm vibration
exposures during the day. - Partial vibration exposure
- The contribution of operation i to the daily
vibration - exposure in m/s². The partial vibration exposure
relates to - the daily exposure from an individual tool or
process, i - (where a worker is only exposed to vibration form
one tool - or process then the daily vibration exposure is
equal to the - partial vibration exposure).
- Exposure limit value
- A value for a workers daily vibration
exposure of 5m/s², above which workers should not
be exposed. - Exposure time.
- The duration per day that a worker is exposure to
a vibration source.
34 Hand Arm Vibration (HAV)
- Measurement of vibration is related to
acceleration (m.s2) of the surface in contact
with the hand. - Depends on the tools used by the operator.
- Many tools do not provide the operator with an
indication of the dosage of vibration received. - Need exists for detailed analyses of the impacts
of continuous/repetitive hand arm vibration.
35The American Conference of Governmental
Industrial Hygienists Threshold Limit Values
Total Daily Exposure Duration (Hours) Maximum Value of Frequency Weighted Acceleration (m.s2) in any Direction
4 to less than 8 hours 4
2 to less than 4 hours 6
1 to less than 2 hours 8
Less than 1 hour 12
Directions of Axes in a 3-D System
36The effects of vibration on performance
- Decreased hand steadiness (important for motor
control). - Problems related to sight (for example, blurring
and fixation difficulties).
37A vibration standardInternational
Standardization Organizations Guideline (ISO)
2631 Guide for Evaluation of Human Exposure to
Whole Body Vibration
38Vibration-related Disorders
- Vascular disorders
- dead or white finger,
- Raynaud's phenomenon of occupational origin,
- vibration-induced white finger.
- Neurological disorders
- Carpal Tunnel Syndrome
- Musculoskeletal disorders
39Jobs and Hearing
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41LIGHTING
42Vision and the Role of Lighting
- Problems associated with poor lighting can often
be solved by low cost interventions and careful
design consideration. - Arrangement of working surfaces, such as
placement of machines. - Placement of work benches for natural lighting.
- Improved overhead lighting.
- Changing the paint colour of walls.
43Why is vision so important in the working
environment?
- 70 80 of information entering the brain from
the sensory system is visual
44Some Lighting Terminology
- Luminous Flux (lumen) quantity of energy of the
light emitted per second in all directions. - Luminous Intensity ability of a source or
illuminated surface to emit light. - Luminance the amount of light emitted by a
surface. - Illuminance (lux) amount of light falling on a
surface.
45Visual Acuity
- a measure of the resolving qualities of the eye
(ability to see fine detail). - Affected by physiological factors such as
receptive ability of the visual receptors. - Integrity of the nerve pathways to the brain.
46CHERNCK (1983) considers the following visual
skills important
- Visual acuity
- Near point of convergence (i.e. the closest point
to the person along the median line at which he
can continue to fixate the target with both
eyes). - Stereopsis (i.e. the perception of
three-dimensional visual space as a result of
binocular cues). - Fusion (i.e. the integration of two similar
ocular images into a single precept). - Colour Vision
- Accommodative facility (i.e. the ability to
change focus efficiently from near to far and
back again). - Eye movement ability (i.e. the ability to follow
a moving target smoothly, keeping both eyes on
the target). - Visual motor integration (i.e. co-ordination
between the eyes and the extra-ocular muscles).
47Other Factors Influencing Performance
- Depth Perception
- Contrast Sensitivity
- Peripheral Awareness
- Motion Detection
- Eye Movement
- Dynamic Visual Acuity
- Visuo-motor Integration
- Vestibulo-occular Reflex
- Reaction Time
48Good visual acuity depends on appropriate
lighting conditions based on
- Good illumination
- Sufficient contrast
- Adaptation in the central and peripheral visual
field
49For visual comfort and good optical performance,
the following criteria apply
- 1. Balanced arrangements of lights.
- 2. Suitable level of illumination (lux levels).
- 3. Avoidance of glare and reflection.
50Some Lighting Recommendations
- 1. No source of light should appear in the visual
field of any worker during operation. - 2. The line from eye to light source should be
at an angle of more than 30. - 3. Lights should be provided with shades.
- 4. Rather use more lamps of lower power than
fewer high powered lamps. - 5. Reflective colours and materials should be
avoided. - 6. There should be a contrast in colour between
working surface and working materials.
51Natural Lighting
- 1. High windows are more effective than broad
ones since the light penetrates further into the
room. - 2. Use clear glass as it has a transparency of
90. - 3. Positioning of work benches to avoid looking
directly into the sun. - 4. When working at a VDU windows should be at
the side of the monitor and lighting should be to
the left or right and not directly overhead, or
behind.
52Signs of Visual Fatigue
- Painful irritation and reddening of the eyelids
- Double vision
- Headaches
- Reduction in the power of accommodation and
convergence
53Flickering Lighting
- Flickering light may influence basic brainwave
patterns induce nausea, epileptic seizures. - Stroboscopic effect makes rotating or oscillating
machine parts to appear stationary or moving more
slowly.
54RECOMMENDED ILLUMINATIONS
- Table 10.3 Examples of recommended naturally
occurring illuminances - Area/activity Illuminance on a horizontal
surface (lux) - Clear sky in summer 150 000
- Overcast sky in summer 16 000
- Performance of extremely low contrast
10 000 - tasks (certain surgical operations)
- Textile inspection 15 000
- Office work (writing, reading poor quality
documents) 1 000 - Precise assembly work 1 000
- Office work (without VDUs) 500
- Office work (data entry) 500
- Heavy engineering 300
- Rough assembly work 200
- Min. illuminance for MMH tasks (NIOSH) 150
- Rarely visited places where little perception of
detail is required 50 - Good street lighting 10
- Emergency lighting 2
- Moonlight 0.5
55Jobs and Vision
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57Climate/Thermal Environment
58 Temperatures
Ventilation
Humidity
Poor respiratory function
Dehydration
Reduced work capacity!!
59Assessing Thermal Conditions
- Six Factors to assess human response to thermal
conditions - Air temperature
- Radiant temperature
- Air velocity
- Humidity
- Activity of the person
- Clothing worn by the person
60Cramps Exhaustion Stroke Syncope
(fainting) Rash Miliaria Profunda inability to
sweat
Work
Work Pace
Criteria Health Comfort Performance
Heat Stress
Heat Strain
Climate
Operator
Clothing
Individual Factors Age/Sex Work Capacity Health
Status Acclimatization
61Heat Balance (homeostasis)
Optimal human internal (core) temperature is
around 37C
62Body under heat stress
- Two main mechanisms
- Vasodilation
- Where the peripheral blood vessels dilate and
transfer blood (heat) to the surface of the body
where it can be lost to the surrounding
environment. - Sweating
- Heat lost by evaporation
63Maximum Core Temperature
- A maximum core temperature of 38C is often used
as a limit for working environments. - Death will occur in the region of 42C core
temperature.
64Body under cold stress
- Two main mechanisms
- Vasoconstriction
- Peripheral blood vessels constrict to reduce the
flow of blood to the body surface that reduces
heat loss. - Shivering
65Psychological Responses to Poor Ambient
Conditions
- Less Severe
- Decreased Concentration
- Decreased Response Time
- More Severe
- Mental confusion
- Unconsciousness
- Death due to Ventricular Fibrillation (heart
failure)
66Permissible Heat Exposure Threshold Limit Values
in Degrees C, WBGT
Workload Workload Workload Workload
Work/Rest (per hour) Light Moderate Heavy
Continuous 30.0 26.7 25.0
75 / 25 30.6 28.0 25.9
50 / 50 31.4 29.4 27.9
25 / 75 32.2 31.1 30.0
67Wet Bulb Temperature (WBT)
- Temperature associated with moisture content of
the air. WBT is taken by surrounding the
thermometer with a wet wick and measuring the
reading as the water evaporates. WBT readings
are typically lower than dry-bulb temperatures. - With high relative humidity, little evaporative
cooling occurs, and the reading is similar to
that of a dry-bulb thermometer. - On a dry day, significant evaporation occurs from
the wetted bulb, which maximized the differences
between the two thermometer readings (air
velocity is obviously a factor).
68Dry Bulb Temperature (DBT)
- Temperature we measure with a standard
thermometer that has no water surface on it.
When people refer to temperature of the air they
are usually referring to this.
69Relative Humidity (RH)
- How saturated the air is with water vapor. The
amount of moisture air can hold increases a the
dry bulb temperature increases. When referring
to the relative humidity it is important to
define the dry bulb temperature of the air as
well.
70Methods of Heat Loss
- Convection
- Air flows along the skin
- Heat transferred from skin to air
- Conduction
- Heat transferred by touch
- i.e. working in water, handling cold products,
etc. - Evaporation
- i.e. sweating.
- Respiration
- Both convective and evaporative heat loss
- Occurs from the lungs by respiration as inspired
air
71Heat Production/Loss
72Heat Production/Loss
73Heat Disorders
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75Prevention
- Slow Moving Fans increase air circulation
- Cooling Jackets
- Increased Hydration
- Amount and Composition of Clothing
- Education about signs and symptoms
76Cold Disorders
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77Cold-related Disorders
- Frost-nip versus Frostbite
- With frost nip, there is freezing of the
superficial tissues commonly diagnosed by a
blanching of fingers, noses, ears, etc. Frost
bite is significantly more serious. There we find
freezing of the deep tissues resulting in the
formation of ice crystals. - Hypothermia
- Trench Foot and Immersion Foot
- conditions that present much like frost bite
however, they occur at temperatures above
freezing when the foot is continuously immersed
in water
78Prevention
- Apply skin moisturizer to the face, hands, and
any other body part that may be exposed to the
cold. - Dress warmly, wear dry clothing, and stay out of
the wind. Wear a face mask for extra protection.
Wear heavy mittens instead of gloves in freezing
cold weather. - Be extremely careful when pumping gas into your
car if the temperature is below freezing.
Gasoline on exposed skin evaporates very quickly,
lowers the temperature of the skin, and makes it
more susceptible to frostbite. - When you exercise in below-freezing temperatures,
wear layers of clothing. The innermost garment
must be nonabsorbent and loosely woven. - Go inside, if possible, when you feel too cold.
Remember that fatigue, lack of oxygen in high
elevations, and consumption of alcohol may cause
you to disregard discomfort and cold. - Avoid smoking or drinking before venturing out
into extreme cold. Tobacco decreases circulation
by constricting blood vessels, and alcohol
interferes with the body's ability to regulate
temperature.
79Thermal Sensitive Jobs
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81Other Environmental Factors that Affect Work
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82Air Quality
- Indoor environment - inadequate temperature,
humidity, lighting, excessive noise - Indoor air contaminants - chemicals, dusts,
moulds or fungi, bacteria, gases, vapours, odours
83Symptoms Indoor Air Quality
- dryness and irritation of the eyes, nose, throat,
and skin, - headache,
- fatigue,
- shortness of breath,
- hypersensitivity and allergies,
- sinus congestion,
- coughing and sneezing,
- dizziness, and/or
- nausea
84Motion
- Motion-sickness
- Fatigue
- Motion-induced Interruptions