Module 3: Hazardous ExposuresDr. Neyens
NOTE: Readings for Module 3 and 4 are not
required
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Ambient air pollution
• A risk factor for respiratory and cardiovascular morbidity and
mortality
• Air pollution consists of:
– Primary pollutants
• Sulfur dioxide
• Nitrogen oxides
• Particulate matter
– Secondary acidic aerosols and particles
– Oxidant pollutants (e.g., ozone)
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Exposure assessment
• Individuals within a population may differ in exposure to air
pollution
• Most assessment techniques are at specific locations, but people
are mobile
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Susceptibility Factors
• Intrinsic factors (e.g., age, gender, preexisting health factors
and genetic factors)
• Extrinsic factors (e.g., profile of exposure, nutrition factors,
lifestyle factors)
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Indoor air quality
• Big issue: Sick building syndrome
Worse breathing
– Mucous membrane irritation, fatigue, headaches,
asthma, etc.
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Hazardous Waste
• Hazardous waste is defined as discarded solid or liquid material
that may cause adverse health effects
• More specific classification
– Ignitability—likelihood of bursting into flames
– Corrosivity—strong acids or bases to eat through steel or burn skin
– Reactivity—likelihood of exploding or emitting toxic gas
– Toxicity—capability to poison
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Chemical and other environmental
exposures
• Industrial Hygiene
– Study of the anticipation, recognition, evaluation, prevention and
control of environmental factors that cause sickness, impaired health
and well being and discomfort for workers and communities.
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Chemical and other environmental exposures
• Radiation
• Chemicalsà Heavy medals, pesticides, organic solvents, etc.
• Biological hazardsà HIV, Hepatitis B and C, tuberculosis
(TB), common cold, flu, MMR
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Chemical exposures
• In many settings
workers are exposed
to very potent
chemicals that can
have immediate and
long lasting effects.
• How do we deal
with that?
Fit the task and equipment
to people
rather than fitting people to
task and equipment
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Identify problems with:
Productivity, Safety, Acceptance,…
Brain
System
Design solutions
Body
Human Factors
tools and
principles
Task
Equipment
Environment
Selection
Training
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Exposure pathway
10
• Toxicant
distribution
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Biological hazards
• Design approaches to preventing biological
hazards
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Physical Hazards (Vibration)
Chapter 12A
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Vibration
• Two major type of vibration exposure:
– Whole body vibration
– Hand-arm vibration
– Which is worse for your body, high frequencies or low
frequencies?
• Hand-Arm Vibration Syndrome (HAVS)
(AKA Raynaud’s phenomenon and vibration white
finger)
• No current government regulation in the US, but there
are recommendations
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Vibration (HAVS)
• Exact pathology has not been determined, but probably involves damage
to the nerves and smooth muscles of the blood vessels in the hand
http://drugster.info/medic/term/vibration-white-finger/
– Primary, reduction in blood flow to the fingers and hand: Results in
nerve, blood vessel, and tendon damage
– Feeling of ‘pins-and-needles’, numbness or cold
– Reduced skin temperature, decreased sensitivity and dexterity
– Vascular attacks- hand or fingers blanch (turn white), similar effects
to frostbite: flesh dies.
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Controlling Hand-Arm Vibration Exposure
1.
2.
3.
4.
5.
Select tools with the lowest level of vibration
Properly maintain tools and keep cutting tools sharpened
Use vibration-reduction (damping) gloves
Minimize grip force needed to hold and control the tool
Alternate work tasks that do not require use of vibrating tools
with those that do
6. Limit daily use of vibrating tools
7. Provide long rest breaks while using vibrating tools
8. Limit the number of days per week that vibrating tools are
used by a worker
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Skin temperature, degrees C
Vibration’s effect on skin temperature
Time, minutes
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Physical Hazards (Temperature Extremes)
Chapter 12B
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Work schedule for heat acclimatized and
unacclimatized employees
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Occupational Stress
Chapter 14
NOTE: This lecture deviates from the textbook, so
both are important
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Stressors
• Stress is how we respond to certain
situations (stressors)
• Stressors can be:
– Lighting, noise, vibration, repetitive motion
– Divorce, weddings, births, deaths
– Threats (e.g., terror, getting fired, failure)
– Isolation, crowds
• Human factors engineering objective
– To modify the work environment to reduce or
eliminate stressors and encourage appropriate
workload
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Stress effects
• Direct effect on human performance
– interferes with perception and action
• Indirect effect through psychological
mechanisms, such as arousal
• Long-term debilitating effects
Perception
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Long term health effects of chronic stress
• Cardiovascular conditions
• Hypertension/high blood pressure
• Immune related disorders
– increases likelihood of some bacterial
infections
• Ulcers and digestive disorders
• Migraines/headaches
• Some research show a relationship between
stress and cancer http://www.cancer.gov/cancertopics/factsheet/Risk/stress
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Stress in Employment
• Physicians
– Many trainees work more than 80 hours a
week, and 100-120 hr-weeks are common
• Truck Drivers
• Firefighters
• Power Plant Operators
• Military Combat
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Life stressors
• Individual characteristics that lead to stress
• Personal Life
– Death in family
– Marital issues
– Financial difficulties
• Professional Life
– Malcontent with labor-management relations
– Poor working conditions
– Inequitable wages
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Environmental Stressors
• Lighting
– Low illumination or high glare exert direct detrimental
effects on performance
– Indirect effects (eye health and visual acuity)
• Noise
– Direct effects (signal masking)
– Indirect effects (hearing losses)
• Motion
– Vibration (cyclical motion)
– Whole body vibration
– Cumulative motion disorders (vibration white finger)
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Environmental Stressors
• High frequency vibrations
– Extremities
• Cumulative trauma disorders (carpel tunnel synd., white finger)
• Low precision in hand work
– Whole body
• Some health effects: posture, oxygen consumption
• Major issue for displays and controls
• Low frequency vibrations (e.g., sea, light airplane)
– As a stressor, the effect is distraction (e.g., concentration)
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Environmental stressors
• Thermal (heat, cold)
– Comfort zone
• 73 -79° F [23-26°C] for summer
• 68-75° F [20-24°C] for winter
• Varying humidity
– Heat—primarily indirect effects
• Efficiency of information processing
– Cold—primarily direct effects
• Manipulating controls
• Moderating variables
– Air movement, clothing, and physical work
• Air quality (industrial hygiene)
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Psychological stressors
• Perceived threat of harm to:
– Esteem, something valued, bodily function (injury or death)
• Cognitive appraisal:
– Recognition and evaluation of psychological stressors on the individual
• Research in this area is difficult because of ethical issues. Why is
that?
• Level of arousal: how awake or reactive to stimuli
– Can be objectively measures through heart rate, pupil diameter and
hormone changes.
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Arousal and the Yerkes-Dodson Law
• Yerkes and Dodson (1908) did research with
mice in discrimination learning
Behavior of the dancing
mice
Black box was a shocker
White box: no shocker
3 conditions: varied by
visual discrimination
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The Yerkes and Dodson paper can be found at: http://psychclassics.yorku.ca/Yerkes/Law/
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Arousal and the Yerkes-Dodson Law
(Continued)
• Varied difficulty of a brightness discrimination and intensity of
a shock used to punish incorrect response
• Found that the various levels of stress or arousal induced by
electric shock affected performance
• Inverted U-function produced
• Increasing level of arousal initially increases performance, then
decreases it
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Yerkes-Dodson Law
Optimum level of
arousal
Performance Increasing
Alertness
Level of Arousal
The optimal level of arousal is:
• lower for more difficult or intellectual (cognitive) tasks
• the learners need to concentrate on the material
• higher for tasks requiring endurance and persistence
•the learners need more motivation.
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Why does this pattern happen?
• Positive stress: Upward limb result of an energizing–an
expansion of the amount of resources available
– Can improve performance on a low-arousal vigilance task with the threat of shock
• Negative stress: Downward limb increases selectivity of
attention or cognitive tunneling to specific cues
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Overarousal
• Sense of danger or threats have been imposed
• Perceptual or attentional narrowing
– Cognitive tunneling
• Working memory losses—less capable of using working memory
to store or rehearse new material
• Strategic shifts—”Do something NOW”
– Speed accuracy tradeoffs
• Potential long term memory enhancements (over- learned
behaviors) (e.g., steering while skidding on ice)
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Remediation of psychological stress
• Stress more likely to occur in emergency situations.
• Simplify design of displays, controls and procedures
• Emergency instructions should be easy to locate and clear to the intended
recipient
• Depend as little as possible on holding information in working memory
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Recommendations for
psychological stress
• Auditory alerts and warnings should be designed to avoid excessively
loud and more stressful noises
• Training
– Extensive training of emergency procedures can make them habitual
– Generic training of emergency stress management (guidelines)
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Human error
• Usually a human error is only one component of a complex
series of situations that contribute to accident probability
• Human errors can be broken down into:
– Mistakes
– Slips
– Lapses and mode errors
– Violations
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Mistakes
• Failing to formulate the right intentions.
• Mistakes can be knowledge- or rule-based
• Knowledge-based
– Results from failing to understand situation
• Rule-based
– Results from applying the wrong rules
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Slips
• The right intention is not carried out correctly.
– Pouring orange juice on your waffles instead of syrup.
– Putting contact lens solution on my toothbrush
• They are sometimes referred to as Freudian slips when verbal.
– If you turn in your homework and I say “Your welcome”, you might
say “Thank you”
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Lapses and Mode Errors
• Lapses
– When someone fails to do something due to a failure of memory
and/or attention
– Typically called forgetfulness
• Mode errors
– An operator makes some action that is appropriate for one mode but is
incorrect for another mode
– Wanting to driver forward but having the car in neutral or reverse and
then accelerating.
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Violations
• Human errors that are deliberate and illegal or incorrect.
– Doing something that you know is against the rules
– Deliberately failing to follow the rules
• Cheating on an exam
• Speeding, aggressive driving
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