INDUSTRIAL HYGIENE - 1
Lesson 3: Recognition of Hazards
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Objectives of the Lecture
At the end of this lecture, you will:
• Know the definition of hazard
• Recognize the types of hazards
• Learn the effects of different type hazards
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Definition
Industrial Hygiene – the science of protecting the health and
safety of workers through:
•
•
•
•
Anticipation,
Recognition,
Evaluation and
Control
…of workplace conditions that
may cause workers’ injury or illness.
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What is hazard?
• Hazard is a condition, object or activity with the
potential of causing:
– injuries to personnel,
– damage to equipment or structures,
– loss of or reduction of ability to perform a
prescribed function.
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Categories of Health Hazards
Hazards can be classified into five groups:
Physical hazards
Chemical hazards
Biological hazards
Ergonomic hazards
Psychosocial hazards
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Categories of Health Hazards
Chemical
Physical
Biological
Ergonomic
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PHYSICAL HAZARDS
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Physical Hazards
A physical hazard is an agent, factor or circumstance
that can cause harm with or without contact. Physical
hazards include:
• Heat and cold stress
• Illumination
• Vibration
• Noise
• Pressure
• Ionizing radiation
• Radon daughter exposure
• Electromagnetic field
• Solar ultraviolet exposures
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Physical Hazards
HEAT AND COLD STRESS THERMAL
COMFORT
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Effects of Heat
• The effect of heat on human being should be
considered together with:
– relative humidity,
– air velocity, and
– barometric pressure.
• Any discomfort about the work:
– Decreases efficiency
– Cause carelessness
– Inattentiveness which leads to accidents, injury,
fatality, or occupational disease.
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Effect of Temperature on Work and Rest
Slow but steady increase in the time taken to load mine cars as the effective temperature
increases from 66 °F to 82 °F (17 °C to 28 °C). Time taken for resting also increased, but
more markedly at temperatures higher than 75 °F (24 °C).
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Effect of Temperature on Performance
°C
As temperature increases above 30 °C, the rate of performance decreases.
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Metabolic Heat Balance
At equilibrium: Metabolic Heat Generation (MHG)= Heat Loss to Surrounding
If equilibrium is not achieved, either of the following will occur:
MHG < Heat Loss (Heating)
• Heart rate decreases
• Capillary blood vessels contract
• Involuntary muscular action
(shievering)
• Body cure temperature decreases
(with excessive heat loss)
• Possible collapse (hypotherma) (if
it continues).
MHG > Heat Loss (Cooling)
• Frequent rest required
• Body regulatory mechanism adjusts to give
higher skin temperature and evaporative
cooling by sweating increases
• Suffering progressively from heat strain
(psychological lethargy-lack of care, headache,
sickness, nausea, coma and death)
• Heart rate increases, mild increase in blood
flow to the skin, increase in rate of sweating
• Circulatory instability, considerably discomfort,
loss of working efficiency,
• Body gains heat, possible heat stroke and
collapse.
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Thermal Comfort Temperatures
Type of Work
Thermal Comfort (°C)
Work done while sitting
19 °C
Work done at standing
17 °C
Work requires active body motion
12 °C
Offices
20 °C
Laboratories
18 °C
Shopping malls
19 °C
Mental work done while sitting
21-23 °C
Light duty work while sitting
19 °C
Light duty work while standing
18 °C
Heavy duty work while standing
17 °C
Heavy duty work
15-16 °C
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Physical Hazards
ILLUMINATION
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Illumination
• Illumination: Lighting of the surfaces or objects in order to
make objects visible. At normal levels of illumination, the
ability to see increases as the log of the illumination.
• Visibility: Refers to how well the human eye can see
something.
• Luminance: The amount of light per unit area reflected from or
emitted by a surface. For most purposes, this is the important
measurement, because a portion of this light usually enters
the eye and is influenced by contrast, adaptation, and other
factors besides the physical energy in the stimulus.
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Illumination
• Contrast is a measure of luminance difference, usually between
that of the luminance of the object of interest and the
luminance of the background against which the object is seen.
It is computed by following formula:
• Contrast can vary:
• from 100% (positive) to 0 for objects darker than their
backgrounds, and
• from zero to infinity (negative) for targets brighter than their
backgrounds.
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Illumination
• As the shading of the block on the right
becomes lighter and the contrast between
the blocks becomes greater, the visibility of
the vertical border between them increases.
• The human eyes sensitivity to contrast is
affected by the level of illumination.
• If the illustration is viewed in a dimly lit room,
the point where it is possible to distinguish
the border would be farther down the figure.
• Stated another way, the less light there is, the
higher the contrast necessary between
objects to distinguish them.
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Good illumination is required for
• Early recognition of conditions that might give pre-warning of
potential safety hazards in the peripheral field and performance
of tasks that require knowledge of the relative spatial
relationships among objects separated by significant distance.
• Eliminating the tunnel vision effect of the narrow cap lamp
beam
• Overcomes shadowing by machine or roof support structures.
• Providing safe working conditions in and on all surface
structures, walkways, stairways, switch panel, loading and
dumping sites and working areas.
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Illumination
Required Standards
A uniform illumination of work surfaces,
Absence of fluctuations and abrupt changes of illumination,
Minimizing or eliminating of any usual discomfort,
Elimination of any undesirable glare from illuminated surfaces in
the direction of the eye,
• Illumination that satisfies requirements of both health and
economics is called rational,
•
•
•
•
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Physical Hazards
NOISE
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Sound vs. Noise
• Sound is a form of energy carried by waves through
an elastic medium. The intensity of sound depends on
the amplitude of its constituent waves. The greater
the amplitude the greater will be sound pressure
transmitted.
• Noise is an unwanted sound.
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Sound vs Noise
Sound is a change in pressure in a medium, typically air, that can be
detected by the ear.
The word noise is often used to mean unpleasant sound that the
listener does not want to hear.
Sound creates vibration and the vibrations lead to sound. It is a coupled
phenomena. The disturbance of the eardrum is translated into a neural
sensation in the inner ear and is carried to the brain, where it is interpreted
as sound. The physical quality of the eardrum and its vibratory response
affect the level of hearing.
‘www.utpb.edu
docs’ and ‘Fundamentals of Industrial Hygiene, Plog & Quinlan, 5th Edition’
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Transmission of sound in ear
In the human ear, a sound wave is
transmitted through four separate
mediums along the auditory
system before a sound is
perceived:
- in the outer ear—air,
- in the middle ear— mechanical,
- in the inner ear liquid and
- to the brain—neural.
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Outer ear
Middle
ear
Inner
ear
Definitions
• Amplitude: is a measure of the energy content of the
wave motion.
• Frequency: the number of wave passing a point per
second.
• Hertz: the unit of cycles per second is called the hertz
(Hz).
• Speed: frequency x wavelength
– 344 m/s in air
– 1410 m/s in water
– 5000 m/s in rock
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Noise
• Human can hear between:
0-20,000 Hz frequencies
• Human ears are the most sensitive to:
1,000-4,000 Hz frequencies
Most
sensitive
1 - 4 kHz
Infrasound 20 Hz
20 kHz Ultrasound
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Health Effects of Noise
• Psychological Impacts
– Frustation, anger, change in behaviour pattern
• Physical Impacts
– Permanent or temporary hearing loss called
presbycusis
• Physiological Impacts
– Blood pressure change, circulation change, breathing
increase, pulse increase
• Impacts on Performance
– Concentration loss, performance decrease, startle
reaction
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Health Effects of Noise
Extent of the damage depends on:
• the susceptibility of the
individual,
• the amount by which the noise
exceeds the damage risk level,
• the length of exposure and
whether the noise is steady or
intermittent (pneumatic
hammer).
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Sound Pressure vs. Sound Pressure Level
SOUND PRESSURE (Pa)
•
•
SOUND PRESSURE LEVEL (dB)
•
Is the local pressure
deviation from the average
ambient atmospheric
pressure, caused by a sound
wave.
Can be measured using a
microphone (in air), and a
hydrophone (in water).
•
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Or acoustic pressure level is a
logarithmic measure of the
effective sound pressure of a
sound relative to a reference
value.
Sound pressure level
instruments measure the wave
pressure in units of decibels
(dB).
Decibel
• DECIBEL is defined as ten times the log to the base 10 of
the ratio between two quantities of power.
Sound Pressure Level = 10 log!"
Sound Pressure #
Reference Pressure
Reference pressure is the lowest sound
pressure that human can hear and it
equals to 2x10-5 N/m2.
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#
Example
• What is the Sound Pressure Level if the sound
pressure at 3 m distance from noise source is
0.2 N/m2?
Sound Pressure Level = 10 log12
Sound Pressure Level = 10 log12
Sound Pressure 6
Reference Pressure
2×1051
2×1057
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6
6
6
= 10 log 108 = 80 dB
Physical Hazards
‘Fundamentals of Industrial Hygiene,
Plog & Quinlan, 5th Edition’
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Sound Pressure Level of Some Sources
Sound Pressure
(Pa)
Sound Pressure
Level (dB)
Source of Sound
Description
2x10-5
0
Normal hearing level
Reference
2x10-4
20
Broadcast studio
Very little sound
6.3x10-3
50
Low sound
-
6.3x10-2
70
Talking radio sound
Noisy
2x10-1
80
Intensive traffic
Noisy
2.0
100
Drilling, Lathe
Very Noisy
6.3
110
Rock drilling
Very Noisy
63.0
130
Jet engine
Unbearable
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Treshold Limit Values
According to the Regulation on Protecting Workers
from Noise-related Risks, enacted on 28.07.2013:
• Limiting exposure level is 87 dB.
• Maximum allowable effective exposure level is 85 dB.
• Minimum allowable effective exposure level is 80 dB.
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Permissible Noise Levels
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Physical Hazards
VIBRATION
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Vibration
• Vibration is mechanical oscillation of elastic bodies or a
system capable of vibration.
• An oscillation is one complete cycle of vibration.
• The time of one oscillation is called the period, and its inverse
is frequency (c/s).
• Vibration is characterized by three parameters:
i. amplitude of displacement,
ii. oscillary velocity,
iii. acceleration.
To characterize vibration for a given time interval "The rootmean-square value" of parameters i and ii is considered.
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Vibration Types
According to the resistance:
• Natural oscillation: no resistance to the motion, free oscillation,
• Damp oscillation: there is a resistance to the motion,
• Forced oscillation: resonance, there is external force to the
motion.
According to the frequency:
• Low Frequency Vibration: 1-6 c/s
– Can be seen in ships and vehicles and may have an amplitude about 1090 cm and cause motion sickness.
• Medium Frequency Vibration: 6- 60 c/s,
• High Frequency Vibration: > 60 c/s.
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Health Effects of Vibration
• The effect of vibration on human body varies depending on
whether the whole body (general vibration) or part (local
vibration) of it is involved.
• General vibration from the jolting of the floor or operating
platform or the operator's seat affects the whole body.
• Local vibration from the operation of hand tools, drills etc. affects
mostly the hands of the operator.
• It may:
– Interrupt blood supply to the blood vessels in the hands and arms
– Cause loss of sensitivity of the skin and lead to deformation and articular
immobilization.
– Osteoarticular changes
– Spasms
– Low back pain
– Spinal damage
– Vibration white finger.
– Loss of concentration which can cause secondary accidents
– Vibration sickness
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Vibration Sickness
• Occupational disease caused by prolonged effect on the body of a
local or general vibration or both.
• Develops gradually and for a long time does not effect the ability to
work.
• Main indications are pain, weakness, increased sensitivity to chilling,
cramps and whitening of the fingers, decrease in skin sensitivity.
• Functional disorders of the nervous system as rapid fatigue,
headaches and dizziness is seen.
• If it progresses, disruption of the cardiovascular activity and of
internal secretion, disturbance of metabolic processes and so on are
unavoidable.
• Vibration may have the effect of producing a displacement of the
internal organs of the body and under extreme conditions damage
may occur.
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Potential Health Effects of Vibration
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CHEMICAL HAZARDS
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Chemical Hazards
A chemical hazard is caused by exposure to chemicals in
the workplace. Exposure to chemicals in the workplace
can cause acute or long-term detrimental health effects.
• Toxic gases
• Crystalline silica
• Diesel particulate matters
• Acids
• Solvents
• Pesticides
• Insecticides
• Sensitizers
• Flammable materials
• Asthmagens
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Forms of Chemical Hazards
•
•
•
•
Solids
Liquids
Gases and vapors
Aerosols - dust, mist, fumes
Multiple chemical
hazards
Welding fumes
Dust particulates
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Spraying mist
Effect of Chemical Exposures
Health Risks
Heart Ailments
Lung Damage
Sterility
Central nervous system
Damage
Kidney Damage
Burns
Cancer
Liver Damage
Rashes
Safety Risks
Fire
Explosion
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Corrosion
Exposure Entry Routes
Inhalation
Breathed in
(most common route)
Ingestion
Swallowing via eating or
drinking
Absorption
Drawn through skin or eye
surface
Injection
Penetration through the skin
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Warning Signs of Potential
Chemical Exposure
• Dust, mist, smoke in the air
• Accumulation of particulates (dust) on surfaces
• Unusual tastes and/or smells
• Eye, nose, throat, upper respiratory, and/or skin
irritation
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Examples of Chemical Exposure Symptoms
• Eye, nose, throat, upper respiratory, skin irritation
• Flu-like symptoms
• Difficulty breathing
• Fatigue
• Loss of coordination
• Memory difficulties
• Sleeplessness
• Mental confusion
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Types of Health Effects
Exposure Condition
Exposure
Example
ACUTE
Immediate
Short-term, high
concentration
H2S exposure within a
confined space
CHRONIC
Delayed; generally for
years
Continuous; for long
periods of time
Asbestosis
Acute
Chronic
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Toxicology
What is toxicology?
• The science that studies the poisonous or toxic
properties of substances.
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Toxic Effects
Dose
1. Concentration – amount
2. Duration of Exposure – time
Effective Doses (EDs) are used to indicate the effectiveness of a substance. Normally,
effective dose refers to a beneficial effect such as relief of pain. It may also stand for a
harmful effect such as paralysis. Thus, the specific endpoint must be indicated.
Toxic Doses (TDs) are used to indicate doses that cause adverse toxic effects.
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Toxic Effects
• Toxic chemicals disrupt the normal functions of the body. Effects
can be:
– Local - at the site of exposure
– Systemic
• Affects the entire body
• Target organs - organs or systems where symptoms of
exposure appear
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Local Effects
Local (direct) effects:
• Irritation (dryness, redness, cracking) - fiberglass
• Corrosion (chemical burn) - acid
• Upper Respiratory Track Infection – inhaling particles
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Systemic Effects
Group
Affected organ
Chemicals
Hepatotoxins
Liver
Carbon tetrachloride, nitrosamines
Nephrotoxins
Kidney
Uranium, halogenated hydrocarbons
Neurotoxins
Nervous system
Mercury, lead, carbon disulfide
Hematotoxins
Blood system
Carbon monoxide, cyanides
Anesthetics
Nervous system
Hydrocarbons, propane, isopropyl ethers
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Permissible Exposure Limits (PEL)
– Local and international regulations that establish the
acceptable amount or concentration of a substance in the
workplace
– Intended to protect workers from adverse health effects
related to hazardous chemical exposure
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Types of Exposure Limits
TWA = Time - Weighted Average
14
12
Levels vary over the shift duration
Exposure in PPM
PEL
10
T
8
6
4
Protect from chronic diseases
2
0
8:00
ÖÖ
9:00
ÖÖ
10:00
ÖÖ
11:00
ÖÖ
12:00
ÖS
1:00
ÖS
2:00
ÖS
Time
“C” = ceiling limit:
Level never to be exceeded during
the work shift
60
Ceiling
50
Protect from acute disease or
health effects
Exposure
40
30
20
10
PEL
0
Time
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3:00
ÖS
4:00
ÖS
BIOLOGICAL HAZARDS
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Biological Hazards
• Also known as biohazards refer to biological
substances that pose a threat to the health of
living organisms, primarily humans.
• Biological hazards include:
–
–
–
–
–
–
–
–
Bacteria
Viruses
Fungi
Moulds
Pollen
Protozoa
Vertebrates
Parazites
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Biological Hazards
Insects
Poisonous Plants
Animals
Water/Sewage
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Contaminated
Soil
Bloodborne
Pathogens
Ways of Exposure to Biological Hazards
•
Ingestion (contaminated fingers)
•
Injection (use of sharps)
•
Inhalation (gases, powders, aerosols)
•
Skin contact (organisms, neurotoxins)
•
Absorption through the skin (various chemicals)
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Biological Agents
Biological agents (bacteria, viruses, fungi, prions) are
classified into four Hazard Groups. Classification is based
on whether:
•
•
•
•
the agent is pathogenic to humans
the agent is a hazard to employees
the agent is transmissible to the community
there is effective prophylaxis or treatment available
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Group 1
Unlikely to cause human disease. e.g. Tissues and cell
lines of non primate/non human origin.
Human/primate cell lines that are long established and
have long history of safe use [e.g. HeLa cells]
Disabled/attenuated/non-pathogenic strains of some
bacteria and virus.
Does not usually require health assessment or health
surveillance unless there is a specific risk or it is required
by the Government Institution enforcing the Control of
Substances Hazardous to Health (COSHH) Regulations
2002.
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Group 2
A biological agent that can cause human disease and
may be a hazard to employees;
It is unlikely to spread to the community and there is
usually effective prophylaxis or effective treatment
available;
Does not usually require health assessment or health
surveillance unless there is a specific risk (e.g. pregnant
workers).
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Group 3
Can cause severe human disease and may be a serious
hazard to employees;
It may spread to the community, but there is usually
effective prophylaxis or treatment available.
HIV, Hepatitis B, E. coli 0157, Salmonella typhi. All work
with hazard group 3 biological agents or class 3
genetically modified organisms requires health
surveillance.
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Group 4
Causes severe human disease and may be a serious
hazard to employees; it is likely to spread to the
community, and there is no effective prophylaxis or
treatment available. e.g. Rabies, Ebola Virus.
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ERGONOMIC HAZARDS
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Ergonomic Hazards
• An ergonomic hazard is a physical factor within
the
environment
that
harms
the
musculoskeletal system.
• Ergonomic hazards include themes such as:
– repetitive movement
– manual handling
– workplace/job/task design
– uncomfortable workstation height
– poor body positioning
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Examples
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Effects of Exposure to Ergonomic Hazards
• Musculoskeletal Disorders (MSDs)
– Exposure to ergonomic risk factors for MSDs increases a worker's
risk of injury
• Repetition
• High force
• Awkward postures
– Work-related MSDs are among the
most frequently reported causes
of lost or restricted work time.
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PSYCHOSOCIAL HAZARDS
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Psychosocial Hazards
Drug and alcohol use
Fly-in-fly-out operations
Expatriate placements
Post-traumatic stress
disorders
• Feeling guilty and
personally responsible
due to fatal accidents
•
•
•
•
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Try to Identify the Type of Hazards
Source: https://www.combinedworkplacesafetyconsulting.ca/hazard-identification-and-control.html
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Try to Identify the Type of Hazards
Physical hazard:
work at height
Physical hazard:
noise, UV
exposure, chip
splashing
Physical hazard:
pressure, vibration,
noise
Physical hazard:
splashing of metal
chips, noise
Bad housekeeping
Ergonomic hazard:
manual handling
Chemical hazard: chemical
exposure and
Physical hazard:
slipping
Source: https://www.combinedworkplacesafetyconsulting.ca/hazard-identification-and-control.html
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