Introduction to Occupational Hygiene
Associate Professor Brian Davies
Davies, SHS, Nov 2006
Assoc. Prof. Brian Davies AM
• Worked as an Occupational
Hygienist in industry for > 30 years
• Certified Occupational Hygienist
(ABIH & AIOH)
2
Assoc. Prof. Brian Davies AM
• Worked in the steel, aviation &
mining sectors (including
petroleum exploration)
• Currently Associate Professor
of Occupational Hygiene &
Toxicology at the University
of Wollongong, Australia
3
Aim of This Course
To introduce participants to the
discipline of Occupational
Hygiene & demonstrate how it
can be applied in the workplace
4
Learning Outcomes
At the conclusion of this course you
should be able to:
1) Understand the principles of
occupational hygiene and workplace
sampling
2) Conduct a walk through survey
and recognise the chemical, physical
& biological agents present
5
Occupational Disease
Causes of occupational disease
fall into four major areas
–Chemical agents
–Physical agents
–Biological agents
–Psycho-social causes
6
Chemical Agents
•
•
•
•
•
7
Dusts
Metals
Vapours
Gases
Pesticides
Diseases of the Skin
• Dermatitis
– inflammation of the skin
– two types (irritative & sensitising)
• Irritative: alkalis, acids, cement, solvents, some
metals & their salts
• Sensitising: chrome salts, nickel, cobalt, urea or
phenolic resins, some woods
• Skin cancer
– Coal tar pitch, shale oil, mineral oils (unrefined)
• Erythema
– Pitch
8
9
10
Diseases of the Respiratory System
• Pneumoconiosis
– Reaction of lung to presence of dust
– Benign (iron, tin, barium)
– Symptomatic (coal dust)
• Silicosis
– Fibrosis & lung cancer
• Asbestosis
– Fibrous thickening in lower parts of
lung, loss of elasticity
11
Diseases of the Respiratory System
• Lung Cancer
– Mesothelioma (crocidolite)
– Chromates, Nickel compounds, CTPV
• Bronchial Asthma
– Mainly sensitisation
– Isocyanates, Colophony fumes, hardwood dusts (cedar,
oak & mahogany)
– Byssinosis ,Bagassosis
• Extrinsic Allergic Alveolitis
– Farmers lung (mouldy hay), Pigeon fanciers lung
(droppings)
12
Diseases from Metals
•
•
•
•
•
Lead - systemic poison
Mercury - organic mercury more toxic
Chromium -ulceration, nasal cancers
Arsenic - skin cancer
Metal fume fever - fumes of metal
oxides (eg zinc)
• Manganese – motor neuron disorders
• Cadmium- kidney disease
13
Vapours
• Vapours (Solvents)
– Dermatitis
– Cause narcosis (CNS depressants)
– Some damage peripheral nerves
– Some damage kidneys & liver
– Some interfere with blood formation
– Some can penetrate the skin
– Most decompose on heating to toxic
compounds
14
Gases
• Simple asphyxiants
– Replaces oxygen in the lungs (Carbon
dioxide)
• Irritants
– Can cause bronchitis and pulmonary
oedema (sulphur dioxide)
• Toxic
– Causes a metabolic interference with the
oxygen taken up by the body (carbon
monoxide)
15
Pesticides
• Insecticides
– Organo-phosphorous compounds
– Interfere with enzyme called
cholinesterase
• Herbicides
– Liver ,kidney & lung damage
possible with some products
16
Physical Agents
• Noise induced hearing loss
(NIHL)
• Vibration
• Ionising radiation
• Non-ionising radiation
• Heat & cold stress
17
EFFECTS OF NOISE
18
EFFECTS OF NOISE (Cont)
Healthy Cochlea
Photos showing actual damaged
‘hair cells’ in the inner ear
Damaged Cochlea
19
Biological Agents
• Viruses-Hepatitis A B & C, HIV
• Bacteria-Legionella, Q fever,
Anthrax, Leptospirosis
• Fungus- Moulds, Histoplasmosis,
Farmers lung
• Plant-Poison Ivy,
20
Psycho-Social Causes
• Stress
– The person (lack of physical & mental
fitness, inadequate training or skills,
poor reward & prospects etc)
– Work demand (long hours, shift work,
repetitive work)
– Environment ( noise, heat, humidity,
fumes etc)
– Organisation (poor industrial relations,
communication, supervision)
21
Relationship to Occupational
Hygiene
22
What is Occupational Hygiene ?
'Occupational Hygiene is the
discipline of anticipating,
recognising, evaluating and
controlling health hazards in the
working environment with the
objective of protecting worker health
and well-being and safeguarding the
community at large.'
23
Aims of Occupational Hygiene
• Recognition of health problems
created within the industrial
environment
• Evaluation in terms of long and
short term effects
• Development of corrective
measures to control problems
24
Recognition
• Need to recognise the problem
– What health effects are presenting
– What health effects are a possible
(walkthrough audits)
• Need to understand the process
– What is causing the health effect
– How are people being exposed
25
Coal Mining
Dust
Noise
Diesel emissions
Hazardous substances
Fungi
Vibration
26
Aluminium Smelter
CTPV
Heat stress
Metal fumes
27
Welding
Welding fumes
Toxic gases & vapours
Radiation
28
Sand Blasting
Silica exposure
Noise
RPE
29
Pipe Laying
Welding fumes
Heat stress
UV radiation
30
Aviation Industry
Composites
Cu Beryllium
Hazardous
substances
Noise
Confined spacesfuel vapours
31
Oil Industry
Noise
Hydrocarbons
Hydrogen sulphide
Heat stress
32
What are the risks here ?
Gold
processing
plant in West
Africa
33
Gold Processing Plant
34
Gold Room
35
Group Exercise 1
• Break up into allocated groups
• List all the health issues you think
are present at this gold processing
plant (see notes)
36
Evaluation
• How can the contaminant of concern be
quantified
– Chemical, physical or biological
– Dust, vapour ,mist, gas, fibre
– Sampling method
– Is quantification actually necessary
37
Preventative Principles
• Substitution
• Segregation
• Enclosure and mechanical handling
• Ventilation
• Work practices
• Personal protection
38
How do substances effect the body?
• Workers need to come in contact with
them - gases, vapours, dusts, noise
• Need to reach a target organs different target organs for different
things
• Need to be in sufficient dose to cause
harm
dose = concentration x duration of
exposure
39
Routes of Entry
Contaminant
IN THE AIR
BREATHING
SPILL
Other ways:
Eyes &
Ingestion
SURFACE
SKIN
Source :Airmet Scientific
40
Routes of Entry
• Inhalation
– By far the major entry point for contaminants
• Skin Adsorption
– Major source of entry for some organic
compounds such as phenol and
organophosphate pesticides
• Eye
– Entry point for some solvents
• Ingestion
– Poor hygiene can allow contaminants (eg lead)
to enter the body
41
Target Organs
• Upon entry to the body contaminants can
have an adverse effect on one or more
organs (target organs)
– Lungs
– Blood
– Central Nervous System
– Liver
– Kidneys
42
What does an MSDS tell you?
Detailed information on
a dangerous goods or
hazardous substance
Product Name
Codes, Listings
Major Uses
Ingredients
Physical Characteristics
Precautions for Use
Safe Handling and
Storage Information
First Aid/Emergency
43
To be useful, MSDS’s, must have…
Issue Date
Company Details (Not O/S)
Substance Name
Health Effects/First Aid
Engineering Controls
Flammable/Fire & Expl. Haz.
Storage & Handling
Spills & Disposal
44
How do Hygienists Use MSDSs?
• As a source of information on
– Toxic effects
– Exposure standards
– Control technologies
• Engineering
• PPE
– Reference to other analogous
compounds
45
Group Exercise 2
Evaluating MSDS
• Review of some MSDS
• What are the key issues wrong
with the MSDS’s provided?
46
Hazard Identification
• Review the materials , processes &
procedures used in the plant
– Process flowcharts
– MSDSs
– Health effects of possible
contaminants
– International literature
47
A Case Study-Know The Process
• Copper, Gold and Silver mine
• 200 PPM arsenic in the copper ore
– Known by geologist
– Solid solution with the copper
• Beneficiated with the copper in the float
cells
– Known by the metallurgist
48
A Case Study- Know The Process
• As Concentration now 5000 PPM (0.5%)
– 50% slurry, no dust
• At port slurry de-watered and dust
generated
• 10 mg/m3 inhalable dust => 0.05 mg/m3 As
• As ES is 0.01 mg/m3 thus possible to have
overexposures at dust levels below
inhalable dust exposure standard
49
Purpose of a Walk Through Survey
• To familarise yourself with the process
• To establish potential health risks
• Identify any engineering controls
• To establish what, where & whom should
be monitored
50
Walk Through Survey
• When conducting a walk-through survey
– Look for signs of possible exposure
(emissions escaping from system,
hazardous chemicals, deposits on floors
& surfaces, noise equipment etc)
– Condition of any control technologies
including PPE
– Location of workers to sources of
contamination
51
Group Exercise 3
• Break into allocated groups
• Conduct a walk through survey of
area indicated by Brett Young
• Return to room and list all potential
health risks (if any) you identified
• How would you decide which of the
possible health risks to quantify
52
How do we evaluate hazards?
• Need to establish what the hazard is
(or likely to be)
• Need to develop a suitable
monitoring programme
• Need to follow established
monitoring techniques
53
How do we evaluate hazards?
• Evaluate the results in terms of the
hazard (chronic, acute etc)
• Make improvements to the workplace
if necessary and conduct follow-up
sampling
• Keep a record of everything
54
What is Monitoring?
Process of conducting measurement
(s) of the concentrations of airborne
contaminants.
To estimate risk the following are
required;
a reliable estimate of exposure
a standard for means comparison
55
Exposure Standards
“No substance is a poison by
itself, it is the dose that makes a
substance a poison” (Paracelsus
16th Century)
• Hazard <=> Toxicity
• Hazard = Toxicity x Exposure
56
Dose Effect Relationship
• For each chemical there is a doseeffect relationship
– Acute effects (irritants, carbon
monoxide)
– Chronic effects (benzene , asbestos
fibres)
Basis of exposure standards
57
Threshold
• The dividing line between noeffect and effect levels of
exposure
• For each substance there is a
threshold of intoxication which is
usually different for individual
substances
58
Dose-Response Curve
59
Individual Susceptibility
60
Threshold of Intoxication
For each substance, no matter
how toxic, there exists a dose
level called the threshold of
intoxication which the human
body is capable of accepting and
detoxifying without injury to
itself.
61
Basis of Exposure Standards
• Toxicity
• Biological action
– Asphyxiants
– Anesthetics
– Carcinogens
– Irritants
– Systemic poisons
62
What limits exist?
•
•
•
•
•
•
63
ACGIH (USA)
HSE (UK)
OSHA (USA)
MAK (Germany)
ASCC (Australia)
Many other countries
What do they exist for?
• Chemical hazards
– Vapours, gases, dusts, fibres
• Physical hazards
– Noise, vibration
• Biological hazards
– Linked in most cases to chemical
hazards
64
Types of exposure standards
•
•
•
•
•
•
•
65
TWA (time weighted average)
STEL (short term exposure limit)
Ceiling/Peak (never to be exceeded)
Skin Notation
General Excursion Advice
Carcinogen category
Not otherwise classified
Limitations of Exposure Standards
• Values do not exist for all
substances
• They are guides only not fine
lines between safe and unsafe
• They may not protect all workers
but “nearly all workers”
66
Extended Workshifts
• Brief and Scala model
• OSHA model
• Pharmacokinetic model
• A more practical approach uses the
total time worked per month
67
Which Substance is the Most Toxic ?
• 50 PPM
• 10 PPM
• 2 PPM
• 0.5 PPM
Each person is allocated only one vote
68
Which Substance is the Most Toxic?
• 50 PPM HALOTHANE(ACGIH- USA)
• 10 PPM HYDROGEN CYANIDE
• 2 PPM
SULPHUR DIOXIDE
• 0.5 PPM HALOTHANE (ASCC-Australia)
Why is there this difference?
69
Why Monitor Workplaces?
• To establish the level of risk in
respect to adverse health effects
in workplaces
• To meet regulatory or corporate
requirements
• To develop appropriate control
measures
70
Why Monitor Workplaces (Cont) ?
• To measure the effectiveness
of control measures
• For research purposes
• To dispel anxiety
71
Types of Surveys
• Initial - to gain information
• Basic – qualitative assessment
• Detailed - quantitative assessment
• Routine – monitor compliance/controls
72
Sampling Strategy
•WHO
•WHERE
•WHEN
•WHAT
•HOW
METHOD
73
Exposure Judgement Outcome
• Acceptably low
• Too high
– Fix the problem
• Cannot make a judgement
– Need for more information
(samples/assistance from others)
74
Inputs to Judgement
•
•
•
•
•
•
75
Process experience
Material characteristics
Toxicity
Workforce characteristics
Statistical tools
Confidence in exposure limit
Who should be monitored?
• Everyone?
• Those identified as potentially
exposed from walkthrough
survey or risk assessment?
• Controls?
76
Types of Sampling
• Grab
• Short-term
• Long-term
• Continuous
• Bulk
77
78
Bulk Sampling
• Substance(s) identification only
• Cannot be related back to airborne
concentration
• Can sometimes be used with other
direct methods to calculate worstcase scenarios
79
What should be monitored
• Contaminants identified in
walkthrough survey or risk
assessment
80
What type of sample?
• Area
– Should only be used to assess the
effectiveness of control strategies
– Does not take account of an individuals
movements
– Has no legal standing
• Personal
– Accounts for movement of workers
– All exposure standards are based on personal
sampling
81
How many samples?
• Single samples
– Some legislation is based on single sample
compliance
– Approach has issues due to variability within
an exposure cloud
• Multiple samples
– Improved accuracy but how many samples are
enough
• Statistically based sampling
– Most accurate approach but time consuming and very
costly
82
How long should samples be collected?
• Substance properties
– Acute or chronic adverse health
effects
• Duration of work shift
– Shift length
– Work pattern within shift
83
What method should be used?
• If possible always use recognised
standard methods
– Some industries have statutory methods
• Some reference methods are:
– NIOSH
– UK HSE (MDHS)
• Always check validity of non standard
methods to ensure they withstand external
scrutiny
84
After Data Collection
• How will the data be evaluated?
• How will data be stored and
communicated to stakeholders?
• What is unacceptable?
– Statutory requirement
– Corporate requirements
85
Statistical Based Monitoring
• Approach developed in 1970’s by NIOSH
• Collect a statistical sub-set of worker
exposure to represent all persons’
exposure in a SEG (HEG or KEG)
• Sampling must be random
• Number of samples collected determined
by required confidence level
86
87
Process of statistical monitoring
• Establish similar exposure
groups (SEGs)- This may require
preliminary sampling
• Develop statistically based
sampling schedule
• Collect data according to
defined programme
88
Process of statistical monitoring
• Statistically analyse data
• Modify exposure groups (if
required)
• Final report or ongoing reports
• Ongoing data collection
(maintenance sampling)
89
Establish Similar Exposure Groups (SEGs)
• Can be defined by:
– process and environmental agent
– process, job and environmental agent
– process, job, task and environmental agent
– process, task and environmental agent
– work teams
– non-repetitive work
90
Establish Similar Exposure Groups
• Observational
– Simplest form but least accurate
• Sampling
– Preliminary sampling to establish groups
• Combination of observation and sampling
– Most accurate approach
91
Longwall Mining
92
Continuous Miner (Panel)
93
Basic SEG Structure- Coal Mine
SEG
Description No. Workers
1
2
3
4
5
6
Longwall
Panel
Methane Drillers
Tailgate Workers
Outbye Workers
Surface Workers
94
60
70
14
8
60
16
Outbye Workers- Secondary SEG Structure
Task
Materials crew
Belts
Diesel workshops
Cable crews
95
Number
35
5
8
12
Revision of SEGs
• SEGs should be revised when:
– New data is available
– A change to the process occurs
– New jobs are created
– New contaminants may be present
96
Methods of estimating No. of Samples
• Q: How many times do I need to make
measurements for the results to be
statistically valid and useful?
A: Depends on information you need.
Compliance
Research
Corporate requirement
Degree of confidence
97
Practical Options
• Point of diminishing returns
• Reasonable approximation of
exposure profile possible with about
6-10 samples (AIHA 1998)
• As exposure standard approaches
exposure limit this number increases
depending on level of confidence
required
98
Source : AIHA (1998)
99
Random Sampling
• Need for defined sampling period
– 64 weeks normal but can be as low as you wish
– Very hard to manage major programmes below
16 weeks
• All samples must be collected without bias
– Sampling schedule based on random numbers
• Need to write a detailed sampling protocol
– Any deviations must be accounted for in
protocol and noted at time of event
100
Sampling Schedule
101
Lets do some monitoring
• Dusts & fibres
• Vapours & gases
• Noise
• Biological monitoring
102
Dusts & Fibres
103
Composition of Dusts
Fibrogenic reactions (quartz)
Carcinogenic response (chromates)
Irritation (acid mists)
104
ISO/CEN Convention
(PM 10)
Source :Airmet Scientific
105
Relative size of particles
Inhalable dust
100 micron
RESPIRABLE
Thoracic dust
30 micron
THORACIC (PM10)
Respirable
dust 10 micron
INHALABLE
• 1 3
7
Source :Airmet Scientific
106
10
30
100
Respirable Dust
•Gets deep into the lung
•Not easily removed
•Invisible to human eye
• 4.0 micron at 50% cut
Source :Airmet Scientific
107
The Cyclone
Separates the
RESPIRABLE dust
•Inlet points down
Suction from top
Contains cassette
Source :Airmet Scientific
108
Parts of a Cyclone
•Retaining ring
•Cyclone top
•Cassette (filter)
•Main Body
•Grit pot
Source :Airmet Scientific
109
Inhalable Dust
•Affects the whole of
the respiratory
system
•100 micron at 50%
cut
Source :Airmet Scientific
110
The I.O.M. sampler
•Inhalable sampler
•Cassette system
•All collected dust is
IOM
cassette
Transport
clip
measured
•Easily handled
IOM
sampler
•No contact with filter
•Multi fraction sampling with
foam inserts
Front
cover
Cassette
front
Source :Airmet Scientific
111
Filter
Support
grid
O ring
Body
IOM Cassette
FILTER
Source :Airmet Scientific
112
•IOM Cassette.
•Cassette and
filter are pre and
post weighed as
a single unit
The IOM complete
•Place
cassette in
body
Screw front
cover on
Source :Airmet Scientific
113
Sample Train
•Is made up of :
•Pump
•Connecting tube
•Sampler
•Any accessory
SAMPLER
CONNECTING
TUBE
PUMP
Source :Airmet Scientific
114
Calibration
•Connect from
pump to
sampling
head
•Connect from
sampling
headto
calibrator
Adjust flow to require flowrate
Source :Airmet Scientific
115
Soap Film Meter
116
Electronic Flowmeter
117
Position of Sampling Device
•ALL Exposure
limits are based
300mm
Hemisphere
on
around the nose
•PERSONAL
SAMPLES
and mouth
And MUST be taken
in the Breathing
Zone
Source :Airmet Scientific
118
Taking the Sample
•Place sample train on person:
Start pump
Note start time
At end of sample:
Note stop time
Source :Airmet Scientific
119
Direct Reading Instruments
• Hund Tyndalometer
• Dust Trak
• R & P PDM
120
Hund Tyndalometer
121
Dust Trak
122
Problems with direct reading instruments
• Most devices cannot distinguish
between water droplets from
suppression sprays and dust
particles
123
R & P Personal Dust Monitor
124
TEOM Series 3600 Personal Dust Monitor
125
Real Time Data
126
Remote Control Miner Operator, Major
Exposure Variables
Mass Concentration [mg/m
³]
5
Mass
Concentration
4
Cumulative
Concentration
3
2
1
Projected
Exposure
0
6:00
7:12
8:24
9:36
10:48
12:00
Time
127
Source:
CDC-NIOSH Pittsburgh Research Laboratory
13:12
14:24
15:36
16:48
18:00
Fumes
• Use open face sampling head (IOM
or other)
• Analyse collected material for
contaminants
• Need to be careful of filter pore size
– Welding fume typically <1 um
128
Types of Fibres
• Asbestos
• Synthetic or MMMF
129
Asbestos
• Fibrous silicate minerals
• Main types
– Chrysotile
– Amosite
– Crocidolite
– Actinolite
– Anthophylite
– Tremolite
130
Health Effects
• Pleural Plaques
• Asbestosis
• Lung Cancer
• Mesothelioma
131
Management of Asbestos
• Identification – dispersion
staining microscopy, XRD & IR
• Assessment - Membrane filter
method
• Control- Removal, encapsulation,
monitor
132
Bulk Amosite
Copyright A Rogers
133
Asbestos-Ships Lagging
Copyright A Rogers
134
Tremolite Rock and Fibre
Copyright A Rogers
135
Calcium Silicate and Amosite
Copyright A Rogers
136
Dispersion Staining for Identification
Copyright A Rogers
137
Polarised Light – Ist order Red
Copyright A Rogers
138
Types of SMF
• Glass fibre
– Reinforcing filament
– Glass wool
– Ultra fine glass fibre
• Mineral wool
– Rock wool
– Slag wool
• Ceramic fibre
– Refractory ceramic fibres
139
Health Effects of SMF
• Significantly less potent than asbestos
• Larger fibre sizes induce irritation
• No fibrosis has been demonstrated
• Some slight risk of lung cancer but debate
continues
140
Measuring Airborne Fibres
MEMBRANE FILTER METHOD
Pump and filter (cellulose ester)
Phase contrast microscopy
Sampling (Occupational & Paraoccupational)
Filter mounting and clearing
Kohler illumination
Specific counting rules
Certified counters
141
Membrane Filter Method Slide
Copyright A Rogers
142
Vapours & Gases
143
Sampling Systems
Sampling systems
– Active
• Pump and adsorption tube (vapours)
• Pump and liquid absorption (gases &
vapours)
– Passive
• Solid adsorption (vapours)
• Direct reading (gases & vapours)
144
Vapour Sampling
•With sorbent tubes
Main bed
Precision drawn
glass tube
Back-up bed
Retaining clip
Foam separator
Source :Airmet Scientific
145
Breakthrough?
•When a
sorbent if full
to capacity,
breakthrough
occurs
Source :Airmet Scientific
146
Breakthrough
is when a tube
becomes full
and rereleases the
hazard
Tube Holder
147
Gas/Vapour Sampling Train
•Break off both ends of
a sorbent tube (2mm
min dia, or 1/2 dia of
body)
Put tube in low flow
adapter/tube holder
Make sure tube is in
correct way around
Source :Airmet Scientific
148
Calibration of a tube
•Connect to
calibrator
•Adjust flow at
low flow adapter
Use soap film
or electronic
meter
Source :Airmet Scientific
149
Taking the Sample
Place sample train on person:
•Start pump
•Note start time
•At end of sample:
•Note stop time
Source :Airmet Scientific
150
After the sampling
•Remove tube
•Place covers on
tube
•Send off for
analysis with
details of sample
Don’t forget to send a BLANK
Source :Airmet Scientific
151
Sample bags - gases
•Made from Tedlar
•Inert
•Valve/inlet with septum
•No auto shut off
•Fill by flow X time
•Designed as single use
Source :Airmet Scientific
152
Bag filling
•Do not overfill
•Bag will take 3 times
stated volume
Fill to correct volume
by setting flow rate
and time… otherwise?
More pressure means
more migration
Source :Airmet Scientific
153
Badges - Dosimeters
Protective disk
Sorbent bed
Small
Light
Membrane
Support grid
Void for solvent
Source :Airmet Scientific
154
No pump
Needs air movement
to work
Badges and their sorbents
•Activated sorbent
•Over 100 chemicals
•No need for backup
layer if method
followed
•Larger molecules can
dislodge smaller ones
•Does not work in ‘still
air’ conditions
Source :Airmet Scientific
155
Direct Reading Instruments
156
Cross Sensitivity (CO Sensor)
H 2S
SO2
NO
NO2
Cl2
H2
HCN
C 2H 4
157
~ 315
~ 50
~ 30
~ -55
~ -30
< 40
40
90
Challenge
concentration 100ppm of each
gas
Filters for Contaminant Gases
H2S
SO2
NO
NO2
Cl2
H2
HCN
C2H4
158
Unfiltered
Filtered
~ 315
~ 50
~ 30
~ -55
~ -30
< 40
40
90
< 10
<5
< 10
~ -15
< -5
< 40
< 15
< 50
‘Port’a’man!’
159
Noise
160
Common Terms
• SLM – Sound Level Meter (instrument
consisting of a microphone, amplifier and
indicating device (SLM/dosimeter)
• Dosimeter – SLM that can record history
• dB – decibel – measurement of Sound
Pressure Level
• Sound power – total sound energy
radiated by a source
161
Common Terms
• Leq – equivalent continuous noise
level of a fluctuating sound over time
ie LAeq8hr = 8 hrs (A weighted).
• A Weighting – scale with frequency
response - human ear
• C Weighting – scale to determine
level of hearing protection required
(high)
162
Introduction to Sound Level Meters
• Integrating or nonintegrating
• Type 0,1 – precision
• Type 2 –
general/industrial use
• Type 3 – indication only
• Filters and weighting
networks A, C, lin
• Frequency analysis – 1/3
and octave band
• Primarily for walkthrough survey work
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Introduction to Dosimeters
• SLM with ability to provide an integrated
noise exposure over a given period (ie
work shift – 8, 10, 12 hr)
• Most provide data logging with ability to
set statistical parameters, alarm levels,
and record peaks in addition to exposure
in increments – normally 60 sec.
164
What is Noise Dosimetry?
• Noise dosimetry is used to determine
occupational exposure over a work
period.
• Particularly relevant where noise
sources are cyclic or where an
operator moves around a large area
of a workplace with many difference
noise sources.
165
Typical Dosimeter
166
How do you determine what is required?
• Noise survey, contour plans,
dosimetry
• Is the survey based on reaction
to specific complaints or issues.
• Is it a baseline survey to
establish “hearing protection
zones”.
167
How do you determine what is required?
• Does the employer wish to
assess suitability of hearing
protection.
• Where does/do the worker/s
spend the bulk of their time
168
Noise Exposure Dosage Guide (unprotected)
169
Limiting dB(A)
Maximum duration
85
8 hr
88
4 hr
91
2 hr
94
1 hr
97
30 min
100
15 min
103
7 min
106
4 min
109
2 min
112
1min
115
30 sec
Evaluation of data
170
Types of data evaluation
• Statutory requirement
– Straight comparison to exposure
standard
• Statistical sampling
– Statistical evaluation
171
Statutory Requirement
• <<ES - acceptable
• ES – unacceptable but more sampling
may improve situation
• >>ES - unacceptable
172
Statistical evaluation of exposure data
• Need to define what you are trying to
achieve
• Need some understanding of statistics
• Need to realise that nothing is perfect and
there is still a possibility of overexposure
• Need to define when it is better to fix the
problem rather than keep sampling
173
Statistical Computer Packages
• Many packages available
– Hygienist (Dutch), LogNorm2, IH stats
• IH Stats
(AIHA as part of book package)
– Excel based but limited in application (50 data
points), no ANOVA
• LogNorm2 (AIHA but also visit www.lognorm.net)
– Easy to use, good graphics but problems when
applied to noise exposure
– Requires minimum of 6 data points
174
Statistical Metrics
•
•
•
•
•
175
GM & GSD
MVUE
95 % UCL
95 % ile
UTL
Data Treatment-Typical Example
Inhalable Dust – Personal sampling on a
random schedule over 16 weeks.
5.5
6.8
214
10.
4.2
33
11.2
38
1.4
4.4
22
22
Total = 20 samples
176
13
13
1.4
26
9.7
43
2.3
40
Sequential Plot of Data
177
Log Probability Plot
Logprobability Plot and
Least-Squares Best-Fit Line
99%
98%
95%
90%
84%
75%
50%
25%
16%
10%
5%
2%
1%
0
1
10
Concentration
178
100
1000
Typical Example - Descriptive Statistics
(LogNorm 2 with ES of 10mg/m3)
•
•
•
•
•
•
GM
GSD
MVUE (estimate of mean)
Lands 95% UCL
UTL (95%,95%)
Exceedance Fraction 95%UCL
= 13.9 mg/m3
= 3.7
= 30.7 mg/m3
= 82.1 mg/m3
= 326 mg/m3
= 73.2 %
95% confidence that 95% exposures < 326 mg/m3
95 % confidence that exposures > ES 73.2% of the
time
179
BHP Billiton (Chronic effects)
• 95 % UCL of MVUE < 0.5 ES
(Acceptable)
• 95% UCL of MVUE >0.5 but <ES
(ALARP)
• 95% UCL of MVUE > ES
(Unacceptable)
180
BHP Billiton (Acute effects)
95% Upper Tolerance Limit < ES
Note=Only where warning properties are
adequate and olfactory fatigue is not a
problem
181
Other Approaches
• RioTinto
– Prefer the use of 95% UCL of MVUE
• South African mining industry must supply
90 % ile and GM to check for correct
banding
• Alcoa and Merck Inc No more than 5% of exposures to exceed
ES (95% ile)
182
Other Approaches
• AIHA suggests using UTL < ES
(considered good statistic for
comparison to ES but very
conservative)
183
Using Data to Drive Improvement
• Need accessible database to
store information
• Graphical presentations to
management have best effect
• Useful to measure effectiveness
of controls overtime
• Useful to dispel myths
184
Data Presentation
Exposure to Kryptonite
1
0.9
0.8
Unacceptable
0.7
mg/m3
0.6
0.5
0.4
ALARP
0.3
Acceptable
0.2
0.1
0
Transport
185
Gen Hand
Maintenance
Management
Surface
Mining
Drilling
What can companies do?
• Inspect workplaces for potential
health hazards
• Seek advice from occupational
hygienists to evaluate those hazards
• Introduce appropriate control
strategies
• Ensure any control strategies are
maintained
186
What are the benefits ?
• Healthy & happy workforce
– Evidence to show this leads to increased
productivity
• Lower compensation payments
– It is illogical to harm people and then
compensate them for their suffering. Fix the
problem so no one gets hurt
• Reduced corporate pressure
– Always a good outcome
187
A point to remember
In many cases it is simpler
and cheaper to fix the
problem rather than conduct
a sampling programme!
188
bdavies@uow.edu.au
189