Davies, SHS, Nov 2006 Introduction to Occupational Hygiene Associate Professor Brian Davies

Davies, SHS, Nov 2006

Introduction to Occupational Hygiene

Associate Professor Brian Davies

2

Assoc. Prof. Brian Davies AM

• Worked as an Occupational Hygienist in industry for > 30 years

• Certified Occupational Hygienist (ABIH & AIOH)

3

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

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Aim of This Course

To introduce participants to the discipline of Occupational Hygiene & demonstrate how it can be applied in the workplace

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Learning Outcomes

At the conclusion of this course you should be able to:1) Understand the principles of occupational hygiene and workplace sampling2) Conduct a walk through survey and recognise the chemical, physical & biological agents present

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Occupational Disease

Causes of occupational disease fall into four major areas

–Chemical agents

–Physical agents

–Biological agents

–Psycho-social causes

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Chemical Agents

• Dusts

• Metals

• Vapours

• Gases

• Pesticides

8

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

9

10

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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

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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)

13

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

14

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

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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)

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Pesticides

• Insecticides

– Organo-phosphorous compounds

– Interfere with enzyme called cholinesterase

• Herbicides

– Liver ,kidney & lung damage possible with some products

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Physical Agents

• Noise induced hearing loss (NIHL)

• Vibration

• Ionising radiation

• Non-ionising radiation

• Heat & cold stress

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EFFECTS OF NOISE

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EFFECTS OF NOISE (Cont)

Healthy Cochlea

Damaged Cochlea

Photos showing actual damaged ‘hair cells’ in the inner ear

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Biological Agents

• Viruses-Hepatitis A B & C, HIV

• Bacteria-Legionella, Q fever,

Anthrax, Leptospirosis

• Fungus- Moulds, Histoplasmosis,

Farmers lung

• Plant-Poison Ivy,

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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)

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Relationship to Occupational Hygiene

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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.'

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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

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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

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Coal Mining

Dust

Noise

Diesel emissions

Hazardous substances

Fungi

Vibration

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Aluminium Smelter

CTPV

Heat stress

Metal fumes

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Welding

Welding fumes

Toxic gases & vapours

Radiation

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Sand Blasting

Silica exposure

Noise

RPE

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Pipe Laying

Welding fumes

Heat stress

UV radiation

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Aviation Industry

Composites

Cu Beryllium

Hazardous

substances

Noise

Confined spaces-

fuel vapours

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Oil Industry

Noise

Hydrocarbons

Hydrogen sulphide

Heat stress

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What are the risks here ?

Gold processing

plant in West

Africa

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Gold Processing Plant

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Gold Room

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Group Exercise 1

• Break up into allocated groups

• List all the health issues you think are present at this gold processing plant (see notes)

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Evaluation

• How can the contaminant of concern be quantified

– Chemical, physical or biological

– Dust, vapour ,mist, gas, fibre

– Sampling method

– Is quantification actually necessary

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Preventative Principles

• Substitution

• Segregation

• Enclosure and mechanical handling

• Ventilation

• Work practices

• Personal protection

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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

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Routes of EntryContaminantContaminant

IN THE IN THE AIRAIR

SKINSKIN

SURFACESURFACE

SPILLSPILL

BREATHINBREATHINGG

Source :Airmet Scientific

Other ways:

Eyes &

Ingestion

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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

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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

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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

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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

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How do Hygienists Use MSDSs?

• As a source of information on

– Toxic effects

– Exposure standards

– Control technologies

• Engineering

• PPE

– Reference to other analogous compounds

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Group Exercise 2

Evaluating MSDS

• Review of some MSDS

• What are the key issues wrong with the MSDS’s provided?

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Hazard Identification

• Review the materials , processes & procedures used in the plant

– Process flowcharts

– MSDSs

– Health effects of possible contaminants

– International literature

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Dose Effect Relationship

• For each chemical there is a dose-effect relationship

– Acute effects (irritants, carbon monoxide)

– Chronic effects (benzene , asbestos fibres)

Basis of exposure standards

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Threshold

• The dividing line between no-effect and effect levels of exposure

• For each substance there is a threshold of intoxication which is usually different for individual substances

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Dose-Response Curve

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Individual Susceptibility

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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.

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Basis of Exposure Standards

• Toxicity• Biological action

– Asphyxiants

– Anesthetics

– Carcinogens

– Irritants

– Systemic poisons

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What limits exist?

• ACGIH (USA)

• HSE (UK)

• OSHA (USA)

• MAK (Germany)

• ASCC (Australia)

• Many other countries

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What do they exist for?

• Chemical hazards

– Vapours, gases, dusts, fibres• Physical hazards

– Noise, vibration• Biological hazards

– Linked in most cases to chemical hazards

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Types of exposure standards

• 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

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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”

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Extended Workshifts

• Brief and Scala model

• OSHA model

• Pharmacokinetic model

• A more practical approach uses the total time worked per month

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Which Substance is the Most Toxic ?

• 50 PPM

• 10 PPM

• 2 PPM

• 0.5 PPM

Each person is allocated only one vote

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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?

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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

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Why Monitor Workplaces (Cont) ?

• To measure the effectiveness of control measures

• For research purposes

• To dispel anxiety

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Types of Surveys

• Initial - to gain information

• Basic – qualitative assessment

• Detailed - quantitative assessment

• Routine – monitor compliance/controls

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•WHO

•WHERE

•WHEN

•WHAT

•HOW

Sampling Strategy

METHOD

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Exposure Judgement Outcome

• Acceptably low

• Too high

– Fix the problem

• Cannot make a judgement

– Need for more information (samples/assistance from others)

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Inputs to Judgement

• Process experience

• Material characteristics

• Toxicity

• Workforce characteristics

• Statistical tools

• Confidence in exposure limit

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Who should be monitored?

• Everyone?

• Those identified as potentially exposed from walkthrough survey or risk assessment?

• Controls?

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Types of Sampling

• Grab

• Short-term

• Long-term

• Continuous

• Bulk

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Bulk Sampling

• Substance(s) identification only

• Cannot be related back to airborne

concentration

• Can sometimes be used with other direct methods to calculate worst-case scenarios

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What should be monitored

• Contaminants identified in walkthrough survey or risk assessment

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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

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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

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How long should samples be collected?

• Substance properties

– Acute or chronic adverse health effects

• Duration of work shift

– Shift length

– Work pattern within shift

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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

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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

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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

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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

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Process of statistical monitoring

• Statistically analyse data

• Modify exposure groups (if required)

• Final report or ongoing reports

• Ongoing data collection (maintenance sampling)

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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

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Establish Similar Exposure Groups

• Observational

– Simplest form but least accurate

• Sampling

– Preliminary sampling to establish groups

• Combination of observation and sampling

– Most accurate approach

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Longwall Mining

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Continuous Miner (Panel)

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Basic SEG Structure- Coal Mine

SEG Description No. Workers1 Longwall 60

2 Panel 70

3 Methane Drillers 14

4 Tailgate Workers 8

5 Outbye Workers 60

6 Surface Workers 16

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Outbye Workers- Secondary SEG Structure

Task Number

Materials crew 35

Belts 5

Diesel workshops 8

Cable crews 12

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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

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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

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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

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Source : AIHA (1998)

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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

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Sampling Schedule

102

Lets do some monitoring

• Dusts & fibres

• Vapours & gases

• Noise

• Biological monitoring

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Dusts & Fibres

104

Composition of Dusts

Fibrogenic reactions (quartz)

Carcinogenic response (chromates)

Irritation (acid mists)

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(PM 10)(PM 10)

ISO/CEN Convention


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Relative size of particles

• 1 3 7 10 30 100

Inhalable Inhalable dust dust 100 100 micronmicron

Thoracic dust Thoracic dust 30 micron30 micron

Respirable Respirable dust dust 10 10 micronmicron

RESPIRABLERESPIRABLE

THORACIC THORACIC (PM10)(PM10)

INHALABLEINHALABLE


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Respirable Dust

•Gets deep into the lung

•Not easily removed

•Invisible to human eye

• 4.0 micron at 50% cut

•Gets deep into the lung

•Not easily removed

•Invisible to human eye

• 4.0 micron at 50% cut


108

The Cyclone

•Inlet points down

Separates theRESPIRABLE

dust

Suction from top

Contains cassette


109

•Retaining ring•Cyclone top

•Cassette (filter)

•Main Body

•Grit pot


Parts of a Cyclone

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Inhalable Dust

•Affects the whole of

the respiratory

system

•100 micron at 50% cut

•Affects the whole of

the respiratory

system

•100 micron at 50% cut


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The I.O.M. sampler

•Inhalable sampler

•Cassette system

•All collected dust is

measured

•Easily handled

•No contact with filter

•Multi fraction sampling with

foam inserts

IOM IOM samplersampler

IOM IOM cassettecassette

TransporTransport clipt clip

Front Cassette Filter Support O Front Cassette Filter Support O ring Bodyring Bodycover front gridcover front grid


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IOM Cassette

•IOM Cassette.•Cassette and filter are pre and post weighed as a single unit

FILTERFILTER


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The IOM complete

•Place cassette in body

Screw front cover on


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Sample Train•Is made up of :

•Pump•Connecting tube

•Sampler•Any accessory

SAMPLESAMPLERR

CONNECTINGCONNECTINGTUBETUBE

PUMPPUMP


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Calibration

•Connect from pump to sampling head•Connect from sampling headto calibrator

Adjust flow to require flowrateSource :Airmet Scientific

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Soap Film Meter

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Electronic Flowmeter

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Position of Sampling Device

•ALL Exposure limits are based

on

•PERSONAL SAMPLES

And MUST be And MUST be taken in the taken in the

Breathing ZoneBreathing Zone

300mm 300mm Hemisphere Hemisphere around the around the nose and nose and

mouthmouth


119

Taking the Sample

•Place sample train on person:

Start pumpNote start time

At end of sample:

Note stop time


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Direct Reading Instruments

• Hund Tyndalometer

• Dust Trak

• R & P PDM

121

Hund Tyndalometer

122

Dust Trak

123

Problems with direct reading instruments

• Most devices cannot distinguish between water droplets from suppression sprays and dust particles

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R & P Personal Dust Monitor

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TEOM Series 3600 Personal Dust Monitor

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Real Time Data

127

Remote Control Miner Operator, Major Exposure Variables

6:00 7:12 8:24 9:36 10:48 12:00 13:12 14:24 15:360

1

2

3

5

Mass

Con

cen

trati

on

[m

g/m

³]

Time

4

16:48 18:00

MassConcentration Cumulative

Concentration

ProjectedExposure

Source: CDC-NIOSH Pittsburgh Research Laboratory

128

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

129

Types of Fibres

• Asbestos

• Synthetic or MMMF

130

Asbestos• Fibrous silicate minerals

• Main types

– Chrysotile

– Amosite

– Crocidolite

– Actinolite

– Anthophylite

– Tremolite

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Health Effects

• Pleural Plaques

• Asbestosis

• Lung Cancer

• Mesothelioma

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Management of Asbestos

• Identification – dispersion staining microscopy, XRD & IR

• Assessment - Membrane filter method

• Control- Removal, encapsulation, monitor

133

Bulk Amosite

Copyright A Rogers

134

Asbestos-Ships Lagging

Copyright A Rogers

135

Tremolite Rock and Fibre

Copyright A Rogers

136

Calcium Silicate and Amosite

Copyright A Rogers

137

Dispersion Staining for Identification

Copyright A Rogers

138

Polarised Light – Ist order Red

Copyright A Rogers

139

Types of SMF• Glass fibre

– Reinforcing filament

– Glass wool

– Ultra fine glass fibre• Mineral wool

– Rock wool

– Slag wool• Ceramic fibre

– Refractory ceramic fibres

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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

141

Measuring Airborne Fibres

MEMBRANE FILTER METHODPump and filter (cellulose ester)Phase contrast microscopySampling (Occupational & Para-

occupational)Filter mounting and clearingKohler illuminationSpecific counting rulesCertified counters

142

Membrane Filter Method Slide

Copyright A Rogers

143

Vapours & Gases

144

Sampling SystemsSampling systems

– Active

• Pump and adsorption tube (vapours)

• Pump and liquid absorption (gases & vapours)

– Passive

• Solid adsorption (vapours)

• Direct reading (gases & vapours)

145

Vapour Sampling

•With sorbent tubes

Main bedMain bed

Back-up bedBack-up bed

Retaining clipRetaining clip

Foam separatorFoam separator

Precision drawnPrecision drawn

glass tubeglass tube


146

Breakthrough?•When a sorbent if full to capacity, breakthrough occurs

BreakthrougBreakthrough is when a h is when a tube tube becomes full becomes full and re-and re-releases the releases the hazardhazard


147

Tube Holder

148

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


149

Calibration of a tube

•Connect to calibrator•Adjust flow at low flow adapter

Use soap Use soap film or film or electronic electronic metermeter


150

Taking the Sample

•Start pump

•Note start time

•At end of sample:

•Note stop time

SKC

SKC

Place sample train on person:


151

After the sampling•Remove tube

•Place covers on tube

•Send off for analysis with details of sample

Don’t forget to send a Don’t forget to send a BLANKBLANKDon’t forget to send a Don’t forget to send a BLANKBLANK


152

Sample bags - gases

•Made from Tedlar•Inert•Valve/inlet with septum•No auto shut off•Fill by flow X time•Designed as single use


153

Bag filling

•Do not overfill•Bag will take 3 times stated volume

More pressure means more migration

Fill to correct Fill to correct volume by setting volume by setting flow rate and flow rate and time… otherwise?time… otherwise?


154

Badges - Dosimeters

Sorbent bed

MembraneMembrane

Protective Protective diskdisk

Support gridSupport grid

SmallSmall

LightLight

No pumpNo pump

Needs air Needs air movement to movement to

workwork Void for solventVoid for solvent


155

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


156

Direct Reading Instruments

157

Cross Sensitivity (CO Sensor)

H2S ~ 315

SO2 ~ 50

NO ~ 30

NO2 ~ -55

Cl2 ~ -30

H2 < 40

HCN 40

C2H4 90

Challenge concentration - 100ppm of each gas

158

Filters for Contaminant Gases

H2S ~ 315 < 10

SO2 ~ 50 < 5NO ~ 30 < 10

NO2 ~ -55 ~ -15

Cl2 ~ -30 < -5

H2 < 40 < 40HCN 40 < 15

C2H4 90 < 50

Unfiltered Filtered

159

‘Port’a’man!’

160

Noise

161

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

162

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)

163

Introduction to Sound Level Meters

• Integrating or non-integrating

• 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 walk-

through survey work

164

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.

165

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.

166

Typical Dosimeter

167

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”.

168

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

169

Noise Exposure Dosage Guide (unprotected)

Limiting dB(A) Maximum duration85 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

170

Evaluation of data

171

Types of data evaluation

• Statutory requirement

– Straight comparison to exposure standard

• Statistical sampling

– Statistical evaluation

172

Statutory Requirement

• <<ES - acceptable

• ES – unacceptable but more sampling may improve situation

• >>ES - unacceptable

173

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

174

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

175

Statistical Metrics

• GM & GSD

• MVUE

• 95 % UCL

• 95 % ile

• UTL

176

Data Treatment-Typical Example

Inhalable Dust – Personal sampling on a random schedule over 16 weeks.

5.5 4.2 1.4 1 3 9.7

6.8 33 4.4 1 3 43

214 11.2 22 1.4 2.3

10. 38 22 26 40

Total = 20 samples

177

Sequential Plot of Data

178

Log Probability PlotLogprobability Plot and

Least-Squares Best-Fit Line

99%98%

95%

90%84%

75%

50%

25%

16%10%

5%

2%1%

0 1 10 100 1000

Concentration

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Typical Example - Descriptive Statistics (LogNorm 2 with ES of 10mg/m3)

• GM = 13.9 mg/m3• GSD = 3.7• MVUE (estimate of mean) = 30.7 mg/m3• Lands 95% UCL = 82.1 mg/m3• UTL (95%,95%) = 326 mg/m3• Exceedance Fraction 95%UCL = 73.2 %

95% confidence that 95% exposures < 326 mg/m395 % confidence that exposures > ES 73.2% of the time

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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)

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BHP Billiton (Acute effects)

95% Upper Tolerance Limit < ES

Note=Only where warning properties are adequate and olfactory fatigue is not a problem

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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)

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Other Approaches

• AIHA suggests using UTL < ES

(considered good statistic for comparison to ES but very conservative)

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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

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Data PresentationExposure to Kryptonite

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Transport Gen Hand Maintenance Management Surface Mining Drilling

mg

/m3

Unacceptable

ALARP

Acceptable

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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

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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

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A point to remember

In many cases it is simpler and cheaper to fix the problem rather than conduct a sampling programme!

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[email protected]

Documents

Davies, SHS, Nov 2006 Introduction to Occupational Hygiene Associate Professor Brian Davies