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CTEC 493 GENERAL NOTES

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CTEC 493:
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OCCUPATIONAL SAFETY AND HYGIENE IN
CHEMICAL AND ALLIED INDUSTRIES
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COURSE OUTLINE
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1. Industrial Hazards

Recognition and identification

Hazard, risk and exposure

Clearance mechanisms

Adverse health effects
2. Monitoring Hazardous Substances

Sampling and evaluation

Quality control

Health surveillance

Legislation
3. Risk Assessment

Information sources

Task analysis
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
Recording and reviewing
4. Workplace Control

Ventilation

Respirators

Noise
COURSE ASSESSMENT (3 credit hours)
1. Assignments (10 %)

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2 assignments on section 1 and 2; 1 assignment each on section 3 and 4
2. Tests (10 %)

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1 test on section 1 and 2; 1 test on section 3 and 4
3. Project (20 %)
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Industrial assessments
4. Final examination (60 %)
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CTEC 493:
OCCUPATIONAL SAFETY AND HYGIENE IN
CHEMICAL AND ALLIED INDUSTRIES
COURSE NOTES
Synopsis: This is an introductory course in Occupational Safety & Hygiene (OSH) dealing
mainly with chemical hazards in the workplace.
Lecture1: 1. INTRODUCTION

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Definition of OSH; and Significance
Key Questions: (1) What is Occupational Hygiene? (2) What is Occupational safety? (3) How
does Occupational Hygiene differ from Environmental Hygiene? (4) How does OSH contribute
to occupational health as well as productivity and profit?
OSH is the cross-disciplinary area concerned with the protection of the safety, health and welfare
of people engaged in work or environment.
Occupational Hygiene is the discipline of anticipating, recognizing, 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.
The term is generally synonymous with Industrial Hygiene
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Environmental Hygiene addresses similar topics to Occupational Hygiene, but is not confined to
the work-place concerned.
In common usage Occupational hygiene has taken on a much narrower definition linking it to
cleanliness, frequently leading to the misunderstanding of the term Occupational hygiene, which
is NOT about hand washing or handling food properly at work.
The Occupational Hygienist may be involved with the assessment and control of physical,
chemical, environmental and or psychosocial hazards in the workplace that could cause disease or
discomfort.

Physical hazards may include noise, temperature extremes, illumination extremes,
ionizing or non-ionizing radiation, and ergonomics.

Indoor air quality (IAQ) and safety may also receive the attention of the Occupational
Hygienist.

As part of this activity, the Occupational Hygienist may be called upon to:
o
communicate effectively regarding hazard, risk, and appropriate protective
procedures;
o
to evaluate and occasionally to design ventilation systems; and
o
to manage people and programs for the preservation of health and well-being of
those who enter the workplace.
In brief, Occupational Hygienists are responsible for recognizing, evaluating and controlling
environmental hazards resulting from physical, chemical or biological factors in the workplace.
By assessing and resolving practical problems in a wide range of settings, occupational
hygienists help protect workforce health and wellbeing at all levels, and in all areas.
Occupational hygienists play a vital role in assessing potential risks to workforce safety in
environments including factories, offices and building sites.
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They enable organizations to respond effectively to the requirements of legislation on issues
such as asbestos, noise and manual handling.
Occupational hygienists often work within a team with other professionals, such as doctors,
nurses and engineers.
Typical work activities
Work activities will vary according to specialist area and employer but may include:

undertaking workplace surveys;

assessing the risks to health arising from many different factors, for example chemicals,
noise, poor lighting or ventilation;
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accurately measuring and sampling levels of exposure;
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using specialist equipment in a precise way;

accurately recalling facts or details of procedures in the workplace;

evaluating situations in the workplace;

analyzing and resolving specific problems;

recommending remedies or control methods;

compiling data and writing reports;

presenting report findings to clients;

liaising with a wide range of people in the process of evaluating workplaces, which may
include company management and staff;

considering all options of control (ventilation, containment, personal protective
equipment etc);
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deciding upon or devising the most appropriate method for specific situations;
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providing clear and accurate information on complex health and safety issues;

training organization staff on health and safety issues, such as asbestos and COSHH
(Control of Substances Hazardous to Health) awareness;
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
gaining the confidence and co-operation of the workforce;

persuading company management to develop effective hazard controls when required;

writing guidance information on health and safety;

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

working as part of a team to meet the same objective;
keeping up to date with scientific and legal developments;
providing expert witness services;
Liaising with outside bodies, such as The Health and Safety Executive (HSE) and the
Royal Society for the Prevention of Accidents (RoSPA).
Every business needs these six professional pillars of an occupational health program. Do
you have them in your business?
1.
Occupational Hygienist: trained to recognize, evaluate, control and
workplace exposures.
prevent
2.
Safety Professional: engaged in the prevention of accidents, incidents, and events that
harm people, property, or the environment
3.
Occupational Health Nurse (OHN): specialist that provides and delivers health care
services to workers and worker populations
4.
Occupational Physician: a licensed medical doctor with special training and experience
in the health hazards of workers
5.
Emergency Preparedness Professional: responsible for defining and
each employee's role during an emergency
communicating
6.
Environmentalist: responsible for the management of several programs related to
environmental protection, most commonly: Hazardous Waste Management and Disposal, Air
Quality, Water Quality and Recycling/Reclamation.
Usually these professionals will report to the Safety, Health and Environment (SH&E) Manager
of the respective company where they work. The SH&E manager will have a program called
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SH&E program driven by an SH&E policy. This policy integrates all the above functions into
one program, the SH&E program. Do you have such a program at your workplace? This is one
of the determinants of sustainability of your business.
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End of Lecture1: 12/08/2009………………………………………………………………
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Lecture 2: Introduction (Cont……)
Why Managing Health & Safety?
There are lots of reasons why corporations need to manage Health & Safety; but these may be
into 3 broader groups given below
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Moral & ethical issues/reasons:
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Respect human resources /workforce
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Respect their families
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Legal Issues:
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Compensation claims
o
Disruptions during legal processes
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Financial Issues:
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Increase of insurance premiums – bad reputation attracts higher premiums
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o
Direct losses – results of costly incidents with direct financial implications
o
Indirect losses – costs of an indirect nature e.g. reduced productivity of individual
workers due to work-related illness.
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Costs of hazard or risk reduction/elimination.
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Moral regard for human life and well-being.
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It is important to note that, the struggle to eliminate or reduce occupation hazards & risks, which
often result in illness, injuries and damages that result is chiefly complicated by two mutually
opposing aspects:

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Good news: Many of the large corporations have found the mutual consideration and
compromise beneficial and workers are safer to a higher degree than before.
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In return:

fewer walkouts, strikes, and inefficient operations because workers were slowed by their
need to prevent and protect themselves against hazards;

Less costly litigation and lower insurance premium costs.
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Bad News: Many small companies still believe erroneously that safety programs are
nonproductive and unprofitable. Consequently, their safety efforts are minimal and accident
and injury rates are higher than those of large companies.
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The chief complaint when any new law or mandatory standard concerning safety is being
considered or has been enacted is that the increased costs will put them out of business.

To such organizations, it therefore appears that monetary aspects are more important than
the moral considerations.

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NB. Different states take different approaches to legislation, regulation, and enforcement. Some
have enforcing authorities to ensure that the basic legal requirements relating to occupational
safety and health are met. In most developed countries, there is strong cooperation between
employer and worker organizations (e.g. Unions) to ensure good OSH performance as it is
recognized this has benefits for both the worker (through maintenance of health) and the
enterprise (through improved productivity and quality).
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EMPLOYER - EMPLOYEE OBLIGATIONS.
What should my employer do to protect my health?
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Follow relevant Regulations,
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Use safer alternatives
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Exposure assessment
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Steps to prevent exposure or reduce exposure to lowest possible level
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Information, training, education
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Protective clothing
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Demarcation and labeling
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Adequate washing and changing facilities, separate storage facilities for personal
protective equipment (PPE) and personal clothing
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Monitoring: air and health checks
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Issue correct mask / respirator
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Do everything reasonably possible to protect you
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What should I do to protect my health?
•
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Make full use of control measures provided by employer
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•
Report faults in air extraction systems
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Use protective clothing and masks / respirators when required
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Make sure mask / respirator fits properly
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Do not go into respirator zone without wearing correct mask / respirator
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Follow recommended working procedures to reduce dust levels, keep material damp
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Work in well ventilated areas or open air
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Keep work areas clean by using vacuum cleaning or wet methods
•
Never use compressed air for cleaning
•
Never use dry sweeping methods
•
Cooperate if asked to wear devices to measure your exposure while you work
•
Do not smoke or cut down as much as possible
•
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Wash your hands and face thoroughly before eating, drinking or smoking
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Do not eat, drink or smoke in the working area
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Do not take home clothing contaminated –e.g. with asbestos
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Wash and change before you go home
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2. RECOGNITION & IDENTIFICATION OF HAZARDS
Sub-topics: Types of industrial hazards. Hazard, risk and exposure. Sources of exposure.
Routes of entry into the body. Clearance mechanisms. Adverse health effects of chemical
exposure to elemental, inorganic & organic dust, fumes, gases & vapors.
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Lect. 3:
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2.1. Hazard, Risk; and Types of Hazard
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Hazard –a chemical or physical condition that has the potential to cause damage to people,
property or the environment
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Risk – chance or probability of danger, loss or injury occurring.
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
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A measure of economic loss or human injury in terms of both the accident
likelihood and magnitude (consequence) of loss or injury
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A combination of incident, probability and consequences.
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Types of hazards
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Can be classified in three groups which are physical, chemical & biological:

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Chemical hazards – these come in different forms/types - gas, liquid, vapor, fumes, mist, or
dust.
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Well known typical chemical hazards are Asbestos, Lead, Hg, etc

Physical, e.g., lighting, noise, vibration, slippery floors, sharp protrusions, improperly tacked
attire or long plated hair (sometimes) etc.

Biological, e.g. fungi, bacteria, viruses
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Relationship between Hazard and Risk
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In OSH Management System, the risk assessment process invariably includes:

Identifying the hazard

Assessing the risk

Controlling the risk
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o Eliminating the hazard, if possible
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o Minimizing, if possible
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o Controlling the hazard
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Checking and Reviewing the risk control
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How to Assess the Risk?
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Subjective (Qualitative)
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-Perception
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‘
‘-Likelihood and Consequences
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–Likelihood: Very Often, Often, and Seldom
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–Consequence: Fatal, Major and Minor
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Objective (Quantitative)
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o Historical data
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o Probability of occurrence (Frequency): Incidents/200,000 MH/Year
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o Consequence: Measured in terms of Direct and Indirect Cost
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Qualitative
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Quantitative
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Example: Historical data for a particular industrial site shows an average-fall-Accident
(AFA) of 10 incidents /200,000 MH/year. On average one fall accident costs (FAC) USD
1000. Given: MH = man-hrs; a person works for 50 weeks a yr, 5 days a week and
8hrs/day.
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Determine the estimate fall accident related costs if the site has 200 workers.
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Solution: Estimate of fall related cost = total MH x AFA x FAC.
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Field Code Changed
(
8hr 5dy 50wk 200man
10accident
US1000



)(
)(
)  US 2000 / yr
dy wk
yr
1
200000man.hr
1accident
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Alternatively:
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200,000 = number of hours that 100 employees work in a year (i.e. 40 hrs per week x 50
weeks x 100)
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So, 100 workers result in 10 accidents, thus 200 workers results in 20 accidents per yr
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Estimated Cost = 20 x 1000 = USD 20,000 / year
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Fig 1.1 Position of the workplace hazards and workplace accidents in the procedure of risk assessment
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Fig 1.2 Risk assessment and risk management in the procedure of the quantitative risk assessment
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Fig 1.3 The overlap of the legislation in the field of OSH with the procedure of the quantitative risk
assessment
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HAZARD – RISK REALATIONSHIP
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Risk Assessment
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Prioritize: categorizing the hazards into different groups
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We cannot control all hazards due to limited resources
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Select certain groups for risk elimination, reduction and control
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Risk Elimination
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This is the best solution, however sometimes it is not practicable
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Example: Lead-based paint can cause lung cancer
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Solution: replace the type of the paint with water-based paint
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Risk Minimization
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
Reduce the number of people exposed to the hazard

Change with other types although new ‘safer’ hazards may occur

Reduce the exposure of the hazards
Risk Control
Control the energy/intensity:

Fall wear body harness and land-yard
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Noise wear earmuff
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Welding wear mask
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Vibrator wear leather glove
Chemical wear safety clothe
Review and Check


Check the effectiveness of the safety risk management
Review new hazards and technology
Risk Management Steps:
1. Look for hazards
2. Decide who might be harmed & how
3. Evaluate the risk & decide whether existing precautions are adequate or whether
more should be done.
4. Record your findings
5. Review your assessment & revise it if necessary.
End of lecture 3………………………………………………………………………….
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Lect 4:
2.2. OSH from risk analysis and management position
Modern occupational safety and hygiene legislation usually demands that a risk assessment be
carried out prior to making an intervention. This assessment should:
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Identify the hazards at workplace
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Identify all workers that can be affected by the hazard and how they can be affected
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Evaluate the risk.
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Identify and prioritize the required actions.
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The calculation of risk is based on the likelihood or probability of the harm being realized and the
severity of the consequences. This can be expressed mathematically as:
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a quantitative assessment (by assigning low, medium and high likelihood and severity
with integers and multiplying them to give a risk factor), or
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as a description of the circumstances by which the harm could arise i.e. qualitative.
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The assessment should be recorded and reviewed periodically and whenever there is a significant
change to work practices.
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The assessment should include practical recommendations to control the risk. Once recommended
controls are implemented, the risk should be re-calculated to determine of it has been lowered to
an acceptable level.
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Generally speaking, newly introduced controls should lower risk by one level, i.e., from high to
medium or from medium to low. The precautionary principle of OSH is an increasingly used
method for reducing potential chemical or biological OSH risks.
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Fig 1.4 The overlap of the legislation in the field of OSH with the procedure of the quantitative risk
assessment
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End of lecture 4…………………………………………………………………………..
2.3 Toxicology
Toxicology is the study of harmful effects to living organisms from substances which are foreign
to them. The toxins may be naturally occurring in the environment or synthetic chemicals. The
following definitions will describe some basic concepts in toxicology.
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Acute toxicity: refers to the rapid development of symptoms/effects after the intake of relatively
high doses of the toxicant. Acute toxicity refers to immediate harmful effects generated by
sufficiently large doses.
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Chronic toxicity: refers to the harmful effects of long-term exposure to relatively low doses of
toxicant. This would include traces of pesticides in foods, air pollution, etc.
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A single compound may generate both acute and chronic toxic effects depending on the dose and
duration of exposure.
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There are two general types of toxic effect:
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Lethal Effects: resulting in the death of individuals
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Sub- lethal Effects: other effects not directly resulting in death
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There are four basic types of damage caused by toxic materials:
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1. Physiological damage: reversible/irreversible damage to the health of the organism
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2. Carcinogenesis: induction of cancer
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3. Mutagenesis: induction of genetic damage / mutation(s)
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4. Teratogenesis: induction of birth defects
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ERGONOMICS.
"Ergonomics is about ’fit’: the fit between people, the things they do, the objects they use and the
environments they work, travel and play in. If good fit is achieved, the stresses on people are
reduced. They are more comfortable, they can do things more quickly and easily, and they make
fewer mistakes."
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Ergonomics Society (Europe)
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"Ergonomics (or human factors) is the scientific discipline concerned with the understanding of
interactions among humans and other elements of a system, and the profession that applies
theory, principles, data and methods to design in order to optimize human well-being and overall
system performance."
"Ergonomists contribute to the design and evaluation of tasks, jobs, products, environments and
systems in order to make them compatible with the needs, abilities and limitations of people."
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Epidemiology
In contrast to the rapid effects observed in toxicology, epidemiology examines the relationship
between exposure to a specific toxic agent and the development of health problems in a
group of humans. In essence epidemiology examines the health patterns in humans with
respect to an agent/toxicant. An example might include the health effects of chronic, lowlevel exposure to pesticides found on un-washed fruit.
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Simply put, epidemiology looks for trends and effects in human health following exposure to a
specific compound or other toxic agents.
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iii. Effect of Dose
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Relative toxicity of a substance is often expressed in the dose-response relationship. This simply
relates the dose (quantity administered) of a substance to the response generated in a test
organism. In order to relate this information to humans, dose is often expressed as dose per
organism weight, or mg / kg (where mg represents toxicant dose and kg expresses animal
weight.). It is also important to consider the method of application, whether oral, dermal,
intravenous, etc., as these may greatly affect relative toxicity of a given compound.
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Very commonly the quantity of a toxicant required to cause death is used as an indication of
relative toxicity. This is most often expressed as: LD50 . This expresses the mg/kg dose required
to kill 50% of a test population. For example the LD50 for sugar is >10,000 mg/kg, while for the
botulism toxin is ~ 0.0001 mg/kg. Obviously the botulinum toxin is highly toxic even in
relatively low doses. An alternative measurement of dose response is the ED50 where there is an
effect on 50% of the test population. This represents a measurement of sub-lethal effects.
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Some Example LD50Values
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Substance
LD50 (mg/kg)
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Sugar
>10,000
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Caffeine
100
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Strychnine sulfate
2
Nicotine
1
Rattlesnake venom
0.1
Botulism toxin
0.0001
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Dose-response curves are generated for various agents by plotting "percent of population
affected vs. Dose (mg/kg). When examining such graphs, often there is a minimum concentration
(or "threshold") of dose below which there is no observable effect in the test population. This is
referred to as the NOEL (no observable effects limit).
With respect to human safety, NOEL dose information is often obtained from animal
experimentation and then divided by a "safety factor" (i.e. 100) in order to establish safe levels for
humans. This generates two kinds of values: ADI (acceptable daily intake) and MDD (maximum
daily dose). While these values suggest a large margin of safety, in reality it is quite possible that
the more sensitive individuals in a population may still suffer ill effects within the dose limits set
by these guidelines.
Pharmaceutical safety / effectiveness can be indicated by the pharmaceutical TI (therapeutic
index). The therapeutic index is the ratio of LD50 / ED50. A high TI value indicates an effective
treatment at low doses and a lethal effect at higher doses. A low TI value indicates an ineffective
treatment at low doses with lethality at the same low levels. The objective of using the therapeutic
index is to have a pharmaceutical that is highly effective at low doses with
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2.4. Exposure Types & Routes:
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Exposure Typess:
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Typically exposures can be classified according to the duration of the exposure.
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There are four main categories of exposure:
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Acute Exposure: describes exposures over a short period of the life of an individual (which may
be relatively intense) & the reaction happen in short period of time. An acute exposure is often
referred to as being less than 24 hours duration.
Sub-acute Exposure: describes exposures over a relatively short period of time, often less than
one month.
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Chronic Exposure: describes repeated small exposures for a long period of time or for
"significant" portion of an individual’s life-span. (More than three months for mammals).
Sub-chronic Exposure: describes exposures shorter than chronic exposures but longer than subacute (1-3 months is typical for mammals).
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Exposure Routes:
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In order for a toxic agent to have an effect an individual (or population) must be exposed. There
are several exposure routes: oral (mouth), dermal (through the skin), inhalation (breathing) and
/or injection (subcutaneous, intravenous, intramuscular, and intraperitoneal). The specific route of
exposure may have a significant impact on relative toxicity: specific substances may even have
substantially reduced or enhanced toxicity dependent upon the type of exposure.
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Routes of Entry of Toxic Agents
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•Respiratory
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•Skin and eye contact
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•Mouth (Ingestion)
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–Headache, Drowsiness, Unconsciousness
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–Many solvents (toluene, xylene, ether, and acetone) produce this effect if the vapor
concentration is high
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It is rare for chemical interactions with living systems to occur in complete isolation. Often there
are specific interactions between multiple agents / chemicals which can be quite different than the
action of an individual toxicant. Generally, these interactions can be described as being:
1. additive: compounds X + Y combine toxicity proportionally (i.e. 2+3 = 5)
2. antagonistic: compounds X +Y combine to less toxic than either individually (i.e. 2+3 = 1)
3. synergistic: compounds X + Y combine to be more toxic than either individually (i.e. 2+3 =
9)
With these distinctly different interactive effects being possible, it is often very difficult to
anticipate combined effects purely on the basis of chemical structure or other isolated data. It is
obviously much easier to acquire toxicity-effect data for individual compounds as opposed to
complicated mixtures with many unknown interactions.
Data on individual toxicity's and safety can be obtained from a number of sources, chiefly:
MSDS (Material Safety Data Sheets) - listings that describe (in detail) the known potential
hazards for many individual compounds. This type of information usually accompanies
commercial chemicals and is also offered on numerous websites. MSDS information includes
handling, equipment, safety measures and potential risks / hazards associated with a given
substance and can be an excellent starting point for assembling information on a specific
compound.
Common Typical Toxic/Adverse Effect of Exposure To Chemical Hazards
•Irritations
–Lung: by inhaling some chemicals, e.g. ozone, sulfur dioxide and nitrogen dioxide
–Skin: chemical, physical, mechanical and biological
•Central Nervous System (CNS) Depression –Organ affected: brain
•Asphyxia - a condition of severely deficient supply of oxygen to the body .
–Interfere with the transfer of oxygen
–Suffocated because the bloodstream cannot supply enough oxygen
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–When the oxygen level of 21% drop to 16%
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–Sources: Gas from sewerage; Argon, propane, methane, Carbon monoxide, Hydrogen sulphide
and hydrogen cyanide
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•Cancer
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–The effect is about 20-30 yearsvc
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–Sources:
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Benzene →Leukemia (cancer of blood or bone marrow characterized by proliferation of
blood cells – especially white blood cells;
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Chromium, Beryllium and Arsenic Trioxide →Lung Cancer;
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Asbestos →Larynx, Lung and Abdomen cancer
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Vinyl Chloride →Liver Cancer;
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Coal Tar Pitch →Skin Can cer; &
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Benzidine→Bladder Cancer
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–Reduce the elasticity of the lung
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–Sources: Silica, beryllium, asbestos, iron oxide, tin
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•Reproductive Effect
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–Causes the inability to reproduce and fetal development
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Mercury →Low birth weight;
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Polychlorinated biphenyls (PCBs) →Brown patches;
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Lead →Miscarriage; &
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•Pneumoconiosis – occupational lung disease caused by the inhalation of dust, especially from
coal, graphite, or man-made carbon over a long period of time
–Dusts retained in the lung
X-Rays and Some Pesticides (e.g., 2, 6-di-tert-butyl-p-cresol -DBPC) →Decreased sperm
cell and sterility
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•Systemic Poisons
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–Affect more than one organ
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–Sources:
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Cadmium: causes lung irritation; impairs kidney function & may cause sterility
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Mercury: accumulation in the brain causes tremors and mood changes; decreases
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Kidney efficiency; gum inflammation & excess saliva
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Silicosis (also known as Potter's rot) is a form of occupational lung disease caused by inhalation
of crystalline silica dust, and is marked by inflammation and scarring in forms of nodular lesions
in the upper lobes of the lungs.
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Silicosis (especially the acute form) is characterized by shortness of breath, fever, and cyanosis
(bluish skin). It may often be misdiagnosed as pulmonary edema (fluid in the lungs), pneumonia,
or tuberculosis.
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Factors Affecting Toxic Effect
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•Factors related to the agent
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–Chemical Composition
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–Physical properties
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–Solubility in body fluids
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–Dose: how much and how long?
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–Co-factors: Presence of other materials
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•Factors related to the individuals
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–Individual differences: genetic status and allergic status
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–Age
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–Presence of predisposing disease: e.g. Angina (Heart Disease) →cannot tolerate carbon
monoxide, & Emphysema (lung ailment)
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Diseases associated with asbestos
•
•
•
Asbestosis – lung disease, scar surrounding lung tissue. Impair lung function, 25 – 40
years later.
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Mesithelioma – cancer of outer lining of lung and chest cavity and or lining of abdominal
wall, 15 – 30 years later
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Lung cancer and GI cancer, 15 – 30 years later
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Respiration & Work (C.Winder, Occupational Toxicology 2nd Ed, CRC Press; Edited: C Winder
& N Stacey)
To appreciate the amount of air that can be inhaled by people at work its necessary to have rough
estimates of amount of air a worker might breathe over a day at work:

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3
Conservative estimate of 500ml per breath & 15 breaths per minute gives 3.6 m per 8-hr
day.
3
Over full day a person breathes 3x the amount giving 10.8m .
o
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Human lung comes in contact with 20kg air per day; along with the air is a chemical
& microbiological load.
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Factors affecting deposition of inhaled materials.
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Various factors influence deposition once the material reaches the respiratory system, but many
of those factors also depend on what is happening in the particular region of the respiratory
system; but these include: air flow rate, particle size, particle density, and solubility in mucus.
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Inhalation & exhalation entails variations in air flow rate & direction; this in turn affects
absorption (which occurs in all regions of respiration system) and deposition. Absorption also
depends on solubility in mucus (important for soluble gases, vapors & particulates). In the upper
airways, air flow rate is so high that many inhaled particles are propelled into the lining of the
airways where they are absorbed (in the size range 5-30m). This is called inertial impact.
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Further down the system, in bronchi & bronchioles, speed & direction changes are less traumatic
and smaller particles (in the size range 1-5m) which were carried down by force respiration
begin to drop out of the air flow. This is called sedimentation; depends on gravity.
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Finally, at the end of airways, the terminal bronchioles, and in the gas exchange areas, there is
hardly any change in air movement at all, and gases, vapors, and small particles (less than 1m
tend to diffuse across a concentration gradient (e.g. O2 in, CO2 out). This is the process of
diffusion; requires low air speed.
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Role of the nasal passages’.
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Nasal passages plays important role when looking at respiration & work interaction:
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Human beings are nose-breathers under normal O2 demand, and air passes thru nasal
passages and the mucous linings where it is humidified and removal of particulates as well as
soluble gases & vapors also occur. The region thus acts like a filter.
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
When O2 demand increases beyond what can be supplied through the nose, human beings
become mouth-breathers. This means bypassing of the nasal passages (the filtering
mechanism) in an attempt to get enough air to the lungs. This increases the risk that carry out
hard work in contaminated environment.
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Care should be given to inhalational exposure for workers with heavy workloads.
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Defences: Clearance or retention of inhaled materials
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Mechanisms of clearance or retention of inhaled substances depends on the region of the
respiratory system.
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The nasopharyngeal compartment has following mechanisms:
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Smell/avoidance
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Coarse nose hairs
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Impaction & collection in the nasal turbunines
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Irritation of the nasal epithelium (lining) evoking sneeze
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Some production of mucous.
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Cough
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Irritation of epithelial lining
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Bronchoconstriction - is the constriction of the airways in the lungs due to the tightening
of surrounding smooth muscle resulting from exposure to irritant chemicals, with
consequent coughing
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Tracheobroncheal compartment has following mechanisms:
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Mucociliary clearance moves dissolved or suspended material through the respiratory
system to the back of the mouth where it can be expectorated (ejected as saliva or mucus)
or swallowed.
Pulmonary compartment has following mechanisms:
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Phagocytosis, primarily by alveolar macrophage activity
Some drainage of material
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Inevitably some materials are retained by the lung tissue.
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Heavy Metals
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Heavy metals are extremely dense metals found naturally as trace elements. Some examples
include mercury (Hg), Lead (Pb), Cadmium (Cd), etc. While some heavy metals are not highly
toxic as elements, their cationic states are far more reactive.
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The degree of relative toxicity of a given heavy metal can vary with the exact chemical form
of the element, including oxidation state. One particularly toxic form involves attachment of
alkyl groups which permit passage through the blood-brain barrier. Heavy metals in these
states are responsible for immediate, long-term and fetal toxic effects and can cause
irreversible damage.
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WHO Heavy Metal limits for Drinking Water
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Heavy Metal
Limit (ppb)
Hg
1
Cd
3
Pb
10
As
10
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Mercury, (perhaps more than any other heavy metal) has achieved a high level of notoriety.
Mercury poisoning is, and will continue to be a major issue in environmental chemistry for
years to come.
Industrial production of certain chemicals (eg. NaOH, Cl2) often results in inadvertent /
fugitive release of both gaseous and solid amalgams of mercury.
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Accumulation and bio-concentration of mercury in fish is a well-publicized concern in many
water systems world-wide.
Mercury often forms methyl-mercury in aqueous systems, by reacting with light and various
organic compounds. Methyl-mercury is of particular concern because of its affinity and
persistence in fatty tissues and lipids in humans.
Mercury can also enter the ecosystem through leaching from soils/rocks and can be
exasperated by activities such as dams (altering water levels) and flooding.
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Lead, a soft heavy metal, is now used far less in most western industrialized nations than
previously. Previously used in leaded gasolines, many paints and as "shot" for shotgun
ammunition, these sources of lead contamination have been banned in countries like Canada.
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Lead is still a component of certain solders used in electrical wiring and exists as a
component of the plumbing in even in such countries as Canadian, especially in older
residences.
The current major source of lead exposure for most countries including Canada continues to
be drinking water.
Long term accumulation of lead results in accumulation in the brain, often as a result of
numerous years exposure and accumulation. Most vulnerable are fetuses and young children
undergoing rapid brain growth/development.
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Cadmium, is a by-product of industrial activities (such as zinc production) and is often found in
high-power batteries in phones, portable tools and video cameras. When such batteries are
incorrectly disposed of, each battery can release as much as several grams of cadmium,
particularly a concern during incineration.
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Higher levels of cadmium can be found near smelters and mines, but the greatest general
human exposure is through diet.
Cadmium is absorbed by plants and is consumed by humans and animals.
Acute toxicity is high (lethal dose < 1g) but cadmium itself is not biomagnified like mercury.
Arsenic, is commonly known as an acute poison but is introduced into the environment through
the smelting / mining of metals (nickel/gold, etc.), through the burning of coal and as a
component of pesticides. Considerable amounts of arsenic continue to be leached from
abandoned gold mines resulting in considerable water contamination.
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Human intake is largely through drinking water, leading to carcinogenic toxicity, particularly
in combination with smoking, although elevated skin cancer has also been associated with
chronic exposure to arsenic.
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3. MONITORING HAZARDOUS SUBSTANCES
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3.1 Hazard Surveillance and Survey Methods
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Employment screening programmes if they are used to determine Occupational surveillance
involves active programmes to anticipate, observe, measure, evaluate and control exposures to
potential health hazards in the workplace.
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Surveillance often involves a team of people that includes an occupational hygienist,
occupational physician, occupational health nurse, safety officer, toxicologist and engineer.
Obviously it is not always practical to enlist such a group of workers; however, each person
evaluating the work environment must be knowledgeable of the contributions of other professions
to the solution of specific problems.
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Depending upon the occupational environment and problem, three surveillance methods can be
employed: medical, environmental and biological.
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Medical surveillance is a planned programme of periodic examination, which may include
clinical examination, biological monitoring, or medical testing of employees by an occupational
health practitioner or an occupational medical practitioner.
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Environmental surveillance is a planned programme of periodic documentation of potential
exposure to contaminants for a group of employees, by measuring the concentration of
contaminants in the air, in bulk samples of materials, and on surfaces.
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Biological surveillance is a planned programme of periodic collection and analysis of body fluid,
tissues, and excreta or exhaled air in order to detect and quantify the exposure to or absorption of
any substance or organism.
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Medical Surveillance
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Is performed because diseases can be caused or exacerbated by exposure to hazardous
substances. It requires an active programme with professionals who are knowledgeable
about occupational diseases, diagnoses and treatment.
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Medical surveillance programmes provide steps to protect, educate, monitor and, in some
cases, compensate the employee.
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It can include pre-employment screening programmes, periodic medical examinations,
specialized tests to detect early changes and impairment caused by hazardous substances,
medical treatment and extensive record keeping.
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Pre-employment screening involves the evaluation of occupational and medical
history questionnaires and results of physical examinations. Questionnaires
provide information concerning past illnesses and chronic diseases (especially
asthma, skin, lung and heart diseases) and past occupational exposures. There are
ethical and legal implications of pre-employment eligibility. However, they are
fundamentally important when used to
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
(1) provide a record of previous employment and associated
exposures,

(2) establish a baseline of health for an employee and
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(3) Test for hyper-susceptibility.
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Medical examinations can include audiometric tests for hearing loss, vision tests, and tests
of organ function, evaluation of fitness for wearing respiratory protection equipment, and
baseline urine and blood tests.
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Periodic medical examinations are essential for evaluating and detecting trends in
the onset of adverse health effects and may include biological monitoring for
specific contaminants and the use of other biomarkers.
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Environmental and Biological Surveillance
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Environmental and biological surveillance starts with an occupational hygiene survey (normally
called the walk-through inspection) of the work environment to identify potential hazards and
contaminant sources, and determine the need for monitoring.
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General principles in evaluating the occupational environment
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The general principles in evaluating the occupational environment involves
i.
Recognition of potential hazards
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ii. Preparation for field study
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iii. Conducting the field study
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iv. Interpretation of survey results
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Recognition of potential hazards
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The investigator must become familiar with all processes, chemicals, inter-mediate and byproducts used in the particular plant or establishment. This information is gathered by conducting
a walk-through inspection.
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The Walk-Through Inspection
The purpose of the walk-through inspection is to systematically gather information to judge
whether a potentially hazardous situation exists and whether monitoring is indicated. An
occupational hygienist begins the walk-through survey with an opening meeting that can include
representatives of management, employees, supervisors, occupational health nurses and union
representatives. The occupational hygienist can powerfully impact the success of the survey and
any subsequent monitoring initiatives by creating a team of people who communicate openly and
honestly with one another and understand the goals and scope of the inspection. Workers must be
involved and informed from the beginning to ensure that cooperation, not fear, dominates the
investigation.
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During the meeting, requests are made for process flow diagrams, plant layout drawings, past
environmental inspection reports, production schedules, equipment maintenance schedules,
documentation of personal protection programmes, and statistics concerning the number of
employees, shifts and health complaints. All hazardous materials used and produced by an
operation are identified and quantified. A chemical inventory of products, by-products,
intermediates and impurities is assembled and all associated Material Safety Data Sheets are
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obtained. Equipment maintenance schedules, age and condition are documented because the use
of older equipment may result in higher exposures due to the lack of controls.
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After the meeting, the occupational hygienist performs a visual walk-through survey of the
workplace, scrutinizing the operations and work practices, with the goal of identifying potential
occupational stresses, ranking the potential for exposure, identifying the route of exposure and
estimating the duration and frequency of exposure. The occupational hygienist uses the walkthrough inspection to observe the workplace and have questions answered.
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Examples of observations and questions are given in Fig. 1.
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In addition to the questions shown in Fig. 1, questions should be asked that uncover what is
not immediately obvious. Questions could address:
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1. Non-routine tasks and schedules for maintenance and cleaning activities
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2. Recent process changes and chemical substitutions
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3. Recent physical changes in the work environment
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4. Changes in job functions
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5. Recent renovations and repairs.
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Non-routine tasks can result in significant peak exposures to chemicals that are difficult to
predict and measure during a typical workday.
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Process changes and chemical substitutions may alter the release of substances into the air and
affect subsequent exposure.
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Changes in the physical layout of a work area can alter the effectiveness of an existing
ventilation system.
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Changes in job functions can result in tasks performed by inexperienced workers and increased
exposures.
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Renovations and repairs may introduce new materials and chemicals into the work environment
which off-gas volatile organic chemicals or are irritants.
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After the walk-through inspection is completed, the occupational hygienist must determine
whether sampling is necessary; sampling should be performed only if the purpose is clear. The
occupational hygienist must ask, “What will be made of the sampling results and what questions
will the results answer?” It is relatively easy to sample and obtain numbers; it is far more
difficult to interpret them.
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Preparing and conducting the field survey
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The objective is to determine the intensity of exposure and to do this one must collect samples of
the air or use direct reading instruments. Every effort must be made to obtain representative
samples. To achieve this sampling strategy must be designed addressing the following questions:
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What to sample (selection of chemical agents);
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Where to sample (personal, area or source sample);
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Whom to sample (which worker or group of workers);
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Sample duration (real-time or integrated);
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How often to sample (how many days);
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How many samples
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How to sample, (analytical method).
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Traditionally, sampling performed for regulatory purposes involves brief campaigns (one or two
days) that concentrate on worst-case exposures. While this strategy requires a minimum
expenditure of resources and time, it often captures the least amount of information and has little
applicability to evaluating long-term occupational exposures. To evaluate chronic exposures so
that they are useful for occupational physicians and epidemiological studies, sampling strategies
must involve repeated sampling over time for large numbers of workers.
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What to sample
Most occupational environments have exposures to multiple contaminants. Chemical agents are
evaluated both individually and as multiple simultaneous assaults on workers. Chemical agents
can act independently within the body or interact in a way that increases the toxic effect. The
question of what to measure and how to interpret the results depends upon the biological
mechanism of action of the agents when they are within the body. Agents can be evaluated
separately if they act independently on altogether different organ systems, such as an eye irritant
and a neurotoxin. If they act on the same organ system, such as two respiratory irritants, their
combined effect is important. If the toxic effect of the mixture is the sum of the separate effects of
the individual components, it is termed additive. If the toxic effect of the mixture is greater than
the sum of the effects of the separate agents, their combined effect is termed synergistic.
Exposure to cigarette smoking and inhalation of asbestos fibers gives rise to a much greater risk
of lung cancer than a simple additive effect.
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Sampling all the chemical agents in a workplace would be both expensive and not
necessarily defensible. The occupational hygienist must prioritize the laundry list of
potential agents by hazard or risk to determine which agents receive the focus.
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Factors involved in ranking chemicals include:
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· Whether the agents interact independently, additively or synergistically
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· Inherent toxicity of the chemical agent
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· Quantities used and generated
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· Number of people potentially exposed
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· anticipated duration and concentration of the exposure
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· Confidence in the engineering controls
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· anticipated changes in the processes or controls
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· Occupational exposure limits and guidelines.
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Where to sample
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To provide the best estimate of employee exposure, air samples are taken in the breathing zone of
the worker (within a 30 cm radius of the head), and are called personal samples. To obtain
breathing zone samples, the sampling device is placed directly on the worker for the
duration of the sampling. If air samples are taken near the worker, outside of the breathing zone,
they are called area samples. Area samples tend to underestimate personal exposures and do not
provide good estimates of inhalation exposure. However, area samples are useful for evaluating
contaminant sources and measuring ambient levels of contaminants. Area samples can be taken
while walking through the workplace with a portable instrument, or with fixed sampling
stations. Area sampling is routinely used at asbestos abatement sites for clearance sampling and
for indoor air investigations.
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Whom to sample
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Ideally, to evaluate occupational exposure, each worker would be individually sampled for
multiple days over the course of weeks or months. However, unless the workplace is small (<10
employees), it is usually not feasible to sample all the workers. To minimize the sampling burden
in terms of equipment and cost, and increase the effectiveness of the sampling programme, a
subset of employees from the workplace is sampled, and their monitoring results are used to
represent exposures for the larger work force.
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To select employees who are representative of the larger work force, one approach is to classify
employees into groups with similar expected exposures, called homogeneous exposure groups
(HEGs) (Corn 1985). After the HEGs are formed, a subset of workers is randomly selected from
each group for sampling. Methods for determining the appropriate sample sizes assume a
lognormal distribution of exposures, an estimated mean exposure, and a geometric standard
deviation of 2.2 to 2.5. Prior sampling data might allow a smaller geometric standard deviation to
be used. To classify employees into distinct HEGs, most occupational hygienists observe workers
at their jobs and qualitatively predict exposures.
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There are many approaches to forming HEGs; generally, workers may be classified by job task
similarity or work area similarity. When both job and work area similarities are used, the method
of classification is called zoning (see Fig. 2). Once airborne, chemical and biological agents can
have complex and unpredictable spatial and temporal concentration patterns throughout the work
environment. Therefore, proximity of the source relative to the employee may not be the best
indicator of exposure similarity. Exposure measurements made on workers initially expected to
have similar exposures may show that there is more variation between workers than predicted. In
these cases, the exposure groups should be reconstructed into smaller sets of workers, and
sampling should continue to verify that workers within each group actually have similar
exposures (Rappaport 1995).
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______________________________________________________________________________
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Figure 2.
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Factors involved in creating HEGs using zoning
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______________________________________________________________________________
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Exposures can be estimated for all the employees, regardless of job title or risk, or it can be
estimated only for employees who are assumed to have the highest exposures; this is called
worst-case sampling.
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The selection of worst-case sampling employees may be based upon production, proximity to the
source, past sampling data, inventory and chemical toxicity. The worst-case method is used for
regulatory purposes and does not provide a measure of long-term mean exposure and day-to-day
variability. Task-related sampling involves selecting workers with jobs that have similar tasks
that occur on a less than daily basis.
There are many factors that enter into exposure and can affect the success of HEG classification,
including the following:
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1. Employees rarely perform the same work even when they have the same job description, and
rarely have the same exposures.
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2. Employee work practices can significantly alter exposure.
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3. Workers who are mobile throughout the work area may be unpredictably exposed to several
contaminant sources throughout the day.
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4. Air movement in a workplace can unpredictably increase the exposures of workers who are
located a considerable distance from a source.
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5. Exposures may be determined not by the job tasks but by the work environment.
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Sample duration
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The concentrations of chemical agents in air samples are either measured directly in the field,
obtaining immediate results (real-time or grab), or are collected over time in the field on
sampling media or in sampling bags and are measured in a laboratory (integrated) (Lynch 1995).
The advantage of real-time sampling is that results are obtained quickly onsite, and can
capture measurements of short-term acute exposures. However, real-time methods are limited
because they are not available for all contaminants of concern and they may not be analytically
sensitive or accurate enough to quantify the targeted contaminants. Real-time sampling may not
be applicable when the occupational hygienist is interested in chronic exposures and
requires time-weighted-average measurements to compare with OELs.
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Real-time sampling is used for emergency evaluations, obtaining crude estimates of
concentration, leak detection, ambient air and source monitoring, evaluating engineering controls,
monitoring short-term exposures that are less than 15 minutes, monitoring episodic exposures,
monitoring highly toxic chemicals (carbon monoxide), explosive mixtures and process
monitoring. Real-time sampling methods can capture changing concentrations over time and
provide immediate qualitative and quantitative information. Integrated air sampling is usually
performed for personal monitoring, area sampling and for comparing concentrations to timeweighted-average with OELs. The advantages of integrated sampling are that methods are
available for a wide variety of contaminants; it can be used to identify unknowns; accuracy
and specificity is high and limits of detection are usually very low.
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Integrated samples that are analyzed in a laboratory must contain enough contaminant to
meet minimum detectable analytical requirements; therefore, samples are collected over a
predetermined time period.
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In addition to analytical requirements of a sampling method, sample duration should be
matched to the sampling purpose. For source sampling, duration is based upon the process or
cycle time, or when there are anticipated peaks of concentrations. For peak sampling, samples
should be collected at regular intervals throughout the day to minimize bias and identify
unpredictable peaks. The sampling period should be short enough to identify peaks while also
providing a reflection of the actual exposure period.
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For personal sampling, duration is matched to the occupational exposure limit, task duration or
anticipated biological effect. Real-time sampling methods are used for assessing acute
exposures to irritants, asphyxiants, sensitizers and allergenic agents. Chlorine, carbon monoxide
and hydrogen sulphide are examples of chemicals that can exert their effects quickly and at
relatively low concentrations.
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Chronic disease agents such as lead and mercury are usually sampled for a full shift (seven hours
or more per sample), using integrated sampling methods. To evaluate full shift exposures, the
occupational hygienist uses either a single sample or a series of consecutive samples that cover
the entire shift. The sampling duration for exposures that occur for less than a full shift are
usually associated with particular tasks or processes. Construction workers, indoor maintenance
personnel and maintenance road crews are examples of jobs with exposures that are tied to tasks.
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How many samples and how often to sample?
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Concentrations of contaminants can vary minute to minute, day to day and season to season, and
variability can occur between individuals and within an individual. Exposure variability affects
both the number of samples and the accuracy of the results. Variations in exposure can arise
from different work practices, changes in pollutant emissions, the volume of chemicals used,
production quotas, ventilation, temperature changes, worker mobility and task
assignments. Most sampling campaigns are performed for a couple of days in a year; therefore,
the measurements obtained are not representative of exposure. The period over which samples are
collected is very short compared with the unsampled period; the occupational hygienist must
extrapolate from the sampled to the unsampled period. For long-term exposure monitoring, each
worker selected from a HEG should be sampled multiple times over the course of weeks or
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months, and exposures should be characterized for all shifts. While the day shift may be the
busiest, the night shift may have the least supervision and there may be lapses in work practices.
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Sampling Techniques
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Sampling equipments are generally classified according to type as follows: (1) direct reading; (2)
those that remove the contaminant from a measured quantity of air; and (3) those which collect a
known volume of air for subsequent laboratory analysis.
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Most equipment used by industrial hygienist fall under the first two types.
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Active and passive sampling
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Contaminants are collected on sampling media either by actively pulling an air sample through
the media, or by passively allowing the air to reach the media. Active sampling uses a batterypowered pump, and passive sampling uses diffusion or gravity to bring the contaminants to
the sampling media. Gases, vapours, particulates and bioaerosols are all collected by active
sampling methods; gases and vapours can also be collected by passive diffusion sampling.
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For gases, vapours and most particulates, once the sample is collected the mass of the
contaminant is measured, and concentration is calculated by dividing the mass by the volume of
sampled air. For gases and vapours, concentration is expressed as parts per million (ppm) or
, and for particulates concentration is expressed as
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(Dinardi 1995).
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In integrated sampling, air sampling pumps are critical components of the sampling system
because concentration estimates require knowledge of the volume of sampled air. Pumps are
selected based upon desired flowrate, ease of servicing and calibration, size, cost and suitability
for hazardous environments. The primary selection criterion is flowrate: low-flow pumps (0.5 to
500 ml/min) are used for sampling gases and vapours; high-flow pumps (500 to 4,500 ml/min)
are used for sampling particulates, bioaerosols and gases and vapours. To insure accurate sample
volumes, pumps must be accurately calibrated. Calibration is performed using primary standards
such as manual or electronic soap-bubble meters, which directly measure volume, or secondary
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methods such as wet test meters, dry gas meters and precision rotameters that are calibrated
against primary methods.
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Gases and vapours: sampling media
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Gases and vapours are collected using porous solid sorbent tubes, impingers, passive monitors
and bags.
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Sorbent tubes are hollow glass tubes that have been filled with a granular solid that enables
adsorption of chemicals unchanged on its surface. Solid sorbents are specific for groups of
compounds; commonly used sorbents include charcoal, silica gel and Tenax. Charcoal
sorbent, an amorphous form of carbon, is electrically nonpolar, and preferentially adsorbs organic
gases and vapours. Silica gel, an amorphous form of silica, is used to collect polar organic
compounds, amines and some inorganic compounds. Because of its affinity for polar compounds,
it will adsorb water vapour; therefore, at elevated humidity, water can displace the less polar
chemicals of interest from the silica gel. Tenax, a porous polymer, is used for sampling very low
concentrations of nonpolar volatile organic compounds.
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The ability to accurately capture the contaminants in air and avoid contaminant loss
depends upon the sampling rate, sampling volume, and the volatility and concentration of
the airborne contaminant. Collection efficiency of solid sorbents can be adversely affected
by increased temperature, humidity, flowrate, concentration, sorbent particle size and
number of competing chemicals. As collection efficiency decreases chemicals will be lost
during sampling and concentrations will be underestimated. To detect chemical loss, or
breakthrough, solid sorbent tubes have two sections of granular material separated by a
foam plug. The front section is used for sample collection and the back section is used to
determine breakthrough. Breakthrough has occurred when at least 20 to 25% of the
contaminant is present in the back section of the tube. Analysis of contaminants from solid
sorbents requires extraction of the contaminant from the medium using a solvent. For each batch
of sorbent tubes and chemicals collected, the laboratory must determine the desorption efficiency,
the efficiency of removal of chemicals from the sorbent by the solvent. For charcoal and silica
gel, the most commonly used solvent is carbon disulphide. For Tenax, the chemicals are extracted
using thermal desorption directly into a gas chromatograph.
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Impingers are usually glass bottles with an inlet tube that allows air to be drawn into the bottle
through a solution that collects the gases and vapours by absorption either unchanged in solution
or by a chemical reaction. Impingers are used less and less in workplace monitoring, especially
for personal sampling, because they can break, and the liquid media can spill onto the employee.
There are a variety of types of impingers, including gas wash bottles, spiral absorbers, glass bead
columns, midget impingers and fritted bubblers. All impingers can be used to collect area
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samples; the most commonly used impinger, the midget impinger, can be used for personal
sampling as well.
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Passive, or diffusion monitors are small, have no moving parts and are available for both organic
and inorganic contaminants. Most organic monitors use activated charcoal as the collection
medium. In theory, any compound that can be sampled by a charcoal sorbent tube and pump can
be sampled using a passive monitor. Each monitor has a uniquely designed geometry to give an
effective sampling rate. Sampling starts when the monitor cover is removed and ends when the
cover is replaced. Most diffusion monitors are accurate for eight-hour time-weighted-average
exposures and are not appropriate for short-term exposures.
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Sampling bags can be used to collect integrated samples of gases and vapours. They have
permeability and adsorptive properties that enable storage for a day with minimal loss. Bags are
made of Teflon (polytetrafluoroethylene) and Tedlar (polyvinylfluoride).
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Sampling media: particulate materials
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Occupational sampling for particulate materials, or aerosols, is currently in a state of flux;
traditional sampling methods are being replaced by particle size selective (PSS) sampling
methods. Traditional sampling methods will be discussed first, followed by PSS methods.
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Traditional Sampling methods: The most commonly used media for collecting aerosols are fibre
or membrane filters; aerosol removal from the air stream occurs by collision and attachment of
the particles to the surface of the filters. The choice of filter medium depends upon the
physical and chemical properties of the aerosols to be sampled, the type of sampler and the
type of analysis. When selecting filters, they must be evaluated for collection efficiency, pressure
drop, hygroscopicity, background contamination, strength and pore size, which can range from
0.01 to 10 mm. Membrane filters are manufactured in a variety of pore sizes and are usually
made from cellulose ester, polyvinylchloride or polytetrafluoroethylene. Particle collection occurs
at the surface of the filter; therefore, membrane filters are usually used in applications where
microscopy will be performed. Mixed cellulose ester filters can be easily dissolved with acid
and are usually used for collection of metals for analysis by atomic absorption (AAS).
Nucleopore filters (polycarbonate) are very strong and thermally stable, and are used for
sampling and analysing asbestos fibres using transmission electron microscopy (TEM). Fibre
filters are usually made of fibreglass and are used to sample aerosols such as pesticides and lead.
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For occupational exposures to aerosols, a known volume of air can be sampled through the
filters, the total increase in mass (gravimetric analysis) can be measured (mg/m(3) air), the
total number of particles can be counted (fibres/cc) or the aerosols can be identified
(chemical analysis). For mass calculations, the total dust that enters the sampler or only the
respirable fraction can be measured. For total dust (sum of insipirable and non-insiperable
fraction), the increase in mass represents exposure from deposition in all parts of the respiratory
tract. Total dust samplers are subject to error due to high winds passing across the sampler and
improper orientation of the sampler. High winds, and filters facing upright, can result in
collection of extra particles and overestimation of exposure.
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For respirable dust sampling, the increase in mass represents exposure from deposition in the
gas exchange (alveolar) region of the respiratory tract. To collect only the respirable fraction, a
preclassifier called a cyclone is used to alter the distribution of airborne dust presented to the
filter. Aerosols are drawn into the cyclone, accelerated and whirled, causing the heavier particles
to be thrown out to the edge of the air stream and dropped to a removal section at the bottom of
the cyclone. The respirable particles that are less than 10 mm remain in the air stream and are
drawn up and collected on the filter for subsequent gravimetric analysis.
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Sampling errors encountered when performing total and respirable dust sampling result in
measurements that do not accurately reflect exposure or relate to adverse health effects.
Therefore, PSS has been proposed to redefine the relationship between particle size, adverse
health impact and sampling method. In PSS sampling, the measurement of particles is related to
the sizes that are associated with specific health effects.
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The International Organization for Standardization (ISO) and the ACGIH have proposed three
particulate mass fractions: inhalable particulate mass (IPM), thoracic particulate mass (TPM)
and respirable particulate mass (RPM).
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IPM refers to particles that can be expected to enter through the nose and mouth, and would
replace the traditional total mass fraction.
TPM refers to particles that can penetrate the upper respiratory system past the larynx
μm<aerodynamic diameter<20 μm; cut size 10 μm).
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RPM refers to particles that are capable of depositing in the gas-exchange region of the lung, and
would replace the current respirable mass fraction (aerodynamic diameter < 7 μm; cut size
4
μm).
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A number of PSS samplers are now commercially available.
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Note: The nasal passages are the first line of defense and will trap all particles with an
aerodynamic diameter > 7 μm. The nose is less effective in preventing particles less than 7 μm
entering the lungs and the lung defenses can still prevent particles reaching the airway walls in
the tracheobronchial tree. However, approximately 30% of inspired particles in the range 1-3 μm
will be deposited in the lung tissue.
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Aerodynamic diameter is equal to the diameter of spherical particles of unit density which have
the same falling velocity in air as the particle in question. However, asbestos fibres are
characterized by their length.
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Sampling media: biological materials
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There are few standardized methods for sampling biological material or bioaerosols. Although
sampling methods are similar to those used for other airborne particulates, viability of most
bioaerosols must be preserved to ensure laboratory culturability. Therefore, they are more
difficult to collect, store and analyse. The strategy for sampling bioaerosols involves collection
directly on semisolid nutrient agar or plating after collection in fluids, incubation for several
days and identification and quantification of the cells that have grown. The mounds of cells
that have multiplied on the agar can be counted as colony-forming units (CFU) for viable bacteria
or fungi, and plaque-forming units (PFU) for active viruses. With the exception of spores, filters
are not recommended for bioaerosol collection because dehydration causes cell damage.
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Viable aerosolized micro-organisms are collected using all-glass impingers (AGI-30), slit
samplers and inertial impactors. Impingers collect bioaerosols in liquid and the slit sampler
collects bioaerosols on glass slides at high volumes and flowrates. The impactor is used with one
to six stages, each containing a Petri dish, to allow for separation of particles by size.
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Interpretation of sampling results must be done on a case-by-case basis because there are no
occupational exposure limits. Evaluation criteria must be determined prior to sampling; for
indoor air investigations, in particular, samples taken outside of the building are used as a
background reference. A rule of thumb is that concentrations should be ten times background to
suspect contamination. When using culture plating techniques, concentrations are probably
underestimated because of losses of viability during sampling and incubation.
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Skin and surface sampling
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There are no standard methods for evaluating skin exposure to chemicals and predicting dose.
Surface sampling is performed primarily to evaluate work practices and identify potential
sources of skin absorption and ingestion. Two types of surface sampling methods are used to
assess dermal and ingestion potential: direct methods, which involve sampling the skin of a
worker, and indirect methods, which involve wipe sampling surfaces.
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Direct skin sampling involves placing gauze pads on the skin to absorb chemicals, rinsing the
skin with solvents to remove contaminants and using fluorescence to identify skin contamination.
Gauze pads are placed on different parts of the body and are either left exposed or are placed
under personal protective equipment. At the end of the workday the pads are removed and are
analysed in the laboratory; the distribution of concentrations from different parts of the body are
used to identify skin exposure areas. This method is inexpensive and easy to perform; however,
the results are limited because gauze pads are not good physical models of the absorption and
retention properties of skin, and measured concentrations are not necessarily representative of the
entire body.
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Skin rinses involve wiping the skin with solvents or placing hands in plastic bags filled with
solvents to measure the concentration of chemicals on the surface. This method can underestimate
dose because only the unabsorbed fraction of chemicals is collected.
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Fluorescence monitoring is used to identify skin exposure for chemicals that naturally fluoresce,
such as polynuclear aromatics, and to identify exposures for chemicals in which fluorescent
compounds have been intentionally added. The skin is scanned with an ultraviolet light to
visualize contamination. This visualization provides workers with evidence of the effect of work
practices on exposure; research is underway to quantify the fluorescence intensity and relate it to
dose.
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Indirect wipe sampling methods involve the use of gauze, glass fibre filters or cellulose paper
filters, to wipe the insides of gloves or respirators, or the tops of surfaces. Solvents may be added
to increase collection efficiency. The gauze or filters are then analysed in the laboratory. To
standardize the results and enable comparison between samples, a square template is used to
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area.
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Biological media
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Blood, urine and exhaled air samples are the most suitable specimens for routine biological
monitoring, while hair, milk, saliva and nails are less frequently used. Biological monitoring is
performed by collecting bulk blood and urine samples in the workplace and analysing them in the
laboratory. Exhaled air samples are collected in Tedlar bags, specially designed glass pipettes or
sorbent tubes, and are analysed in the field using direct-reading instruments, or in the laboratory.
Blood, urine and exhaled air samples are primarily used to measure the unchanged parent
compound (same chemical that is sampled in workplace air), its metabolite or a biochemical
change (intermediate) that has been induced in the body. For example, the parent compound lead
is measured in blood to evaluate lead exposure, the metabolite mandelic acid is measured in urine
for both styrene and ethyl benzene, and carboxyhaemoglobin is the intermediate measured in
blood for both carbon monoxide and methylene chloride exposure.
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For exposure monitoring, the concentration of an ideal determinant will be highly correlated with
intensity of exposure. For medical monitoring, the concentration of an ideal determinant will be
highly correlated with target organ concentration.
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The timing of specimen collection can impact the usefulness of the measurements; samples
should be collected at times which most accurately reflect exposure. Timing is related to the
excretion biological half-life of a chemical, which reflects how quickly a chemical is eliminated
from the body; this can vary from hours to years. Target organ concentrations of chemicals with
short biological half-lives closely follow the environmental concentration; target organ
concentrations of chemicals with long biological half-lives fluctuate very little in response to
environmental exposures. For chemicals with short biological half-lives, less than three hours, a
sample is taken immediately at the end of the workday, before concentrations rapidly decline, to
reflect exposure on that day. Samples may be taken at any time for chemicals with long half-lives,
such as polychlorinated biphenyls and lead.
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Measurement Techniques
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Real-time monitors
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Direct-reading instruments provide real-time quantification of contaminants; the sample is
analysed within the equipment and does not require off-site laboratory analysis (Maslansky and
Maslansky 1993). Compounds can be measured without first collecting them on separate media,
then shipping, storing and analysing them. Concentration is read directly from a meter, display,
strip chart recorder and data logger, or from a colour change. Direct-reading instruments are
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primarily used for gases and vapours; a few instruments are available for monitoring particulates.
Instruments vary in cost, complexity, reliability, size, sensitivity and specificity. They include
simple devices, such as colorimetric tubes, that use a colour change to indicate concentration;
dedicated instruments that are specific for a chemical, such as carbon monoxide indicators,
combustible gas indicators (explosimeters) and mercury vapour meters; and survey instruments,
such as infrared spectrometers, that screen large groups of chemicals. Direct-reading instruments
use a variety of physical and chemical methods to analyse gases and vapours, including
conductivity, ionization, potentiometry, photometry, radioactive tracers and combustion.
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Commonly used portable direct-reading instruments include battery-powered gas
chromatographs, organic vapour analysers and infrared spectrometers. Gas chromatographs and
organic vapour monitors are primarily used for environmental monitoring at hazardous waste
sites and for community ambient air monitoring. Gas chromatographs with appropriate detectors
are specific and sensitive, and can quantify chemicals at very low concentrations. Organic vapour
analysers are usually used to measure classes of compounds. Portable infrared spectrometers are
primarily used for occupational monitoring and leak detection because they are sensitive and
specific for a wide range of compounds.
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Small direct-reading personal monitors are available for a few common gases (chlorine, hydrogen
cyanide, hydrogen sulphide, hydrazine, oxygen, phosgene, sulphur dioxide, nitrogen dioxide and
carbon monoxide). They accumulate concentration measurements over the course of the day and
can provide a direct readout of time-weighted-average concentration as well as provide a detailed
contaminant profile for the day.
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Colorimetric tubes (detector tubes) are simple to use, cheap and available for a wide variety of
chemicals. They can be used to quickly identify classes of air contaminants and provide ballpark
estimates of concentrations that can be used when determining pump flow rates and volumes.
Colorimetric tubes are glass tubes filled with solid granular material which has been impregnated
with a chemical agent that can react with a contaminant and create a colour change. After the two
sealed ends of a tube are broken open, one end of the tube is placed in a hand pump. The
recommended volume of contaminated air is sampled through the tube by using a specified
number of pump strokes for a particular chemical. A colour change or stain is produced on the
tube, usually within two minutes, and the length of the stain is proportional to concentration.
Some colorimetric tubes have been adapted for long duration sampling, and are used with batterypowered pumps that can run for at least eight hours. The colour change produced represents a
time-weighted-average concentration. Colorimetric tubes are good for both qualitative and
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quantitative analysis; however, their specificity and accuracy is limited. The accuracy of
colorimetric tubes is not as high as that of laboratory methods or many other real-time
instruments. There are hundreds of tubes, many of which have cross-sensitivities and can detect
more than one chemical. This can result in interferences that modify the measured concentrations.
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Direct-reading aerosol monitors cannot distinguish between contaminants, are usually used for
counting or sizing particles, and are primarily used for screening, not to determine TWA or acute
exposures. Real-time instruments use optical or electrical properties to determine total and
respirable mass, particle count and particle size. Light-scattering aerosol monitors, or aerosol
photometers, detect the light scattered by particles as they pass through a volume in the
equipment. As the number of particles increases, the amount of scattered light increases and is
proportional to mass. Light-scattering aerosol monitors cannot be used to distinguish between
particle types; however, if they are used in a workplace where there are a limited number of dusts
present, the mass can be attributed to a particular material. Fibrous aerosol monitors are used to
measure the airborne concentration of particles such as asbestos. Fibres are aligned in an
oscillating electric field and are illuminated with a helium neon laser; the resulting pulses of light
are detected by a photomultiplier tube. Light-attenuating photometers measure the extinction of
light by particles; the ratio of incident light to measured light is proportional to concentration.
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Laboratory Analytical Techniques
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There are many available methods for analysing laboratory samples for contaminants. Some of
the more commonly used techniques for quantifying gases and vapours in air include gas
chromatography, mass spectrometry, atomic absorption, infrared and UV spectroscopy and
polarography.
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Gas chromatography is a technique used to separate and concentrate chemicals in mixtures for
subsequent quantitative analysis. There are three main components to the system: the sample
injection system, a column and a detector. A liquid or gaseous sample is injected using a syringe,
into an air stream that carries the sample through a column where the components are separated.
The column is packed with materials that interact differently with different chemicals, and slows
down the movement of the chemicals. The differential interaction causes each chemical to travel
through the column at a different rate. After separation, the chemicals go directly into a detector,
such as a flame ionization detector (FID), photo-ionization detector (PID) or electron capture
detector (ECD); a signal proportional to concentration is registered on a chart recorder. The FID
is used for almost all organics including: aromatics, straight chain hydrocarbons, ketones and
some chlorinated hydrocarbons. Concentration is measured by the increase in the number of ions
produced as a volatile hydrocarbon is burned by a hydrogen flame. The PID is used for organics
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and some inorganics; it is especially useful for aromatic compounds such as benzene, and it can
detect aliphatic, aromatic and halogenated hydrocarbons. Concentration is measured by the
increase in the number of ions produced when the sample is bombarded by ultraviolet radiation.
The ECD is primarily used for halogen-containing chemicals; it gives a minimal response to
hydrocarbons, alcohols and ketones. Concentration is measured by the current flow between two
electrodes caused by ionization of the gas by radioactivity.
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The mass spectrophotometer is used to analyse complex mixtures of chemicals present in trace
amounts. It is often coupled with a gas chromatograph for the separation and quantification of
different contaminants.
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Atomic absorption spectroscopy is primarily used for the quantification of metals such as
mercury. Atomic absorption is the absorption of light of a particular wavelength by a free,
ground-state atom; the quantity of light absorbed is related to concentration. The technique is
highly specific, sensitive and fast, and is directly applicable to approximately 68 elements.
Detection limits are in the sub-ppb to low-ppm range.
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Infrared analysis is a powerful, sensitive, specific and versatile technique. It uses the absorption
of infrared energy to measure many inorganic and organic chemicals; the amount of light
absorbed is proportional to concentration. The absorption spectrum of a compound provides
information enabling its identification and quantification.
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UV absorption spectroscopy is used for analysis of aromatic hydrocarbons when interferences are
known to be low. The amount of absorption of UV light is directly proportional to concentration.
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Polarographic methods are based upon the electrolysis of a sample solution using an easily
polarized electrode and a nonpolarizable electrode. They are used for qualitative and quantitative
analysis of aldehydes, chlorinated hydrocarbons and metals.
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Interpretation of Results
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Occupational exposure limits
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Air and biological sampling data are usually compared to recommend or mandated occupational
exposure limits (OELs). Occupational exposure limits have been developed in many countries for
inhalation and biological exposure to chemical and physical agents.
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The philosophical bases for the limits are determined by the organizations that have developed
them. The most widely used limits, called threshold limit values (TLVs), areand are those issued
in the United States by the American Conference of Governmental Industrial Hygienists
(ACGIH).
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For airborne exposures, there are three types of TLVs:
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an eight-hour time-weighted-average exposure, TLV-TWA, to protect against chronic health
effects;
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a fifteen-minute average short-term exposure limit, TLV-STEL, to protect against acute health
effects;
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and an instantaneous ceiling value, TLV-C, to protect against asphyxiants or chemicals that are
immediately irritating.
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Guidelines for biological exposure levels are called biological exposure indices (BEIs). These
guidelines represent the concentration of chemicals in the body that would correspond to
inhalation exposure of a healthy worker at a specific concentration in air. Outside of the United
States as many as 50 countries or groups have established OELs, many of which are identical to
the TLVs. In Britain, the limits are called the Health and Safety Executive Occupational Exposure
Standards (OES), and in Germany OELs are called Maximum Workplace Concentrations
(MAKs).
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OELs have been set for airborne exposures to gases, vapours and particulates; they do not exist
for airborne exposures to biological agents. Therefore, most investigations of bioaerosol
exposure compare indoor with outdoor concentrations. If the indoor/outdoor profile and
concentration of organisms is different, an exposure problem may exist.
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There are no OELs for skin and surface sampling, and each case must be evaluated separately. In
the case of surface sampling, concentrations are usually compared with acceptable background
concentrations that were measured in other studies or were determined in the current study. For
skin sampling, acceptable concentrations are calculated based upon toxicity, rate of absorption,
amount absorbed and total dose. In addition, biological monitoring of a worker may be used to
investigate skin absorption.
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Formulas
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Occupational exposure limits
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Ti C i T1C1  T2 C 2  .....  Tn C n

T1  T2  ....  Tn
i 1 Ti
TLV  TWA  
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Ti - time interval
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n
C i - concentration value that existed during the i th time interval (Note : any time interval can be
used)
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 TWA1 TWA2
 n TWAi 
TWAn 
% REL  100

 ........ 

  100
REL n 
 i 1 REL i 
 REL1 REL 2
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%REL gives the effective combined effects of all potentially irritating toxic or hazardous
components in any ambient air system. Any established parameter e.g. MAK, TLV, PEL may be
used as the REL and this standard needs to be known
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If %REL≤100 then it can be inferred that the effective REL for the mixture as a whole has not
been exceeded and vice-versa.
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TLV effective


1
 n
fi

  TLV
i
 i 1
 
 
1

fn
f2
  f1
  TLV  TLV  ....  TLV
1
2
n
 






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f i - weight fraction of i th component
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TLV i - established OEL of i th component in mg/m3 not ppm
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TLV effective - effective TLV (mg/m3 NOT ppm) for any established exposure limit
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The above equation is used to determine the effective exposure limit that exists for any
equilibrium vapour phase that is in contact with any well defined liquid mixture containing 2 or
more different volatile components.
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The value of the exposure limit standard for each component in the liquid mixture must be
known.
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This formula assumes that the overall composition of the vapour phase is identical to that of the
liquid phase, although this would rarely –if ever- be true. However the equation is still considered
a useful tool for evaluating certain vapour mixtures.
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Conversion of concentration units
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C vol ( ppmv ) 
C vol ( ppmv ) 


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24.45
C mass (mg / m 3 ) @ NTP (1 atm and 25 oC)
MWi

22.41
C mass (mg / m 3 )
MWi

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@ STP (1 atm and 0 oC)
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Note: The common practice among hygienists is to assume that air samples taken in normal
factory air are at NTP.
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Sampling particulates
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Minimum volume of air sample 
10  analytical sensitivity
hygiene standard concentration
Minimum sampling duration per sample 
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10  analytical sensitivity
hygiene standard concentration  flowrate of sampler
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Minimum duration of sampling 
0.01 weight of paper
hygiene standard concentration  flowrate of sampler
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TLV (mg/m 3 ) weight of paper (mg)

10
volume of sample (l)
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Note: In all the above formulas units must be consistent
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