NTRODUCTION

Occupational health: a definition

Occupational health is a multidisciplinary activity aimed at:

♦ the protection and promotion of the health of workers by preventing and
controlling occupational diseases and accidents and by eliminating occupational
factors and conditions hazardous to health and safety at work;
♦ the development and promotion of healthy and safe work, work environments
and work organizations;
♦ the enhancement of the physical, mental and social well-being of workers and
support for the development and maintenance of their working capacity, as
well as professional and social development at work;
♦ enabling workers to conduct socially and economically productive lives and to
contribute positively to sustainable development.
Occupational health has gradually developed from a mono-disciplinary, risk-
oriented activity to a multi-disciplinary and comprehensive approach that considers
an individual’s physical, mental and social well-being, general health and personal
development.

POSITIVE HEALTH EFFECTS OF WORK

There is a continuous two-way interaction between a person and the physical and
Two-way interaction
psychological working environment: the work environment may influence the person’s
health either positively or negatively and productivity is, in turn, influenced by the
worker’s state of physical and mental well-being. Work, when it is well-adjusted and
productive, can be an important factor in health promotion, e.g. partially disabled workers
may be rehabilitated by undertaking tasks suited to their physical and mental limitations
and, in this way, may substantially increase their working capacity. However, the fact that
1
work can have a positive influence on health has not yet been fully exploited; knowledge
of work physiology and ergonomics needs to be further developed and applied to benefit
worker’s health.
HEALTH HAZARDS

When work is associated with health hazards, it may cause occupational disease, is one of
the multiple causes of other disease or may aggravate existing ill-health of
non-occupational origin. In developing countries, where work is becoming increasingly
mechanized, a number of work processes have been developed that
treat workers as tools in production, putting their health and lives at risk. The
occupational health lessons learned during the Industrial Revolution should be
borne in mind in planning for health in developing countries if such problems are to
be avoided.

Unemployment

Job loss may adversely affect a worker’s physiological and mental health. If
unemployment persists, the person’s health continues to decline and chronic
disorders can appear. The mental and financial distress caused by the job loss can
spread to other family members. In a developing country, job loss can have profound
effects that spread beyond the worker’s own family since, where there is limited
paid employment, a person in a well-paid job exerts an important influence in the
community. In addition to having an obvious economic influence and high social
standing, such a worker may serve as a good source of health information and set
an example with a healthy lifestyle. Loss of employment for such a person can also
affect the immediate community as well as the person’s family. A worker’s health
may also suffer well before the actual job loss. Both feelings of job insecurity and
knowledge of impending job loss have been associated with mental and physical
health complaints.
Similarly, those who have never had the opportunity to be employed, e.g. because of
unavailability of jobs, have no chance to develop an identity or sense of belonging
through work which is important for psychological and social well-being. Such people are
not accessible to health messages in the workplace and may be unaware of the positive
relationship between work and health. In addition, because they have a lot of free time,
sometimes associated with anxiety and depression, the never- employed are more likely
than those in employment to consume alcohol, cigarettes and drugs.

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3
 WORK AS A FACTOR IN HEALTH PROMOTION

WHO defines health as a state of complete physical, mental and social well-being
and not merely the absence of disease or infirmity. According to the WHO Study
Group on Early Detection of Health Impairment in Occupational Exposure to Health
Hazards:
Health ... connotes rather a way of functioning within one’s environment (work,
recreation, living). It not only means freedom from pain or disease, but also
freedom to develop and maintain one’s functional capacities. Health develops
and is maintained through interaction between the genotype and the total
environment. The work environment constitutes an important part of man’s
4
total environment, so health is to a large extent affected by work conditions.1
 Health promotion was defined by the Ottawa Charter for Health Promotion, 1986, as:
... the process of enabling people to increase control over, and to improve, their
health. To reach a stage of complete physical, mental and social well-being, an
individual or group must be able to identify and to realize aspirations, to satisfy
needs, and to change or cope with the environment. Therefore, health promotion
is not just the responsibility of the health sector, but goes beyond healthy
lifestyles to well-being.2
Health promotion is a continuum ranging from the treatment of disease to the
prevention of disease including protection against specific risks, to the promotion
of optimal health. Achieving optimal health includes: improving physical abilities in
relation to sex and age; improving mental ability; developing reserve capacities;
adaptability to changing circumstances of work and life and reaching new levels of
individual achievement in creative and other work. In a work setting these health-
HEALTH PROTECTION AND PROMOTION ACTIVITIES IN THE WORKPLACE
indicators may be evaluated quantitatively by indices of absenteeism, job
satisfaction and work stability.
1. National governments

National governments have an interest in workers’ health partly because it has a direct
influence on national productivity. Governments are responsible for establishing and
maintaining safe working conditions and ensuring, through legislation, that occupational
health services are provided for all workers in all branches of economic activity,
MANAGEMENT
including those in the public sector. Health promotion programmes are not usually a
statutory
Those requirement
responsible butmanagement
for the occupational
of ahealth services
workplace havecan provideinaworkers’
an interest focus for their
implementation.
health promotion for the same reason as national governments: healthy workers are
essential for optimal productivity. In addition to the humanitarian value of improving
workers’ health, the economic value is therefore particularly important to employers. This
is also true for self-employed workers as their productivity is often completely dependent
on their own health.
The prime responsibility for health and safety in a workplace rests with the Management,
which therefore plays an essential role in the success of any health promotion programme.
To ensure the success of a programme, management must allow the necessary resources
and time to be dedicated to it, demonstrate its desire for employees to participate and be
willing to accept suggestions from employees on what should be done. Management must
also have sufficient appreciation of the need for health promotion and disease prevention
to be able to assess the relative merits of various programmes, determine priorities and
5
delegate responsibility for achieving programme success.
 WORKERS

The worker stands to benefit from health promotion programmes by having a safe
and healthy work environment, a convenient location to learn about and put into
practice a healthy lifestyle, readily available opportunities for screening and health
care and an opportunity ultimately to achieve optimal health. Health has an all-
encompassing impact on the worker’s life, by affecting his or her ability to interact
with others, to work and to be self-reliant.
The worker’s contribution to workplace health promotion is essential to any
programme’s success. Workers should be involved in the programme’s design and
encourage their co-workers to participate.

Workers’ representatives and unions

The role of workers’ representatives, organizations and unions is to negotiate with

the management to ensure that appropriate health programmes are implemented
and that an appropriate balance is achieved between the various health programmes.
The workers’ organizations should also ensure that certain principles be followed,
e.g. confidentiality and non-discrimination.

COMMUNITIES

Health is influenced by many factors outside the workplace. Consequently, health

promotion for the workforce cannot be regarded solely as the responsibility of
occupational health professionals. The community, through its primary health workers
and public health professionals, has clear-cut responsibilities for individual and group
health education as a means of health promotion. Wherever possible, health education
In developing countries, particularly in rural areas and small workplaces, the primary health worker may be
programmes should be a joint activity of occupational and community health
the sole provider of health protection and promotion services for both workers and the rest of the
professionals. Mass media can also play an important role in health education.
community.

Health promotion is an essential part of the occupational health professional’s

mandate. Physicians, nurses, safety officers, health educators and PHC workers will
play different roles in work place health promotion and should be trained
accordingly e.g. the role of the occupational health nurse is to educate, screen and
counsel workers, whereas that of an occupational hygienist is to assess the control
of health hazards while keeping in touch with the development and progress of
Together with others, such as ergonomists, nutrition specialists and psychologists,
health promotion programmes.
occupational health professionals can:
♦ protect workers’ health by controlling hazards
6 in the workplace and by
introducing ergonomics
♦ advise workers and managers on health promotion activities and on how to
improve working conditions
Occupational health training manual for primary health care workers 19

♦ monitor the work environment and workers’ health with a view to early
identification of health risks and evaluation of the effectiveness of health
protection and promotion programmes.
In many circumstances, in developing as well as developed countries, occupational
health professionals can cover only a small proportion of workplaces and workers.
In such cases, others responsible for providing health care for workers should
recognize health promotion as one of their major tasks and should receive some
training in occupational health.

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8
WORK ENVIRONMENT

1. OBJECTIVES

♦ Detect work hazards as related to occupation, work and work environment

♦ Inspect workplaces for the discovery of actual hazards and unsafe workers’
behaviour
♦ Use simple methods and techniques for evaluation of work hazards and for
testing control measures
♦ Report work and environmental hazards to concerned bodies
♦ Know principles of the control of work hazards and work environment and
participate in selecting appropriate control measures and optimal use of
available resources
♦ Participate in the management of work emergency plans and in first aid
♦ Educate workers on the principles of safe conduct at work
♦ Participate in investigating work complaints, compensation cases, rehabilitation,
social welfare, etc.
♦ Coordinate with other professionals in the occupational multi-disciplinary
team: safety officer and committee, occupational hygienist, physician and
nurse, sanitarian, first aid attendant, plant engineer and foreman.

INTRODUCTION AND BASIC CONCEPTS

OCCUPATIONAL HYGIENE

This is the practice of assessment and control of environmental factors and stresses
arising in or from the workplace, which may cause injury, sickness, impaired health
and well-being or significant discomfort and inefficiency among workers or among
the citizens of the community.
It encompasses the study of:
♦ toxicology
♦ industrial processes
♦ the chemical and physical behaviour of air contaminants
♦ 9
environmental sampling techniques and statistics
♦ the design and evaluation of ventilation systems
♦ noise control
♦ radiation protection
♦ the health effects of occupational hazards.
Occupational/industrial hygienists use environmental monitoring and analytical
methods to detect the extent of worker exposure and employ engineering, work
practice controls and other methods to control potential health hazards.
Occupational/industrial hygienists must work with physicians to develop
comprehensive occupational health programmes and with epidemiologists to
perform research on health effects.

WORK-SITE ANALYSIS

This is an essential procedure that helps in determining what jobs and workstations
are the sources of potential problems. During the work-site analysis: exposures,
problem tasks and risks are identified and measured. The most-effective work-site
analyses include all jobs, operations and work activities. The occupational/industrial
hygienist inspects, researches or analyses how the particular chemicals or physical
hazards at the work-site affect worker health. If a situation hazardous to health is
discovered, he or she recommends the appropriate corrective action.
Example

An occupational/industrial hygienist might be asked to determine the composition and

concentrations of air contaminants in a workplace where there have been complaints of
eye, nose and throat irritation. The hygienist in this situation would also determine if the
contaminant exposures exceeded the permissible exposure limits required by the national
regulations and standards. If the problem was the result of airborne materials (a
conclusion that might be reached in consultation with a physician or epidemiologist), then
the hygienist would be responsible for selecting the techniques used to reduce or
eliminate the exposure e.g. installing exhaust ventilation around the source of the air
RECOGNITION OF HEALTH HAZARDS
contaminants and isolating it from the general work area. Follow-up sampling to verify
that the controls had been effective would also be the hygienist’s responsibility.
3.

Inspection

This is the first step in the process leading to evaluation and control and entails the
identification of materials and processes that have the potential to cause harm to workers.

Inspection of the workplace is the best source of directly relevant data about health
hazards. There is no substitute for observation
10 of work practices, use of chemical and
physical agents,
distinguish thoseand
thatthe apparent
require effectiveness
formal evaluation of
bycontrol measures.
the industrial The worker should be
hygienist.
able to recognize major and obvious health hazards and
POTENTIAL HEALTH HAZARDS

Air contaminants

These are commonly classified as either particulate or gas and vapour contaminants
(a) Particulate contaminants
♦ Dusts: solid particles generated by handling, crushing, grinding, colliding,
exploding, and heating organic or inorganic materials such as rock, ore, metal,
coal, wood and grain. Any process that produces dust fine enough to remain
in the air long enough to be inhaled or ingested should be regarded as
hazardous until proven otherwise.
♦ Fumes: formed when material from a volatilized solid condenses in cool air. In
most cases, the solid particles resulting from the condensation react with air
to form an oxide.
♦ Mists: liquid suspended in the atmosphere. Mists are generated by liquids
condensing from a vapour back to a liquid or by a liquid being dispersed by
splashing or atomizing.
♦ Aerosols: a form of a mist characterized by highly respirable, minute liquid
particles.
♦ Fibres: solid particles whose length is several times greater than their diameter,
e.g. asbestos.
(b) Gas and vapour contaminants
♦ Gases: formless fluids that expand to occupy the space or enclosure in which
they are confined. They are atomic, diatomic or molecular in nature as opposed
to droplets or particles, which are made up of millions of atoms or molecules.
Through evaporation, liquids change into vapours and mix with surrounding
♦ atmosphere.
Vapours: the volatile form of substances that are normally in a solid or liquid state
at room temperature and pressure.
Chemical hazards

Harmful chemical compounds in the form of solids, liquids, gases, mists, dusts, fumes
and vapours exert toxic effects by inhalation (breathing), absorption (through direct
contact with the skin) or ingestion (eating or drinking). Airborne chemical hazards exist
as concentrations of mists, vapours, gases, fumes or solids. Some are toxic through
inhalation and some of them irritate the skin on contact; some can be toxic by absorption
through the skin or through ingestion and some are corrosive to living tissue. The degree
of worker risk from exposure to any given substance depends on the nature and potency
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of the toxic effects and the magnitude and duration of exposure.
Biological hazards

These exist in exposures to bacteria, viruses, fungi and other living organisms that can
cause acute and chronic infections by entering the body either directly or
through breaks in the skin.
Occupations that deal with plants or animals or their products, or with food and
food processing may expose workers to biological hazards. Laboratory and medical
personnel also can be exposed to biological hazards. Any occupations that result in
contact with bodily fluids expose workers to biological hazards.
In occupations where animals are involved, biological hazards are dealt with by
preventing and controlling diseases in the animal population as well as properly
caring for and handling infected animals.
Also, effective personal hygiene, particularly proper attention to minor cuts and
scratches especially on the hands and forearms, helps keep worker risks to a
minimum. In occupations where there is potential exposure to biological hazards,
workers should practice proper personal hygiene, particularly hand washing.
Hospitals should provide proper ventilation, proper personal protective equipment
such as gloves and respirators, adequate infectious waste disposal systems and
appropriate controls including isolation in instances of particularly contagious
diseases, e.g. tuberculosis.
Physical hazards

These include excessive levels of noise, vibration, illumination and temperature, and
ionizing and non-ionizing electromagnetic radiation.
Noise, for example, is a significant physical hazard, which can be controlled by:
♦ installing equipment and systems that have been engineered, designed and
built to operate quietly
♦ enclosing or shielding noisy equipment
♦ making certain that equipment is in good repair and is properly maintained
with all worn or unbalanced parts replaced
♦ mounting noisy equipment on special mounts to reduce vibration
♦ installing silencers, mufflers or baffles
♦ substituting quiet work methods for noisy ones, e.g. welding parts rather than
riveting them
♦ treating floors, ceilings and walls with acoustic material to reduce reflected or
reverberant noise
♦ erecting sound barriers at adjacent workstations around noisy operations to
reduce worker exposure to noise generated
12 at adjacent workstations
♦ increasing the distance between the source and the receiver, e.g. by isolating
workers in acoustic booths, limiting workers’ exposure time to noise and
providing hearing protection.
Occupational hygiene regulations require that workers in noisy surroundings be
periodically tested as a precaution against hearing loss.
Ionizing radiation can be controlled by:
♦ Reducing exposure time: danger from radiation increases with the
amount of time one is exposed to it. The shorter the time of exposure the
smaller the radiation danger.
♦ Increasing distance: a valuable tool in controlling exposure to both
ionizing and non-ionizing radiation. Radiation levels from some sources can be
estimated by comparing the squares of the distances between the worker and
the source.
♦ Shielding: the greater the protective mass between a radioactive source
and the worker, the lower the radiation exposure. Similarly, shielding
workers from non-ionizing radiation can also be an effective control
method.
In some instances, however, limiting exposure to or increasing distance from certain
forms of non-ionizing radiation, e.g. lasers, is not effective. An exposure to laser
radiation that is faster than the blinking of an eye can be hazardous and would
require workers to be miles from the laser source before being adequately protected.
Radiant heat exposure can be controlled by: installing reflective shields and by
providing protective clothing in factories such as steel mills.
Ergonomic hazards

The science of ergonomics studies and evaluates a full range of tasks including, but
not limited to, lifting, holding, pushing, walking and reaching.
Many ergonomic problems result from technological changes:
♦ increased assembly line speeds
♦ adding specialized tasks
♦ increased repetition.
Some problems arise from poorly designed job tasks. Any of those conditions can
cause ergonomic hazards:
♦ excessive vibration
♦ noise
♦ eye strain
♦ repetitive motion
♦ heavy lifting problems
♦ 13areas.
poorly designed tools or work
Repetitive motions or repeated shocks over prolonged periods of time as in jobs
involving sorting, assembling and data entry can often cause irritation and
inflammation of the tendon sheath of the hands and arms, a condition known as
carpal tunnel syndrome. Ergonomic hazards are avoided primarily by the effective
design of a job or job-site and by better designed tools or equipment that meet
workers’ needs in terms of physical environment and job tasks.
Through thorough work-site analyses, employers can set up procedures to correct
or control ergonomic hazards by:
♦ using the appropriate engineering controls, e.g. designing or redesigning work
stations, lighting, tools and equipment
♦ teaching correct work practices, e.g. shifting workers among several different
tasks, reducing production demand and increasing rest breaks
♦ providing and mandating personal protective equipment where necessary.
Evaluating working conditions from an ergonomic standpoint involves looking at the
total physiological and psychological demands of the job on the worker. Overall, the
benefits of a well-designed, ergonomic work environment can include increased
efficiency, fewer accidents, lower operating costs and more effective use of personnel.

Psychosocial factors

These may include boring, repetitive tasks, production pressure, stress, low pay and lack
of recognition.
Accident factors

The main causes of accidents include:

♦ unsafe mechanical and physical conditions
♦ unsafe acts
♦ unsafe personal factors.

TECHNIQUES USED IN RECOGNIZING HEALTH HAZARDS

Material inventory

A material inventory is used for keeping an account of raw materials, intermediate

and end products, waste products and by-products. It is tailored to meet the specific
requirements of local circumstances taking into consideration the following.
(a) Who will use the inventory
♦ safety advisers and representatives
♦ occupational hygienists
♦ doctors
♦ nurses 14

♦ emergency service personnel

♦ purchasing staff.
(b) What information is required
♦ the nature of the material, i.e. composition, physical data, fire and
explosion data, basic toxicological and safety data, etc.
♦ the use of the material, including storage, handling and control procedures,
first aid, etc.
♦ administrative details, i.e. trade and chemical names, company reference
numbers, address of manufactures/suppliers, labelling and packing
requirements, waste disposal, etc.
(c) How the inventory will be updated
♦ any new substances should be considered from a health and safety
viewpoint before purchasing, use and inclusion in the inventory
♦ for existing materials, health and safety staff should have a system for
ensuring, through their information sources, that the hazard data
contained in the data sheet is the best information currently available
♦ the availability of computerized data-handling systems augments the
use of a materials inventory.
Process inventory

The aim is to document hazards associated with each process and to record how each
is being managed and controlled. The process inventory should include details of:
♦ the process
♦ the materials involved (including intermediate and wastes)
♦ points of material entry and exit
♦ normal operating procedures
♦ potential hazards
♦ the potential for emissions into the atmosphere
♦ the potential for exposure
♦ arrangements for engineering controls
♦ other precautions including protective equipment.
The process inventory also provides the opportunity to document hazards other
than those associated with chemicals, e.g. heat, noise and radiation, and to include
disposal procedures for hazardous waste products.
The inventory could be based on:
♦ flow of a particular product or material
15
♦ departmental or equipment flow
♦ geographic location.
 Walk-through occupational hygiene survey

A walk-through survey of the premises permits observation of all plant operations

and is carried out to make a preliminary assessment of potential hazards. Possible
sources and potential contaminants from specific types of processes can be
identified. The walk-through survey provides an important
opportunity to meet plant personnel and to interact with engineers, foremen and
other workers who know the process problems and are aware of complaints or
symptoms among workers.
(a) General principles addressed by the walk-through survey
♦ hazards present in the work place
♦ estimated/likely scale of the identified hazards
♦ the control measures currently in force for each hazard
♦ procedures implemented to maintain the control measures
♦ the monitoring required.
(b) Survey methods
♦ Surveys are usually carried out without the use of measuring instruments.
♦ Much of the information required can be assembled in advance of the survey.

♦ The following aids are required to carry out the work:

– survey report forms

– notepad or dictation machine
– plan of premises
– camera
♦ The
– occupational hygienist (or whoever is nominated to undertake the task by the
PHC workers) proceeds through each of the work areas, preferably in accordance
with the
Sources of information working
used during functions,
the surveyoften
are: commencing with production from goods inward
to dispatch, and preferably accompanied in each area of the premises by either a
♦ local supervisor or engineer
workers involved withdaily
in their general
tasksresponsibilities.
– senses of smell, hearing and touch for detection of odours, heat and
– noise

– photography for documenting the general visual appearance of each

environment and any activity deserving further attention
–
smoke tube test for local exhaust ventilation
– 16
observation, the key to an effective survey, noting any ergonomics
problems, e.g. poorly designed lighting, unsafe working practices,
unguarded equipment, etc.
(c) Reports
The report should be written clearly and concisely and should be structured as
follows:
♦ introduction
♦ summary of immediate hazards and action taken or recommended to resolve
the problem permanently and/or temporarily pending further evaluation
♦ summary of hazards requiring further monitoring/evaluation
♦ walk-through survey report forms as completed during survey
♦ discussions of methods arising from survey
♦ proposed occupational hygiene work plan.
(d) Summary of a survey
♦ a survey is a preliminary assessment designed to identify hazards and control
measures, carried out by competent staff with the help of local supervising
staff
♦ it should be comprehensive by location and by time for cyclical/occasional
processes
♦ it is a necessary prelude to detailed investigations of specific hazards
♦ it is necessary to gather a range of data pertaining to the subject in order to fully
prepare for the survey
♦ the two main elements of the survey data source are the workforce and
observation
♦ photography is very important
♦ reports should be structured carefully and be concise.

Air-sampling programmes

An air-sampling programme must be designed to answer specific questions

otherwise it may not fulfil the need for which it was initiated, e.g. a prospective
epidemiological
predictions to be programme requires
valid. Sampling randomprotection,
for worker sampling inonorder for statistical
the other hand, will
require selection of persons at maximum risk.
Reasons for sampling are varied and may include the following:
♦ health risk evaluation: to measure worker exposure in order to estimate the risk
of undesirable health effects and the need for control measures
♦ environmental protection: to determine the amount of any toxic or hazardous
17
materials released to the environment
♦ compliance: to ensure that exposure levels for workers or environmental
releases are within regulatory limits and to satisfy legislative monitoring
requirements
♦ process control: to evaluate the performance of engineering or other process
controls and to ensure that contaminant control remains adequate
♦ source identification: to find and control contaminant sources
♦ documentation of exposure: to maintain records of exposure for prospective
studies or for institutional protection against future legal action.
The sampling strategy for each of the stated purposes will require different
protocols and sampling systems. The types of samples refer to whether a personal
exposure sample should be collected in the breathing zone of a worker, or whether
an area, stack or other environmental sample is preferable. Sampling from exhaust
stacks is commonly done for process and emission control. Health protection
requires personal exposure monitoring.
Occupational hygiene sampling protocols

Purpose Type of sample

Health risk evaluation Personal
Environmental protection Area, environmental
Compliance Personal, environmental, stack
Process control Area, personal, stack
EVALUATION OF HEALTH HAZARDS
Source identification Area, stack
Documentation of exposure Personal

Evaluation of health hazards within a plant includes measurement of exposures (and

potential exposures), comparison of those exposures to existing standards and
recommendation of controls if needed.
Exposure measurement techniques

These techniques are based on the nature of hazards and the routes of
environmental contact with the worker, e.g.
♦ air sampling can show the concentration of toxic particulates, gases and
vapours that workers may inhale
♦ skin wipes can be used to measure the degree of skin contact with toxic
materials that may penetrate the skin
♦ noise dosimeters record and electronically integrate workplace noise levels to
determine total daily exposure.
Selection and calibration of instruments

Instruments are generally classified as follows:

18
♦ direct reading instruments
♦ sampling instruments which remove the contaminant (for subsequent laboratory
analysis) from a measured quantity of air
♦ sampling instruments which collect a known volume of air for subsequent
laboratory analysis.
All these types of equipment must be calibrated against a standard air flow
measuring device before and after use in the field. Furthermore, direct reading
instruments must be calibrated against a known concentration of the substance for
which they are used.

Establishing proper analytical methods

The use of accurate, sensitive, specific and reproducible analytical methods is as

important as the proper calibration of the sampling equipment. Among difficulties
that should be overcome in the measurements (sampling/analysis) are:
♦ interference and reactions when dealing with mixtures of chemicals, which is
often the case
♦ fluctuations in concentration.
Other factors affecting a worker’s uptake of the contaminants include:
♦ routes of entry of material other than respiration, e.g. skin absorption
♦ physical activity of workers, which affects the respiration rate
♦ whether or not respirators are used in the workplace.
When available, standard methods of analysis should be used such as those
recommended by:
♦ WHO
♦ International Organization for Standardization
♦ European Community
♦ American Industrial Hygiene Association (AHIA) Analytical Committee
♦ U.S. National Institute for Occupational Safety and Health (NIOSH)
♦ U.S. Occupational Safety and Health Administration (OSHA)
♦ American Conference of Governmental Industrial Hygienists (ACGIH)
♦ The American Public Health Association (APHA)
♦ The American National Standards Institute (ANSI).

Strategy of sampling and measurement

Every effort must be made to get measurements (or samples) that represent the
workers’ exposures. This is achieved by answering the following:
♦ Where to sample?
19
♦ Whom to sample?
♦ How long to sample?
♦ How many samples to take?
♦ When to sample?
A sufficient number of samples must be collected or readings made with direct
reading instruments, for the proper duration, to permit the assessment of daily,
time-weighted average (TWA) exposures and to evaluate peak exposure
concentrations when needed.

Interpretation of findings

A great deal of judgment must be used in interpretation and reporting the results.
The investigator must have the following facts:
♦ nature of substance or physical agents
♦ intensity (concentration) of exposure
♦ duration of exposure.
The hygienists decision on whether a hazard is present is based on three sources of
information:
♦ scientific literature and various exposure limit guides
♦ the legal requirements of the national occupational health and safety regulations
♦ interactions with other health professionals who have examined the exposed
workers and evaluated their health status.
Occupational exposure limits refer to airborne concentrations of substances
conditions under which it is believed that nearly all workers may be repeatedly
exposed day after day without adverse health effect. They are based on available
information from industrial experience, from experimental human and animal
studies; and, when possible, from a combination of the three
Recommended exposure limits

Many standards have been recommended by different national and international agencies.
The most popular and comprehensive however are the list of threshold limit values
There are three categories of TLV:
(TLVs) for chemical substances and physical agents and the biological exposure indices
(BEIs).

♦ Time-weighted average (TWA8): the employees average airborne exposure in any

8–hour work shift of a 40–hour work week, which shall not be exceeded.
♦ Short-term exposure limit (STEL): the employees 15–minute TWA exposure,
which shall not be exceeded at any time 20 during a work day unless another time limit
at any time over a work day.
is specified in a parenthetical notation below the limit. If another time
period is specified, the TWA exposure over that time limit shall not be exceeded
♦ Ceiling-C: the employees exposure, which shall not be exceeded during any
part of the work day. If instantaneous monitoring is not feasible, the ceiling
shall be assessed as a 15–minute TWA exposure, which shall not be exceeded
at any time over a work day.
Considerations are included for:
♦ skin notation (for probable skin absorption)
♦ mixtures (for exposure to mixtures of contaminants)
♦ total, inhalable, thoracic and respirable particulate matter
♦ Particulate not otherwise classified (PNOC)
♦ simple asphyxiates: inert gases or vapours
♦ Biological exposure indices (BEI)
♦ physical factors
♦ unusual work schedules.

CONTROLLING HAZARDS

Occupational/industrial hygienists recognize that engineering, work practice and

administrative controls are the primary means of reducing employee exposure to
occupational hazards.
Engineering controls

These minimize employee exposure by either reducing or removing the hazard at

the source or isolating the worker from the hazard. They include:
♦ eliminating toxic chemicals and substituting non-toxic chemicals
♦ enclosing work processes or confining work operations
♦ installing general and local ventilation systems.

Work practice controls

These alter the manner in which a task is performed. Some fundamental and easily
implemented work practice controls include:
♦ changing existing work practices to follow proper procedures that minimize
exposures while operating production and control equipment
♦ inspecting and maintaining process and control equipment on a regular basis
♦ implementing good housekeeping procedures
♦ providing good supervision 21
♦ prohibiting eating, drinking, smoking, chewing tobacco or gum and applying
cosmetics in regulated areas.
Administrative controls

These include:
♦ Controlling employees’ exposure by scheduling production and tasks, or both,
in ways that minimize exposure levels; e.g. the employer might schedule
operations with highest exposure potential during periods when the fewest
employees are present.
♦ When effective work practices or engineering controls are not feasible or while
such controls are being instituted, appropriate personal protective equipment
must be used, e.g. gloves, safety goggles, helmets, safety shoes, protective
clothing and respirators. To be effective, personal protective equipment must
be individually selected, properly fitted and periodically refitted, conscientiously
and properly worn, regularly maintained and replaced as necessary.

22
POTENTIALLY HAZARDOUS OPERATIONS AND ASSOCIATED AIR
CONTAMINANTS1

Process types Contaminant type Contaminant examples

Hot operations
Gases (g) Chromates (p)
Welding
Particulates (p) Zinc and compounds (p)
Chemical reactions
(Dust, fumes, mists) Manganese and compounds (p)
Soldering
Melting
Liquid operations
Moulding Vapours (v) Benzene (v)
Painting
Burning Gases (g) Trichlorethylene (v)
Degreasing
Mists (m) Methylene chloride (v)
Dipping
1,1,1-Trichloroethylene (v)
Spraying
Hydrochloric acid (m)
Brushing
Sulfuric acid (m)
Coating
Hydrogen chloride (g)
Etching
Cyanide salts (m)
Cleaning
Chromic acid (m)
Dry cleaning
Solid operations
Dusts Hydrogen
Cement cyanide (g)
Pickling
Pouring
TDI, MDI
Quartz (v)silica)
(free
Plating mixing
Mixing
Hydrogen sulfide (g)
Fibrous glass
Galvanizing
Separation
Sulfur dioxide (g)
Chemical reactions
Extraction
Carbon tetrachloride (v)
Crushing
Pressurized
Conveying spraying
Vapours (v) Organic solvents (v)
Cleaning
Loading parts
Dust (d) Chlordane (m)
Applying
Bagging pesticides
Mist (m) Parathion (m)
Degreasing
Trichloroethylene (v)
Sand blasting
Shaping operations 1,1,1-Trichloroethane (v)
Painting Dusts Asbestos
Cutting Methylene chloride (v)
Beryllium
Grinding Quartz (free silica, d)
Uranium
Filing
Zinc
Milling
23 Lead
Moulding
Sawing
1
Drilling
.

24
OCCUPATIONAL AND OTHER WORK-RELATED DISEASES

1. OBJECTIVES

♦ Understand the relationship between work and health

♦ Understand the interaction of man, environment and work
♦ Know the various types of stresses or hazards that may be present in different
types of occupations including industry, agriculture etc.
♦ Know the concept of occupational and work-related diseases and the concept
of aggravation
♦ Recognize general health problems of workers and whether or not they are
work-related
♦ Survey the workplace, recognize signs and symptoms of early impairment of
health and carry out simple tests to support the diagnosis of an occupational
and/or work-related disease
♦ Give advice to management regarding the control and prevention of the
identified hazards
♦ Give advice to workers and educate them regarding the nature of hazards they
are exposed to, control measures, personal hygiene, early symptoms and first
aid
♦ Refer patients and affected workers for further investigation and treatment
♦ Consult with the related authority on environmental monitoring of the workplace
and on implementation and maintenance of control measures (especially
engineering)
♦ Know the laws, rules and regulations governing occupational safety and health
including hazard control at the workplace, recommended standards and
threshold limit values, pre-placement and periodic medical examinations,
schedule of occupational diseases (as applicable), insurance and compensations
♦ for occupational
Keep disease
medical records and accidents
including personal medical files, records of accidents
and occupational diseases, records of pre-placement and periodic examinations
♦ Keep records of environmental monitoring, safety activities, workplace surveys
25
and report on health and safety trends at the workplace.
 INTRODUCTION AND BASIC CONCEPTS

Occupational and work-related disease

“Occupational diseases … stand at one end of the spectrum of work-relatedness

where the relationship to specific causative factors at work has been fully
established and the factors concerned can be identified, measured, and eventually
controlled. At the other end [are] diseases [that] may have a weak, inconsistent,
unclear relationship to working conditions; in the middle of the spectrum there is a
possible causal relationship but the strength and magnitude of it may vary.”1

Degree of work-relatedness

The degree of work-relatedness of a work-connected disease condition varies in

different situations and determines whether a disease is considered an occupational
disease, a work-related disease or aggravation of a concurrent disease, e.g.
♦ A specific agent like lead or silica, which is present essentially in the workplace,
causes a disease condition which cannot occur due to other causes; this is an
occupational disease.
♦ Where infection can occur at the workplace, an occupational disease can also
be caused by a specific agent, such as tuberculosis among health care workers
in a tuberculosis treatment centre. Of course infection can also occur in the

♦ general population under non-occupational conditions.

Work-related diseases occur much more frequently than occupational diseases.
They are caused by the interaction of several extrinsic risk factors and a
number of intrinsic factors each of which may or may not operate in any
individual case. Occupational hazards are among the risk factors which can
contribute to the occurrence of work-related diseases. Examples are many and
–include:
behavioural responses
– psychosomatic illness
– hypertension
– coronary heart disease
– chronic non-specific respiratory disease
– locomotor disorders.
♦ Work conditions can aggravate pre-existing disease: hepatic dysfunction can
be aggravated by exposure to certain chlorinated hydrocarbons; bronchial
asthma can be aggravated by dust exposure and renal disease can be aggravated
by inorganic mercury, cadmium and certain solvents.

26
 ♦ Exposure to combinations of occupational hazards may result in synergistic
effects which are much more pronounced than effects of individual exposures
simply added together.
♦ Individual susceptibility to the effects of some occupational exposures varies.
Genetic factors are important determinants of individual susceptibility.

OCCUPATIONAL DISEASES

Definition

Occupational diseases are adverse health conditions in the human being, the
occurrence or severity of which is related to exposure to factors on the job or in the
work environment. Such factors can be:
♦ Physical: e.g. heat, noise, radiation
♦ Chemical: e.g. solvents, pesticides, heavy metals, dust
♦ Biological: e.g. tuberculosis, hepatitis B virus, HIV
♦ Ergonomic: e.g. improperly designed tools or work areas, repetitive motions
♦ Psychosocial stressors: e.g. lack of control over work, inadequate personal
support
♦ Mechanical: these mainly cause work accidents and injuries rather than
occupational diseases.

Characteristics of occupational diseases

The occupational cause of occupational disease is often overlooked by health care

providers. This is due to several special characteristics of occupational disease that
may obscure its occupational origin.
♦ The clinical and pathological presentation of most occupational diseases is
identical to that of non-occupational diseases; e.g. asthma (excessive airway
narrowing in the lungs) due to airborne exposure to toluene diisocyanate is
clinically indistinguishable from asthma due to other causes.
♦ Occupational disease may occur after the termination of exposure. An extreme
example would be asbestos-related mesothelioma (a cancer affecting the lung
and abdomen) which can occur 30 or 40 years after the exposure.
♦ The clinical manifestations of occupational disease are related to the dose and
timing of exposure; e.g. at very high airborne concentrations, elemental
mercury is acutely toxic to the lungs and can cause pulmonary failure, while at
♦ lower levels offactors
Occupational exposure,
canelemental mercury has no
act in combination pathologic
with effect on the
non-occupational factors to
27
lungs butdisease;
produce can have
e.g.chronic adverse
exposure effects
to asbestos on increases
alone the central
theand
riskperipheral
of lung nervous
systems.
 cancer five-fold; and the long-term smoking of cigarettes increases the risk of lung
cancer between 50 and 70 fold.

Prevention of occupational diseases

Primary prevention

Primary prevention is accomplished by reducing the risk of disease. In the

occupational setting, this is most commonly done by reducing the magnitude of
exposure to hazardous substances. As the dose is reduced so is the risk of adverse
health consequences. Such reductions are typically managed by industrial hygiene
personnel and are best accomplished by changes in production process or
associated infrastructure, e.g. the substitution of a hazardous substance with a
safer one, or enclosure or special ventilation of equipment or processes that
liberate airborne hazards. These are known as engineering controls.
Other methods of exposure reduction include use of personal protective equipment
and rotation of workers through areas in which hazards are present to reduce the
doseisto
This each worker by
accomplished (NB: this method does, however, increase the number of
workers exposed to the identifying
hazard). health problems before they become clinically
apparent (i.e. before workers report feeling ill) and intervening to limit the adverse
Secondary prevention
effects of the problem. This is also known as occupational disease surveillance. The
underlying assumption is that such early identification will result in a more fvourable
outcome.
An example of secondary prevention is the measurement of blood lead levels in workers exposed to
favourable outcome.
lead. An elevated blood lead level indicates a failure of primary
prevention but can allow for corrective action before clinically apparent lead
poisoning occurs. Corrective action would be to improve the primary prevention activities
listed above.
Tertiary prevention

This is accomplished by minimizing the adverse clinical effects on health of a disease or

muscle andTypically
exposure. joint pain,this
abdominal pain,
is thought of anaemia, kidney
as clinical dysfunction)
occupational by An example of
medicine.
administration of chelating
tertiary prevention medication.
is the treatment Thepoisoning
of lead goal is to (headache,
limit symptoms or discomfort,
minimize injury to the body and maximize functional capacity.

28
Physical hazards at the workplace

Thermal stress

(a) Thermal environment

The temperature of the human body when healthy is at a constant of around 37 °C
through a dynamic balance between heat production and heat loss. The heat
regulating centre in the hypothalamus controls this balance.
Heat is produced by the metabolic processes, by muscular activity and by food
consumption. Heat is exchanged with the surrounding environment by conduction,
convection, radiation and evaporation of sweat. Heat exchange is influenced by air
temperature, air velocity, relative humidity and radiation. Various combinations of
these factors can cause different degrees of comfort and discomfort and several
indices have been described to express the degree of thermal stress resulting from
combinations of these factors, e.g. the effective temperature, the corrected effective
temperature and wet-bulb-globe temperature indices.
(b) Types of thermal stress
Cold stress:
This exists when the surrounding temperature falls, as occurs when entering cold
storage rooms. A human tries to reduce the exposed skin surface (by bending the
joints if possible or by wearing thick woollen clothes). Peripheral vasoconstriction
of skin vessels occurs resulting in vascular injury, chilblains, frost bite (dry
gangrene) or trench foot (wet gangrene). Heat production increases through
increased muscle tone and shivering. Extreme cases result in hypothermia, lowering
Heat stress: the stages
of the temperature of core organs and death.
Vasomotor control: As the heat stress increases, more blood is pumped to the skin
and less to the visceral organs and brain. There is cardiovascular stress and
tachycardia. Muscular work is reduced since it produces more heat. Heat exhaustion
is manifested by headaches, dizziness, sleepiness, lack of concentration and anorexia.
Evaporative cooling: The body starts to sweat with the amount related to the degree
of stress and acclimatization. Loss of sodium chloride through sweating causes heat
cramps
muscles)(painful cramps starting
and dehydration whichinaggravates
the working muscles andproblems.
cardiovascular spreadingThe
to other
volume
of urine is reduced. High air velocity and low relative humidity help cooling through
the evaporation of sweat. Dry heat exposure is encountered in foundries, steel mills
and in the glass industry and moist heat exposure in textile mills, mines, the food
canning industry
Heat stroke: and laundries.
If sweating is not sufficient to keep the body temperature within the
physiological range, the heat regulating centre fails, sweating stops, the skin is
29
flushed
death andfollow.
may the patient
Heatisstroke
said to sufferinfrom
occurs heat in
workers stroke. Unconsciousness
hot humid and
environments
especially when exposed to direct sunlight. It is an emergency situation where rapid
cooling, rehydration and replacement of electrolytes are indicated.
(c) Prevention of heat stress
A gradual exposure to a hot environment results in acclimatization and better
tolerance. Heat stress is especially dangerous for children, the elderly and patients
with cardiovascular, renal and skin diseases.
Engineering control measures should be used to prevent heat exposure including
shielding, insulation and ventilation. Pre-placement and periodic medical
examinations are important; lost fluids and sodium chloride should be replaced;
personal protective clothes can help in some situations and workers should be given
adequate rest periods to be spent in a more comfortable environment.

Noise

Noise is unwanted sound. Workers are exposed to noise in:

♦ textile and glass industries
♦ ship building
♦ aeroplane manufacture
♦ engineering industries
♦ manufacture of boilers and pressure vessels
♦ power plants.
Sound is propagated in the form of waves, each of which can be described in terms
of frequency or number of cycles per second measured in hertz (Hz) and intensity
as expressed in decibels (dB). The human ear can hear sounds ranging in frequency
from 20 Hz to 20 000 Hz. The intensity of very faint sounds is around 0 dB and a jet
engine can produce sounds of 130 dB, which is painful to the ear. The sounds we
and intensities. Ordinary speech is heard at frequencies of 500 Hz to 2000 Hz.
normally hear are complex sounds formed from many waves of varying frequencies
In addition to interference with the hearing of normal speech, noise can cause
annoyance and stress and can lead to increased accident rates and lower
productivity. Extra-auditory effects are observed in different systems, including
endocrine, gastrointestinal and cardiovascular systems, and interfere with sleep.
The most important effect of exposure to noise is noise-induced hearing loss (NIHL).
Hearing impairment is at first temporary; as exposure to noise (about 85 dB)
continues, hearing impairment becomes permanent. NIHL usually takes many years
(7–10 years) to develop. The most hazardous is high intensity, high frequency,
continuous noise.
Audiometry Personal
reveals susceptibility
early hearing has aatdefinite
impairment effect.of 3000–6000 Hz
frequencies
before hearing of normal speech is affected. Hence, the importance of measurement
of hearing on pre-placement and periodic hearing examinations.
Measures to control noise in the workplace include:
30
♦ design and maintenance of machinery
♦ segregation and dispersion of noise sources
♦ prevention of propagation and reflection of noise by the use of sound proofing
materials for floors, walls and ceilings
♦ rotation of workers
♦ reduction of work exposure hours
♦ use of personal protective devices, e.g. ear plugs, ear muffs and helmets.

Vibration

Workers exposed to whole vibrations include tractor drivers, transport workers,

workers involved in drilling for petroleum and those in the textile industry. Whole
body vibrations cause various ailments related to congestion of pelvic and
abdominal organs.
Segmental vibrations affect workers using pneumatic or electrical vibrating tools in
mining, road construction, shoe manufacture and sawing. Vascular changes in the
upper limbs lead to “dead hands” and “white fingers” and prolonged exposure leads
to rarefaction in the small bones and wrist.

Poor or defective illumination

Lighting standards depend on the type of work performed and degree of precision
required. Adequate lighting should be provided either by natural or artificial means,
avoiding shadows and glare and observing appropriate colours and contrast.
Defective illumination leads to eye strain, fatigue and increased accident rates.
Defective illumination in miners leads to miner’s nystagmus (rapid, involuntary
movement of the eyes).
Radiation

(a) Non-ionizing radiation

Ultraviolet radiation
Exposure occurs in welding, metal cutting and exposure to carbon arc and causes
skin erythema, burns and hyperpigmentation. Exposure of the eyes causes “arc eye”
with conjunctivitis and severe pain and may lead to corneal ulceration. Eye
protection using special face shields is necessary. Prolonged exposure causes
atrophy of
Infrared the skin and epitheliomas.
radiation
Exposure occurs in front of furnaces, in steel mills, in the glass industry, in
blacksmiths and in chain manufacture. Exposure of the eyes can cause cataracts or
corneal affection. Skin burns can also occur. Complete protection of the eyes can be
achieved by wearing special goggles.
(b) Ionizing radiation
31
Sources of radiation include radioactive isotopes and X-ray machines. Ionizing
radiation is used in medicine, industry, agriculture, research and atomic warfare.
Radiations are either electromagnetic waves, like X-rays and gamma-rays, or minute
particles, like alpha, beta and neutrons. Both types cause ionization or excitation of
atoms which leads to tissue destruction.
The effect of ionizing irradiation depends on the dose, type of radiation, whether
exposure was continuous or interrupted and whether it was total body or localized,
as well as the type of tissue irradiated. The power of penetration of different types
of radiation varies from very high, such as X-ray and gamma-ray radiation, to very
low, such as alpha radiation.
Different tissues vary in their sensitivity to radiation, with the tissues of the
haemopoietic system and the gastrointestinal mucosa being the most sensitive and
those of the bones and muscles being the least sensitive.
Effects may vary:
♦ Death occurs within hours if the whole body is exposed to a high dose.
♦ Acute radiation syndrome occurs if the dose is less. Signs and symptoms
appear within 24–48 hours and are due to affection of the gastrointestinal
mucosa causing severe bloody diarrhoea and shock of the haemopoietic
system and of the skin. If death occurs it is due to haemorrhage (due to
thrombocytopenia) or infection (due to damage of intestinal mucosa and
leukopenia).
♦ Beta-radiation affects the skin only, causing skin burns and alopecia.
♦ Chronic radiation effects may follow long after an acute exposure or follow
repeated exposure to doses not enough to cause acute effects.
♦ Chronic effects include skin atrophy, loss of finger prints, alopecia, nail
changes, telaniectasia, pigmentation, keratoses and epitheliomas. Other effects
include sterility, abortion, mutagenic effects and birth defects.
Control of exposure to external radiation sources rests on three general principles:
1. Keeping sufficient distance between source and worker.
2. Reducing time of exposure.
3. Containment and shielding.
Control of exposure to internal irradiation (uptake of radioactive materials) follows
more stringent regulations.
Laboratories or establishments in which radioactive materials are handled should
be constructed in such a way as to offer maximum containment, enclosure and
shielding of radioactive material, and to ensure easy and complete cleaning in case
of spills. Handling by remote control is very useful.
Ventilation and waste disposal systems should be separate from those of other areas
and radioactive waste should not reach public waste systems. Radioactive waste
32
should be disposed of in such a way that environmental contamination is not likely.
Environmental monitoring should be practised and alarm systems should be
provided.
Other measures include:
♦ pre-placement and periodic medical examinations with special emphasis on
eyes, skin and blood
♦ personal protective clothing
♦ personal monitoring badges
♦ pocket dosimeters
♦ whole body counters
♦ monitoring of radioactivity in biological fluids.

Changes in barometric pressure

(a) Increased barometric pressure

Workers exposed to increased barometric pressure are divers, frogmen, submarine
crew and workers engaged in underwater construction of piers, bridges etc.
Barometric pressure increases by 1 atmosphere for every 10 metres descended
underwater.
During descent: if the openings leading to the paranasal sinuses or the middle ear
are blocked (e.g. due to catarrh and oedema of a mucous membranes), the pressure
in the cavities cannot be equalized with the outside pressure and this results in
severe pain, oedema of the lining mucous membrane, haemorrhage and maybe
rupture the
During of the
stayearunder
drum.water, because of the dissolution of excess amounts of gases
in the blood and tissues, oxygen poisoning and nitrogen narcosis may occur with
serious consequences. Divers may also suffer asphyxia and even drowning.
If rapid ascent occurs with the glottis closed (e.g. if the worker panics) the lung may
rupture due to expansion of gases, especially in the presence of a weak spot. Rapid
ascent, not following the recommendations of standard surfacing tables, results in
the formation of gas bubbles in the blood and tissues due to liberation from solution
of the excess gases that were dissolved under pressure. In the blood stream, gas
(especially N2) causes air embolism and paralysis and in tense tissues (ligaments
around
Workersjoints) causesunder
who work severe pain known
increased as “the
pressure bends”,
under wateralso referred
for many to asmay
years “Caisson
suffer
disease” or decompression
from aseptic bone necrosis,sickness.
especially in the head of the femur. Caisson disease may
manifest within 24 hours of ascent and calls for urgent compression in a
compression chamber until symptoms disappear. Pressure is then released
according
A to recommended
worker with steps. infection should not be allowed to dive to avoid
an upper respiratory
complications during descent. 33
(b) Reduced barometric pressure
Passenger planes are normally pressurized but military pilots may be exposed to
reduced atmospheric pressure. In this case expansion of intestinal gases may cause
respiratory embarrassment but before decompression sickness occurs they will have
landed.
Workers at high altitude suffer from effects of reduced partial pressure of oxygen.
The body compensates by increasing the pulse rate, increasing the breathing rate
and polycythemia.

3.5 Chemical hazards (occupational poisoning)

Workers in different occupations are exposed to thousands of chemicals, some of

which can cause occupational diseases. For the sake of discussion, these chemicals
are classified according to their physical state, chemical composition or
physiological action.

Gases and vapours

These can be classified according to their physiological action into: asphyxiants,

irritant gases, organometallic compounds and anaesthetic vapours.
(a) Asphyxiants
Can cause asphyxia either by replacing oxygen or by some other mechanism. They
are classified into: simple asphyxiants and chemical asphyxiants.
Simple asphyxiants: replace oxygen, e.g. nitrogen, methane, hydrogen and carbon
dioxide.
Nitrogen: a simple asphyxiant used in the fertilizer industry and present in mines
when O2 is consumed. In mines it can be detected by the safety lamp which is
extinguished at O2 concentration of 17%. At 12% O2 there is dyspnea, cyanosis,
unconsciousness, loss of motor power, convulsions and death.
Methane (marsh gas): results from decomposition of organic matter and is present
in marshes, sewers and mines. It is a simple asphyxiant, inflammable and lighter
than air.
Carbon dioxide (CO2): results from combustion of fuels; it is a colourless gas,
heavier than air. It can be found in mines, wells, caves and close to furnaces and
brick kilns. It is also present in the manufacture of soft drinks, beer, in the sugar
industry and is used as dry ice. In addition it can be used to extinguish fires. CO2 is
a simple asphyxiant but in low concentrations stimulates rapid respiration.
Resuscitation calls for O2 inhalation, warmth, cardio-respiratory stimulants and if
Chemical asphyxiants: interfere through some chemical action with the respiratory
respiration stops, artificial respiration.
function of the blood, tissue cells or respiratory34centre, e.g. carbon monoxide (CO),
hydrogen sulfide and hydrocyanic acid.
Carbon monoxide (CO): a colourless, odourless gas which results from incomplete
combustion of fuel. It is a product of coal distillation plants, steel furnaces, fuel
boilers and furnaces and home heating appliances. It is also present in vehicle
exhaust fumes.
CO has a great affinity to haemoglobin (HbCO) (210 times that of O2) and thus
interferes with O 2 transport. Exposure causes headaches, dizziness, chest
oppression, loss of motor power, unconsciousness, convulsions, cardiovascular
effects, coma and death (depending on the percentage of HbCO in the blood).
Prevention of CO poisoning depends on proper design, maintenance and regular
inspection of home appliances and industrial sources and also on control measures
in garages.
In a case of poisoning, O2 inhalation is indicated (with 5% CO2), with warmth,
stimulants and artificial respiration provided if needed; the worker should be
removed from exposure first.
Hydrogen sulfide (H2S): a colourless gas, heavier than air; it has the odour of rotten
eggs. Exposure occurs in oil fields and refineries, tanneries, sewers and in the
manufacture of rayon and artificial rubber. It can be detected by its smell and causes
paralysis of the olfactory nerve after a short while.
In addition to being a chemical asphyxiant, it has an irritant effect on the eyes and
upper respiratory centre; it also causes asphyxia by combining with cytochrome
oxidase enzyme and preventing tissue respiration. If respiratory paralysis occurs
artificial respiration is indicated. Nitrites (sublingual and intravenous) serve to break
the combination between the gas and cytochrome oxidase enzyme by forming
Hydrocyanic acid (HCN): a colourless gas that has the odour of bitter almonds. HCN
methaemoglobin.
is used in fumigation of ships as a pesticide and its salts are used in photography,
metal hardening, electroplating and in extraction of gold from ore.
The gas can be absorbed through the skin and its inorganic salts are among the most
potent poisons. They produce their effects through inhibiting cytochrome oxidase
enzyme thus interfering with tissue respiration. Signs and symptoms appear within
minutes in the form of dizziness, oppression of the chest, cardio-respiratory
manifestations,
minutes. Organicunconsciousness and death which, in severe cases, occurs within
salts are not as toxic.
First aid includes the inhalation of amyl nitrite and intravenous injection of sodium
nitrite followed by sodium thiosulfate. Cobalt EDTA and hydroxocobalamin are also
used in the treatment of cyanide poisoning. Cardio-respiratory stimulants, warmth
and artificial respiration may also be indicated.
Since HCN is a very rapid poison, the first aid equipment should be very close to the
work site and a well-trained first aid attendant available at all work shifts.
(b) Irritant gases 35
These can cause irritation or inflammation of the mucous membranes with which
they come into contact. This property depends on their degree of solubility in water.
Highly soluble gases, like ammonia, affect the upper respiratory passages. Less
soluble gases like chlorine and sulfur dioxide affect both the upper respiratory
passages and the lung tissues. Gases which are even less soluble, like nitrogen
oxides and phosgene, act essentially on the lungs and in this case the irritant affect
may be delayed for hours.
Sulfur dioxide (SO2): one of the most common air pollutants. It results from the
combustion of fuels containing sulfur and is present in vehicle exhaust fumes, in
front of furnaces and is also produced in the extraction of metals from sulphide
ores. It is used in the production of sulfuric acid, in the preservation of fruits, in
sugar industry and in the bleaching of wool.
It is colourless, has a pungent odour and is oxidized in air into sulfur trioxide.
Exposure causes irritation of the eyes and upper respiratory passages. High
concentrations may cause oedema of the larynx, pulmonary oedema, pneumonia
and even death.
Ammonia (NH3): a common upper airway tract irritant. It is a highly soluble alkaline
gas that is widely used in industry as a refrigerant and in the manufacture of
fertilizers, explosives and plastics. It attacks the skin, the conjunctiva and the
mucous membranes of the upper respiratory tract. Oedema of the larynx and
pulmonary oedema can occur with exposure to high concentrations and can cause
death.
Management consists of removing the patient from exposure followed by supportive
care with oxygen and attention to fluid and electrolyte homeostasis. Most patients
gradually improve over time and make a full recovery without parenchymal lung
damage except for bronchiectasis.
Formaldehyde (HCHO): a potent upper respiratory tract irritant that is used as a
disinfectant and industrial cleaner and may release gas from particle board. It is an
animal carcinogen and may cause acute bronchial irritation in humans.
Hydrogen fluoride (HF): a potent upper respiratory tract acid irritant that causes
pulmonary oedema. It is used in the microelectronics industry for etching silicon
chips and is also used to etch glass.
Ozone (O3): an important irritant produced by photochemical oxidation of vehicle
exhaust fumes and which is generated in arc welding. Ozone causes nose and eye
irritation and is also a potent respiratory tract irritant causing coughing, tightness
in the chest and shortness of breath.
Chlorine (Cl2): a greenish yellow gas with a pungent irritating odour. It affects the
upper and lower respiratory tract. Exposure occurs in the production of sodium
hydroxide. The gas is used in bleaching and water disinfection and exposure can
occur during the transport of liquid chlorine. Exposure causes irritation of the eyes
and upper respiratory tract and larger concentrations
36 may result in pulmonary
Phosgene (COCl2):
oedema and death. results from decomposition of chlorinated hydrocarbons when
they come into contact with a hot surface (CCl4 is used in fire fighting). Phosgene is
sparingly soluble in water, therefore upper respiratory irritation is slight. However,
delayed pulmonary oedema can occur and therefore the patient should be observed
for 48 hours and given rest, warmth stimulants and O2.
Nitrogen oxides (NOx ): nitrous oxide (N2O) is an anaesthetic and in the absence of
O2 is a simple asphyxiant. Nitrogen oxides are a mixture of NO2 and N2O4 and are
brown in colour. Exposure occurs in chemical laboratories, in the explosive industry,
in the manufacture of nitric or sulfuric acids, fertilizer industry and on slow
combustion of nitrogen-containing materials. It is present in welding operations and
in soils.
Due to their poor water solubility, nitrogen oxides can be inhaled in high
concentration without sufficient warning irritation but it has a severe irritant effect
on the lung tissue. Symptoms may be delayed 2–20 hours, after which fatal
pulmonary oedema may occur. Therefore, regardless of the condition of the patient
when first seen, he/she should be put under close observation, preferably in
hospital, for at least 24 hours.
(c) Organometallic compounds
Arsine (ASH3): produced during chemical treatment of metals when arsenic is
present as an impurity and nascent hydrogen is evolved. It is colourless and has a
garlic odour. Exposure results in haemolysis, anaemia, jaundice and anuria in severe
cases.
Nickel carbonyl [Ni(CO)4]: a volatile liquid produced during the extraction of nickel.
Inhalation causes severe pulmonary irritation.
(d) Anaesthetic vapours
Many of these have some other systemic effect as well and tend to accumulate in
low, closed, poorly ventilated places.
The following precautions should be observed when there is potential exposure to
noxious gases.
♦ Workplaces should be ventilated or steamed repeatedly.
♦ If there is likelihood of the presence of noxious gases or insufficient oxygen,
gas masks should be provided.
♦ Workers should be properly trained and should always work in teams with one
team member nominated to observe from a distance, away from possible
contamination.
♦ First aid equipment, including oxygen, should be readily available with a
trained team of rescuers.
♦ An affected worker should be removed from the exposure and kept warm and
rested. If breathing stops, artificial respiration should be continued until
recovery or death is ascertained.
37
Metals

In industry, poisoning with metals usually takes the chronic form and results from
the absorption of small amounts over long periods of time. Acute poisoning may
result from accidental (or suicidal) intake of large doses of some of the more toxic
compounds (like arsenicals).
Metals and their compounds gain access into the body by inhalation, ingestion and,
in a few cases, through the skin. A large number of metallic compounds are used in
industry with the following being some of the more important.
(a) Lead
Inorganic lead: Exposure to inorganic lead compounds occurs in mining, extraction,
smelting, metal cutting, manufacture of lead pipes, lead paints, manufacture of lead
batteries, crystal glass and hot metal typesetting.
It is absorbed as dust via the respiratory tract, and via the gastrointestinal tract with
food and drinks. Inorganic lead is not absorbed through the skin. The signs and
symptoms of exposure include a blue line on the gums, intestinal colic and
constipation, anaemia, general weakness and, in severe cases, foot drop and wrist
drop. Encephalopathy due to lead is now very rare.
Engineering control methods to prevent exposure are ventilation, mechanization
and housekeeping. Personal cleanliness, change of clothes, washing facilities and
provision of clean areas for eating and storing food will reduce uptake of lead by
mouth. Periodic medical examination helps detect early affection.
Organic lead (tetraethyl lead): Organic lead is still used as a fuel additive in gasoline.
It is a volatile liquid and can be absorbed by inhalation and through the skin.
(b) Mercury
Exposure causes excitation of the central nervous system then depression and may end in
death.

Mercury is a volatile liquid metal. Exposure occurs in mining, extraction, chemical

laboratories, the chemical industry in general, the pharmaceutical industry, the
manufacture of thermometers and barometers, the explosive industry, the
manufacture
in dentistry. of mercury vapour lamps, the manufacture of pesticides, mirrors and
Inorganic mercury compounds: cause stomatitis, a brown line on the gums, loose
teeth, metallic taste, tremors and personality changes. There is kidney affection and
gastrointestinal disturbances.
Organic mercury (pesticides): exert their effect on the central nervous system.
Mercury fulminate (an explosive) causes skin ulcers and perforation of the nasal
septum.
(c) Manganese
38
Exposure occurs in mining, extraction, the steel industry, the dry battery industry,
the glass and ceramics industry, the manufacture of welding rods and in the
chemical industry. Manganese exposure can cause pneumonia and can affect the
central nervous system causing Parkinson disease, tremors, mask face, rigidity and
personality change.
(d) Arsenic
Exposure occurs in mining and extraction. Arsenic compounds are used in
pesticides, wood preservatives, medicines, paints and the chemical industry. Acute
exposure causes severe gastroenteritis, shock and even death. Chronic exposure to
arsenic causes affection of the peripheral nerves, skin lesions, skin cancer, anaemia,
perforation of the nasal septum and lung cancer.
Organic solvents

Organic solvents are organic liquids in which other substances can be dissolved
without changing their chemical composition. They are used in the extraction of oils
and fats in the food industry, the chemical industry, paint, varnishes, enamel, the
degreasing process, dry cleaning, printing and dying in the textile and rayon
industries. Organic solvents are volatile: many of them are inflammable and they
are considered fire hazards.
Chemical groups include:
♦ hydrocarbon solvents
♦ alcohols and ethers
♦ ketones
♦ esters
♦ glycols and their compounds.
Solvents are absorbed mainly through the lungs, via the gastrointestinal tract if
taken by mouth, and many of them can be absorbed via intact skin. As a group,
solvents affect several of the body’s systems and can cause the following effects:
♦ nervous system: dizziness, unconsciousness and death, peripheral neuritis,
affection of vision, insomnia, headache and easy fatigue
♦ gastrointestinal system: dyspepsia, anorexia and nausea and may be secondary
to liver affection
♦ respiratory tract: may show upper respiratory irritation in some cases
♦ kidney: affection may cause nephritis or renal failure
♦ blood forming organs: may be affected causing anaemia or even leukaemia
♦ skin: may show contact dermatitis or acne.
Specific examples of poisoning by organic solvents:
♦ Petroleum products: may cause unconsciousness and when swallowed by
39
accident cause gastritis or pneumonia due to aspiration into lungs.
♦ Benzol (benzene, C6H6): is a product of coal distillation and is used in the paint
industry, artificial rubber manufacturing, the pharmaceutical and chemical
 industries, rubber products manufacturing and degreasing. The central nervous
system toxicity is the most important aspect of acute high dose exposure to
benzol. Aplastic anaemia is the classic cause of death in chronic benzol
poisoning. Benzol-induced leukaemia may develop in some cases in persons
who previously
prevented have had
by replacing aplastic
it with lessanaemia. The toxic There
toxic compounds. effectsare
of many
benzolsolvents
are best
safer than benzol.
♦ Chlorinated hydrocarbons: the addition of chlorine to carbon and hydrogen
increases the stability and decreases the flammability of the resulting
compounds. They have slightly pungent odours. Six chlorinated aliphatic
hydrocarbons are commonly used as solvents:

– trichlorethylene
– perchloroethylene (tetrachloroethylene)
– 1-1-1-trichloroethane (methyl chloroform)
– methylene chloride (dichloromethane)
– carbon tetrachloride
– chloroform.

Acute effects include:

♦ anaesthesia: dizziness, headache, nausea, vomiting, fatigue,
“drunkenness”, slurred speech, disequilibrium, disorientation, depression,
loss of consciousness
♦ respiratory tract irritation: sore nose, sore throat, cough.
Chronic effects include: dermatitis, neurobehavioural dysfunction,
hepatocellular injury and renal tubular dysfunction.
Pulmonary dust diseases

If the work atmosphere is dusty, dust will inevitably be inhaled. Dust particles below
five microns in diameter are called respirable since they have the chance to penetrate
to the alveoli. The respiratory tract has certain defence mechanisms against dust
but when the environment is very dusty a significant amount of dust can be retained
in the lungs.
Different kinds of dust have different effects:
♦ Soluble particles of toxic compounds reach the blood and cause poisoning, e.g.
lead.
♦ Irritant dusts cause irritation of the upper respiratory tract and the lungs and
certain metal fumes cause chemical pneumonia, e.g. cadmium, beryllium and
manganese.
♦ Some others cause sensitization resulting in asthma or extrinsic allergic
alveolitis, e.g. some organic dusts. 40
♦ Metal fume fever is caused by inhalation of fumes of zinc and copper causing
fever, body aches and chills for 1–2 days.
♦ Pneumonic anthrax is caused by inhalation of wool dust containing the spores.
♦ Benign pneumoconiosis which causes X-ray opacities (nodulation) without
symptoms or disability is caused by inhalation of iron, barium and tin dust.
♦ Byssinosis is caused by prolonged exposure (7–10 years) to cotton dust in the
textile industry especially in the ginning, bale opening and carding. It is
manifested by chest tightness on the first day following a weekend. Initially, the
patient is free of symptoms for the rest of the week. Chronic bronchitis,
emphysema and disability are common complications.
♦ Pneumoconiosis is disabling pulmonary fibrosis that results from the inhalation
of various types of inorganic dust, such as silica, asbestos, coal, talc and china
clay, e.g. silicosis and asbestosis:
Silicosis: silicosis results from the inhalation of respirable particles of free
crystalline silica (SiO2). Exposure occurs in mining and quarrying operations, stone
cutting and shaping, foundry operations, glass and ceramics manufacture,
disease (7–10and
sandblasting years, sometimesofless)
manufacture and this
abrasive depends
soaps. onmany
It takes the concentration of the
years to develop the
dust at the workplace, its silica content, the particle size and on individual
susceptibility. The dust particles settle in the lungs and cause small nodules of
fibrosis that progressively become more numerous, enlarge and coalesce causing
fibrosis and progressive loss of lung function and disability. There may be coughing
and expectoration. In the early stages there may be signs detectable by X-ray but
later on the worker complains of increasing dyspnoea on exertion. Complications
include pulmonary tuberculosis and cardiac or respiratory failure. The disease can
Asbestosis: asbestosis
be detected even beforeisthe
caused by inhalation
symptoms appear of
by asbestos fibres. It is which
X-ray examination a hydrated
shows
magnesium silicate nodular
numerous bilateral which isshadows
resistantoftodifferent
heat andsizes
manyorchemicals. In addition
large masses to
of fibrosis.
mining and extraction, exposure to asbestos occurs in its use for insulation, in the
making of asbestos cloth, in the manufacture of asbestos cement pipes and other
products, vinyl floor tiles and in brake and cloth lining. Asbestos fibres, when
inhaled, will cause diffuse interstitial fibrosis of the lungs, pleural thickening and
calcification. Bronchogenic carcinoma or pleural and peritoneal mesothelioma are
known effects. The early symptoms include progressive dyspnoea on exertion,
cough, expectoration, chest pain, cyanosis and clubbing of the fingers. The disease
takes about seven
Dust control yearsinclude:
measures to develop and depends upon the dust concentration at the
workplace.
♦ Early detection
substitution of harmfuldepends on asymptoms
dust with harmless and
one signs and the X-ray picture.
Smoking
♦ increases the risk of developing lung cancer several fold.
automation and mechanization of dusty processes
♦ segregation of dusty jobs 41

♦ enclosure of dusty operations

♦ ventilation of general and local exhaust fumes
♦ housekeeping and general cleanliness
♦ the use of water in dust suppression
♦ for toxic dust: personal cleanliness, washing facilities, changing work clothes
before going home, washing of work clothes, provision of separate areas for
eating, drinking and smoking
♦ health education
♦ pre-placement medical examination
♦ personal protective equipment.

Pesticides

Pesticides are a group of chemicals used to destroy various kinds of pests including
insects, rodents, weeds, snails, fungi, etc. The degree of toxicity of different
pesticides varies greatly from deadly poisons to slightly harmful pesticides.
Exposure to pesticides occurs in industries where the pesticides are manufactured
and formulated, and during their application in agriculture or in public health.
Pesticides are also used at home.
They are classified into several groups, according to their chemical composition. The
most frequently used nowadays are organophosphates, carbamates and
thiocarbamates, pyrethroids and organochlorine pesticides. Other groups include
lead arsenate, organic mercury, thallium compounds, coumarin, bromomethane,
cresols, phenols,
Pesticides nicotine,
are absorbed zinc phosphide,
through etc.gastrointestinal tract and sometimes
the lungs, the
through the intact skin and eyes (organophosphates).
(a) Organochlorine
Examples are DDT, aldrin, dieldrin, toxafene and gammaxane. They are slightly to
moderately toxic, and are not biodegradable in the environment or in the human
body. They accumulate in the environment and for this reason have been banned in
many countries.
Acute exposure causes irritability of the central nervous system. Symptoms appear
after 30 minutes to several hours (usually not more than 12 hours). They include
headache, dizziness, nausea, abdominal pain, irritability, convulsions, coma,
pyrexia, tachycardia, shallow respiration and death.
If the patient survives, convulsions stop within 24 hours but weakness, headaches
and anorexia may continue for two weeks or more. Chronic exposure may cause
gastrointestinal, liver, kidney or nervous affection.
First aid treatment:
42
♦ Remove contaminated clothing.
♦ Wash skin with soap and water but do not rub the skin.
♦ Induce vomiting, stomach wash and saline cathartic.
♦ Administer sedative for convulsions.
♦ Administer cardio-respiratory stimulants.
(b) Organophosphates
These include parathion, methyl parathion, malathion and tetraethyl
pyrophosphate. Organophosphates include some extremely toxic and some slightly
toxic compounds. They do not accumulate in the environment or in the human body.
They are biodegradable within a few weeks.
Organophosphates cause the inhibition of the choline-esterase enzyme resulting in
accumulation of acetyl choline in the body. Symptoms and signs include dyspnoea,
sweating, nausea, abdominal colic, diarrhoea, constriction of the pupils, muscle
twitches, irritability, anxiety, headaches, ataxia, convulsions, respiratory and
circulatory failure, coma and death. In severe cases symptoms appear within
minutes and in slight cases after hours but never exceeding 24 hours. Death may
occur within hours in severe cases. If recovery occurs it takes a few weeks for the
patient to return to normal. Blood examination reveals reduction of choline-esterase
activity; the test is used in periodic medical examinations.
First aid treatment:
♦ Take patient to hospital.
♦ Remove contaminated clothing.
♦ Wash skin with water without rubbing (if available, a solution of 5%
ammonia or 2% chloramine is more effective than water). However, if eyes are
contaminated they must be washed with water.
♦ If the pesticide has been swallowed, first give the patient water to drink and
then induce vomiting by putting your finger down the patient’s
throat.
♦ Administer atropine (the antidote) intravenously.
♦ Administer artificial respiration if required.
♦ Administer cardio-respiratory stimulants.
♦ Later, treat the patient with oximes.
(c) Carbamates and thiocarbamates
These are moderately toxic (carbaryl) and cause toxicity through the same
mechanism as organophosphates except that inhibition of choline-esterase enzyme
is temporary and recovers spontaneously within 48 hours if death does not occur.
(d) Pyrethroids 43

These are synthetic pesticides of low toxicity used in homes. Toxic symptoms take
the form of sensitivity reactions.
Safe handling of pesticides
♦ Pesticides are licensed for use by the government following careful consideration
of their toxicity to humans.
♦ Extremely toxic substances should not be handled freely by the public.
♦ Extra care should be taken during transportation of chemicals to ensure that
containers are not crushed nor their contents spilt. If any spillage occurs, it
should be reported and decontamination procedures carried out.
♦ All pesticide containers should be properly labelled in the local language.
♦ Storage sites should be properly cleaned and ventilated and should not be used
by unauthorized personnel.
♦ Before using such chemicals application, workers should be well trained and
have received health education.
♦ Public health measures should be taken to avoid contamination of water bodies
and residential areas by chemicals.
♦ Crops should not be harvested before the time necessary for pesticides to
biodegrade.
♦ Empty containers and pesticide waste should be properly disposed of.
♦ Workers should practise good personal hygiene.
♦ First aid treatment and antidotes should be available.
♦ Pre-placement and periodic medical examinations should be undertaken.
♦ All concerned, including the public, should receive health education regarding
pesticides.
♦ Personal protective equipment should be supplied to workers.
♦ Engineering control measures should be in place within the chemical industry.

Biological hazards

Occupational infections

Human diseases caused by work-associated exposure to microbial agents, e.g.

bacteria, viruses, rickettsia, fungi and parasites (helminths, protozoa), are called
occupational infections. An infection is described as occupational when some aspect
of the work involves contact with a biologically active organism.
Exposure occurs among health care workers in fever hospitals, laboratories and
general hospitals; among veterinarians and agricultural workers in animal
husbandry and dairy farms and pet shops; and 44
among sewerage workers, wool
sorters and workers in the leather industry.
(Occupational) pulmonary tuberculosis

Health care workers in tuberculosis treatment centres, in laboratories and in

veterinary clinics are particularly affected. The disease is caused by Mycobacterium
tuberculosis (Koch’s bacillus) and is transmitted occupationally by droplet infection,
contact with infected material from humans (sputum) or animals. The organism can
survive in dust and away from direct sunlight for many days and enters the body
through the respiratory tract or abraded skin where it causes a skin ulcer.
The disease usually affects the lungs but can also affect the gastrointestinal tract,
bones, kidneys, meninges, pleura and peritoneum. Pulmonary tuberculosis is
manifested by coughing, expectoration, haemoptysis, loss of weight, loss of appetite,
night sweats and night fever. It can be diagnosed by chest X-ray and bacteriological
examination of the sputum.
Workers should undergo a pre-placement examination and be tested with tuberculin
and vaccinated with BCG if the tuberculin test is negative. Pre-placement and
periodic X-rays should be taken. Health education is important and proper disposal
of infected material should be observed.
Brucellosis

Brucellosis is caused by an organism which can infect cattle, sheep and pigs. The
disease causes recurrent abortion in animals and is present in the placenta, in animal
secretions, in milk and in urine. Exposed workers are veterinarians, workers in
agriculture and animal husbandry, shepherds and laboratory and slaughterhouse
workers. Most occupational cases occur through contact with infected animals or
The
theiracute stage and
secretions (undulant fever)
products. Theextends for 2–4
incubation weeks
period withweeks.
is 2–4 fever, enlarged spleen
and lymph nodes. In the subacute phase the organism localizes in joints, intestines,
reproductive organs, pleura or meninges. In the chronic phase the localized disease
continues with occasional fever or the only symptom may be general weakness.
During this stage the disease is difficult to diagnose. Therefore, periodic medical
Control of theofdisease
examination in humans
all exposed depends
workers shouldonbecontrol
carriedinout
animals. Workers should
using serological tests.
wear protective clothing and observe proper cooking of animal products and boiling
of milk since the disease can also be transmitted through food.

Anthrax

Anthrax is essentially an animal disease. Exposed workers are those in agriculture

and animal husbandry, slaughter houses, tanneries and those working in the
manufacture of goods from wool, hair, bones and leather. The disease affects cattle,
sheep, horses and pigs and when the animal dies the anthrax bacillus forms spores
which arecan
Infection extremely resistantthe
occur through and canthe
skin, survive
lungsfor
or years.
the intestine. Infection through
45
the skin causes a “malignant pustule”. It starts with erythema 1–8 days after
infection which leads to a papule then pustule with surrounding swelling and local
lymph node enlargement. Infection through the lung occurs in wool stores causing
severe fatal pneumonia. Infection through the intestines causes septicaemia.
Animal products intended for use in industry should be carefully examined and
disinfected.

Viral hepatitis B and C

Health care workers who are likely to come into contact with the blood and body
fluids of infected persons are at great risk of infection. An acute onset of hepatitis
is the exception; more often there are vague general symptoms or none at all and
the infection is discovered on routine serological examination.
The disease may pass into chronic active hepatitis: liver cirrhosis, hepatic failure
and liver carcinoma.
Because of the exposure to patients’ body fluids via contaminated glassware and
other contaminated equipment, such as needles, which may provide an opportunity
for contact with mucous membranes or parenteral innoculation, strict “infection
control” procedures should be developed for situations where there is potential risk,
such as phlebotomy, dentistry and haemodialysis.
Workers at increased risk of hepatitis B infection should receive hepatitis B
immunization.
Acquired immunodeficiency syndrome (AIDS)

Transmission of the acquired immunodeficiency syndrome (AIDS) agent, the human

immunodeficiency virus (HIV), occurs only through sexual contact, perinatally from
an infected mother and through contaminated blood or blood products.
Seroconversion after a needle-stick injury is estimated to be less than 1%, which is
muchvirus
The lower thantransmitted
is not the risk (6%–30%) of acquiring
through casual, hepatitisworkplace
non-intimate B after a needle-stick
contact or injury.
social encounters, such as eating in restaurants or using public transportation or
bathroom facilities.
The following groups are at potential risk of contact with HIV-infected body fluids:
♦ blood bank technologists
♦ dialysis technicians
♦ emergency room personnel
♦ morticians
♦ dentists
♦ medical technicians
♦ surgeons
♦ laboratory workers 46

♦ prostitutes.
For occupational health professionals, employees trained in first aid and public
safety personnel who may provide medical services to HIV-infected individuals,
reasonable steps should be taken to avoid skin, parenteral or mucous membrane
contact with potentially infected blood, plasma or secretions.
♦ Hands or skin should be washed immediately and carefully if blood contact
occurs.
♦ Mucous membranes (including the eyes and mouth) should be protected by eye
glasses or masks during procedures that could generate splashes or aerosols
of infected blood or secretions (suctioning, endoscopy).
♦ Contaminated surfaces should be disinfected using 5% sodium hypochlorite.
Workers in the personal service sector, who work with needles or other instruments
that can penetrate intact skin, such as tattooists and hairdressers, should follow
precautions indicated for health care workers and practise aseptic techniques and
Other exposures
sterilization and their All
of instruments. health effects
personal service workers should be educated
concerning transmission of blood-borne infections, including AIDS and hepatitis B.

Occupational dermatoses

Occupational dermatoses are the most common occupational diseases and are
almost always preventable by a combination of environmental, personal and medical
measures.
The skin can be affected by many factors:
♦ repeated mechanical irritation may cause callosities and thickening of the skin
♦ various kinds of radiation (see Module 1, 3.2, Potential health hazards)
♦ tuberculosis and anthrax
♦ chemicals can cause irritation or sensitization.
Types of occupational dermatosis:
♦ acute contact eczema due to irritation or sensitization
♦ chronic contact eczema due to irritation or sensitization
♦ chloracne (lubricating and cutting oils, tar and chlorinated naphthalenes)
♦ photosensitization (chemicals, drugs and plants)
♦ hypopigmentation and hyperpigmentation (dyes, heavy metals and chlorinated
hydrocarbons)
♦ keratoses (ionizing radiation, ultraviolet radiation)
47
♦ benign tumours and epitheliomas (UV, ionizing radiation, tar, soot, arsenic)
♦ ulcers (trauma, burns).
Occupational cancer

The cause of cancer is still not completely understood. It has been observed
however, through epidemiological studies and statistical data that cancer of certain
organs has been associated with certain exposures.
Occupational cancer is no different from ordinary cancer as far as signs and
symptoms or histopathology are concerned. A positive history of exposure to a
carcinogenic agent can be obtained in occupational cancer. Examples of some
carcinogenic agents and the organs affected are given below.
Carcinogenic agent Organ affected
Arsenic Skin and lung
Chromium compounds, hexavalentsLung
Nickel Lung and nasal sinus
Polycyclic aromatic hydrocarbons Skin
Coal tars Skin, scrotum, lung, bladder
Benzol Blood (leukaemia)
Reproductive effects
B-naphthalamine Bladder
Occupational exposure
Ionizing to certain chemicals or physical
radiation factors
Skin, bone, lung,(like ionizing
blood (leukaemia)
radiation) has been found to have certain effectsLung,
Asbestos on reproductive functions:
pleura, peritoneum
♦ dysfunction in males (sterility or defective spermatozoa) and females
(anovulation, implantation defects in the uterus)
♦ increased incidence of miscarriage, stillbirth and neonatal death
♦ induction of structural and functional defects in newborn babies
♦ induction of defects during the early postnatal development stage.
Exposure of either parent may lead to reproductive defects.
Chemicals which have been suspected of reproductive effects include:
♦ alcohols
♦ anaesthetic gases
♦ cadmium
♦ carbon disulfide
♦ lead
♦ manganese
♦ polyvinyl chloride.

Occupational asthma 48
Asthmatic patients suffer from attacks of shortness of breath. Although bronchial
asthma can be caused by a large number of substances or combinations of
substances outside the workplace, many occupational exposures can be associated
 with the occurrence of asthma. Although in many cases it is difficult to evaluate
how much of the problem is caused by workplace exposure, in certain instances it is
obvious that asthmatic attacks are caused by work exposure only and not by factors
outside work.
Examples of substances that may cause occupational asthma:
♦ Plant origin:
– wood dust
– flour and grain dust
fungal spores
– formaldehyde
– gum arabic
♦ –Animal origin:

–wool
– hair
feathers
–
♦ Other substances:
–antibiotics (penicillin)
WORK-RELATED DISEASES
–toluene diisocyanate
–platinum salts.

Characteristics of work-related diseases

This category has certain characteristics which were identified and stated by a WHO
Expert Committee as follows:
“Multifactorial diseases”, which may frequently be work-related, also occur
among
partiallythecaused
general by
population,
adverse and working
working conditions they
conditions; and exposures
may be need not be
aggravated,
risk factors in
accelerated oreach case of any
exacerbated one disease.exposures;
by workplace However, and
when such
they diseases
may impairaffect the
working
worker,
capacity.they
It may
is be work-related
important in a numberthat
to remember of ways: they may
personal be
characteristics, other
environmental and sociocultural factors usually play a role as risk factors for these
diseases....

Multifactorial “work-related” diseases are often more common than occupational

diseases and therefore deserve adequate attention by the health service
infrastructure, which incorporates the occupational health services.
The work-related diseases which deserve particular attention are:
♦ behavioural 49 disorders
Identification andand psychosomatic
control of work-related diseases. Report of a WHO Expert Committee
(WHO
2
Technical Report Series No. 714), Geneva, World Health Organization, 1985.
♦ hypertension
♦ coronary heart disease
♦ peptic ulcers
♦ chronic nonspecific respiratory disease
♦ locomotor disorders.

Behavioural and psychosomatic disorders

Both home and work environments can be a major source of adverse psychosocial
factors. Individuals differ widely in their responses.

Risk factors for behavioural and psychosomatic disorders

(a) Environmental psychosocial risk factors

♦ work overload and underload
♦ boredom and lack of control over work situation
♦ shift work
♦ migration (migrant workers)
♦ organizational structure at the work establishment and the role of the
individual in the organization; role ambiguity and role conflict
♦ opportunity for career development and promotion
♦ physical insecurity (fires, explosions) and responsibility for other people’s
safety
♦ job design and degree of interest
♦ low wages
♦ job turnover
♦ early or involuntary retirement
♦ unemployment.

(b) Physical stressors

♦ thermal environment
♦ noise
♦ vibration
♦ radiation
50
♦ poor lighting.
(c) Environmental chemical stressors
These can increase the risk of psychosomatic illness. Some chemical hazards
however, have specific effects on the central nervous system, e.g. carbon monoxide,
carbon disulfide, alcohols and some other solvents.
(d) Social support system
This improves the ability of an individual to adapt to environmental psychosocial
stress. Support can be from the family, the work community or the community
outside of work.
(e) Individual psychosocial factors
♦ inter-individual relationship at work
♦ personality type
♦ individual susceptibility
♦ age
♦ sex.

Behavioural and psychosocial reactions to stress

♦ overeating leading to obesity
♦ smoking
♦ alcohol and drug abuse and drug addiction, any of which can be a risk factor
for psychosomatic illness
♦ fatigue
♦ anxiety
♦ depression
♦ hostility and aggression
♦ neurosis causing a range of mental and emotional disorders
♦ mental disorders and psychiatric disorders
♦ mass psychogenic illness (mass hysteria)
♦ psychosomatic disease: headache, backache, muscle cramps, disturbed sleep,
peptic ulcer, diabetes mellitus, cardiovascular disorders etc.

Hypertension

In over 90% of patients with hypertension, the disease is called “essential hypertension”
and no causeof can
development be identified.
hypertension. 51Genetic
Other predisposition
risk factors is an important
in the development risk factor.
of hypertension
Exposure to lead,
include dietary cadmium
habits (excessand
saltnoise is a obesity
and fats), risk factor
andin developing
physical hypertension and it
inactivity.
has also been suggested that psychosocial stress is a factor in the
CORONARY HEART DISEASE (CHD)

Narrowing of the coronary arteries causes inadequate blood supply to the heart
muscle causing “angina pectoris” or recurrent brief attacks of chest pain often
associated with exercise. Occlusion of any artery causes myocardial infarction or
necrosis of part of the heart muscle which may cause death within a short time or
later on due to complications.
The incidence of the disease is increasing and more and more younger people are
being affected. It is more common in men than women below 45 years of age, but in
older age the two sexes may be equal.
The risk of coronary heart disease is associated with hypertension, high dietary fat
intake, high serum cholesterol and being overweight. In addition there is a
significant familial tendency. A coronary-prone personality has been described as
the aggressive, competitive person who takes on too many jobs, fights deadlines
and is obsessed by lack of adequate time to finish his work. Overload at work has
also been associated with coronary heart disease.
Psychosocial stress increases serum cholesterol, causes hypertension and enhances
clot formation. Cigarette smoking is another risk factor for CHD. Other occupational
factors related to CHD are sedentary work, exposure to carbon disulfide, carbon
monoxide and nitrates and chronic exposure to noise, heat and cold. Solvents such as
benzene, trichlorethylene, chloroform, ethyl chloride and fluorocarbon compounds
directly affect the myocardial tissue. Lead and mercury cause CHD, secondary to
hypertension, and cobalt, arsenic and antimony produce myocardial damage.

Peptic ulcer

Several risk factors have been associated with the development of gastric and
duodenal ulcers. These include heredity, certain medicines (analgesics and non-
steroidal anti-inflammatory drugs), cigarette smoking, medical illness, surgical
procedures, type of personality, local infection (Helicobacter pylori) and occupation.
Occupational factors associated with the risk of developing peptic ulcers include
jobs with a high degree of responsibility and irregular shift work; the higher the work
stress the higher the ulcer rate. Also peptic ulcers are related to inhaled irritant
gases which dissolve in sputum and are ingested.
Chronic nonspecific respiratory diseases (CNRD)

CNRD is a general term used to describe a group of diseases in which there is chronic
cough and sputum production and/or shortness of breath at rest and/or during
exercise. These conditions include chronic bronchitis, emphysema, bronchial
asthma and asthmatic bronchitis. All these diseases may be acutely or chronically
52 multiple etiology and represent a
exacerbated by infection. CNRD are diseases of
classic
When theexample
risk ofofthese
disorders that is
disorders may be occupational
strongly in origin,
related to specific work-related or
occupational
related
exposureto such
the social phenomena of
as non-fibrogenic urbanization
dusts andrice
(e.g. cotton, industrialization.
and flax) or irritants, they
may easily be thought of as occupational diseases. It is well known, however, that
other factors, such as smoking, climatic conditions, community air pollution, atopy,
familial genetic factors, individual susceptibility, bronchial hyper-reactivity,
childhood respiratory infections, repeated respiratory infections in adult life and
socioeconomic status,
ascertain how much can play has
synergism a major role. between
occurred In any individual case, it isofdifficult
any combination two or to
more. It is generally believed however, that in smokers who are exposed to community or
workplace air pollution, smoking plays a more important role in the
causation of CNRD than does air pollution.
In dusty occupations where dust is known to cause specific pulmonary diseases
(silicosis, asbestosis, coal workers’ pneumoconiosis, byssinosis, etc.), dust
concentrations lower and durations shorter than those which cause the specific
disease may be sufficient to contribute to the causation of CNRD.
Examples of occupations where work-related CNRD may occur are those where dust
(organic or inorganic), irritant gases or aerosols are present. These pollutants may
contribute to the causation of CNRD by causing irritation of the respiratory mucous
membrane or through allergic mechanisms. These occupations include the chemical
industry, mining, foundries, textile mills, silos, cement factories, the glass industry,
the fertilizer industry, steel mills, smelters and a multitude of other occupations.

Locomotor disorders

Two examples of locomotor disorder will be given for which evidence of work
relatedness is available: low back pain syndrome and shoulder−neck pain syndrome.
Low back pain

Low back pain is a symptom of common occurrence in the general population,

affects males and females at all ages, but is more common between the ages of 25
and 64 years. It is said to affect over half the working population at some time during
their active working life and it is estimated that 2%–5% of industrial workers
experience low back pain each year.
Pain in the lumbosacral area can result from inflammatory, degenerative, traumatic,
neoplastic or other disorders. In some instances it is claimed to be psychogenic in
origin. The most common type of occupational low back pain is nonspecific, of
and injurious (twisting)
indeterminate pathologymovements of occupational
and often associated or non-occupational
with posture, origin.
lifting of heavy objects
The risk factors for low back pain include congenital back defects, weak
musculature, rheumatic affection and degenerative conditions of the spine and
intervertebral discs. Certain occupations carry a higher risk of developing low back
pain. These include heavy manual work, mining, docking, material handling, jobs
requiring awkward postures and postures that have to be maintained for prolonged
53
periods or involve frequent bending, twisting or whole body vibration, nursing and
policing. These occupations require proper selection, physical training, proper
placement and adoption of safe criteria for load lifting.
Shoulder−neck pain

A variety of diseases may result in shoulder and neck pain: examples are
inflammatory8. reactions in the synovial membrane and bursa system and
degenerative disorders in the cartilage, ligaments and tendons. In addition,
muscular, vascular and neuromuscular disorder may result in shoulder pain and
pain may be9.referred from the chest.
Disorders associated with general muscle weakness and general malaise, such as
infections, may also result in an increased susceptibility to shoulder and neck
complaints from loads on the shoulder which a worker can normally tolerate. From
the occupational health standpoint, individual predisposing factors such as age,
difficulties in organizing the work task and inflammatory rheumatic predisposition
play a role.
It has been found that working with the hands above shoulder height is more
frequent in workers with both acute and chronic shoulder and neck pain. However,
increased work loads on shoulder and neck muscles can also be produced without
lifting the arms above the shoulders.
Further proof of the work-relatedness of shoulder and neck pain is presented by the
fact that application of ergonomic principles to improve methods of work reduces
the pain.

5.

1.

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