The document outlines the objectives, functions, and principles of occupational health services (OHS) focusing on the health and safety of workers, particularly in agriculture and petroleum industries. It highlights the various occupational hazards such as physical, chemical, biological, mechanical, and psychosocial risks, and emphasizes the importance of managing these hazards through education, monitoring, and compliance with health policies. Additionally, it discusses the relevant laws governing occupational health in Nigeria.

1. OCCUPATIONAL
HEALTH SERVICES
By
Dr Olatunde Ajibola
MBBS (Lagos); MSc [Bournemouth]

2. OBJECTIVES
• Definition
• Functions of OHS
• Terms in OHS
• Occupational Hazards
• General Principles of OHS Management
• Focus on the OH of agricultural workers, and
petroleum workers
• Laws on OHS in Nigeria

3. DEFINITION
Occupational health should aim at the promotion and
maintenance of the highest degree of physical,
mental and social well-being of workers in all
occupations; the prevention among workers of
departures from health caused by their working
conditions; the protection of workers in their
employment from risks resulting from factors
adverse to health; the placing and maintenance of
the worker in an occupational environment adapted
to his physiological and psychological equipment,
and, to summarize, the adaptation of work to man
and of each man to his job.

4. Epidemiology of OH
• 3.5 billion people are working (nearly half of
the world’s population are workers).
• 4-6% of GDP annual economic loss from
illnesses & injuries due to unhealthy &
hazardous working conditions.
• Over 2 million people die as a result of
workplace-related accidents or diseases
(yearly), translating to one death every 15
seconds.
• There is an additional 374 million non-fatal
work-related injuries annually.

5. Functions of OHS
1. Control of Hazards:
It must identify and bring under control at the
workplace all chemical, physical, mechanical,
biological, and psychosocial agents that are
known to be or suspected of being hazardous.
2. Match Suitable Workers and Jobs:
It must ensure that the physical and mental
demands imposed on people at work by their
respective jobs are properly matched with their
anatomical, physiological, and psychological
capabilities, needs and limitations.

6. Functions of OHS
3. Provide Protection:
It should provide effective measures to protect
those who are especially vulnerable to adverse
working conditions and to raise their level of
resistance.
4. Improve the Work Environment:
It should discover & improve work situations that
may contribute to the overall ill health of
workers in order to ensure that the burden of
general illness in different occupational groups
is not increased over the community level.

7. Functions of OHS
5. Implementation of Health Policies:
To educate management and workers to fulfil their
responsibilities relevant to health protection and
promotion.
6. Provision of Occupational Health:
To carry out comprehensive in-plant health
programmes dealing with man’s total health,
which will assist public health authorities to
raise the level of community health.

8. Terms in OHS
 Ergonomics: It is derived from the Greek term
ergon, meaning work and nomos, meaning law. It
simply means: “fitting the job to the worker”.
The purpose of ergonomics is to achieve the best
mutual adjustment of man and his work, for the
improvement of human efficiency and wellbeing.
The process of ergonomics involves designing of
machines, tools, equipment and manufacturing
processes, lay-out of the places of work, methods
of work and environment in order to achieve
greater efficiency of both man and machine.

9. Terms in OHS
Occupational Environment: It refers to the sum
of external conditions and influences which
prevail at the place of work and which have a
bearing on the health of the working
population.
There are three types of interaction in a working
environment:
(a) Man and physical, chemical and biological
agents
(b)Man and machine
(c) Man and man

10. Occupational Environment: Man &
physical, chemical & biological agents
1. Physical Agents: These agents in the working
environment which may be adverse to health are
heat, cold, humidity, air movement, heat radiation,
light, noise, vibrations and ionising radiation.
These factors act in different ways on the health &
efficiency of the workers, singly or in different
combinations.
The amount of working & breathing space, toilet,
washing & bathing facilities are also important
factors in an occupational environment.

11. Occupational Environment: Man &
physical, chemical & biological agents
2. Chemical Agents: These comprise a large
number of chemicals, toxic dusts & gases which
are potential hazards to the health of the
workers. Some cause respiratory illnesses, some
cause injury to skin & some deleteriously affect
the blood & other organs of the body.
3. Biological Agents: The workers may be exposed
to viral, rickettsial, bacterial & parasitic agents
which may result from close contact with
animals or their products, contaminated water,
soil or food.

12. Occupational Environment: Man and
Machine
An industry or factory implies the use of machines
driven by power with emphasis on mass production.
The unguarded machines, protruding & moving parts,
poor installation of the plant, lack of safety
measures are the causes of accidents which is a
major problem in industries.
Working for long hours in un-physiological postures is
the cause of fatigue, backache, diseases of joints &
muscles & impairment of the worker’s health and
efficiency.

13. Occupational Environment: Man and
Man
There are numerous psychosocial factors which
operate at the place of work; these are human
relationships among workers themselves on the
one hand, and those in authority over them on
the other hand.
These psychosocial factors include: the type and
rhythm of work, work stability, service
conditions, job satisfaction, leadership style,
security, workers participation, communication,
system of payment, welfare conditions, degree of
responsibility, trade union activities, incentives
and many other human relationship factors.

14. Occupational Health: Man and Man
(Cont’d)
The emphasis of OH is upon the people: the
conditions in which they live and work, their
hopes and fears and their attitudes towards their
job, their fellow-workers & employers.
The occupational environment cannot be divorced
from the domestic environment of the worker.
The worker takes his worries home, and brings to
his work disturbances which arise in his domestic
environment. Stress at work may disturb his
sleep, just as stress at home may affect his work.

15. Occupational Health: Man and Man
(Cont’d)
Severe prolonged stress, no matter where it has
been aroused, may produce serious physical or
mental symptoms which do not allow man to
work efficiently.
According to ecological approach, occupational
health represents a dynamic equilibrium or
adjustment between the industrial worker and
his occupational environment.

16. Occupational Hazards
An industrial worker may be exposed to five types
of hazards, depending upon his occupation:
(a) Physical hazards
(b)Chemical hazards
(c) Biological hazards
(d)Mechanical hazards
(e) Psychosocial hazards.

17. Occupational Hazards: Physical
Hazards
1. Heat & Cold: The most common physical hazard
in most industries is heat. The direct effects of
heat exposure are burns, heat exhaustion, heat
stroke, heat cramps; the indirect effects are
decreased efficiency, increased fatigue &
enhanced accident rates.
Important hazards associated with cold work are
chilblains, erythrocyanosis, immersion foot, and
frostbites (due to cutaneous vasoconstriction).
General hypothermia is not uncommon.

18. Occupational Hazards: Physical
Hazards
2. Light: The workers may be exposed to the risk of poor
illumination or excessive brightness.
The acute effects of poor illumination are eye strain,
headache, eye pain, lachrymation, congestion around
the cornea and eye fatigue. The chronic effects on
health include “miner’s nystagmus”.
Exposure to excessive brightness or “glare” is associated
with discomfort, annoyance & visual fatigue.
Intense direct glare may also result in blurring of vision
and lead to accidents.

19. Occupational Hazards: Physical
Hazards
3. Noise: It is a health hazard in most industries.
(i) Auditory effects: these consist of temporary or
permanent hearing loss
(ii) Non-auditory effects: these consist of nervousness,
fatigue, interference with communication by
speech, decreased efficiency and annoyance.
The degree of injury from exposure to noise depends
upon a number of factors such as intensity &
frequency range, duration of exposure and
individual susceptibility.

20. Occupational Hazards: Physical
Hazards
4. Vibration: Vibration, especially in the range 10 to
500 Hz, may be encountered in work with
pneumatic tools such as drills and hammers.
Vibration usually affects the hands and arms.
After some months or years of exposure, the fine
blood vessels of the fingers may become
increasingly sensitive to spasm (white fingers).
Exposure to vibration may also produce injuries of
the joints of the hands, elbows and shoulders.

21. Occupational Hazards: Physical
Hazards
5. Ultraviolet Radiation: Occupational exposure to
UV radiation occurs mainly in arc welding. Such
radiation mainly affects the eyes, causing intense
conjunctivitis & keratitis (welder’s flash).
Symptoms are redness of the eyes and pain,
these usually disappear in a few days with no
permanent effect on the vision or the deeper
structure of the eye.

22. Occupational Hazards: Physical
Hazards
6. Ionizing Radiation: These include X-rays and
radio-active isotopes.
The radiation hazards include genetic changes,
malformation, cancer, leukaemia, depilation,
ulceration, sterility and in extremes case death.
The International Commission on Radiological
Protection (1957) has set the maximum
permissible level of occupational exposure at 5
rem per year to the whole body.

23. Occupational Hazards: Chemical
Hazards
There is hardly any industry which does not make
use of chemicals.
The chemical hazards are on the increase with the
introduction of newer and complex chemicals.
Chemical agents act in three ways: local action,
inhalation and ingestion.
(i) Local action: some chemicals cause dermatitis,
eczema, ulcers and even cancer by primary
irritant action; some cause dermatitis by an
allergic action.

24. Occupational Hazards: Chemical
Hazards (cont’d)
Other causes of occupational dermatitis include
machine oil, rubber, X-rays, caustic alkalis and lime.
(ii) Inhalation: This includes dusts, gases, and metals
and their compounds. Dusts are finely divided solid
particles with size ranging from 0.1 to 150 microns.
Dusts less than 5 microns are directly inhaled into
the lungs and are retained there. This dust is the
cause of pneumoconiosis. Other dust diseases
include silicosis and anthracosis

25. Occupational Hazards: Chemical
Hazards (Cont’d)
Exposure to inhalational gases is a common hazard in
industries. Asphyxiating gases include Carbon II
oxide, cyanide gas, sulphur IV oxide & chlorine.
Anaesthetic gases include chloroform, ether,
trichloroethylene. CO hazard is common in coal-gas
manufacturing plants & steel industry.
Metals & their Compounds: They are mainly inhaled as
dust or fumes. These metals include lead, antimony,
arsenic, beryllium, cadmium, cobalt, manganese,
mercury, phosphorus, chromium, zinc, etc. Most
chemical intoxications respond to cessation of
exposure & medical treatment.

26. Occupational Hazards: Chemical
Hazards (Cont’d)
(iii) Ingestion: Occupational diseases may also
result from ingestion of chemical substances
such as lead, mercury, arsenic, zinc, chromium,
cadmium, phosphorus etc.
Usually these substances are swallowed in minute
amounts through contaminated hands, food or
cigarettes.
Often times, only a small proportion reaches the
systemic circulation, yet this little amount is
enough to cause deleterious health effects.

27. Occupational Hazards: Biological
Hazards
Agricultural workers and people working among
animal products (e.g. hair, wool, hides) are specially
exposed to biological products.
These occupational diseases include brucellosis,
leptospirosis, anthrax, hydratidosis, psittacosis,
tetanus, encephalitis, fungal infections,
schistosomiasis, etc.
Healthcare workers are also susceptible to biological
hazards: Blood-borne pathogens(HBV, HCV, HIV);
others are tuberculosis, varicella, measles, pertussis,
parvovirus, influenza and the enteritidis
(enteroviruses, Salmonella, Shigella, hepatitis A
virus).

28. Occupational Hazards: Mechanical
Hazards
The mechanical hazards in industry centre round
machinery, protruding and moving parts, etc.
About 10% of accidents in industry are said to be
due to mechanical causes.

29. Occupational Hazards: Psychosocial
Hazards
The psychosocial hazards arise from the workers’
failure to adapt to an alien psychosocial
environment.
These hazards which can undermine both the physical
& mental health of the workers include– frustration,
lack of job satisfaction, insecurity, poor human
relationships and emotional tension.
Furthermore, long hours, rotating shifts, demanding
jobs, limited decision latitude, competing time
demands, repetitive tasks, threat of violence, job
insecurity & poor management also contribute to
workplace stress.

30. Occupational Hazards: Psychosocial
Hazards (Cont’d)
The level of education, cultural background, family
life, social habits & what the worker expects
from employment determine the capacity to
adapt to different working environments.
The health effects of psychosocial hazards can be
classified into two main groups:
(a) Psychological & behavioural changes: hostility,
aggressiveness, anxiety, depression, tardiness,
alcoholism, drug abuse, sickness and
absenteeism

31. Occupational Hazards: Psychosocial
Hazards (Cont’d)
(b) Psychosomatic ill-health: fatigue, headache; pain in
the shoulders, neck & back; propensity to peptic
ulcer, hypertension, heart disease and rapid aging.
Physical factors such as heat, noise & poor lighting also
play a major role in adding to or precipitating mental
disorders among workers.
It is said that psychosomatic hazards are now assuming
more importance than physical or chemical hazards.

32. General Principles of OHS Management
Measures Examples and Comment
Educate the workers Inform the workers of the hazards in the working
environment and how they can protect themselves and
other workers
Replace hazardous chemical Use alternate safer compound as replacement for
hazardous chemicals.
Modify the Process Engineering & other modifications can make a process
safer. E.g. wet drilling to reduce dust in mining.
Eliminate toxic process Remove the hazardous product to minimise
contamination of the environment, e.g. use exhaust fans
to remove dust at the point of drilling.
Limit the number of workers
exposed
Confine the hazardous process to restricted area to
which essential workers have access. The use of robots,
of remote action may further reduce human exposure.

33. General Principles of OHS
Management (Cont’d)
Measures Examples & Comment
Protect workers PPE (gowns, gloves, goggles, etc) should be
used. Compliance should be monitored by
management. Erring workers should be
sanctioned.
Monitor the environment Measurement of environmental contamination
e.g. dust level, will indicate risks & impact of
control measures.
Monitor exposure of workers Measure the degree to which individual workers
are exposed, e.g. using film &
thermoluminescent dosimeters( usu. worn as
badges) to measure individual exposure of
radiographers & radiologists to ionizing
radiation.
Monitor the health of workers Workers in hazardous employment should be
monitored to look for early signs of adverse
effects, e.g. blood tests in workers exposed to
lead.

34. General Principles of OHS
Management (Cont’d)
Measures Examples and
Comment
Establish emergency and first aid services Workers & health staff should be trained
to deal with emergencies such as
accidental spillage of hazardous chemicals
or exposure of individuals. Appropriate
first aid equipment should be easily
accessible, e.g. emergency showers.

35. Occupational Health Hazards of
Agricultural Workers
Agricultural workers have a multitude of health
problems.
The health problems of workers in agriculture may
be enumerated as below:
(1) Zoonotic Diseases: The close contact of the
agricultural worker with animals or their
products increases the likelihood of contracting
certain zoonotic diseases such as brucellosis,
anthrax, leptospirosis, tetanus, tuberculosis
(bovine) and Q fever.

36. Occupational Health Hazards of
Agricultural Workers (Cont’d)
(2) Accidents: These accidents are due to
agricultural machinery, insect and snake bites.
(3)Toxic Hazards: Agric. Workers are exposed to
chemicals (fertilizers, insecticides or pesticides)
which are increasingly being used in the sector–
these constitute toxic hazard exposure.
Associated factors such as malnutrition &
parasitic infestation may increase susceptibility
to poisoning at relatively low levels of exposure.

37. Occupational Health Hazards of
Agricultural Workers (Cont’d)
(4) Physical Hazards: Exposure to extremes of
climatic conditions such as temperature,
humidity, solar radiation are common.
The agric. worker may have to endure excessive
noise & vibrations, inadequate ventilation & the
necessity of working in uncomfortable positions
& posture for long periods of time.

38. Occupational Health Hazards of
Agricultural Workers (Cont’d)
(5) Respiratory Diseases: Exposure to dusts of
grains, rice husks, coconut fibres, tea, tobacco,
cotton, hay and wood are common where the
products are grown.
The resulting diseases—e.g., byssinosis,
bagassosis, farmer’s lung & occupational
asthma, appear to be widespread in those
places

39. Occupational Health Hazards of
Petroleum Workers
Safety & health hazards and dangerous conditions
that can result in fatalities for oil and gas workers
include:
o Vehicle Accidents
o Struck-By/ Caught-In/ Caught-Between
o Explosions and Fires
o Falls
o Confined Spaces
o Chemical exposures

40. Occupational Health Hazards of
Petroleum Workers (Cont’d)
Other hazards include:
o Silica
o Hydrogen sulphide
o Hydrocarbon Gases and Vapours (HGVs) & low
oxygen environments; Diesel Particulate Matter
o Fatigue
o Naturally Occurring Radioactive Material (NORM)
o Noise
o Temperature Extremes

41. Laws on Occupational Health in
Nigeria
 Factories Act, 1987
 Factories Act, 2004
 Factories Act, 2010

42. THE END