Transcript Document

Retrospective Cohort Study
and
Prospective Cohort Study
Retrospective Cohort Study
A retrospective cohort study starts
at a point in the past and follows
cohort forward in order to
determine past exposure histories
and health outcomes from records
Both methods involve looking for
a link between cause
(exposure) and effect
(disease);
using two cohorts in order to
compare those that have been
‘exposed’ against those that
were ‘unexposed’ and looking
for a dose/response link
Reliability may be affected by
factors such as:
Prospective Cohort Study
A prospective cohort study starts at
the present time and follows cohort
forward and enables monitoring of
exposure and health outcomes
Cohort size;
Accuracy of historical data on
exposure and health effects;
Accuracy of diagnosis;
Long latency periods for the effect;
Non-occupational exposure;
Frequency of disease in unexposed cohort;
Lifestyle factors such as alcohol
consumption, diet, smoking etc;
Selection bias (cohort may not be
representative of exposed
population); the ‘healthy worker
effect’ (sick people leave);
Difficulty in following all of cohort for instance
a geographic move, non co-operation
Controls
Nature and properties
Maximise distance from source and
minimise amount of time employees
exposed since effect of exposure is
dose dependant.
Non particulate electromagnetic
radiation
Specific doses stated in Ionising
Radiation Regulations for classified
workers.
Artificially generated, normally by the
use of electrical energy and emitted
when a machine is switched on.
Likely to receive doses over 6 mSv
a year.
Over exposure to be investigated
and reported to enforcement
authority.
Monitoring of staff overseen by a
Radiation Protection Supervisor,
records kept for fifty years or until
person they refer to has reached
seventy five years of age.
Monitored by use of personal
devices such as film badges or
thermoluminescent dosimeters
(tld’s). These should then be
processed by an approved
dosimetry service and results
checked against specified regs.
X- Rays
Can travel a few metres in air, present an
external radiation hazard for an
individual in the same room or space.
Can penetrate much further into body
but can be shielded with lead or
concrete.
Controls
Nature and properties
Maximise distance from source and
minimise amount of time employees
exposed since effect of exposure is
dose dependant.
The source should be shielded or
contained in a sealed unit or
container and where possible the
work undertaken in a glove box or
fume cupboard to minimise chance
of ingestion, inhalation or
absorption.
Equipment and surfaces should be
decontaminated following work
with the particles.
Type of ionising radiation formed as
a result of radioactive decay.
Consists of two protons and neutrons (ie
a Helium nucleus)
Alpha Particles
Travel for only a few centimetres
through air
Can be stopped by skin or paper
Taking of food and drink should not
be allowed in areas where the
particles are likely to be present.
Ensure all wounds cuts and
grazes are covered and
protected.
Use of a Radiation protection
adviser / supervisor.
Surveillance
More hazardous if source is taken into
body
Controls
Nature and properties
Maximise distance from source and
minimise amount of time employees
exposed since effect of exposure is
dose dependant.
The source should be shielded or
contained in a sealed unit or
container and where possible the
work undertaken in a glove box or
fume cupboard to minimise chance
of ingestion, inhalation or
absorption.
Equipment and surfaces should be
decontaminated following work
with the particles.
Type of ionising radiation formed as
a result of radioactive decay.
Consists of two protons and neutrons (ie
a Helium nucleus)
Beta Particles
Longer range than Alpha Particles
Low energy can be stopped by skin
High energy can penetrate soft tissue to
a depth of over 1cm.
Taking of food and drink should not
be allowed in areas where the
particles are likely to be present.
Ensure all wounds cuts and
grazes are covered and
protected.
Use of a Radiation protection
adviser / supervisor.
Surveillance
More hazardous if source is taken into
body, but not as intense as Alpha
particles.
Occupational Health
Practitioners
Information from
RIMEC
• Ergonomists
• EMAS - (Employment Medical
Advisory Service)
• Recognition / Identification
• THOR - The Health and
Occupational Reporting Network
• Evaluation
• Toxicologists
• Epidemiologist
• Occupational Hygienists
• Occupational Health physicians
• Occupational Health nurses
• Occupational Psychologists
• Radiation Protection Advisers /
supervisors / health physicists.
• Industrial Injuries Disabled Board
• HSE fatality statistics
• Measurement
• Control
Structure of the Skin
•
•
•
Epidermis - the outer layer of
the skin.
Dermis - the layer of the skin just
beneath the epidermis.
Subcutaneous tissue - fatty
tissue located under the dermis
•
•
•
•
blood vessels - Tubes that carry
blood as it circulates. Arteries bring
oxygenated blood from the heart
and lungs; veins return oxygendepleted blood back to the heart
and lungs.
Sebaceous gland - a small, sackshaped gland that releases oily
(fatty) liquids onto the hair follicle
(the oil lubricated and softens the
skin). These glands are located in
the dermis, usually next to hair
follicles.
Sweat gland - a tube-shaped
gland that produces perspiration
(sweat). The gland is located in the
epidermis; it releases sweat onto
the skin.
hair follicle - a tube-shaped
sheath that surrounds the part of
the hair that is under the skin. It is
located in the epidermis and the
dermis. The hair is nourished by
the follicle at its base (this is also
where the hair grows).
Heat and Cold receptors- Detect
heat and cold and pass info via
nerves to central nervous system.
The Human Ear
1.
Pinna - (also called the
auricle) the visible part of the
outer ear. It collects sound
and directs it into the outer
ear canal.
2.
Outer ear canal - the tube
through which sound travels
to the eardrum.
7.
Oval Window- link between
stirrup and cochlea.
8.
Semicircular canals - three loops
of fluid-filled tubes that are
attached to the cochlea in the
inner ear. They help us maintain
our sense of balance.
9.
Cochlea - a spiral-shaped, fluidfilled inner ear structure; it is lined
with cilia (tiny hairs) that move
when vibrated and cause a nerve
impulse to form.
10. Auditory nerve - this carries
electro-chemical signals from the
inner ear (the cochlea) to the
brain.
3.
Hammer - (also called the malleus) a tiny
bone that passes vibrations from the eardrum
to the anvil.
4.
Anvil - (also called the incus) a tiny bone that
passes vibrations from the hammer to the
stirrup.
5.
Stirrup - (also called the stapes) a tiny, Ushaped bone that passes vibrations from the
stirrup to the cochlea. This is the smallest
bone in the human body.
6.
Eardrum - (also called the tympanic
membrane) a thin membrane that vibrates
when sound waves reach it.
11. Eustachian tube - a tube that
connects the middle ear to the
back of the nose; it equalizes the
pressure between the middle ear
and the air outside. When you
"pop" your ears as you change
altitude (going up a mountain or in
an airplane), you are equalizing
the air pressure in your middle
ear.
LD50 and LC50
•
•
LD50 In toxicology, the median
lethal dose, (abbreviation for
“lethal dose, 50%”), relates to a
single oral dose) of an agent
required to kill half the members of
a tested population.
Since it is oral dose it is measured
in grams or mg per Kilogram body
weight.
NOAEL – No Observed Adverse Effect Level
•
Exposure level at which there are no statistically or
biologically significant increases in the frequency or
severity of adverse effects between the exposed
population and its appropriate control; some effects may
be produced at this level, but they are not considered as
adverse.
•
LC50 (lethal concentration, 50%) or LCt50
(lethal concentration & time) Inhaled
concentration of an agent required to kill
half the members of a tested population
after a specified test period.
•
Measured in ppm (parts per million )or
grams / milligrams per cubic metre of air.
•
No account is taken of bodyweight in this
measurement.
LOAEL - Low Observed Adverse Effect Level
•
lowest concentration or amount of a substance found by
experiment or observation that causes an adverse
alteration of morphology, function, capacity, growth,
development, or lifespan of a target organism
distinguished from normal organisms of the same species
under defined conditions of exposure.
Limitations
Advantages
•
Ethics / Public opinion
•
Costly and time consuming
•
Dose response varies.
• Data can be collected more quickly than for epidemiological
studies.
•
May not display synergistic effects that may arise in humans
exposed to other agents at the same time.
• Animals provide good models due to their close genomic
relation to humans.
•
Difficulty with no observed effects level for carcinogens.
•
There can be wide variability between species as well; what is
relatively safe for rats may very well be extremely toxic for humans,
and vice versa.
• More likely to show carcinogenic potential than in-vitro tests
such as the Ames test.
•
For example, chocolate, harmless to humans, is known to be toxic to
many animals.
• Avoids human exposure.
Accidents, incidents and emergencies
Reg 13
Requires that employers prepare for
possible accidents, incidents and
emergencies involving hazardous
substances by:
• Preparing emergency procedures,
including provision of First Aid;
• Making available technical information
on possible accidents and hazards
and bringing it to the attention of the
emergency services; and
• Installing alarms and other warnings
and communication systems
Information, instruction and training
Reg 12
• Demands that all employees liable to
exposure to hazardous substances are
provided with suitable and sufficient
information, instruction and training,
Health surveillance Reg 11
Requires that health surveillance of employees
is carried out where:
• An identifiable disease or adverse health
effect may be related to the exposure;
• There is a "reasonable likelihood" that the
disease or health effect may occur under the
particular conditions of work;
• Valid techniques exist for detecting
indications of the disease of health effect; and
The technique presents a low risk to the
employee;
• where there is exposure to certain substances
in specified occupations:
Risk assessment Reg 6
• Requires that an employer not carry out work liable to expose employees and non
Employees to a substance hazardous to health without a risk assessment and
implementation of the steps necessary to comply with the regulations.
• The assessment must include consideration of any information provided by the supplier
of a substance (CHIP)
• Must be reviewed regularly, and also when there is reason to think the assessment is no
longer valid, if the system of work is changed
• Because of the results of health Monitoring. The assessment must also consider any
occupational exposure limit, in particular, those mandated by the HSE.
COSHH as
Amended
Monitoring Exposure Reg 10
• Where the risk assessment
indicates that workplace
monitoring of exposure is
necessary, the employer
must perform such
monitoring
• unless he can demonstrate
another means of preventing
or controlling exposure
• Monitoring must be at
regular intervals in addition
to when a change occurs
that may affect exposure
Prevention or control of exposure Reg 7
Requires that an employer prevent
exposure to hazardous substances or, if this
is not reasonably practicable, that he
adequately controls exposure.
Use of control measures Reg 8
Employers must take all reasonable steps to
ensure that control measures, and any
necessary equipment of facilities, are properly
used or applied. Employees must use the
control measures properly, return them after
use and report any defective equipment.
Maintenance and testing of control measures
Reg 9
Requires that employers maintain control
measures in efficient working order and in
good repair
6 – Risk assessment
7 – Prevention or control of
Exposure. (Adequate control)
Principles of good practice
Schedule 2 of Reg 7
8 – Use of control measures
9 – Maintenance and testing
of control measures
10 – Monitoring exposure
11 – Health Surveillance Schedule 6 - Benzene –
Manufacturing process
12 – Information, instruction
and training
13 – Accidents, incidents and
emergencies
COSHH amended L5
Design process to minimise ex.
Route of exposure.
Controls proportionate to risk
Escape of substance minimised
PPE in addition
Review effectiveness
Info., training and instruction
Higher risk – do not introduce.
Controls
First stage of control strategy is to
assess those people at risk Factors to
consider include:
• Work being carried out
• Susceptibility to infection of the
workers
• How infections might occur
• How likely exposure to infection is.
Zoonoses are animal infections which may be
transmitted to people in the course of their work.
Common examples include:
•
Anthrax
•
Brucellosis
•
Orf
•
Glanders
• Most common route of entry is via
the skin, by way of open cuts, sores
or abrasions which provide direct
entry to blood stream,
• inhalation of contaminated dusts,
• Contact with conjunctiva of eyes,
• Direct injection by cuts from infected
animals or animal bites
• Direct ingestion via hands
• Where animal products likely to emit infected dust are
handled (e.g. wool, skin, hides, pelts), LEV and possibly
RPE should be provided to prevent airborne infection
• Specific immunisation of workers may be necessary
• Clean & hygienic animal living conditions and disinfection
of stalls will also ensure better hygiene in factory
premises and will reduce probability of infection
• Automation to reduce human contact and enclosure of
aerosol-producing activities will reduce exposure to
infection
• Finally, medical checks, training and information,
procedures, instruction and records will give added
protection to workers
Zoonoses
• Anthrax is an acute infectious disease of
farm animals caused by a bacterium
• Transmitted to man by contact with
infected hair, hides, excrement or
products such as bonemeal
• Fatal without treatment
• Initial lesion rapidly becomes ulcerated
• Treatment is by penicillin
• Inhaling the pathogen causes pulmonary
anthrax which is usually fatal in 3 or 4
days
• Brucellosis caused by the bacterium
Brucella abortus, which may infect
people handling cattle or pigs or their
carcasses in abattoirs
• Not very severe but involves loss of
appetite, headache, insomnia and slight
fever
• In the UK a policy of eradication has
been pursued since the 60’s by
destroying any infected cattle
• Orf is a contagious pustular dermatitis of viral
origin, mainly affecting farm workers, shepherds,
sheep shearers, butchers and abattoir workers
• Lesion enlarges and often becomes ulcerated,
exuding fluid and pus
• Complete recovery occurs in about 3 weeks
• Glanders is an infectious disease of horses, donkeys and
mules caused by the pathogen Pseudomonas mallei
• Transmitted to humans by nasal or mouth secretions from
the infected animal
• Abscesses appear on hands, arms or face
• Lasts up to 4 months but is treatable with modern
antibiotics
Aids
• Acquired Immune Deficiency Syndrome
Caused by Human Immunodeficiency
Virus (HIV), which attacks the immune
system
• Virus is found in most body fluids but is
delicate and relatively easy to kill with
heat and chemicals
• It has low infectivity and transmission is
thought to be more likely with repeated
exposure to infection rather than to a
single contact
• Occupational risk comes from
accidental inoculation or contamination
of a cut or abrasion with blood or body
fluids of an infected person
• Doctors, nurses, dentists, laboratory
and hospital staff are at some risk,
since they may come into close contact
with body fluids
• Other workers possibly at risk might
include community, welfare, custodial
and emergency service workers and
first aiders
Many of the precautions taken against other
infections, especially Hepatitis B, will be equally
effective against HIV. They include:
• Prevention of puncture wounds, cuts and
abrasions in the presence of blood and body
fluids;
• Protection of existing wounds and skin lesions
• Control of surface contamination by
containment and disinfection
• Safe disposal of contaminated waste,
especially sharps
Hepatitis
Aids and Hepatitis
• Those at risk include doctors,
surgeons, nurses and porters
• Infection amongst health workers
is a result of contact with blood
or excreta of patients suffering
from viral hepatitis or in whom
the disease is still in its
incubation stage
• Porters and refuse disposal are
at risk from carelessly discarded
syringes and other sharps - the
problem is becoming worse with
the increase in drug addiction
• Course of disease is similar to
Weil’s Disease, but is usually much
less severe and normally selflimiting with recovery in about 6
weeks
• In about 5% of cases, chronic
infectious hepatitis follows, leading
to cirrhosis and possibly death
• Persons exposed to risk can be
protected with injections of
gammaglobulin
• In all cases, protective disposable
gloves should be worn and hands
and arms washed regularly with
disinfectant
Support – this includes the
encouragement,
sponsorship and resources
provided by the
organisation, line
management and
colleagues.
Demands – this includes
issues such as workload,
work patterns and the
work environment.
Control– how much say
the person has in the way
they do their work.
Change– how organisational
change(large or small) is
managed and communicated in
the organisation
HSE Stress
Management Hazards
Relationships – this includes
promoting positive working
to avoid conflict and dealing
with unacceptable behaviour.
Role – whether people
understand their role within
the organisation and
whether the organisation
ensures that they do not
have conflicting roles.
Pre-employment screening
And on-going surveillance
Cold Stress – Difficulty in
controlling core body
temp.
Provision and wearing of
thermal clothing, footwear
undergarment ,high CLO
rating
Reduction in heart rate
Persistent shivering with blue
fingers and lips
Cold Stress
Mental impairment with
stress
Hypothermia and frost bite
which is inflammation of the
skin and tissue damage.
Chillblains causing redness,
tingling and pain in the
affected area.
Monitor activity level, to
generate some heat but not
to sweat. Breaks with warm
rest area.
No possibility of being locked
in, ability to open from inside
Regular maintenance and
alarm to detect leaking
refrigerant
Training on hazards involved
with cold working
Controls in Garage
Physiological Effects
Carbon monoxide
absorbed via the lungs
into bloodstream,
displaces Oxygen by
chemically bonding to the
Haemoglobin. Reducing
oxygen carrying capacity
of blood and therefore
supply to tissues.
CO only slowly displaced
from body.
Causes drowsiness,
headaches, skin colour
changes (blue lips), dizziness
breathlessness,
unconsciousness and death
above 5%
Minimising duration of engine
running time.
Carbon Monoxide
Local exhaust ventilation
attached to hose pipes as well
as good ventilation to
workshop and pits.
Regular maintenance of LEV
system and fitting CO alarms
Specific CO hazard training to
employees .
Segregating area from
customers
Main Function and factors
to consider
Regulations
Regulation 3
• Duty of employer to make
provision for first aid.
• Assessment of need
• First –aid materials, eqpt and
facilities
• First-aid personnel
Regulation 4
• Duty of employer to
provide information to
employees on first-aid
Regulation 5
• Self employed duty to
provide first-aid eqpt
• Duties of self employed
Preservation of life and
minimisation of the
consequences of injury until
medical help is obtained, and
treatment of minor injuries.
Health and Safety
(First-Aid)
Regulations 1981
Number, composition and
distribution of workforce.
Hazard and level of risk
present and past accidents.
Distance from medical
facilities
Number of first-aiders and
level of training as well as
cover for shifts, leave and
sickness
Health effects
Mesothelioma
A form of cancer that affects the
external lining of the lung or
the peritoneum. Long latency
period and almost always
terminal
Asbestosis
Form of pneumoconiosis –lung
fibrosis.
Scarring and inflammation of
the lung tissue.
Irreversible, chest pain, fatigue
laboured breathing
Diffuse pleural thickening
Non- Cancerous
Causes thickening of the tissue
which makes it less able to
expand during breathing
Cancer of the bronchus
Malignant growth within
bronchus of lung, terminal
Control of Asbestos at Work regs
2012
Factors to consider and
control measures
RA – to contain
• Type of asbestos
• Likely to become airborne
and in what
concentration.
Asbestos
Limit number of people
exposed
Limit contamination spread.
Limit fibre emission at source
(work methods)
Licencing and Training on
removal
Use of specific PPE
Information to gather
Review of previous surveys
Assessment of current controls
Exposure limit value – 87dB
Upper exposure action value – 85dB
Lower exposure action value – 80dB
L108 - Controlling noise at work
Basic survey followed by a
more detailed survey
Consultation
Legal requirements and limits
Site layout and location of
machines.
Number and location of
workers and audiometry
records
Shift times and patterns with
likely duration of exposure
Identify noisy machines and
review maintenance records
for identification purposes.
Manufacturers data
Control of
Noise at Work
R. 2005
Noise survey and Eqpt.
Personal noise monitoring and
frequency analysis
Competent assessor
eqpt calibrated before and
after measurements
Use results to plot noise map
for area.
Basic Survey
Simple sound level meter for
spot checks and integrating
sound level meters.
Measure at planned points to
ID exposures at action levels.
Noting machinery in operation
at time.
Detailed Survey
• Integrating sound level meters
• Appropriate sample times to measure Leq (equivalent continuous sound
level), use nonogram to calculate exposure LEPw, LEPd
• Measurement of peak noise levels and plotted on noise map.
• Use of frequency analysis useful to decide on controls such as enclosure
• Personal noise exposure using dosimeter or microphone close to ear
• Selection of hearing PPE with suitable SNR (Single Number Rating)
Reasons for Introduction
and Difficulties
Signs
Sudden mood changes
Safety critical posts.
Following accident or incident.
Part of rehabilitation stage
following discovery of use.
Pre-employment.
Becoming confused
Abnormal fluctuations in
concentration and energy
levels
Impaired job performance /
more accidents
Poor time keeping and more
short term sickness
Deterioration in relationship
with colleagues
Dishonesty or theft
of alcohol or presence of drugs
paraphernalia
Change in appearance, scruffy
or needle marks, slurred
speech.
Drug and Alcohol
Abuse
General statement of aims.
Responsibilities.
Definition of drug misuse.
Rules that will apply.
Notification of prescribed drugs.
Reporting suspicions.
Procedure following failed test.
Support and help available.
How to return following
Treatment.
Union agreement – staff trust
Data protection
Cost – lab, competent tester
False positives / Unexpected results
Measuring Instruments
Black globe thermometer - Radiant Temperature
Dry bulb thermometer– Normal air temp.
Wet bulb thermometer - covered in muslin sleeve
(found in psychrometer. )
Wet bulb Thermomter Index Used for heat stress.
Sorbent tube – full of adsorbent e.g. charcoal.
Cellulose filter paper, Acetone bath. Cowl
Dry weight filter paper – Cyclone head - Respirable
Measuring Instruments
Humidity – Hygrometer (psychrometer)
Combination of wet and dry bulb
thermometers.
Wet bulb globe temperature index
To measure heat stress.
Accelerometer – Measures vibration
Simple sound level meter
Integrated sound level meter
Octave band frequency analysis
Vane anemometer – Wind speed
Kata Thermometer – low wind speed
Smoke tube
Manometer –Pressure differentials
Pitot Tube – Static pressure or velocity by using calculation
Thermal or hot wire anemometer – air velocity
Regulations
Health and Safety (First-Aid) Regulations 1981
Management of Health and Safety at Work regs 1999
Workplace Health safety and Welfare regs 1992
Manual Handling Operations regs 1992 L23
Personal Protective Eqpt regs 1992
Health and Safety (DSE) regs 1992
PUWER 1998
Control of Artificial Optical Radiation at Work regs 2010
Ionising Radiation regs 1999
Radiation Protection Adviser
Radiation Protection Supervisor
Control of Noise at Work Regs 2005
Exposure limit value – 87dB
Upper exposure action value – 85dB
Lower exposure action value – 80dB
L108 - Controlling noise at work
COSHH 2002 as Amended L5
Legionella L8
Control of Lead at Work Regs 2002 L132
Control of Asbestos at Work Regs 2012
Control of Vibration at Work Regs 2005 (L140 HAVs)
Exposure action value of 2.5 m/s2 A(8) at which level employers should
introduce technical and organisational measures to reduce exposure.
Exposure limit value of 5.0 m/s2 A(8) which should not be exceeded