lec 5 Vibration, Pressure and Ionizing Radiation

Vibration, Pressure and Ionizing Radiation
By
Dr. Ashraf Hussain
MBChB, PhD/Com. Med
Vibration
a. Whole body vibration
caused by poorly designed or poorly maintained vehicles, platforms or machinery as
in uneven roads, Fork lift and Quarrying.
Acute effects cause discomfort: nausea, vomiting, loss of balance may appear after
work.
Fatigue, dizziness, headache, sleep disorders also might develop.
Oscillation of organs due to vibration has an effect on body functioning.
Vibra on around 1 Hz affects the sense of balance.
Vibra on in the range of 3-6 Hz affects organs in the thorax and abdomen.
Vibra on in the range of 20-30 Hz targets the head, neck and shoulders.
Whole body vibration of higher frequencies can lead to gynaecological complaints
among women
Long term exposure to WBV may lead to:
Lower back pain (Degeneration of the intervertebral discs is more common, more
severe and its onset is earlier in workers exposed to whole-body vibration than in
the non-exposed population, ligaments loosened from shaking), also it can cause:
Motion sickness
Bone damage
The longer a worker is exposed to WBV, the greater the risk of health effects and
muscular disorders.
PDF created with pdfFactory Pro trial version www.pdffactory.com
Prevention:
i _ Education of workers about vibration transmission and to take breaks , posture
changes , reduce exposure time
ii_ preference for buying machines and vehicles designed to reduce transmission of
vibration
iii_ suspension seats
2- Local body vibration
****hand-arm vibration
Occurs in the arms , hands and fingers when working with a vibration tool or
machinery as in drill hammering
It affects tendons, muscles, bones and joints, and can affect the nervous system
Vibration induced health conditions progress slowly.
In the beginning it usually starts as a pain.
As the vibration exposure continues, the pain may develop into a condition called
Hand Arm Vibration Syndrom (HAVS)
The development of HAVS is gradual and increases in severity over time.
It may take a few months to several years for the symptoms of HAVS to become
clinically noticeable
Symptoms include:
attacks of whitening (blanching) of one or more fingers when exposed to cold
tingling and loss of sensation in the fingers
loss of light touch
pain and cold sensations between periodic white finger attacks, especially upon cold
exposure
loss of grip strength
bone cysts in fingers and wrists
PDF created with pdfFactory Pro trial version www.pdffactory.com
Risk factors
1. Frequency and acceleration of Vibration.
2. Duration of exposure and years of involvement in Vibration work.
3. Protective practices and equipment including gloves, boots, work-rest
periods.
4. Skill, operator control and grip forces - how hard the worker grasps the
vibrating equipment.
5. Position of the hand and arm relative to the body.
6. Medical history of injury to fingers and hands, particularly frostbite.
7. Smoking and use of drugs and exposure to other physical and chemical
agents.
8. State of tool maintenance
9. Hardness of the material being contacted by the machine (for example metal
in grinding and chipping)
Prevention
1- Use of anti vibration gloves
Reduce the vibration from handheld machines
2. Take regular breaks of at least 10 minutes away from the tool
3. Use tools correctly and use the right tool for the job.
4. Avoid use of excessive grip, nor to use a tool for longer than necessary.
Pressure
Decompression sickness is a disease results from exposure to high or
low atmospheric pressure.
Also called Bends or Caisson disease.
It occurs in scuba divers, tunnel workers or high altitude or aerospace events when
dissolved gases (mainly nitrogen) come out of solution in bubbles.
Under increased atmospheric pressure (such as that experienced by deep-sea divers
or tunnel workers), fat-soluble nitrogen gas dissolves in the body fluids and tissues.
During decompression the gas comes out of solution and, if decompression is rapid,
it forms bubbles in the tissues.
PDF created with pdfFactory Pro trial version www.pdffactory.com
Similarly, the gases in solution in the body tissues under normal atmospheric
pressure form bubbles when pressure rapidly decreases, as when aviators in
unpressurized aircraft ascend to high altitudes too quickly.
affect any body area including joints, lung, heart, skin and brain.
Bubbles cause pains in the limbs (known as the bends) and mild cutaneous
symptoms.
Also breathlessness, angina, headache, dizziness, collapse, coma, and in some cases
death.
Emergency treatment of decompression sickness consists of rapid recompression in
a compression chamber with gradual subsequent decompression.
The condition can be prevented by allowing sufficient decompression time for the
excess nitrogen gas to be expelled naturally.
Ionizing Radiation
Ionising radiation
Ionising radiation can be described as the transfer of energy in the form of particles
(such as alpha and beta particles) or electromagnetic waves (such as X-rays and
gamma rays) capable of producing ions directly or indirectly.
Ionising radiation can occur naturally (e.g. from the radioactive decay of natural
radioactive substances such as radon gas and its decay products) or it can be
generated artificially (e.g. man-made radioactive substances or the operation of
certain electrical equipment, such as X-ray sets, which emit ionising radiations).
The effect on body tissues will depend on:
1. the type of radiation,
2. the dose and duration of exposure
3. whether the source is internal or external to the body.
There are three types of nuclear radiation: alpha, beta and gamma.
Alpha is the least penetrating, while gamma is the most penetrating.
Nonetheless, all three are ionising radiation: they can knock electrons out of atoms
and form charged particles.
PDF created with pdfFactory Pro trial version www.pdffactory.com
Types of Ionising Radiation
Alpha radiation represents the nucleus of helium atoms that are often called alpha
particles (?).
They are positively charged particles
These particles are big.
If an alpha source is outside the body, the alpha radiation will not cause any harm to
the human body since radiation will not pentrate the skin.
Types of Ionising Radiation: cont.
Beta radiation consists of small, high-energy, and high-speed electrons emitted by
certain types of radioactive nuclei.
They are actually an ejected electron.
If beta radiation reaches the human body, it can cause skin burn or blindness if the
eyes are exposed.
Internal organs will not be damaged (unless ?-radiation emitters are deposited
internally e.g. by ingestion) since beta radiation stops in 1 to 2 cm of ssue.
Types of Ionising Radiation: cont.
Gamma particles have no mass and no electric charge called photons.
They are the same particles as those that represent visible light but have much
higher energy.
Since they have no mass and no electric charge, it is difficult to stop.
X-rays also ionise atoms. They behave the same as gamma rays, except that their
energy is lower
Sources
Ionising radiation sources are used in medicine (for diagnosis and treatment in
oncology
Industry (for measurement and other purposes as well as for producing energy)
Research and teaching.
PDF created with pdfFactory Pro trial version www.pdffactory.com
Effects
Ionising radiation ionises atoms in all matter including the human body.
Cause cell damage and death.
OR radiation damages cell DNA
If the damaged cell survives, it can mutate and reproduce and cancer can occur.
Dose Limit
The most important dose limit is the annual dose limit of 20 mSv. It means that a
worker can receive a dose of 20 mSv per year from ionising sources they are working
with.
Natural background radiation due to radioactivity in soil, water, air, food, on average
the annual dose is around 2 mSv
So a worker using ionising radiation sources can receive ten times the dose of the
natural background at the workplace.
Pregnant and Nursing Mothers
For women, there are special limitations during pregnancy or breast feeding.
Pregnant woman can work in a radiation area but the dose to the foetus must be
below 1 mSv during pregnancy.
Breast feeding woman can work in a radiation area when only exposure to external
radiation is possible (X-ray devices or encapsulated radioactivity sources). In that
case, the limit of 20 mSv per year applies.
A breastfeeding mother is not allowed to work in an area where contamination and
intake of radioactivity is possible.
Protection
To keep radiation doses low, three methods are used: time, distance and shielding.
The dose is proportional to the time of exposure The more time one is exposed to
ionising radiation, the larger the dose that will be received and the more harmful the
radiation will be.
The radiation reduces with the distance from the source.
Protection: Cont.
PDF created with pdfFactory Pro trial version www.pdffactory.com
Shielding: There are activities that require workers to be close to the source and in a
high radiation field.
In that case, we minimise the doses by using shielding and protective clothing.
When working with X-ray devices in medicine, the most common personal protective
clothing is lead aprons. Led aprons made of 0.25 mm thick lead a enuate X-rays
more than 100 times.
In some cases when eyes are exposed, spectacles made of lead glass are used as
protection. Also, lead gloves can be used, however such gloves are quite thick and
not appropriate for detailed work.
PDF created with pdfFactory Pro trial version www.pdffactory.com