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Safety at NUS


Non-ionizing radiation: radiant energy is NOT capable of stripping electrons ... Curie (Ci) International units SI -Gray (Gy) -Sievert (Sv) -Becquerel (Bq) ... – PowerPoint PPT presentation

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Title: Safety at NUS

Safety at NUS
Radiation Hazards
What is radiation?
  • Matter is composed of atoms. Some atoms are
  • unstable. As these atoms change to become more
  • stable, they give off invisible energy waves or
  • particles called radiation.
  • 2 types
  • -Non-ionizing
  • -Ionizing

What is radiation? (contd)
  • Non-ionizing radiation radiant energy is NOT
    capable of stripping electrons from atoms
  • - E.g. infrared, visible light
  • Ionizing radiation radiant energy is capable of
    removing electrons from their atomic structures
    (approx. gt10-12eV)
  • - E.g. x-rays, gamma rays

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Ionizing Radiation
  • Two fundamental types
  • -Particulate radiation in the form of
    particles, e.g. alpha, beta, neutrons
  • -Wave radiation in the form of
    electromagnetic wave, e.g. Gamma rays, X-rays

Types of Radiation
  • Alpha
  • Identical to a helium nucleus (2 p and 2 n in one
    tightly bound particle)
  • Beta
  • Energetic electron ejected from the nucleus of an
  • One neutron is converted to one proton and one

Types of Radiation (contd)
  • Gamma
  • Electromagnetic radiation from nucleus
  • X-ray
  • Electromagnetic radiation from orbital electrons
  • Neutrons

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Sources of radiation
  • Naturally-occurring radiation accounts for
    approx. 80 of our exposure. Most of our exposure
    is to indoor radon, followed by radiation from
    outer space and from the earths crust.
  • Since the discovery of radiation, people have
    benefited from the use of radiation in medicine
    and industry. Man-made sources of radiation
    account for about 20 of our total exposure to

Sealed vs Unsealed sources
Sealed source Radioactive materials sealed inside
metal/plastic. Most sealed sources can be handled
without concern that the radioactive material
will be dispersed onto hands or clothing Unsealed
source Unsealed sources are usually liquids that
are applied directly and not encapsulated during
use. The contents of these unsealed sources are
readily accessible to the user. Most come in
liquid form, with potential for spills, splashes,
aerosolization, and vaporization. Stock vials may
not provide adequate shielding.
Diff. between radiation radioactivity
  • Radiation is the emission of energy from a
    source, either by particles or photons.
  • There is a difference between Radiation and
  • Radioactivity is radiation that is from a change
    in the nucleus of an atom, other forms of
    radiation are usually the emission of energy from
    a change in the electron orbits.

  • The rate of radioactive decays is described by
    the nuclear disintegrations per unit time
  • Amount of radioactive in Becquerels (Bq)
  • 1 Bq 1 disintegration/second (SI unit)
  • 1 Ci 3.7X1010 disintegrations/second (Older

Half-Life (T1/2)
  • Time taken for the activity of a sample to halve
    as a result of radioactive decay
  • A A0/2n
  • Ao Original Activity
  • A Activity at time t
  • N is the number of half lives expired in time, t
  • Activity of a vial of Tc-99m was 80 GBq, T1/2 for
    Tc-99m is 6 hours
  • After 6 hours, one half life, A 40GBq
  • After 12 hours, two half life, A20GBq
  • After 24 hours, four half lifes, A5GBq

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Measurements of Radiation
  • Common units or special units (US)
  • -Roentgen (R)
  • -RAD (Radiation Absorbed Dose)
  • -REM (Roentgen Equivalent Man)
  • -Curie (Ci)
  • International units SI
  • -Gray (Gy)
  • -Sievert (Sv)
  • -Becquerel (Bq)

Two areas where units are used
  • Units of activity
  • -Quantity amount of radiation emitted from a
    radiation source
  • Units of exposure (dose)
  • -Quantity amount of radiation absorbed or
    deposited in a material

  • Quantity of a radioactive material present at a
    given time
  • -It is the number of disintegrations or
    transformations of a given quantity of material
    in a given period of time
  • Units Ci 3.7X1010 disintegration per second
  • 1 Bq 1 disintegration/sec
  • 3.7X1010Bq1 Ci
  • 1 Ci2.22X1012 disintegration/min (dpm)
    amount of radioactivity in 1 gm of Ra 226

  • T½ Measure of radioactive decay
  • Half-life
  • -Physical
  • -Biological
  • -Effective
  • Examples, Carbon-11 (20min), Sulfur-35 (88 days),
    Calcium-45 (165 days), Tritium (3H) (12.46 yrs),
    Carbon-14 (5730 yrs), Uranium-238 (4.5X109 yrs)

Examples of Half-life
  • If ..was worth only 36 billion dollars, and if
    he were to lose ½ his money each year, how long
    before he is only a millionaire? (t½ 1 yr)

  • Units (US)
  • -Roentgen (R), RAD radiation absorbed dose,
    REM radiation equivalent man
  • -1 R1 RAD1 REM if radiation weighting factor1
  • Units (SI)
  • -1 Gy 1 joule/kg 100 rads
  • -1 Si 100 rem

  • Photon flux related to amount of energy
    transferred to unit mass of air
  • Dose unit
  • -Roentgen (US)
  • -No. of unit C/kggtCoulomb
  • -Quantity of gamma or x-rays producing ions
    carrying a charge of 2.58X10-4C/kg air

Absorbed dose
  • Charge per unit mass
  • -Any type of radiation
  • -Any type of material
  • Dose units
  • - rad62.4X106 MeV/g
  • - Gy100 rads

Dose calculations
  • DLa/d2 where
  • Dabsorbed dose in rad/hr
  • Lgamma ray constant (from table)
  • aactivity in millicuries
  • ddistance
  • Calculate the absorbed dose in mrad per hr at 150
    cm from a 250 millicurie Cesium-137 source
  • - DLa/d23.3X250/150236.7 mrad/hr at 150 cm

Equivalent dose
  • Absorbed dose multiplied by the radiation
    weighting factor (RWF) or quality factor (QF)
  • RWF is the biological effectiveness of a
    radiation type
  • Accounts for the type of radiation and its
    biological effects in human
  • Units-rem

Calculating rem
  • Remrad X QF where
  • QF 1 for x-rays, gamma rays and beta rays
  • 3 for neutrons (fast)
  • 10 for neutrons (slow)
  • 20 for alphas
  • A source of radium-226 produces 0.15 mrad per hr
    in a worker. Calculate rem dose in an 8-hr shift.
  • Rem rad X QF0.15X20 (alpha)X824 rem/8-hr shift

  • Gy and rad measure Absorbed Dose
  • Si and rem Equivalent Dose
  • Bq and Ci Radioactivity

Ionising radiation measurement
  • Monitoring instruments
  • -A large variety available
  • -None universally applicable
  • -Selection of appropriate detector is

Monitoring methods
  • Film badges
  • -Worn on the outside of clothes
  • -Consists of small piece of photographic film
  • Thermoluminescence detectors
  • -Used in finger dosimeters
  • -Amount of light given off is related to the
    absorbed amount of radiation
  • Pocket dosimeter
  • -Direct reading portable unit
  • -Allows individual to determine radiation dose
    as they are working

Ionising chambers
  • Measure gamma, x-, beta-, alpha radiation
  • Very useful and popular
  • Convenient and accurate

Geiger Mueller Counter
  • Used for beta, gamma, x-ray radiation measurement
  • Capable of detecting very small amount of
  • Uses an ionising chamber but filled with a
    special gas and greater voltage is supplied

How Radiation Harm You?
  • Ionizing properties of radiation
  • Lead to molecular changes and form chemical
    species that are harmful to the chromosome
  • Harm can come from changes in construction and
    function of the cells.
  • Radiation can cause
  • Early death of the cell or prevention or delay
    of cell division
  • Permanent modification which is passed on to
    daughter cells

Biological Effects
Chemical bond break
Biological effects of different radiation
Deterministic Effects
  • Below a certain dose, the proportion of cell
    damage from the exposure is not sufficient to
    affect the function of the organ or body and no
    observable effects as a whole
  • Severity increases with dose
  • Eg. 1 Gy can cause nausea and vomiting
  • 5 10 Sv is sufficient to cause Bone Marrow

Stochastic Effects
  • Probability of an effect occurring increase with
  • Effects include cancer induction and hereditary
    effects in future generations
  • This means that even low dose can potentially
    have ill effects its a statistical probability
  • Zero threshold concept

Working Safely with Radiation
  • ALARA principle
  • Time, distance and shielding
  • Safe work practices

  • Exposures are kept As Low Achievable As
    Reasonably Achievable / Allowable
  • Formal ALARA program
  • Keeping all doses, releases, contamination and
    other risks low
  • Achieve 10 of applicable legal limits

Methods of Achieving ALARA
  • Time
  • Distance
  • Shielding

Basic Radiation Protection
  • Justification
  • Benefit must outweigh risk
  • Limitation
  • Dose limits must not be exceeded
  • Optimization
  • ALARA, social and economic factors considered

External radiation dosage
  • - Explanation
  • The dose accumulated by a person working in a
  • Dose Dose rate X Time

External radiation dosage
  • Calculation
  • Dose limit is 400 uSv
  • Dose rate is 20 uSv h-1
  • Dose dose rate X time
  • 400 20 X t
  • t 20 hours

Time Example
  • Annual dose limit for rad worker is 20mSv/year.
    Assume 50 weeks/year, how much is the hourly
    exposure? Ans 0.01 mSv/hour
  • How many hours can a worker spend in a week an
    area with a dose rate of 20 microSv/hour
  • 20 mSv 20 mSv/year 1 year
  • 20 mSv 20 µ Sv/hour time
  • Time 1000 hour
  • Hours/week 1000/50 20 hours

Time Example
  • If rad worker spends 35 hours per week in the
    area, what is the max allowable dose rate per
  • 0.01 mSv/hr40 hr/week 0.4 mSv/week
  • 0.4 mSv/week 1week/35 hr 0.114 mSv/hr
  • 11.4 microSv/hr

Time Example
  • Dose limit for individual member of the public is
    1mSv/year. What is the max dose rate in the area
    which could be continuously occupied by the
    members of the public? 0.11 micro Sv/hour
  • 1mSv/year 1 year/365 days 1 day/24 hour

  • Inverse square law
  • D1r12 D2r22
  • D Dose rate at distance, r
  • R Distance from the radiation source
  • Dose rate at 2m from a gamma source is 500 micro
    Sv/hour. Distance that will give dose rate of 10
    micro Sv/hour? 14.1m

Safe Work Practices (contd)
  • Rehearse operations without radioactive material
  • Inform others in the area of the use of
    radioactive material
  • Minimize the time spent near radioactive
  • Use remote handling tools like tweezers or
    forceps to handle stock vials.

Safe Work Practices (contd)
  • Do not handle the stock vial for a extended
    period of time
  • Use appropriate shielding
  • Minimize the amount of material handled. Only use
    what you need, put the rest away

Safe Work Practices (contd)
  • Make sure the material is properly contained.
  • Drip trays lined with absorbent material
  • Stabilize glassware to prevent it from tipping
  • Dry powder use a glove bag or box
  • Transport items in shielded secondary containers.

Safe Work Practices (contd)
  • Do not contaminate writing materials
  • Segregate items used with radioactive materials
    with those used with non-radioactive materials.
  • Protective clothing shall be worn when handling
    contamination may be expected.

Safe Work Practices (contd)
  • Personal with tears/breaks in skin should wear
    waterproof tape to seal such breaks or not
    manipulate radioactive material
  • Personnel shall monitor themselves (and their
    work surfaces) for contamination after each use
    of radioactive material.

Safe Work Practices (contd)
  • Eating, drinking, smoking and mouth pipetting is
  • Items that are routinely contaminated
    (centrifuges, water baths, tongs, etc) should be
    clearly labeled.
  • Hands should be monitored and washed before
    leaving the lab.

Waste Handling Process
  • Store in a safe location with proper shielding
    until the waste has decayed to a low level
  • Must be lt 1 microSv/hr or 0.1 mrem/hr
  • Proper shielding
  • Beta emitters Perspex enclosure
  • Gamma emitters Lead shielding

Waste Handling Process (contd)
  • Place in secondary containers
  • Proper labeling and designate the storage area
    with clear signages

Radiation Waste Disposal in NUS
  • Permitted types
  • C14 (Licensing exemption limit (LEL) 100microCi)
  • Tritium (1000microCi)
  • I-125 (10microCi)
  • P-32 (10microCi)
  • S-35 (10microCi)

Radiation Waste Disposal in NUS
  • If mixtures of radioisotopes
  • Sum of An/Mn is less than the LEL of the most
    active radionuclides
  • An Activity of nuclide n,
  • Mn LEL of nuclide n

Radiation Waste Disposal in NUS
  • Place waste inside Red Bag (can be obtained from
    Ms. Lisa Lui _at_ oshsec)
  • Tape opening with Red Tapes (From Lisa)
  • Fill up Yellow label and paste onto the Bag
  • Fill up Form RAD01-01
  • Low level biological-incineration
  • Chemical Biological

Radiation Waste Disposal in NUS
  • Liquid Radiation Waste
  • Absorbed into vermiculite at point of use and
    dispose off as solid waste
  • All radioactive bags must be kept in secure and
    safe area
  • OSHE will organize central collection every 4 to
    6 months depending on level at the departments
  • Cost of disposal is borne by OSHE but this may be
    charged to individual departments in the near

Radiation Protection Act (Cap 262)
  • Regulated by Centre for Radiation Protection
    (CRP) under Health Sciences Authority
  • Subsidiary legislations
  • - Radiation Protection (Non-Ionising)
  • - Radiation Protection (Ionising) Regulations
  • - Radiation Protection (Transport of Radioactive
    Materials) Regulations

Radioactive Protection Act
  • CRP has Director appointed by the minister
  • Radiation Advisory Committee- to advise Minister
  • Act focuses on Use, Manufacture, Sale of and
    Dealing with Radioactive Materials and
    Irradiating Apparatus
  • You require to have a license
  • Duties of licensees
  • Disposal of radioactive waste
  • Powers of Director Authorised Officers

Radiation Protection (Ionising) Regulations
  • Exemptions-details
  • Licenses
  • Age limit
  • Condition for engaging in radiation work
  • Arrangements for protection of workers
  • Medical and radiological supervision
  • Labeling of irriadiating apparatus and
    radioactive materials
  • Storage

What Is NIR?
  • Energy waves of oscillating electric and magnetic
    fields traveling at the speed of light
  • Energy levels not great enough to cause the
    ionization of atoms
  • Includes spectrum of UV, IR, microwave (MW),
    radio frequency (RF), extremely low frequency
    (ELF) and visible light

Why Is It Dangerous?
  • Wide range of occupational settings
  • Can pose a considerable health risk to exposed
    workers if not properly uncontrolled

Examples of Non-Ionizing Radiation
  • Extremely Low Frequency (ELF)
  • Radiofrequency (RF) / Microwave (MW)
  • Laser Hazards
  • Infrared Radiation (IR)
  • Visible Light Radiation
  • Ultraviolet Radiation (UV)

  • Refers to an electromagnetic field having a
    frequency much lower than the frequencies of
    signals typically used in communications (From 1
    Hz to 300 Hz).
  • Includes alternating current (AC) fields
  • Most common ELF field is 60 Hz produced by power
    lines, electrical wiring, electrical equipment
  • Two forms Static and ELF fields

Health Hazards
  • Potentially significant due to widespread use of
    electrical power at 50 60 Hz
  • Much concern over consequence of long-term
    exposure to these fields
  • One area is in computing applications where
    cathode-ray tube (CRT) displays are used

Health Hazards
  • ELF fields known to interact with tissues by
    inducing electric fields and currents
  • Research has suggested possible carcinogenic,
    reproductive  and neurological effects
  • Other health effects could include
    cardiovascular, brain and behavior, hormonal and
    immune system changes

Safety and Precautions
  • Inform about possible hazards
  • Increase the worker's distance from the source
    (radiation fields often drop off dramatically
    within about 1m of the source)
  • Stand back from electrical equipment, and work
    station CRT should be at least 0.5m away from

Safety and Precautions
  • Use low-radiation designs wherever possible (for
    the layout of office power supplies, for example)
  • Reduce exposure times. No action should be taken
    to reduce exposure if it increases the risk of a
    known safety or health hazard such as

RF and MW Radiation
  • Electromagnetic radiation
  • RF - any frequency within the electromagnetic
    spectrum associated with radio wave propagation
  • Microwaves are a specific category of radio waves
    that can be defined as radiofrequency energy
    where frequencies range from several hundred MHz
    to several GHz.
  • From 3 kHz - 300 GHz (MW range from several
    hundred MHz to several GHz)

Sources of RF and MW
  • Traffic radar devices
  • Heaters and sealers
  • Wireless communications/cellular phones
  • Radio transmission
  • Radio antennas / masts
  • Magnetic Resonance Imaging (MRI)

Health Hazards
  • RF and MW will damage tissue through heating at
    high intensities
  • MW radiation is absorbed near the skin
  • RF radiation may be absorbed throughout the body
  • Parts of body most prone are the eyes and testes
    due to the relative lack of blood flow to
    dissipate the heat

Health Hazards
  • Levels encountered by the general public are far
    below levels deemed significant
  • Workers working near transmission towers /
    antennas are exposed to large amounts of radiation

Safety and Precautions
  • Engineering Controls
  • Sources of radiation should be properly shielded
  • Devices which can produce acute thermal injuries
    (e.g., industrial MW ovens) should have
    interlocked doors
  • Devices which produce high levels of stray RF
    radiation (e.g., induction heaters and dielectric
    heaters) should be operated remotely whenever

Safety and Precautions
  • Administrative Controls
  • Exposure should not exceed the recommended
    exposure limits
  • Areas where worker exposure is suspected to
    exceed the recommended limits should be surveyed
    to determine the exposure levels
  • Needless exposure should be avoided
  • Exposure times should be kept as short as
    reasonably possible

Safety and Precautions
  • Administrative Controls
  • Potentially hazardous devices should be
    appropriately labeled
  • Areas of excessive exposure around them clearly
  • Notices with warnings and the necessary
    precautions should be posted
  • Electrically-activated explosive devices should
    not be placed near sources of RF/MW radiation

Safety and Precautions
  • Administrative Controls
  • RF/MW devices should not be used in flammable or
    explosive atmospheres
  • Equipment sensitive to RF/MW should not be
    installed near sources of radiation
  • Maintenance of devices used to produce RF/MW
    radiation should be done by qualified personnel.
    The equipment should be turned off whenever

Safety and Precautions
  • Controlling RF Shocks and Burns
  • Metallic structures producing contact shocks
    should be electrically grounded and/or insulated
  • Insulating platforms or shoes can be used to
    reduce energy absorption and currents to ground
  • Workers should wear insulating gloves

Safety and Precautions
  • First Aid
  • Remove worker from exposure area to a cool
    environment and provide cool drinking water
  • Apply cold water or ice to burned areas
  • Seek immediate medical attention
  • Severe MW or RF overexposure may damage internal
    tissues without apparent skin injury, so a
    follow-up physical examination is advisable

  • Stands for Light Amplification by Stimulated
    Emission of Radiation
  • Produces an intense, highly directional beam of
    light is emitted
  • Monochromatic one specific wavelength
  • Coherent - each photon moves in step with the

Types of Lasers
  • Commonly designated by the type of lasing
    material employed
  • Solid-state lasers - lasing material distributed
    in a solid matrix
  • Gas lasers use gases like helium and
  • Excimer lasers - (the name is derived from the
    terms excited and dimers) uses reactive gases,
    such as chlorine and fluorine, mixed with inert
    gases such as argon, krypton or xenon

Types of Lasers
  • Commonly designated by the type of lasing
    material employed
  • Dye lasers - complex organic dyes, such as
    rhodamine 6G, in liquid solution or suspension as
    lasing media
  • Semiconductor lasers - sometimes called diode
    lasers, are not solid-state lasers. Generally
    very small and use low power.

Laser Classes
  • Class I
  • Laser systems that do not pose a hazard under
    normal conditions
  • Examples include enclosed / interlocked lasers or
    lasers with low power output
  • No warning label is required

Laser Classes
  • Class II
  • Low power visible lasers or laser systems
  • Not usually hazardous as natural human body
    reflexes reduces this
  • Hazardous if viewed for prolonged periods of time
    (like many conventional light sources)
  • If manufactured after 1976, will usually have a
    sign Caution Laser Radiation Do not stare
    into beam
  • Sign must be clearly visible

Laser Classes
  • Class IIIA
  • Lasers of laser systems that do not usually pose
    a hazard if viewed momentarily with the unaided
  • Hazardous if viewed using collective optics

Laser Classes
  • Class IIIA
  • Clearly visible sign with words Caution Laser
    Radiation Do not stare into beam or view
    directly with optical instruments
  • Eye protection should be worn

Laser Classes
  • Class IIIB
  • Lasers or laser systems that are hazardous if
    viewed directly, including viewing of reflections
    from smooth surfaces (diffused reflections are
    not hazardous)
  • A clearly visible sign Danger Laser Radiation
    Avoid Direct Exposure to Beam must be in place
  • Eye protection must be worn

Laser Classes
  • Class IIIB
  • A clearly visible sign Danger Laser Radiation
    Avoid Direct Exposure to Beam must be in place
  • Eye protection must be worn

Laser Classes
  • Class IV
  • Lasers or laser systems that produce a hazard not
    only from direct viewing and reflections, but
    also from diffused reflections
  • May produce fire and skin hazards
  • A clearly visible which reads Danger Laser
    Radiation Avoid Eye or Skin Exposure to Direct
    or Scattered Radiation

Laser Classes
  • Class IV
  • Capable of causing serious eye injury
  • Should be enclosed if possible and operated

Health Hazards
  • Common cause of laser-induced tissue damage is
    thermal in nature
  • Tissue proteins are denatured / destroyed due to
    the temperature rise following absorption of
    laser energy
  • Exposure can result in damage to the eye and skin
  • Human eye is most vulnerable to injury than human

Associated Hazards
  • Hazards that are not associated with the beam
  • Electrical Lethal electrical hazards from high
    power lasers.
  • Chemical Eximer, dye and chemical lasers, and
    welding or cutting fumes
  • Non-Beam Optical UV, Infra Red, or Visible Light

Safety and Precautions
  • Special Safety and Control Measures for
  • Medical Applications
  • Special training requirements
  • Special equipment testing requirements
  • Special medical surveillance requirements
  • Laser treatment controlled areas
  • Patient eye protections
  • Evaluation of fiber delivery systems
  • Ventilation systems

Safety and Precautions
  • Other Special Control Measures
  • Laser demonstrations involving the general public
    or exposure of the general public to any laser
    beam hazards.
  • Laser installation procedures
  • Federal, state, or local requirements
  • Personal protective equipment
  • Warning signs, labels, and signal words in
    accordance with local standards.
  • Electrical installations in compliance with local

Radiation Protection (Non-Ionising) Regulations
  • Controlled apparatus
  • (a) Ultraviolet sunlamps
  • (b) Microwave ovens
  • (c) Medical and industrial ultrasound apparatus
  • (d) Magnetic resonance imaging (MRI) apparatus
  • (e) Entertainment lasers
  • (f) High power lasers

Radiation Protection (Non-Ionising) Regulations
  • Licenses (4 types)
  • Age requirement 18 years and
  • Requirements for apparatus as mentioned
  • Requirements for labeling
  • Examples of label in laser apparatus
  • (warning signs) (transparencies)

Biological Hazards
What are biohazards?
  • Any material of biological origin capable of
    causing harm to human and its environment
  • Examples
  • Viruses
  • Bacteria
  • Fungi
  • Human source material
  • Animal source material, etc.

Biosafety Protection Principles
  • Containment
  • Safe methods for managing infectious materials in
    the laboratory to reduce or eliminate exposure of
    laboratory workers, other persons, and the
    outside environment.
  • Include three elements
  • 1. Laboratory practice and technique
  • 2. Safety equipment (Primary containment)
  • 3. Facility design (laboratory design)
  • (Secondary containment)

Safety Equipment
  • Primary Barriers
  • Includes BSC, Centrifuge cups, Personal
    protective equipment, enclosed containers, etc.
  • Will only be effective if they are used properly

Facility Design and Construction
  • Labs must be designed and constructed based on
    the usage requirement
  • Many design and construction factors
    ventilation, plumbing, access, work flow,
    construction material, treatment system, etc.
  • Design and construction are not the most
    important factor but still an essential factor in

Risk Assessment for Work withBiohazardous Agents
or Materials
  • What is known about the agent or material?
  • Is it associated with infections, toxicity, or
  • What role does physical environment and work
    activity play in assessing risk?
  • Are preventive measures available?
  • Do barriers, personal protective equipment (PPE),
    pre- or post-exposure prophylaxis or
    immunizations offer protection?

Biological Agent Characteristics
  • Pathogenicity
  • Virulence - degree of pathogenicity
  • Host range
  • Communicability

Method of Transmission
  • Direct Contact
  • Direct transmission to receptive portal of entry
  • Indirect Contact
  • Vehicle-borne such as inanimate materials or
    objects (fomites)
  • Vector-borne (arthropods)
  • Airborne
  • Dissemination of microbial aerosols to a suitable
    portal of entry

Routes of Transmission
  • Ingestion
  • Inhalation
  • Absorption
  • Penetration of skin or membranes

Other Risk Assessment Criteria
  • Concentration of material to be used
  • Quantity to be used
  • Potential for aerosol generation
  • Infectious dose
  • Stability in the environment
  • Ability to avoid host defence
  • Type of work

Other Risk Assessment Criteria
  • Toxicity (microbial toxins)
  • Enzymes (microbes produce coagulase, hemolysins,
  • Allergenicity (agent or by-products animal
    dander, urine)
  • Genetic modifications
  • Biological/chemical/radiological mixtures and

Risk Group Classification (WHO)
  • Pathogenicity
  • Infectious dose
  • Mode of transmission
  • Host range
  • Availability of effective preventive measures and

Risk Group 1
  • Severity of Disease
  • Unlikely to cause human or animal disease
  • Host Range
  • Human (healthy adult) and animals
  • Individual Risk
  • Low
  • Community Risk
  • Low

Risk Group 2
  • Severity of Disease
  • Can cause disease, unlikely to be serious
  • Effective treatment and preventive measures are
  • Host Range
  • Human (healthy adult) and animals
  • Individual Risk
  • Moderate (potential hazard)
  • Community Risk
  • Low

Risk Group 3
  • Severity of Disease
  • Can cause serious disease
  • Does not ordinarily spread from one person to
  • Other criteria effective treatment and
    preventive measures are usually available
  • Exposure route inhalation (often)

Risk Group 3
  • Host Range
  • Human (healthy adult) and animals
  • Individual Risk
  • High
  • Community Risk
  • Low

Risk Group 4
  • Severity of Disease
  • Likely to cause serious or lethal disease
  • Can be readily transmitted from one individual to
  • Effective treatment and preventive measures are
    not usually available
  • Transmission direct, indirect, inhalation

Risk Group 4
  • Host Range
  • Human (healthy adult) and animals
  • Individual Risk
  • High
  • Community Risk
  • High

Biosafety Levels
  • VERY Important Biosafety Levels and Risk Groups
    are not always the same!!!
  • Biosafety level Containment level
  • Specifies
  • Facility
  • Safety equipment
  • Microbiological and special practices

Biosafety Levels (BSLs)Classification
  • Biosafety level(s) refer to those conditions
    under which the biological agents can be safely
    handled ordinarily.
  • Four laboratory biosafety levels (BSLs) are
    defined by CDC/NIH biosafety guidelines.
  • Principal Investigator (PI) is specifically and
    primarily responsible for assessing the risks and
    appropriately applying the recommended biosafety

Biosafety Level 1
  • Agent
  • Well-characterized agents not known to cause
    disease in healthy adults
  • Escherichia coli K12, Bacillus subtilis
  • Basic lab facility work on the open bench
  • Use standard microbiological practices
  • No containment equipment is required

Biosafety Level 2
  • Agent
  • Agents of moderate potential hazard to personnel
    and the environment
  • Staphylococcus aureus, Hepatitis B virus,
    Salmonella species
  • Basic lab facility, plus autoclave is available
  • Use standard microbiological practices plus limit
    the access
  • Containment equipment is used when aerosols are
    generated or concentrated preps and large volumes
    are handled

Biosafety Level 3
  • Agent
  • Indigenous or exotic agents with potential for
    aerosol transmission that may cause serious or
    potentially lethal disease
  • Mycobacterium tuberculosis, Coxiella burnetii,
    St. Louis encephalitis virus
  • Containment facility
  • Use standard microbiological practices plus
    controlled access
  • Containment equipment, such as Class I or II
    biological safety cabinets (BSCs) are required
    for manipulations of viable material and
    additional PPE is required

Biosafety Level 4
  • Agent
  • Dangerous and exotic agents that pose high risk
    of aerosol transmitted LAI and life threatening
    disease, or related agents with unknown risk of
  • Marburg, Congo-Crimean hemorrhagic fever

Biosafety Level 4
  • Maximum containment facility
  • Standard microbiological practices plus clothing
    change, showers, and decontamination of all
    materials on exit from the lab
  • Containment equipment, such as Class III BSCs or
    Class I or II BSCs in combination with one-piece
    positive pressure suits ventilated by a
    life-support system protected in conjunction by
    HEPA filtration

Disinfection Procedures
  • Why disinfect?
  • to get rid of unwanted pathogenic microorganisms
  • To eliminate - or at least reduce - exposure risk
  • medical waste treatment
  • spill cleanup
  • minimization of nosocomial infections
  • routine surface decontamination
  • To eliminate contamination risk
  • preparation of microbiological media supplies
  • preparation of pharmaceutical production supplies
    and equipment
  • preparation of food (surface sanitization)
  • preparation of work area for cleanliness-critical

Some key disinfection terms
  • sterilization - act or process, physical or
    chemical, that destroys or eliminates all forms
    of life, especially microorganisms
  • disinfectant - an agent, usually chemical, that
    inactivates viruses or kills vegetative microbes
    but not necessarily resistant forms such as
  • antiseptic - a substance that prevents or arrests
    the growth or action of microbes, either by
    inhibiting their activity or by destroying them
    (living tissue use)
  • decontamination - disinfection or sterilization
    of contaminated articles to make them suitable
    for use
  • sanitizer - an agent that reduces the numbers of
    vegetative bacteria only

Resistance to disinfectants
Classes of Disinfectant
  • Chlorine
  • Iodine
  • Alcohol
  • Phenolics
  • Quaternary Ammonium Compounds
  • Glutaraldehyde
  • Formaldehyde
  • Hydrogen Peroxide
  • Chlorhexidine

Transport and Storage
  • Transport pointers
  • Secondary container
  • Planning ahead
  • Spill control
  • Storage
  • Labeling
  • Proper record
  • Freezer management

Biological Waste Handling
  • Must have in place biological waste handling
    procedures in the lab
  • Mixed waste hierarchy

Waste Handling Pointers
  • Use proper sharps bins
  • Do not overfill 80 mark
  • Use yellow bag with biohazard symbol
  • Double bagged and seal securely
  • Use secondary containers