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Radiation Occupational exposures and protection


Radiation Occupational exposures and protection A. H. Mehrparvar, MD Occupational Medicine department Yazd University of Medical Sciences Occupational exposure and ... – PowerPoint PPT presentation

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Title: Radiation Occupational exposures and protection

Radiation Occupational exposures and protection
  • A. H. Mehrparvar, MD
  • Occupational Medicine department
  • Yazd University of Medical Sciences

  • Occupational exposure and
  • health effects

Why is radiation harmful?
  • Radiation deposits small amounts of energy, or
    "heat" in matter
  • Alters atoms
  • Damage to cells DNA causes mutations and cancer
  • Much of the resulting damage is from the
    production of ions

Bioeffects of radiation
  • Stochastic (Probabilistic)
  • versus
  • Non-stochastic (Deterministic)
  • Acute
  • versus
  • Chronic

Biological effects of radiation
  • Cell sensitivity to radiation is determined by
    two primary factors
  • Level of cell activity
  • Rate of cell division

  • approximate order from most to least
    radiosensitive organ
  • Fetal tissue
  • Reproductive cells (for long term genetic
  • Red and white blood forming cells primarily
    located in the bone marrow.
  • Lens of eye.
  • Most internal organs such as the lung and lower
  • Skin of the whole body, thyroid, nerve, etc.
  • Extremities such as hands and feet.

Radiation Bioeffects
  • Deterministic (non-stochastic)
  • Severity increases with radiation dose
  • Threshold 50-100 rem
  • Dose and dose rate dependent
  • Examples
  • Cataract induction
  • Epilation (hair loss)
  • Erythema (skin reddening)
  • Blood changes

Radiation Bioeffects
  • Stochastic (probabilistic)
  • Probability of occurrence increases with
    radiation dose
  • Threshold 10 rem, but regulatory models assume
    no threshold (ALARA!)
  • Examples
  • Cancer induction
  • Genetic mutations
  • Developmental abnormalities

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Stochastic Radiation Effects
  • Cancer
  • incidence begins to increase in populations
    acutely exposed to more than 10 rem
  • continues to increase with increasing dose
  • Genetic Effects
  • more than 100 rem of low-dose rate, low LET
    radiation needed to double the incidence of
    genetic defects in humans
  • no human hereditary effects seen at gonadal doses
    less than 50 rem
  • In Utero Irradiation
  • developmental and other effects begin to increase
    at 10 rem

Somatic effects
  • Short Term
  • ARS
  • Hemopoietic (bone marrow syndrome) 100-1000 rad
  • 25 rad can depress blood count
  • Gastointestinal (600-1000 rad)
  • CNS (5000 rad)
  • Locally
  • Erythema 300-1000 rad
  • Epilation
  • Delay/suppress menstruation 10 rad
  • Temporary sterility (both sexes) 200 rad
  • Cataract
  • Reduced fertility
  • Fibrosis
  • Organ atrophy
  • Sterility
  • Cancer
  • Embryologic effects

Acute exposure
  • Large doses received in a short time period
  • accidents
  • nuclear war
  • cancer therapy
  • Short term effects (acute radiation syndrome 150
    to 350 rad whole body)
  • Anorexia Nausea
  • Fatigue Vomiting
  • Epilation Diarrhea
  • Hemorrhage Mortality

  • Prodromal phase
  • Nausea, vomiting, fever, cramp,
  • Latent phase
  • No symptoms
  • Illness phase
  • Depends on the radiation dose (hematologic, GI,
    respiratory, cerebral)
  • Recovery or death

Acute whole body exposure
  • The cancer that can be ALMOST classified as
    radiounique is leukemia
  • Has a short latency period
  • Has a linear nonthreshold dose response curve
  • Epidemiologic studies indicate a higher
    incidences in leukemia after large exposures
  • Radium watch dial workers bone ca
  • Uranium miners lung ca
  • Early medical radiation workers leukemia
  • Thymus gland treatment thyroid ca
  • Atomic bomb survivors leukemia/breast, lung and

Biologic effects of radiation on pregnant women
  • Spontaneous abortions during first 2 weeks of
    pregnancy-- 25 RAD or higher
  • 2nd week to 10th week major organogenesis IF
    radiation is high enough can cause congenital
  • Principle response after that may be malignant
    disease in childhood

Tissue sensitivity
Very High White blood cells (bone marrow) Intestinal epithelium Reproductive cells
High Optic lens epithelium Esophageal epithelium Mucous membranes
Medium Brain Glial cells Lung, kidney, liver, thyroid, pancreatic epithelium
Low Mature red blood cells Muscle cells Mature bone and cartilage
Loss of Life Expectancy
Radiation workers
  • Any person working with radioactive substances
  • two groups of radiation workers
  • Group A worker can receive more than 30 of the
    annual dose equivalent limit, must undergo
    routine medical examinations and have personal
    monitoring devices.
  • Group B radiation worker will not receive more
    than 30 of the annual dose equivalent limit, do
    not undergo medical examinations or have to carry
    monitoring devices.

Occupational exposure limits
Occupational exposure limits (cont.)
Occupational exposure limit
  • For shielding design purposes
  • Maximum allowable exposure 1 mSv/yr (0.02
    mSv/week) for nonoccupational personnel (members
    of public and non-radiation workers)
  • 5 mSv/yr (0.1 mSv/week) for controlled areas
    where occupational workers are allowed

  • dose a worker can receive in one year is limited
  • Total effective dose equivalent (TEDE) to whole
  • 5 rem (50 mSv) per year
  • 2 rem (20 mSv) per year averaged over 5 years
  • Lens of eye 15 rem (150 mSv)

  • Skin (1 cm2)
  • 50 rem per year
  • Sum of deep-dose and committed dose equivalents
    to all other tissues and extremities 50 rem
  • Pregnant women
  • 0.05 rem per month

  • Action Level of 1.0 mSv/y. If the exposure of the
    worker exceeds or may exceed an annual dose of
    1.0 mSv, employers must
  • provide and ensure the proper use by workers of
    an acceptable dosimeter or radiation badge.
  • perform radiation surveys to measure radiation
    levels in work areas
  • provide written instructions on safe and proper
    procedures and practices related to the use of
    the radiation-emitting device.

  • For type A radiation workers
  • Pre-employment
  • Periodic (usually annual)
  • CBC
  • Urinalysis
  • A complete examination of the hands, eyes and
    fields of vision.
  • Female radiation workers must inform the
    radiation protection officer immediately if they
    should fall pregnant.

Radiation Safety
Technicians who work with radiation must wear
monitoring devices that keep track of their total
absorption, and alert them when they are in a
high radiation area
Radiation Alarm
Radiation Badge
Survey Meter
Pocket Dosimeter
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  • Personal devices
  • 1. Film badges
  • 2. Nuclear emulsion monitors
  • 3. Thermoluminisence monitors (TLD)
  • 4. Ionization dosimeter
  • 5. Scintillation counter
  • Environmental devices
  • 1. Geiger-Muller counter
  • 2. Ionization chamber
  • 3. Scintillation detector

  • Required for personnel expected to get more than
    10 of the occupational dose.
  • The dosimetry report lists the shallow
    equivalent dose, corresponding to the skin dose,
    and the deep equivalent dose, corresponding to
    penetrating radiation
  • Generally placed at waist level or shirt-pocket
  • For fluoroscopy, placed at collar level outside
    the lead apron to measure radiation dose to
    thyroid and lens of eye
  • Pregnant radiation workers typically wear a
    second badge at waist level (behind the lead
    apron, if used) to assess the fetal dose

  • Type A radiation workers must all have personal
    monitoring devices.
  • These must be worn at all times when working with
    radioactivity or when working in a room where
    radioactivity is stored.
  • TLD-meters are worn for a period of 28 days.
  • In some cases, type B radiation workers will be
    asked to get personal monitoring devices or TLDs.

Film badges
  • A pack containing film is placed inside a special
    plastic film holder Using metal filters
    (typically lead, copper, and aluminum)
  • The relative optical densities of the film
    underneath the filters can be used to identify
    the general energy range of the radiation and
    allow for the conversion of the film dose to
    tissue dose
  • Open window (J) where film is not covered by a
    filter or plastic and is used to detect medium
    and high-energy beta radiation
  • Most film badges can record doses from about 100
    mGy to 15 Gy for photons and from 500 mGy to 10
    Gy for beta radiation
  • Excessive moisture or heat will damage film
    inside badge

Thermoluminescent Dosimeters (TLD)
  • TLD is a dosimeter in which consists of a
    scintillator in which electrons become trapped in
    excited states after interactions with ionizing
  • If the scintillator is later heated, the
    electrons can then fall to their ground state
    with the emission of light
  • Thermoluminescent means emitting light when
  • The amount of light emitted by the TLD is
    proportional to the amount of energy absorbed by
    the TLD
  • After TLD has been read, it may be baked in an
    oven and reused

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How to Correctly Wear Your Badge
  • Whole body badges should be worn between the neck
    and the waist.
  • Ring badges can be worn on any finger.  The badge
    should be on the inside of your palm, facing the
    radioactive work.

Radiation Dosimetry
Ring badge
Radiation Detection Instruments
  • A radiation field or contamination can be
    detected by a number of instruments.
  • Geiger Counter ("GM detector")  very sensitive
    instrument used to detect surface contamination
  • Ionization Chamber  used to measure
    higher-exposure fields (milliroentgens per hour
    and above).  Can be used as fixed-position "area
    monitors", or portable survey instruments.
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