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 reasons). Red and white blood forming cells primarily located in the bone marrow. Lens of eye. Most internal organs such as the lung and lower intestine. 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: 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

Deterministic Radiation Effect Thresholds HEALTH EFFECTORGANDOSE (rem) Temporary sterility Testis15 Nausea GI35 Blood cell depression Bone marrow50 Reversible skin effects Skin200 Permanent sterility Ovaries Vomiting GI300 Temporary hair loss Skin Permanent sterility Testis350 Skin erythema Skin

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) rad 25 rad can depress blood count Gastointestinal ( rad) CNS (5000 rad) Locally  Erythema rad  Epilation  Delay/suppress menstruation 10 rad  Temporary sterility (both sexes) 200 rad  LONG TERM  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)  AnorexiaNausea  FatigueVomiting  EpilationDiarrhea  HemorrhageMortality

ARS  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 Absorbed dose (Rads) Effect 10,000 1, Death in a few hours Death within days Death within weeks LD 50/30 Probable recovery No observable effect Blood changes definite 1st blood change obs

Carcinogenesis  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 bone

Biologic effects of radiation on pregnant women  Spontaneous abortions during first 2 weeks of pregnancy-- 25 RAD or higher  2 nd week to 10 th week – major organogenesis – IF radiation is high enough can cause congenital abnormalities  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.)

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 Occupational exposure limit

dose a worker can receive in one year is limited: Total effective dose equivalent (TEDE) to whole body:  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 cm 2 ) 50 rem per year  Sum of deep-dose and committed dose equivalents to all other tissues and extremities: 50 rem (500mSv)  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.

MEDICAL EXAMINATIONS  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.

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 Survey Meter Pocket Dosimeter Radiation Alarm Radiation Badge Radiation Safety

Monitoring  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

Dosimetry  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 level  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

DOSIMETRY  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 TLD’s.

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 radiation  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 heated  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

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.