Health Impact of Ionizing Radiations

Health Impact of Ionizing Radiations

Introduction

• Radiation is an energetic physical agent that propagates through space, depositing energy on obstacles.

• It has many uses in industrial, scientific, and medical fields.

• It exposes living organisms to risks, which should not be ignored.

What is Ionizing Radiation (IR)?

• Energy emitted from a source is referred to as radiation.

• Examples include heat or light from the sun, microwaves from an oven, X-rays, and gamma rays.

• IR can remove electrons from atoms, ionizing them.

• It is a form of energy released by atoms and propagated by electromagnetic waves or particles.

Radionuclides

• Radionuclide/radioisotope/radioelement/radioactive isotope: a nuclide, an atom (element) with an unstable nucleus.

• Unstable elements that disintegrate and emit IR.

• All chemical elements can exist as radionuclides. Radioactive forms of elements (radioisotopes) are called radionuclides.

Ionizing Radiations

Directly Ionizing Radiation (Corpuscular)

• Arise from the decay of the nucleus of unstable atoms.

  • Alpha ($\alpha$): large size and weight, slowed down quickly in material, penetrate only a few microns.

  • Beta ($\beta$): electrons carrying either a negative or positive electric charge (positrons or e+).

  • Neutron: high penetration into matter, difficult to detect and dose.

Indirectly Ionizing Radiation (Electromagnetic)

• Act through charged particles that move when they interact with matter.

• They can go through significant thicknesses.

  • Electromagnetic R X-ray and gamma are similar in nature and properties but have a different origin:

    • Gamma R are emitted during radioactive decays: a nuclear origin.

    • X radiations are emitted when matter interacts with electrons.

How is Radioactivity Measured?

1. Activity (A) of a radioactive source:

   • Corresponds to the number of disintegrations per second (Becquerel (Bq)).

2. Absorbed dose (D):

   • The amount of energy imparted by the radiation to the material through which it passes, per unit mass.

   • Measured in Gray (Gy).

3. Equivalent dose (H):

   • (Sievert (Sv))

   • Measures the effect of radiation on a living organism.

4. Effective dose (H):

   • (Sievert (Sv))

   • For an equal dose, biological effects differ according to:

     • The nature of the radiation

     • The tissues exposed.

5. Dose rate (H):

   • The dose received per unit of time.

   • Expressed in Gy/s or Sv/s.

   • Measured with a dosimeter or dosimeter pen.

Sources of Exposure

Natural

• Cosmic:

  • From the galaxy or the sun

  • High radiation

  • Varies mainly with altitude

• Telluric:

  • Produced by persistent radioelements in the Earth's crust: uranium-238, thorium-232 and potassium-40

  • The dose from this natural exposure is estimated at 2.2 mSv/year

Artificial

• Public exposure: medical, industrial, domestic

• Professional exposure

Public Exposure (Artificial)

Medical Field

• Imaging has become increasingly used in screening and interventional procedures.

• Ranges from simplest (ultrasound guidance of punctures or drainage) to the most complicated (angioplasties, radio-surgical and radio-endoscopic operations…)

• Cardiology and orthopedics: scopy is important.

• Radiotherapy and nuclear medicine use much higher doses but on a limited number of patients.

Radioactive Fallout from Nuclear Tests

• The fallout from nuclear explosions in the open air reaches the population all over the globe:

  • Various radioelements

  • Carbon-14, iodine-131, caesium-137

  • Strontium-90 which follows the metabolism of calcium. Herbivores eat the contaminated grass and humans consume herbivores and ingest strontium-90 which attaches to bones (sarcoma, leucosis).

Other sources

• Industrial Exposures (Radiography, Gauge, Food & Drink).

• Domestic (objects made luminescent with tritium paints, some dental ceramics) contribute only a very small proportion of the exposure of the general population.

Professional Exposure

• Affects more than 150,000 workers.

• Mainly external exposure, more rarely internal when using unsealed sources.

• Occupationally exposed individuals include:

  • Medical field:

    • Cardiology and orthopedics: imaging, scopy - importance of monitoring of operators.

    • A study shows that orthopedic surgeons using fluoroscopy are exposed to doses between those of category A and category B (dose between 8 and 4 mSv concerning the operator).

    • Other medical professions (radiologist, radiotherapist, etc.), paramedics (radio tech, nurses, instrumentalists).

  • Workers in research centers using radioactive substances.

  • Agricultural workers for the study of metabolism, mutation provocation, animal marking.

  • Workers in the nuclear industry (N power plant, mines, etc.).

  • Workers in various industrial sectors using sealed and unsealed sources:

    • Industrial radiography (X-ray or gamma) makes it possible to identify defects and visualize objects without destroying materials. Examples of use: boilermaking, shipbuilding, construction of nuclear power plants, aeronautics, construction

    • Radiometric gauges (control of fill levels, measurement of fluid densities in pipes, measurement of thicknesses, etc.)

    • Industrial irradiation: sterilization of objects by gamma R: Medical-surgical equipment and disposable syringe Food Ingredients: Salmonella removal from Shrimp Irradiation of ethnology and archaeological works of art / elimination of germs during the restoration of works of art

    • Gas ionization: lightning rod, ion smoke detector

    • Material development: paint manufacturing, cement

Types of Exposure to IR

• Two types of exposure to IR are possible:

  • Irradiation: exposure resulting from sources located at a distance from the body.

  • Contamination:

    • External: if radioactive particles come into contact with the skin.

    • Internal: when radioactive elements have penetrated the body.

Irradiation

• Limited in time (possibility of stopping the device).

• Conditioned by space: irradiation decreases as a function of the square of the distance.

• Protection is possible (shielding, lead aprons).

Radioactive Contamination

• Results from: inhalation of radioactive dust or gas (paint from clock dials), skin contact or transcutaneous penetration.

• Once they have penetrated the body, radioactive elements will continue to emit IR.

Ways of Exposure to IR

• Total exposure: sum of external and internal exposure

• Overall exposure: the exposure of the whole body considered as homogeneous

• Partial exposure: exposure of a part of the body or one or more parts of the body, or one or more organs or tissues

Severity Factors

Biological Factors

• Volume of tissue affected: for the same doses, localized irradiation is much less serious than overall irradiation.

• Irradiated tissue: organs have very different radiosensitivities

LAWS OF BERGONIE AND TRIBONDEAU

The effect is more important when:

1. Mitotic activity is increased: seminal tissue, bone marrow

2. Karyokinetic development is long: skin, nails, hair

3. Morphology and function are not definitively fixed: embryonic dystrophy

• The more sensitive tissues are:

  • Hematopoietic organs,

  • Thymus, ovary, testis,

  • Papillae and hairs, mucous membranes,

  • Sweat and sebaceous glands,

  • Epidermis, bones and nerves.

Physical factors

• Amount of absorbed dose/Kg of tissue

• Modality of dose distribution over time

• Nature of radiation

Biological Effects of IR

Molecular effects

• RI Energy transfer

• Ionizing of molecules

• DNA damage

• Radiolysis of water: under the influence of IR, a water molecule breaks down into two highly reactive free radicals, causing damage to neighboring molecules.

• The effects on DNA are due to direct action on the molecule, or indirectly through radiolysis of water.

• The consequences of DNA damage: two main categories: cell death / mutations.

Cellular effects

• Cell death

• Mutations

• Mitoses

1. Cell death: For very high doses (hundreds of Gray), molecular lesions can lead to cell death. → deterministic effects

2. Mutations: Cells may retain their ability to divide but transmit the induced anomalies to their descendants. These mutations can lead to cancers if they affect somatic cells and hereditary anomalies if they affect germ cells. → random effects.

3. Mitoses: IR delays mitosis

Effects of IR on human body

Deterministic Effects - Overall external exposure

• Acute Radiation Syndromes

  • Observed in the case of whole-body exposure to radiation exceeding 1 Gy (1,000 mGy) at one time.

Deterministic Effects - Effects on Fetuses

• Pre-implantation period (0 to 2 weeks after conception): Miscarriage

• Organogenesis period (2 to 8 weeks after conception): Dysplasia (malformation)

• Early fetal period (8 to 15 weeks after conception): Mental retardation

• Late fetal period (15 weeks after conception to delivery)

• The threshold dose is 0.1 Gy or more.

Stochastic Effects

• Cancer and leukemia

• Hereditary effects

Types of Effects

• Consideration is to be given to whether any health effects arise after radiation exposure and what effects, if any, the amount of radiation, parts exposed to radiation (whole-body exposure or local exposure), and exposure modes (acute, chronic or fractionated exposure).

• Deterministic effects (with the threshold value)

  • Acute disorders

    • Symptoms appear within several weeks (Actively dividing cells are affected)

    • Fetal disorders

    • Acute radiation syndromes

    • Skin erythema

    • Hair loss

    • Sterility, etc

    • Embryo-fetal disorders

    • Mental retardation, etc.

    • Bone-marrow disorders

    • Gastrointestinal tract disorders

    • Central nervous system disorders

  • Late-onset disorders

    • Symptoms appear after the lapse of several months to several years or more

    • Hereditary effects

    • Increase in incidence of ordinary hereditary disorders

    • Cataract

    • Glaucoma

    • Leukemia

    • Cancer

• Stochastic effects (assuming that there is no threshold value)

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Effects of IR on human body

Deterministic Effects - Overall external exposure

• Acute Radiation Syndromes- Observed in the case of whole-body exposure to radiation exceeding 1 Gy (1,000 mGy) at one time.

Deterministic Effects - Effects on Fetuses

• Pre-implantation period (0 to 2 weeks after conception): Miscarriage

• Organogenesis period (2 to 8 weeks after conception): Dysplasia (malformation)

• Early fetal period (8 to 15 weeks after conception): Mental retardation

• Late fetal period (15 weeks after conception to delivery)

• The threshold dose is 0.1 Gy or more.

Stochastic Effects

• Cancer and leukemia

• Hereditary effects

Types of Effects

• Consideration is to be given to whether any health effects arise after radiation exposure and what effects, if any, the amount of radiation, parts exposed to radiation (whole-body exposure or local exposure), and exposure modes (acute, chronic or fractionated exposure).

• Deterministic effects (with the threshold value)- Acute disorders- Symptoms appear within several weeks (Actively dividing cells are affected)
  - Fetal disorders
  - Acute radiation syndromes
  - Skin erythema
  - Hair loss
  - Sterility, etc
  - Embryo-fetal disorders
  - Mental retardation, etc.
  - Bone-marrow disorders
  - Gastrointestinal tract disorders
  - Central nervous system disorders

  • Late-onset disorders- Symptoms appear after the lapse of several months to several years or more

    • Hereditary effects

    • Increase in incidence of ordinary hereditary disorders

    • Cataract

    • Glaucoma

    • Leukemia

    • Cancer

• Stochastic effects (assuming that there is no threshold value)