IONIZING RADIATION

….. a discussion of the health hazards associated with handling and use of

materials capable of producing ionization of matter.

Some basics of atomic theory…..• Protons - Atomic particle found in an atom’s nucleus possessing

a positive charge of +1• Electrons – Atomic particle possessing a negative charge (-1)• Neutrons – Atomic particle w/ no electric charge• Atomic weight – Sum of protons and neutrons in the nucleus of

an atom• Atomic number – The number of protons in the nucleus of an

atom• Isotopes – Nuclei of an element differing in atomic weight but

having the same atomic number (e.g., U-235 vs U-238)• Radioactivity – The emission of energy in the form of alpha-,

beta-, or gamma-radiation from then nucleus of an atom

Radiation…

• Radiation has no unique biological effects.

• Concept of “half-life”– Time it takes for a

radioisotope to lose half its strength

Where is data gathered?

• Early radiation workers• Medical personnel who routinely administer radiation for

diagnosis or therapy• Patients treated with radiation• Workers who painted dials with luminous paints containing

radium• Japanese atomic bomb survivors

Where does it come from?

• Natural, non man-made radiation accounts for more than half of the exposure we receive (rays from sun and stars, earthen materials, in food, etc.).

• The biggest man-made contribution to radiation exposure of individuals results from the medical and dental use of x-rays and of radioactive materials to diagnose and treat disease.

Ionizing vs Non-Ionizing

• Ionizing radiation *– Radiation capable of producing ions

– Comes from x-ray machines, nuclear reactors, and radioactive materials

• Non-Ionizing radiation– Comes from microwaves, sound waves, light, lasers,

radiofrequency, electromagnetic fields, etc.

Forms of Ionizing Radiation

• ALPHA– Travel only a short distance in air (~ 4” in air)– Stopped by dead skin, film of water, sheet of paper– Very hazardous when taken into the body– Avoid inhalation or ingestion

• BETA – Penetrate human body to depth of 0.1-o.5”– Can penetrate wood to about 1.5”– Stopped by 0.5” aluminum or Plexiglas

Forms of Ionizing Radiation (cont.)

• GAMMA– Deep penetrating

– Need steel, lead, etc. to shield

• X –Radiation– Commonly thought of as electromagnetic radiation

produced by an x-ray machine

– Penetration depends on wavelength and material being irradiated.

– Often use concrete to shield

Penetrating Abilities

• ALPHA - very limited ability; short range in air, stopped by skin

• BETA - function of originating energy; can penetrate skin

• GAMMA - highly penetrating; can reach all body organs

Specific Ionization

• ALPHA - large particle and short range --> high S.I.

• BETA - lower S.I.• GAMMA - the lowest

S.I. (ionization is a “secondary process” through electrons

What occupations are at risk?

• Healthcare/Medicine– Oncology

– Radiation therapy

– Dentistry

• Researchers

• Miners– Uranium, phosphate, etc.

• Nuclear power plant employees

Symptoms of Exposure

• High level doses of radiation (generally doses of more than 100 rads), if received all at once, cause short-term effects that appear within hours, days, or weeks. Known as acute radiation syndrome– Initial symptoms: nausea, vomiting, and malaise.– After latent period: infections, fever, hemorrhage, loss

of hair, diarrhea, loss of body fluid, CNS effects– >600 rads leads to death

• Low level doses – risk is proportional to dose, but disagreement or uncertainty about exact responses.

Adverse Effects

• Cancer• Birth defects• Cataracts• Shortening of lifespan• If reproductive organs

irradiated:– Genetic mutations may

occur in sperm or egg cells

Damage from Radiation

• When radiation strikes a cell– It may pass through the cell without doing any

damage– It may damage the cell, but the cell partially

repairs the damage– It may damage the cell so that the cell not only

fails to repair itself but reproduces in damaged form over a period of years

– It may kill the cell

Factors Determining Damage

• Amount of radiation absorbed/penetrating ability

• Amount of body area exposed

• Energy of the radiation

• Specific ionization associated with the radiation (how it damages/what it targets)

Significant Considerations

• If the radioactive source is outside the body, control strategies include 1) distance, 2) time, and 3) shielding.

• If the radioactive source is inside the body, hazard is function of radiation type, energy, half-lives, radiosensitivity of tissues, etc., and control strategies must include all we know about controlling hazards.

True or False?

• Man-made sources of radiation, such as atomic weapons and x-rays have caused new diseases never encountered by medical science.

True or False?

• You can reduce the amount of radiation to which you are naturally exposed by living in a house made of brick, rather than wood.