Understanding Radiation

Luiza Gharibyan

Yerevan State Medical University

Ionizing radiation includes electromagnetic radiation with enough energy to break chemical bonds through nonthermal process (X and gamma photons or “rays”); and high-speed subatomic particles.

Ionizing radiation can be produced by electrical devices such as X-ray machines. Ionizing radiation also can arise from nuclear processes such as radioactivity (alpha, beta, and gamma emissions commonly are associated with radioactivity), nuclear fission and fusion and

from outer space.

Nonionizing radiation is electromagnetic radiation with insufficient energy to break chemical bonds through nonthermal processes. Examples of nonionizing radiation include radio and TV transmissions; microwaves and radar; and infared, visible and ultraviolet lihjt (including

that produced by lasers).

Nonionizing radiation is also known as electromagnetic field. The ancients knew of lodestones, static electricity and lightning. They knew that lightning, the thunderbolt of the gods, could kill or injure. But it was not until the 19 century that scientists began to understand electric and magnetic fields and their extend

in space.

X-rays were discovered in 1895 by Rontgen, radioactivity and its associated radiations in 1896 by Becquerel. Soon afterward the harmful effects of ionizing radiation became known and controversies

about its risk benefits began.

Radioactive atoms undergo spontaneous nucleartransformations and release excess energy in the form of ionizing radiation. The body attempts to repair the damage, but sometimes the damage is too severe or widespread, or mistakes are made in the natural

repair process.

The most common forms of ionizing radiation are alpha and beta particles, or gamma and X-rays.

What kinds of health effects occur from exposure to radionuclides? In general, the amount and duration of radiation exposure affects the severity or type of health effect.

There are two broad categories of health effects: stochastic and non-stochastic

Stochastic Health Effects

Stochastic effects are associated with long-term, low-level (chronic) exposure to radiation. ("Stochastic" refers to the likelihood that something will happen.)

Increased levels of exposure make these health effects more likely to occur, but do not influence the type or severity of the effect.

Cancer is considered by most people the primary health effect from radiation exposure.

Radiation can cause changes in DNA, the "blueprints" that ensure cell repair and replacement produces a perfect copy of the original cell. Changes in DNA are called mutations.

Non-Stochastic Health Effects

Is any amount of radiation safe?

How do we know radiation causes cancer?

Aren’t children more sensitive to radiation than

adults?

Effects of Radiation Type and Exposure Pathway.

Non-Radiation Health Effects of Radionuclides.

Do chemical properties of radionuclides contribute to

radiation health effects?

Radioactive iodine concentrates in the thyroid.

Calcium, strontium-90, and radium-226 have similar

chemical properties.

Estimating Health Effects

What is the cancer risk from radiation? How does it compare to the risk of cancer from other sources?

What are the risks of other long-term health effects? Other than cancer, the most prominent long-term health effects are teratogenic and genetic mutations. 

Genetic effects

Protecting Against ExposureWhat limits does EPA set on exposure to radiation?

How does EPA protect against radionuclides that

are also toxic?