The effects of radioactivity on the body
Monday 18 July 2011
, Posted by crazy at 09:58
The effects of radioactivity on the body
The effects of radiation on the body vary greatly depending on the dose received, the exposure time and mode, and the type of radionuclide involved. The pathways are external irradiation or contamination. When the body is in the path of radiation, the person is irradiated. If the person touches, breathes or swallows aradioactive substance, he or she is contaminated
The ionization phenomenon
Alpha, beta, gamma and X radiation disrupts the structure of living matter. Atoms located in their path can loseone or more electrons. These atoms then transform into electrically charged “ions”, which will in turn disrupt the structure of the molecules or cells of which they are constituents.
This is why radioactive radiation is said to be “ionizing”. The ionization phenomenon is the main mechanism by which radioactivity acts on matter.
Radioactivity is detected and measured by highly accurate instruments (Geiger counters, ionization chambers,scintillators) and devices (photographic films)that function using radiation’s properties. Natural radioactivity has no detectable impact nor apparent health effects. The organism incorporates it like a natural component of the biological process
The health effects of radiation
Knowledge on the effects of radioactivity is derived fromanalysis of actual cases of persons exposed to irradiation
by accident or for medical reasons; from epidemiological
studies on highly exposed populations, such as survivors
of Hiroshima and Nagasaki; and from experimental
studies. These studies enabled the development of a
risk scale linked to radiation exposure.
• Early effects of ionizing radiation. Detectable only in the event of exposure to high doses of radiation above a given threshold (0.2 sievert), these effects vary according to the dose received, ranging from a temporary modification of the blood count without any clinical signs (around 0.3 sievert) to a lethal dose beyond therapy (above 15 sieverts).
• Delayed effects of ionizing radiation. Radiation acts on DNA molecules in particular and may result in delayed pathological effects such as cancer, leukemia or genetic alterations. These effects are random; in other words, they do not appear systematically. It is usually considered that the probability of their appearance is propor tional to the radiation dose received: the lower the dose, the lower the probability of cancer. With that as a basis, radiation protection authorities have, for precautionary reasons, set very low limits for exposure to artificial radioactivity: 1 millisievert per year for the public and 20 millisieverts per year for
nuclear workers. These limits are 1,000 and 50 times lower respectively than doses that cause the first detectable signs of an early pathology
TYPES OF RADIATION
Radionuclides emit radiation during the process of nuclear decay. There are very
different types of radiation, which are classified according to their power to penetrate
different types of radiation, which are classified according to their power to penetrate
Alpha rays (α) are low
penetration radiation.
They are produced when a positively
charged helium nucleus (2 protons and
2 neutrons) is expelled. Their range in
the air varies from 2.5 cm to 8.5 cm.
They can be stopped by a sheet of
paper or the outer layer of the skin.
penetration radiation.
They are produced when a positively
charged helium nucleus (2 protons and
2 neutrons) is expelled. Their range in
the air varies from 2.5 cm to 8.5 cm.
They can be stopped by a sheet of
paper or the outer layer of the skin.
Beta rays (β) penetratefurther.
They are produced when an electron is
expelled. Their range in the air is a few
meters. They can cross through the
surface layer of the skin. They can be
stopped by a sheet of aluminum foil or a
glass pane.
Gamma rays (γ) penetratedeeply.
They are produced when a photon is
expelled. They are electromagnetic
rays, like light or X-rays. They travel at
the speed of light. Very thick, dense
materials, such as concrete or lead, are
required to stop them.
