12.2 Biological Effect of Radiation
185
body by weak β-emitters or α-emitters are to the somatic tissues. However, sometimes radioactive isotopes may be taken inside the body through some cut in the body
etc., then the extent of damage will depend upon the nature of the isotopes. The effect
of these damages may be carried over to next generation, and are known as genetic
damage. Hence, the damages caused by the radiation may be classified as (i) external
exposure and (ii) internal exposure. We shall now discuss these two aspects, in the
next section.
12.3 External Exposure
The extent of external hazard depends on the type of radiation, because of their
difference in specific ionizing power and penetrating power. We have seen in the
previous chapters that X -rays and γ -rays have very high penetrating power, hence
can penetrate through the skin into the interior parts of the body or can come out of
the body without being absorbed. These properties have some advantages and some
disadvantages. If these radiations are not stopped by the human body, the chances of
causing ionization to the human cells are low, because most of them will come out
of the body before they have the chance to transfer their energy to the human cell.
However, if these radiations are stopped by hard tissue of the body like bones, then
the damage can be of large magnitude.
In the medical profession, this specific property of radiation has proved a very
useful tool to reveal much information about the human body like condition of bones,
obstructions created in some of veins etc. For this purpose, a specific part of the
human body is exposed with soft X -rays of low intensity by keeping an X -ray film
behind the body. The X -ray film after developing shows a white spot where X -rays
were obstructed by the human body. The examination of the X -ray film thus can give
lots of information, which are useful for medical diagnosis.
On the other hand, particulate radiations depending upon their energy (like energetic β-particles, being less penetrating than X -rays or γ -rays) can produce a greater
amount of external damage to human tissue, because these radiations can be stopped
by the skin or the mussels of human body. Weak β-particles or α-particles, can be
stopped by the skin and hence they can do almost no external damage to the body
except for the skin of the human body.
Neutrons are very hazardous because of their high penetrating power, and monitoring of neutrons is also difficult. In fact, neutrons are considered to be the most
hazardous of all types of radiations.
In a radiochemical laboratory, however, we are not likely to use large quantity
of γ -emitting isotopes and hence chances of encountering external damages due to
these radiations are very unlikely. However, if we are using the neutron sources or
γ -sources for carrying out some experiments, then one has to be extremely careful
185
body by weak β-emitters or α-emitters are to the somatic tissues. However, sometimes radioactive isotopes may be taken inside the body through some cut in the body
etc., then the extent of damage will depend upon the nature of the isotopes. The effect
of these damages may be carried over to next generation, and are known as genetic
damage. Hence, the damages caused by the radiation may be classified as (i) external
exposure and (ii) internal exposure. We shall now discuss these two aspects, in the
next section.
12.3 External Exposure
The extent of external hazard depends on the type of radiation, because of their
difference in specific ionizing power and penetrating power. We have seen in the
previous chapters that X -rays and γ -rays have very high penetrating power, hence
can penetrate through the skin into the interior parts of the body or can come out of
the body without being absorbed. These properties have some advantages and some
disadvantages. If these radiations are not stopped by the human body, the chances of
causing ionization to the human cells are low, because most of them will come out
of the body before they have the chance to transfer their energy to the human cell.
However, if these radiations are stopped by hard tissue of the body like bones, then
the damage can be of large magnitude.
In the medical profession, this specific property of radiation has proved a very
useful tool to reveal much information about the human body like condition of bones,
obstructions created in some of veins etc. For this purpose, a specific part of the
human body is exposed with soft X -rays of low intensity by keeping an X -ray film
behind the body. The X -ray film after developing shows a white spot where X -rays
were obstructed by the human body. The examination of the X -ray film thus can give
lots of information, which are useful for medical diagnosis.
On the other hand, particulate radiations depending upon their energy (like energetic β-particles, being less penetrating than X -rays or γ -rays) can produce a greater
amount of external damage to human tissue, because these radiations can be stopped
by the skin or the mussels of human body. Weak β-particles or α-particles, can be
stopped by the skin and hence they can do almost no external damage to the body
except for the skin of the human body.
Neutrons are very hazardous because of their high penetrating power, and monitoring of neutrons is also difficult. In fact, neutrons are considered to be the most
hazardous of all types of radiations.
In a radiochemical laboratory, however, we are not likely to use large quantity
of γ -emitting isotopes and hence chances of encountering external damages due to
these radiations are very unlikely. However, if we are using the neutron sources or
γ -sources for carrying out some experiments, then one has to be extremely careful