156 Ecology and Applied Environmental Science
It should be noted that despite their low penetrating power alpha particles are particularly dangerous due to their great ionising action, when
the radioactive materials emitting them enter the body with food, water
or respiration. In general, the danger of exposure to radioactive radiation
depends mainly on:
• The type of radioactive radiation
• The number of fissile nuclei of the radioactive substance
• The half-life
• The distance and the involvement of other materials between the
source and the receiver of the radioactive radiation
• The presence of the radioactive substance inside or outside the organism
• The biological half-life (if the radioactive substance has entered
the organism)
The effects of ionising radiation on human health are divided into
short-term effects caused by large doses received in a short time and
long-term effects caused by small doses. The short-term effects of a single
dose, like the long-term effects of small doses, vary from one person to
another. Typical short-term effects of large doses (average value for the whole
human body) are the following: 25 rem is the lowest dose where abnormalities, such as a low white blood cell count, can be discovered through an
ordinary blood test. A normal count is restored after a few days. Doses
of 100–200 rem have the noticeable effects of vomiting, fatigue, temporary sterility in men and miscarriage in pregnant women. Some deaths are
observed at doses of around 200 rem, within about 2 months of exposure.
Susceptibility to infections increases rapidly at doses higher than 200 rem.
Doses of around 400 rem are fatal for 50% of the population, within about
a month. Doses higher than 1000 rem generally cause death within a week.
Humans, like all other organisms, have always received ionising radiation from various natural sources. One category is cosmic radiation,
which is mainly galactic or solar in origin. Cosmic radiation occurs on
the Earth’s surface mainly as secondary radiation caused by the action
of cosmic radiation on the nuclei of atmospheric hydrogen and oxygen.
The load on the human body is on average 45 mrem/year at sea level and
around double that at an elevation of 3000 meters. A second category of
natural radiation is that emitted by the various radioactive isotopes in
the Earth’s crust, which varies widely from one place to another, with a
probable average value of 40 mrem/year. In some places of the planet the
load is many times higher. A third natural source is the radioactive isotope
Potassium-40 in the living tissues of the human body; it entails a load of
around 20 mrem/year. With the addition of the other natural radiations,
it has been estimated that total natural load in the United States ranges
between around 100 and 250 mrem/year, with an average value of around
It should be noted that despite their low penetrating power alpha particles are particularly dangerous due to their great ionising action, when
the radioactive materials emitting them enter the body with food, water
or respiration. In general, the danger of exposure to radioactive radiation
depends mainly on:
• The type of radioactive radiation
• The number of fissile nuclei of the radioactive substance
• The half-life
• The distance and the involvement of other materials between the
source and the receiver of the radioactive radiation
• The presence of the radioactive substance inside or outside the organism
• The biological half-life (if the radioactive substance has entered
the organism)
The effects of ionising radiation on human health are divided into
short-term effects caused by large doses received in a short time and
long-term effects caused by small doses. The short-term effects of a single
dose, like the long-term effects of small doses, vary from one person to
another. Typical short-term effects of large doses (average value for the whole
human body) are the following: 25 rem is the lowest dose where abnormalities, such as a low white blood cell count, can be discovered through an
ordinary blood test. A normal count is restored after a few days. Doses
of 100–200 rem have the noticeable effects of vomiting, fatigue, temporary sterility in men and miscarriage in pregnant women. Some deaths are
observed at doses of around 200 rem, within about 2 months of exposure.
Susceptibility to infections increases rapidly at doses higher than 200 rem.
Doses of around 400 rem are fatal for 50% of the population, within about
a month. Doses higher than 1000 rem generally cause death within a week.
Humans, like all other organisms, have always received ionising radiation from various natural sources. One category is cosmic radiation,
which is mainly galactic or solar in origin. Cosmic radiation occurs on
the Earth’s surface mainly as secondary radiation caused by the action
of cosmic radiation on the nuclei of atmospheric hydrogen and oxygen.
The load on the human body is on average 45 mrem/year at sea level and
around double that at an elevation of 3000 meters. A second category of
natural radiation is that emitted by the various radioactive isotopes in
the Earth’s crust, which varies widely from one place to another, with a
probable average value of 40 mrem/year. In some places of the planet the
load is many times higher. A third natural source is the radioactive isotope
Potassium-40 in the living tissues of the human body; it entails a load of
around 20 mrem/year. With the addition of the other natural radiations,
it has been estimated that total natural load in the United States ranges
between around 100 and 250 mrem/year, with an average value of around