PSY230H1 Lecture Notes - Nuclear Weapons Testing, Plutonium, Salivary Gland
Chapter 12: Radiation and Health:
Smoking and driving are much more dangerous then exposures to low levels of
Types of radiation:
The electromagnetic spectrum is divided into three segments with visible light in
The other two segments are referred to as ionizing and nonionizing, based on their
biological activity and span a wide range of wave lengths.
The ionizing portion of the spectrum includes gamma rays and ultraviolet radiation.
Ionizing radiation is given off by decaying radioisotopes or radionuclide, typically
as beta particles or gamma rays.
Ionizing radiation is genotoxic and can act as a carcinogens
Nonionizing radiation is not energetic enough to disrupt electrons and hence is not
thought to be genotoxic.
The radio-frequency range of the nonionizing-radation spectrum can heat tissues.
Melatonin hypothesis postulates a reduction in the pineal gland’s nocturnal
production of melatonin, which in turn could increase levels of estrogens and
prolactin, reduce melatonin inhibitory effect on cell proliferation and increase
susceptibility to DNA damage through a reduction in melatonin antioxidant action.
Health effects of ionizing Radiation:
What we know about radiation health effects comes principally from three sources:
1) long-term follow up of the survivors of the atomic bombings in Hiroshima and
Nagasaki, which involved an acute exposure to high radiation close at high dose
rates. 2) Studies of patients receiving diagnostic and therapeutic radiation, also high
dose by typically intermittent. 3) Studies of occupational cohorts, typically with
Ionizing radiation produces two kinds of cell injury, one immediate and other
delayed. High level doseses- a term loosely designating exposures over 100rm—
inevitably produces the kind of immediate, direct effects seen in the Chernobyl
firegithers: skin burns, hair loss, bone marrow destruction and damage to the
Scientists believe that such stochastic or probabilistic effects of radiation are also
directly related to the radiation dose and that they can occur at any dose, no matter
how small. This is called the linear, no-threshold hypothesis; it means that all
exposure to radiation presents some risk to human health.
BEIR-V raised the estimate of cancer risk associated with low-level radiational
exposure from estimates in earlier BEIR reports.
Less radiation had produced more cancer.
Atomic Bomb Survivors:
Higher risks have also been seen for leukaemia and thyroid cancer following
radiation exposures in childhood compared to exposures at later ages.
Epidemiologist Problem with Cancer Studies:
Epidemiologist investigates the cause of disease in groups rather than in individual
Low-level radiation is associated with increased cancer incidence, but association is
Scientists test association for strength, consistency, specificity, and plausibility
before making judgements about causation.
Fallout from Nuclear testing:
Exposure led to increase in thyroid cancer and benign thyroid nodules.
Disturbances in growth were also noted among exposed children.
Accidents at nuclear plants:
To estimate exposure, we used a mathematical dispersion model, which accounted
for modifying factors such as weather, wine, and terrain and which was validated
against readings from offsite dosimeters.
A special health hazard associated with nuclear power is the production of vast
inventories of radioactive wastes.
These wastes consist of uranium mill tailings, transuranic wastes (defined as
materials containing more then 100 nanocuries of transuranic material power gram
of waste), high level of wastes (which cludes spent fuel rodes and the slidges left
behind when spent fuel rods are reprocessed to extract plutonium, and low level
wastes many include a wide range of materials many of which are intently
Low-level wastes have been stored at a number of waste dumps.
One unique aspect of the danger associated with radioactive wastes derives not only
from the extreme toxicity of these materials but also from the great longitivity of
many of their isotopes.
Radon represents over half of all the ionizing radiation exposures of the general
Radon is gas can accumulate to high levels in enclosed spaces, such as underground
mines and the basements of residences.
The decay products of radon, called radon progeny, attach to dust particles. Once
inhaled, further decay occurs and can expose the lining of the lung to alpha
radiation, potentially initiating a carcinogenic process.
Although inhalation of radon gas from stone and soil is the main course of
exposure, off-gasing of radon from water can also add to the cumulative radon
Health effects of nonionizing Radiation:
Electromagnetic radiation does not produce ionization products, and energy transfer
to human tissue during exposure is low.
There is an increase in childhood cancer with residential proximity to power lines.
No association of cancer rates with either the direct measurements of magnetic field
or with surrogate measures.
If EMFs are carcinogenic, it is a promoter not an initiator.
Radiation exposures from the use of electric blankets—particularly during
pregnancy have been assessed in relation to a number of adverse reproductive
endpoints, as well as childhood cancer.
Exposure to magnetic field was causally linked to risk of leukemia or brain cancer.
No studies have been found to support the hypothesis of an association between use
of mobile phones and tumours of the brain, salivary gland, leukemia, or other
The most frequent radiation exposure is to radon.