Ionising Radiation Hazard
What is ionising radiation?
The term ionising radiation is used to refer to radiation energetic enough to break molecular bonds and to detach electrons from atoms, thus creating ions and free radicals.
We have all evolved with a certain amount of 'natural background radiation' and this may even have beneficial effects upon human health. Sources include the ultraviolet radiation emitted by the sun, naturally occurring radon gas, the low level of radiation generated by rocks in the earth's crust and the constant shower of incoming cosmic ray particles.
Ionising radiation encompasses both the high energy sub-atomic particles produced as a result of decay of radioactive elements and short wavelength electromagnetic radiation. Each of these categories is addressed briefly below.
Ionising particles
The high energy particles emitted as a result of the decay of radioactive isotopes include alpha, beta and gamma particles.
Contamination of the areas surrounding the Chernobyl nuclear reactor disaster including Belarus, the Ukraine, Russia and Europe with radioactive caesium and strontium are a notable example of particulate ionising radiation.
The radioactive particles can be inhaled and are carried widely by the wind contaminating the soil. These are then absorbed by plants which are eaten by humans or consumed by animals thus creating milk and meat containing radioactive isotopes.
Radioactive strontium is very similar chemically to calcium and is incorporated into the bone and bone marrow of humans. The particles emitted as a result of radionuclide decay then damage the processes of blood production in the bone marrow causing leukaemia and of bone metabolism causing bone cancer.
The deliberate poisoning of the Russian dissident, Alexander Litvinenko, in London in November 2006 using radioactive polonium-210 which resulted in his grisly death is another example.
Electromagnetic radiation
The electromagnetic spectrum consists of light waves ranging in length from very short (gamma rays), through ultraviolet light, visible light and infrared light to very long (radio and television waves). The ultraviolet light, x-rays and gamma rays which have a shorter wavelength and higher frequency than visible light are ionising, whereas those with a longer wavelength and shorter frequency than visible light are non-ionising.
Much of the electromagnetic radiation which arrives on Earth from the Sun is in the form of ultraviolet light. We are afforded a lot of protection by the ozone layer and the Earth's upper atmosphere. For this reason background radiation is higher at altitude and we have greater exposure when flying as we lose a lot of the protection from the atmosphere.
The health effects of ionising radiation
Ionising radiation can have the following health outcomes in humans:
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The DNA of individual cells can be damaged leading to the development of leukaemia and other cancers most typically of the breast, lung and thyroid gland
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Free radicals are created in and around cells overwhelming the immune system and leading to organ damage and cellular dysfunction
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The development of opacity of the lens of the eye and of cataracts
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If a woman is pregnant the developing foetus can be damaged resulting in malformations, brain damage and even death
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Both men and women can be rendered infertile
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The sperm in men and the ovaries/ova in women can be damaged causing abnormalities such as Down's syndrome which will manifest in their offspring
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Endocrine organs can be rendered dysfunctional creating hormonal imbalances
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In the short term, exposed individuals may suffer with radiation sickness which includes nausea, vomiting and hair loss
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Radiation skin burns can appear up to several weeks after exposure
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The tissues most affected are those that are most metabolically active so that in addition to the effects on the gonads and hair follicles already mentioned, the immune system, bone marrow and intestine are particularly vulnerable and
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Last, but not least - death.
There is no lower safe level and the effects of ionising radiation are cumulative over a lifetime unless actively countered. Everyone is different and no two people will be affected by ionising radiation exposure in exactly the same way.
The health outcomes will depend upon nutritional status, the presence of other toxins and microbes, genetics, stress and the timing of exposure eg: whether the sperm or egg that is destined to become a future child is being produced at the time.
Diagnostic uses of ionising radiation
The field of radiology began with the discovery of x-rays by the German physicist Wilhelm Röntgen in 1895. Their diagnostic value is that whilst x-rays pass through soft tissues relatively unchanged, they are diffracted and absorbed by denser materials such as bone.
Since then, techniques including fluoroscopy where the operator can view an x-ray shadow on a TV screen and the use of x-ray techniques using contrast mediums like barium have been commonly used. Computer axial tomography (CAT) scans were introduced in the 1980s which take a number of 360 degree 'slices' using a beam which moves around the patient in a ring.
The Dual Energy Absorptiometry (DEXA) scan has been introduced more recently still to screen for changes in bone density thought to be associated with osteoporosis. Subjects are injected with a radioactive liquid prior to the scan which takes about half an hour and typically concentrates on the spine, heel, hip and forearm.
In fact, so popular have these diagnostic techniques become that approximately 10% of health expenditure in developed countries is currently spent on radiology.
This also means that the population is now being exposed to ever-increasing amounts of ionising radiation as a result of medical tests and procedures and this has become by far the largest man-made contribution to the radiation burden of the population.
Roni Caryn Rabin reported in the New York Times that recent studies indicate that the amount of radiation in the body of a typical American has increased 600% in the 25 years to 2006, with the majority of this increase being attributed to the introduction of diagnostic imaging procedures. Mathias Prokop too has estimated that since the 1980s, the use of computed tomography (CT) has doubled almost every 2 years.
Estimates vary, but between half the total dose of ionising radiation for US citizens is thought to be medical (JAMA. 2010; 304) and according to Professor R. Wootton, director of Medical Physics at Hammersmith Hospital, University of London 90% of the total radiation exposure of the population of developed countries is now medical in origin. CAT scans are thought to account for approximately 20% of total exposure.
Listed below are some natural, diagnostic and other procedures and their associated radiation exposure in millisieverts (mSv) which is a measure that attempts to reflect the biological effects of irradiation.
|
Radiation procedure* or source
|
Approximate effective dose |
Background radiation equivalent |
|
Background radiation
|
3 mSv |
1 year |
|
Airport backscatter scan
|
0.00004 mSv |
7 mins |
|
Flying at cruising altitude
|
5 mSv/hour |
50 hours/hour flight |
|
Dexascan (women)
|
0.001 mSv |
3 hours |
|
X-rays of whole mouth (dental)
|
0.05 mSv |
10 days |
|
Mammogram
|
0.4 mSv |
7 weeks |
|
X-ray of spine
|
1.5 mSv |
6 months |
|
CAT scan chest
|
7 mSv |
2 years |
|
X-ray of lower GI tract
|
8 mSv |
3 years |
|
CAT scan abdomen and pelvis
|
15 mSv |
5 years |
|
64 slice whole body CAT scan (women)
|
21 mSv |
8 years |
|
Exposure of survivors of the atomic bombs at Hiroshima and Nagasaki
|
Average: 5-20 mSv
Some doses: 50 mSv
|
7 - 17 years |
|
Maximum occupational exposure allowable
|
50 mSv/year |
17 years
|
* Doses are best estimates, but may vary greatly depending upon the age of equipment, the operator, the condition being screened for and other variables.
The problem with radiological scans
The US FDA has never approved CAT scans for screening either all or any part of the body in the absence of specific symptoms of disease. It states that there is no evidence to support the notion that whole-body CAT scans are effective in detecting any particular disease early enough for the disease to be ".. managed, treated, or cured and advantageously spare a person at least some of the detriment associated with serious illness or premature death".
Furthermore, no CAT scan manufacturer has ever submitted data to the FDA to support the safety and efficacy of screening claims for whole-body CAT scan screening.
In addition, the American College of Radiology, the American College of Cardiology/American Heart Association, the American Association of Physicists in Medicine, and the American Medical Association do not recommend CAT scans.
Many medical insurance companies also do not cover CAT scans for screening because the scans provide little additional information to that which can be gathered using the traditional methods of examination, blood tests and taking a medical history.
When it comes to the DEXA scan the fundamental premise that bone mineral density is related to bone strength may be erroneous. Of those who test positive for osteoporosis using the DEXA scan, only half will ever go on to suffer a bone fracture.
There are also many problems to do with the sensitivity of the DEXA scan, not least of which is that it has failed to detect one in six cases of known osteonecrosis, is very technique sensitive and the results are adversely affected by the presence of arthritis which commonly co-exists with osteoporosis.
The health risks associated with ionising radiation
Some of the studies examining the health risks posed by exposure to ionising radiation are outlined below.
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The World Health Organisation, the US Center for Disease Control and the US National Institute of Environmental Health Sciences have all classified x-rays as a carcinogen.
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The International Commission on Radiological Protection and US National Cancer Institute found that those with the most x-ray exposure had four times the risk of contracting multiple myeloma (R. Wootton, Radiation Protection of Patients).
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The risk of contracting cancer was found to increase by 40%, the risk of tumours of the nervous system by 50% and the risk of leukaemia by nearly 80% if the individual had been exposed to radiation in utero (Int. J Cancer 1990; 46).
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Professor John Gofman of the Department of Molecular and Cell Biology at the University of California says that the annual mammogram encouraged by some healthcare providers exposes individuals to the same cumulative dose as atomic bomb survivors and attributes between two-thirds and three-quarters of all breast cancers to medical irradiation.
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Generally, the use of CAT scans is estimated to directly cause between 1 and 2% of all future cancers in the United States (JAMA. 2010; 304)
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A committee convened by the US National Academy of Science recently concluded that the real risks posed by radiation may be four times higher than previously supposed.
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Finally, there is no evidence that CAT scans actually reduce illness, length of hospital stays or prevent death.
When you have any kind of radiation exposure, you are in effect being given a lottery ticket for cancer. According to one study reported in the Journal of the American Medical Association the chances of contracting a fatal cancer as a result of various radiological imaging procedures are as shown below (JAMA, July 2007).
|
|
|
Procedure
|
Risk of fatal cancer |
|
Chest x-ray
|
1 in 1,000,000 |
|
64-slice CAT scan
|
1 in 2,000 |
|
Woman aged 20 heart scan |
1 in 143
|
|
Woman aged 40 heart scan
|
1 in 284 |
|
Man aged 20 heart scan
|
1 in 686
|
|
Men aged 40 heart scan
|
1 in 1,007 |
|
|
Reducing medical ionising radiation exposure
The risks posed by exposure to ionising radiation could be greatly reduced by improving the quality of images and reducing the number of procedures unlikely to yield clinically useful results as the following indicates:
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In the UK, a working party jointly formed by the Royal College of Radiologists and the National Radiological Protection Board in 1990 concluded that one-fifth of x-rays were unnecessary or of such poor quality as to be diagnostically worthless.
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An Oxford University study published in The Lancet (2004; 363) estimates that unnecessary radiation from x-rays may cause 700 deaths from cancer a year in the UK and 5,700 in the US.
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In the USA, the Food and Drug Administration has determined that one-third of all medical radiation is unnecessary. The most common unnecessary x-rays were the 7 million x-rays taken each year of the chest, limbs and joints.
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Big variations between the practices in different countries also occur with doctors in the USA and France taking twice as many x-rays as in the UK to the extent that 70% of the population have at least one x-ray a year. In Canada, the figures are even higher, with nearly all the population having at least one x-ray every year.
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Different physicians too have widely differing rates of ordering x-rays which can be as much as 25-fold (BMJ 1991; 303).
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The UK National Radiological Protection Board (NRPB) has determined that the levels of radiation could easily be halved without any loss of diagnostic effectiveness.
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X-rays taken for back pain, skull x-rays taken for detecting brain haemorrhage(s) and chest x-rays for detecting tuberculosis have been determined to be useless by the World Health Organisation.
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Then there are wide variations in the interpretation of the radiological information gathered, with disagreements in up to half of all cases and significant errors in 40% of reports according to a study of Harvard radiologists (Radiology 1977; 123).
Therapeutic uses of ionising radiation
Radiotherapy uses the fact that cancerous cells which are growing and dividing rapidly are more sensitive to ionising radiation. External beams can be directed at the tumour in the hopes of killing it and the dose to adjacent tissues is ameliorated by lead shielding and also by rotating the radiation source.
Radioactively labelled substances are also be used to either diagnose tumours by monitoring the rate of uptake in the tissues or can be used to treat tumours, an example of which would be using radioactive iodine to both diagnose and treat thyroid gland tumours.
In some cases, malignant tumours are treated with brachytherapy, which involves the implanting radioactive metallic rods which then kill the tumour from within.
Other uses of ionising radiation
The new full body scanners being installed in airports, use a low energy beam which concentrates most of the radiation on the skin and then picks up the back-scatter to detect other materials such as metal and plastic. Whilst low doses of radiation are used, these may be 20 times higher than originally claimed according to Dr. David Brenner, head of Columbia University's center for radiological research.
Whilst low, the doses are concentrated on the skin and biochemist David Argard, of the University of California says that the doses delivered to the skin may be dangerously high. Some individuals may also be more susceptible to such ionising radiation for a variety of reasons.
Gamma radiation or high-energy beams of electrons are also being employed in the food industry to irradiate food to kill the microorganisms that cause spoilage. For the industry this offers several advantages including the fact that irradiated foods can last for weeks with little or no refrigeration, the use of chemical preservatives can be avoided and less labour is required to prepare, wrap and preserve foods.
Other sources of ionising radiation include smoke detectors, luminous clock and watch dials and television and computer monitors.
Final thoughts on radiological screening
Before the health dangers were fully realised, it was accepted practice just a few decades ago to x-ray women during pregnancy to determine the size of their pelvis. This obviously seemed like a good idea to those healthcare workers involved at the time.
The problem with all these new technologies is that once the equipment is available, there is a financial imperative to use it and also a very human fascination with a fancy new toy. As they say "To those that have a hammer, everything looks like a nail" and so it is with CAT scans and the like.
As with all things, there is a risk: benefit ratio to be considered. If a diagnosis can be made on the basis of a CAT scan rather than 'exploratory surgery' then the potential dangers of the scan might be heavily outweighed by those of surgery.
However, in the absence of any symptoms, the concept of CAT scan screening - potentially regularly - has to be regarded with a high degree of caution. The concept of regularly irradiating the highly sensitive breast tissue of women under the guise of 'mammographic screening' for breast cancer seems as ludicrous in the absence of any symptoms as the practice of x-raying pregnant women. Furthermore, following the recommendations of some health professionals to have an annual CAT scan health screen could easily expose you to more radiation than even the most highly exposed Hiroshima survivor in just a few years.
If you do have to have a radiological investigation, then antidoting with homeopathic remedies such as Phosphorous or Cadmium iodide may be indicated. Consuming miso soup and supplementing detoxifying herbs or specific herbal blends and/or tinctures intended to counter radiation including herbs such as milk thistle, yellow dock, aniseed, fennel, sacred dock and ginseng root may also be indicated.
When CAT scan machines were first widely introduced in the early 1980s, they were heavily publicized and marketed.
Hammer and nail exploratory operations
Here's what most people do not realize: there is absolutely no data to prove that CAT scans are medically useful for people who do not have any symptoms. According to the FDA website:
The FDA has never approved CT for screening any part of the body for any specific disease, let alone for screening the whole body when there are no specific symptoms of disease at all. No manufacturer has submitted data to FDA to support the safety and efficacy of screening claims for whole-body CT screening.
Even the FDA declares that it knows of no evidence that whole-body CAT scans are effective in detecting any particular disease early enough for the disease to be managed, treated, or cured and advantageously spare a person at least some of the detriment associated with serious illness or premature death.
In addition, the American College of Radiology, the American College of Cardiology/American Heart Association, the American Association of Physicists in Medicine, and the American Medical Association, among others, do not recommend CAT scans. Medicare and most insurance companies do not cover CAT scans for screening because the tests have never been shown to provide information in addition to what we can already learn through doing a medical history, a physical exam, and blood tests.
Further resources
Click to go direct to the National Academy Science Report on The Health Risks From Exposure to Low Levels of Ionising Radation
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