Posted June 26, 2011
It is entirely possible that life on Earth exists thanks to radiation.
One of the theories on the origins of life on our planet says that ultraviolet radiation, along with lightning and volcanoes on ancient Earth, provided the zap of energy needed for non-organic molecules like methane and ammonia, to combine into more complex organic molecules that include the basic building blocks of life, like nucleotides and amino acids.
Of course, as life slowly kickstarted from the combinations of these simple organic molecules into single-cell organisms, and then multicellular ones, the very radiation that helped trigger the process became poisonous to the evolving and rapidly more complex life-forms.
Where radiation once provided energy to simple molecules, it now disrupted the more complicated bonds within more complex organisms.
Strangely enough, the problem was also the solution. UV radiation itself came to the rescue by causing oxygen in the atmosphere to combine and become ozone.
The ozone layer now protects us from being bombarded by UV radiation that can cause unsustainable levels of mutation in all living creatures on Earth.
However, that does not mean that Earth is a radiation-free zone.
The fact is, radiation is present everywhere in our environment.
It comes from the soil, the stones, the sun, and from many of the essential technological items we use in our daily lives.
According to the International Atomic Energy Agency, we are all exposed to an average of about 2.4 milliSievert (mSv) of natural background radiation a year.
However, this amount can vary by several hundred per cent depending on where you live.
The World Nuclear Association (WNA) reports that the highest level of known background radiation exposure is at the city of Ramsar in northern Iran.
The people who live there receive an annual radiation dose of up to 260 mSv.
The area with the largest populations affected by high natural background radiation are the states of Kerala and Madras in India, where some 140,000 people are exposed to over 30 mSv of background radiation a year.
Other areas with unusually high background radiation doses can be found in China, Brazil and Australia, among others.
However, there has been no evidence to date that the people living in these areas have a higher incidence of cancer or genetic mutations than any other community.
Harmful or not?
Most people will be familiar with man-made radiation sources like nuclear power plants and medical imaging equipment, like X-ray machines and CT scanners.
But are you aware that your mobile phone, microwave oven, television and laptop are also among the many sources of man-made radiation?
Radiation in this context is basically the emission of energy in the form of electromagnetic waves or subatomic particles.
Mobile phones, cordless phones, television sets, and radios all emit radiofrequency waves that help transmit information to and from those devices.
Laptops that are WiFi-enabled, also emit these waves that enable us to surf the Internet, while microwave ovens make use of microwaves to heat up and cook our food.
In this modern, technology-dependent era, we are literally surrounded by all these electromagnetic waves that are essential to our lives.
So, the question is: are they harmful to us?
According to a statement released by the International Agency for Research on Cancer (IARC) last month, there is “limited” scientific evidence to show that there is an association between the usage of mobile phones and two types of rare cancer — gliomas and acoustic neuromas, but “inadequate” evidence to link mobile phone usage with other types of cancer.
This followed the gathering of a group of independent scientists at the IARC to analyse the available scientific literature on the possible cancer-causing effects of radiofrequency electromagnetic waves.
The scientists concluded that while studies have shown that there is a possibility that the radiofrequency electromagnetic waves from mobile phones can cause gliomas and acoustic neuromas, those same studies were not able to rule out the possibility that these findings were due to chance or some other bias in their research methods or analysis.
Based on this, the IARC, which is part of the World Health Organisation (WHO), has classified radiofrequency electromagnetic waves as “possibly carcinogenic to humans”.
Although gliomas (a type of brain cancer) and acoustic neuromas (a tumour that grows on the nerve running from the ear to the brain) are quite rare, the worry is that so much of the world’s population, including young children and teenagers, use mobile phones, and would risk exposing themselves to these two cancers.
However, generally speaking, radiofrequency electromagnetic waves are classified under non-ionising radiation, along with visible light, infrared and microwaves. (See The Energy Spectrum)
This means that the energy emitted by these low-frequency waves is not strong enough to ionise, or cause electrons to break their bonds within atoms or molecules. These waves are only able to provide more energy to the atoms or molecules they encounter, and cause them to vibrate or move around within their bonds.
Therefore, non-ionising radiation is mostly considered not harmful to living beings, except in certain cases of excessive exposure.
International guidelines for industries manufacturing devices which emit non-ionising radiation are available from the International Commission on Non-Ionising Radiation Protection (ICNIRP).
This non-profit commission is officially recognised by WHO and the International Labour Organisation as the international independent advisory body for non-ionising radiation protection.
Ionising radiation
The other, more dangerous type of radiation is ionising radiation.
This high-frequency radiation gives out enough energy to break the bonds of electrons in atoms or molecules to create charged particles and free radicals.
There are three main kinds of ionising radiation: alpha particles, beta particles, and gamma rays.
Alpha particles consist of two protons and two neutrons, and are positively charged.
Beta particles are essentially electrons, which are negatively charged.
Gamma rays are pure electromagnetic waves or photons.
Because they are charged, alpha and beta particles can interact directly with atoms and molecules, and disrupt them.
However, they are also easily blocked, as paper is sufficient to halt the progression of alpha particles, while beta particles can be stopped by aluminium.
Gamma rays have a more indirect effect on atoms and molecules as they are not charged, but they can penetrate through anything less thick than heavy concrete.
With high enough dosages, ionising radiation can cause the breaking up and mutation of our DNA, and disruption of our cellular function.
However, the dosage required to cause these conditions is far more than what any average human being is likely to be exposed to, except in highly unusual circumstances, like a nuclear meltdown.
In cases like nuclear bombings and large nuclear power plant explosions, the amount of radiation released is usually sufficient to cause instant radiation poisoning.
Longer-term exposure with smaller doses can result in cancer or genetic diseases in the next generation.
As catastrophes like nuclear bombings and nuclear power plant accidents are thankfully, rare, this leaves the main area of concern as long-term exposure.
Common exposure
In our day-to-day lives, exposure to ionising radiation usually comes in the form of medical imaging — X-rays and CT scans.
At the very least, many of us would have undergone at least a chest X-ray, whether for a general medical check-up for employment or insurance purposes, or as an investigative procedure for a suspected disease.
Chest X-rays are so common and give the lowest radiation dose that they are often used as a standard comparison for the amount of radiation exposure a patient gets.
One chest X-ray is equivalent to 0.02 mSv of radiation dose, which is about the same as three months’ worth of natural radiation exposure.
Imaging different parts of the body results in larger radiation doses, which can go up to the equivalent of 1,000 chest X-rays for a whole body CT scan.
However, despite resulting in increasing radiation exposure, it is generally argued that the benefits obtained from being able to see inside the body for diagnostic and therapeutic purposes far outweigh the small risk of developing cancer from the procedure.
Of course, imaging procedures should only be carried out for a justifiable medical reason, and must be approved by a qualified radiologist, who will judge the necessity of the procedure.
In addition, for cancer cases, fire is used to fight fire, as the very instrument that can cause cancer is also used to destroy cancer cells.
This forms the basis of radiotherapy, which uses radiation to kill off cancer cells.
The reason for this is that, as the patient will die without treatment, it is better to try to save their lives through controlled use of radiation, rather than just letting them die.
An increasingly common use of imaging outside the hospital is the soft X-ray airport scanner.
According to the United Kingdom Health Protection Agency, a full body scan by one of these machines will give a radiation dose of 0.02 to 0.03 microSievert.
Allowing for two to three scans per examination, this means a person would receive a dose equivalent to about one hour’s worth of natural background radiation (about 0.1 microSievert) for one round through the machine.
The agency compares this to flying at 35,000 feet in an aeroplane, where passengers on the plane would receive the same amount of radiation from cosmic rays in the space of one minute.
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Copyright © 2011, The Star, Kuala Lumpur, Malaysia / Asia News Network