Our society has a difficult relationship with radiation. Although a life-saver, through cancer treatment and X-rays, it also holds deadly potential.

This week marks the fifth anniversary of the accident at the Fukushima Daiichi Nuclear Reactor Power Plant, where a tsunami triggered a nuclear meltdown in a power plant on the coast of Japan.

However Professor Gerry Thomas, a top radiation expert from the Department of Surgery and Cancer at Imperial College London, argues we have got radiation all wrong – and think it much more dangerous than it really is.

“Radiation saves far more people every year than it kills, but we still perceive it as a great danger. Yet it is just like any other toxin - such as alcohol or even salt, it is safe in small doses but dangerous in high amounts."

Here Professor Thomas reveals the most common radiation myths, and explains why your waistline poses a greater danger to your life than radiation - and why people who sleep alone receive less radiation than those who sleep with a partner.

MYTH: Radiation is deadly

Many people believe any exposure to radiation is dangerous, explains Professor Thomas - yet we are exposed to radiation every moment throughout our lives. Every year we are exposed to a dose of radiation of 2 milli Sieverts (which is a measure that adds our exposure from different types of radiation). By comparison one X-ray delivers 0.2 milli Sieverts.

"We live on a radioactive planet. We receive radiation from space - so called cosmic radiation - which is why we receive higher amounts of radiation when we fly (around 0.1mSv for a return flight from London-Tokyo), and why astronauts receive high levels of radiation in space.

“And it is released in the soil and from rocks such as granite, due to a naturally occurring element called Radon. Even bananas and brazil nuts contain radioactive elements."

She continues: "If you measured radiation levels in Aberdeen, which is built on granite, there would be higher background levels of radiation than in Fukushima."

And in comparison to other lifestyle factors, the risk of radiation to our health is tiny.

"Research has suggested that being close to the nuclear bomb when it detonated in Hiroshima would be less of a threat to your health than being severely obese. Research published in 2007 calculated a person would lose 2.6 years of life if you were 1.5 km from the atomic bombs when they detonated. In comparison, if you’re severely obese you lose 10 years of your life."

MYTH: People can be radioactive

"Many people believe that once someone has been exposed to radiation they are somehow contaminated, and can cause people around them to be harmed," says Professor Thomas.

However, being exposed to radiation beams - for example during an X-ray or when a patient is receiving conventional radiotherapy for cancer, does not leave any lingering radiation. This is because the radiation passes straight through the body. If someone ingests radiation, their body can remain radioactive. But, crucially, it is not their actual body that remains radioactive - but their bodily fluids such as sweat, saliva and urine.

She adds: "An example of this is when medics give patients with thyroid cancer a drink that contains radioactive iodine. Following surgery to remove the thyroid gland, patients are given radioiodine to kill any remaining thyroid cells that remain in the body. The thyroid cells absorb the radioiodine, and this kills the cells.  However these patients must remain in isolation for around 24 hours until they have excreted all the radioactive iodine from their body. “

She adds that we all carry a small amount of radiation, because the food we eat, such as fruit and vegetables, contain radioactive chemical elements absorbed from the ground.

"The radioactive elements from food cause our body to emit small amounts of radiation in our sweat and bodily fluids. So if you sleep next to somebody you'll receive greater amounts of radiation at night than if you sleep alone."

MYTH: Medical and security body scanners are dangerous

Medical scans, such as X-rays and CT scans, and security scanners at airports deliver very small amounts of radiation, says Professor Thomas.

"If a doctor suggests you have an X-ray or CT scan the benefits to your health far outweigh any risks."

And airport scanners only deliver 0.00002 mSv.

However, she cautions against having 'leisure scans'. "I sometimes see adverts for private CT scans, offered to people who are fit and healthy but just want to check whether they have anything lurking. Almost like a yearly check-up with your doctor. I personally wouldn't opt for these, as you are exposing yourself to radiation to 5 years’ worth of background radiation (around 10mSv) for no clear benefit."

MYTH: Living near a nuclear power station is bad for your health

"Studies have shown that an operational coal-fired power station releases three times more radiation than an operational nuclear power plant," says Professor Thomas.

"This is because fossil fuels naturally contain radioactive elements, which is released when they are burnt. However, the levels of radiation emitted would not pose any danger to health.”

And she adds many people still believe there were radiation-related deaths following the Fukushima accident.

"There have been no radiation-related deaths from the accident. This was because the clean-up workers were on a strict rotation pattern, which kept their doses well below the level at which any direct effects would be seen from radiation exposure.  Doses to the population at large were kept low by sheltering, evacuation and removing contaminated food from the food chain.  These actions meant the doses to members of the general population were kept to below that of a single whole body CT scan – and in more than 90% of cases to less than a tenth of a CT scan.  We learnt the lessons from previous accidents such as Chernobyl, and put them into action."