The spectre of radiation rises again in Japan

 

MEDICAL MATTERS:How great is the risk to Fukushima’s workers, writes MUIRIS HOUSTON

‘OUR CAMP had to all intents and purposes disappeared. The wood had carbonised and turned to ashes. Bodies lay everywhere, some horribly mutilated by falling walls, girders and flying glass. Those people still on their feet ran round in circles, hands pressed to their blinded eyes or holding the flesh that hung in tatters from their faces and arms . . . Most frightening of all was the lack of sunlight. In contrast to the bright August sunshine a few minutes earlier, there was now a kind of twilight. We all genuinely thought this was the end of the world.”

So wrote Irish RAF doctor Aidan McCarthy, describing the scene that greeted him and his fellow prisoners of war at their camp on the outskirts of Nagasaki. It was August 9th 1945 and an American B-29 had just dropped an atomic bomb on the city.

Exposure to massive amounts of ionising radiation, as described by McCarthy, causes radiation sickness. The initial signs and symptoms are usually nausea and vomiting.

The amount of time between exposure and when these symptoms develop is an indicator of how much radiation a person has absorbed. They may have a brief period with no apparent illness, followed by the onset of new, more serious symptoms.

Dizziness, disorientation, weakness and fatigue occur next, followed by bleeding from the gastrointestinal tract, infection and low blood pressure. And, depending on the severity of illness, death can occur within two days to two weeks.

Thankfully, these scenes will not be repeated for those now living in the vicinity of the Fukushima nuclear plant, northeast of Tokyo. Damaged by the recent earthquake and tsunami, the nuclear reactors at the facility have been on fire and released radioactive vapour into the atmosphere; spent fuel rods have also ignited. It is a worrying time for the workers in particular, whom we know have been exposed to potentially harmful levels of radiation. They are being constantly monitored and decontaminated.

The principal concern for the workers – and indeed anyone exposed to higher levels of radiation – is risk of developing cancer. It is estimated 100 millisieverts a year is the lowest level at which any increase in cancer is clearly evident. Above this, the probability of cancer increases with higher doses. A cumulative dose of 1,000 millisieverts would increase the incidence of fatal cancer by about 5 per cent.

Radioactive iodine and caesium are the two elements of primary concern. Iodine -131 has a half-life of eight days; when it is absorbed by the body it accumulates in the thyroid gland. Located in the neck, the thyroid regulates our metabolism. But when radioactive iodine accumulates in the gland it causes cancer. The risk is greatest in children in whom the thyroid is still growing and developing; indeed, some 6,000 cases have been identified in the Ukraine post-Chernobyl.

In the longer term, the greater threat to human health is caesium -137, which has a half-life of 30 years (this is the time it takes for half of it to disappear). Caesium -137 is water-soluble and is chemically similar to potassium and therefore mimics how potassium is metabolised. After entering the body, caesium -137 can cause damage to cells, leading to an increased risk of cancer. Wild mushrooms, berries and animals are still contaminated with caesium in the areas affected by the fallout from Chernobyl.

What treatment options are available? Potassium iodide is used to “flood” the thyroid, so there is no room for radioactive iodine particles to be absorbed by the gland. Instead, they are cleared from the body in urine. Prussian blue is a dye that binds to radioactive elements of caesium and promotes their excretion in faeces.

Interestingly there has been a “run” on potassium iodide tablets and liquid formulations on the west coast of Canada and the US, despite the large expanse of Pacific ocean separating the area from Japan. It emphasises the stoicism of the Japanese, who, despite their outward inscrutability, must be very scared indeed.