The radiation being emitted from the troubled reactors at the Fukushima Dai-ichi facility in northern Japan presents two potentially fatal health dangers: radiation sickness in the short term, and the risk of cancer further down the road.

Acute radiation sickness

Radiation poisoning is a danger for those who are closest to the nuclear plant where three reactors may be partially melting down. Tiny radioactive particles in fallout binds to water droplets and can then be inhaled into the lungs or fall on the skin.

The most severe form of the illness is fatal within weeks about 50 per cent of the time, but many can survive milder forms of radiation sickness. How those closest to the Fukushima facility will fare will come down to a number of factors:

• how much radioactive material they were exposed to
• what kind of radiation
• and for how long

Most people get around 0.3 of a rem (a measurement unit of dose) each year from radiation in the environment, mostly from radon gas in the soil. A chest X-ray delivers about 0.1 a rem of radiation, for example, while a CT scan of the abdomen delivers 1.4 rems. Symptoms of radiation sickness can kick in at exposures of 50 to 100 rems.

Once you get into higher doses, such as 500 to 1,000 rems, the risk of death within a month become much higher.

What makes ionizing radiation from radioactive material so dangerous is that it interferes with the cells' ability to divide and reproduce. The effects are usually seen first in the cells that divide rapidly. These include blood cells in bone marrow and intestinal cells, as well as reproductive and hair cells.

The first symptoms of the illness typically include nausea, fatigue, vomiting, and diarrhea. More severe radiation exposures result in fever, bloody vomit and stools.

Then, weeks later, as the radiation wreaks havoc on their cells, those affected might see hair loss, skin damage, and poor wound healing. This stage may last anywhere from a few hours or several month. It is during this time that the biggest risk for those affected is infection.

Unfortunately, the treatment for radiation poisoning is not simple, though there are some ways to help reduce the amount of radiation a patient absorbs.

If radioactive cesium or thallium are present in the radiation, Prussian blue can bind to those particles, and then be excreted in feces. This treatment speeds up the elimination of the radioactive particles and reduces the amount of radiation cells may absorb. Diethylenetriamine pentaacetic acid, or DTPA, binds to radioactive plutonium, americium and curium and then passed out of the body in urine.

To manage the effects on the destruction of the immune system, there are medications that are often given to cancer patients undergoing radiation therapy, which can increase white blood-cell production. This helps reduce the risk of infections.

Even for those who survive radiation sickness, there are further health dangers, such as cancer.

Cancer risk

Cancer is the biggest long-term risk from radiation exposure. One of the most common forms of cancer seen after radiation disasters is thyroid cancer, an otherwise rare form of cancer. That's because the thyroid gland tends to absorb iodine from wherever it can, including from radioactive iodine in the air.

After the Chernobyl disaster, which released a stunning amount of radiation into the atmosphere, residents of Ukraine and nearby Belarus saw a surge in thyroid cancer rates. One study estimates that radiation exposure will raise the number thyroid cancer cases in Belarus by 80 per cent over 50 years.

To help prevent this form of cancer, the Japanese government is distributing iodine pills. By flooding the thyroid with ordinary iodine, the pills help inhibit absorption of radioactive iodine from the atmosphere.

So far, the Japanese government has not ordered people to take the pills, meaning they do not think radiation levels have been high enough to warrant taking them at this time.

But Dr. David J. Brenner, director of the Center for Radiological Research at Columbia University, is not convinced that's an effective strategy. He tells The New York Times that the risk from inhaling radioactive iodine is low; the bigger danger is contaminated food.

He says almost 98 per cent of people's exposure comes from ingesting contaminated milk and dairy products. In fact, he believes that the epidemic of thyroid cancer around Chernobyl could have been prevented if the government had immediately stopped people from drinking milk.

Leukemia is also a risk, as many of those who survived Chernobyl eventually came down with this blood-based cancer.

The damage caused by exposure to radiation can disrupt the body's ability to regenerate new cells, allowing old cells to "go rogue" and continue to divide and multiply in an uncontrolled fashion, allowing tumours to grow.

Even if the amount of radiation released from the Fukushima plant ends up being small compared to Chernobyl, long-term exposure to event low level radiation in the air, water, and food poses a risk of increases in breast cancer, as well as premature aging, strokes, and heart attacks.

The final risk from radiation exposure is birth defects later down the road.

Radiation can cause mutations to the body's genetic material, which may then be potentially passed down to offspring, leading to deformities in future generations. These can include smaller head or brain size, severe learning difficulties, and stunted growth.

A 2005 United Nations report said there was no evidence for an increase in such birth defects following the Chernobyl disaster. But other studies have found double to triple the normal rate of defects such as spina bifida and conjoined twins in affected regions.