July 17th, 2012
06:21 PM ET
As protests against nuclear power gain momentum in Japan, a new report estimates the worldwide cancer death toll from the March 2011 disaster at Fukushima Daiichi could be anywhere from 15 to 1,300. But researchers say it will more likely be around 130, and mostly in Japan.
"It's not large, but it's not 0," said Mark Jacobson, a civil and environmental engineer at Stanford University and co-author of the new study. "A lot of people were claiming there were no health effects from the radiation. We found that was not the case."
The study, published in the journal Energy and Environmental Science, uses a three-dimensional model of the atmosphere to look at how radioactive materials spread after last year's massive earthquake and tsunami damaged the Fukushima Daiichi nuclear power plant.
The methods of the study were standard, and the estimates were reasonable, although there is still uncertainty around them, said Kathryn Higley, head of Nuclear Engineering & Radiation Health Physics at Oregon State University. But given how much cancer already exists in the world, it would be very difficult to prove that anyone's cancer was caused by the incident at Fukushima Daiichi. The World Health Organization estimates that 7.8 million people died worldwide in 2008, so 130 out of that number is quite small, says Higley.
More than 15,000 people died in northeastern Japan as a result of the natural disaster. No deaths have been attributed to the Fukushima accident itself, but about 600 deaths were confirmed to be tied to the massive evacuation of the area, Jacobson said. Those who passed away during the evacuation may have died from a variety of causes, such as disease, fatigue, stress or moving hospitals.
In terms of cancer morbidities, Jacobson and co-author John E. Ten Hoeve estimated that there will be between 24 and 2,500 cancer cases, with 180 being the most probable number, according to their model. These numbers and the death projections are based on about one year of exposure to radiation from Fukushima - there could be additional effects later, but most impacts from a radioactive disaster would occur within the first year, Jacobson said.
The radition from the damage to the nuclear power plant includes the radioactive isotope Iodine 131, which has a half-life of eight days, meaning it has a short-term, intense effect. Cesium–137 was also released and lasts for about 30 years before half of it decays, meaning its impact is longer lasting, but after a year there wouldn't be much left of it in the air, Jacobson said. It could still be in the soil and food, however.
"Japan is very lucky because only 19% of the emissions ended up over land, where people lived, and 81% was over the ocean," Jacobson said.
By comparison, 90% of the emissions from Chernobyl ended up over land, and the radioactive emissions themselves were about 10 times as great. The resulting health effects were as much as 50 to 100 times higher compared to in Japan, Jacobson said.
To estimate the effects of the Fukushima accident, study authors factored in the radiation concentration people were exposed to, the population that was actually exposed, and the health effect per unit of concentration per person. They looked at health risk studies over the years to inform their estimates, but that data has uncertainty in it, meaning the range for projected number of mortalities is broad.
Researchers also looked at what would happen if a nuclear disaster of this nature were to happen in the United States They focused on the Diablo Canyon, a power plant that could be affected by earthquakes in California. If an accident were to occur, a lot of the impact would depend on meteorological conditions - in Diablo Canyon, 45% of emissions would go over land, and the cancer death rate would probably be about 25% higher compared to the situation in Japan. "Similar to Fukushima, a large majority of the health effect is local," the study authors wrote.
But keep in mind that the population density in California is about one-quarter that of Japan. If California had the same population as Japan, there would have been five times the number of deaths from this theoretical disaster than from Fukushima, Jacobson said.
The study recommends that long-term cancer risk studies be conducted in Japan to compare with the new estimates, and for future modeling of Fukushima's health effects.
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