Bad news keeps leaking from Japan’s tsunami-damaged Fukushima Daiichi nuclear power plant—literally leaking, as in 400 tons of highly radioactive water a day. Or it may be more than that. No one is really sure. The squabbles between the plant’s operator, the Tokyo Electric Power Co. (TEPCO), and Japan’s nuclear regulators are further obfuscating the issue.
But no matter how you parse things, it would be difficult to find a silver lining to this particular mushroom cloud. Over the past few days, it’s been revealed that radiation is much higher at the site than previously thought—by 18 times. Such levels (1,800 millisieverts an hour) would deliver enough radiation to kill a human being in four hours. And the latest dispatches report readings of 2,200 mSV/hour at various hotspots around the complex.
So with thousands of gallons of radioactive effluent sluicing into the Pacific daily, you can’t help but wonder if some of it is working its way up the marine food web into your tuna sandwich.
Well, Cal nuclear experts say you don’t have to worry—much, anyway. It’s hard to keep things in perspective when tropes like “radioactive leakage” are bruited about, but it’s necessary that we keep perspective, advises Richard Muller, a Cal professor of physics and a faculty senior scientist at Lawrence Berkeley Laboratory. There are genuine risks associated with the Fukushima plant, Muller says, but in global—even regional—terms, they are limited.
“Yes, it’s a serious leak,” Muller told us during a phone interview, “and yes, containment (of the radioactive water) is not being handled well. But I haven’t seen anything that would indicate there’s a serious public health hazard.”
The old saw that “dilution is the solution to pollution” isn’t accurate when you’re talking about dumping garbage at sea or spewing carbon dioxide into the atmosphere, says Muller, but when it comes to Fukushima, it applies pretty well.
First, he says, the Pacific Ocean is already a highly radioactive body of water—due mainly to naturally–occurring potassium, which emits both beta and the more highly invasive gamma radiation. Comparatively speaking, the quantity of radioactive isotopes washed into the sea from Fukushima is relatively small, and is ultimately dwarfed by the ionizing radiation emitted by the great extant mass of marine potassium.
Further, the revelations about new leaks notwithstanding, it is generally agreed that the amount of radioactive crud reaching the ocean is far less today than it was in the months following the 2011 tsunami. Certainly, little if any perceptible contamination has penetrated the food webs of the west coast of North America. In its latest update, which was in March, Cal’s Nuclear Engineering Air Monitor Site determined that no radioactive isotopes originating from Fukushima have been detected in Pacific Northwest salmon.
Still, Muller continued, even minute amounts of radiation can raise the statistical odds of developing cancer. But not by a great deal.
Muller has calculated the risk of developing cancer from Fukushima. He notes an exposure of 25 rem produces no overt symptoms of radiation poisoning, but increases the risk of cancer by 1 percent. (A rem is the amount of ionizing radiation that produces a biological effect equivalent to one roentgen of gamma rays or x-rays.)
This hazard is on top of the 20 percent chance of developing cancer from “natural” causes that all humans face. Too, the risk is proportional: An exposure of 50 rem increases cancer risk by 2 percent, and so on. So by this formula, a 2,500 rem exposure would translate as a 100 percent chance of developing cancer—the so-called “cancer dose.”
How does the area around Fukushima stack up cancer-dose-wise? Muller notes that a 10-mile-by-35 mile swath of land area around the plant had the greatest radiation exposure—an average first-year dose of two rem. Some areas within that zone, however, were exposed to 22 rem. Even assuming that the 22,000 people inhabiting the irradiated zone were exposed to the maximum 22 rem (which they weren’t), the risk of any one of them developing a radiation-induced cancer is small. The calculation proceeds as follows: multiply the dose (22 rem) by the population (22,000) and divide by 2,500.By this figuring,194 out of the 22,000 can be expected to develop cancer as a result of exposure.
Following the tsunami, Muller estimated the long-term number of radiation-induced cancers resulting from the Fukushima meltdowns at about 100.
“But our data is better now, and we’ve been able to refine our estimates,” he said. “We now put them at about 60. That includes exposure to radiation immediately following the tsunami, possible cancers from eating contaminated seafood—everything.”
Muller emphasizes each death constitutes a tragedy, and that the Fukushima incident is extremely serious.
“But the great catastrophe here isn’t Fukushima,” says Muller. “It’s the tsunami. We have not been able to confirm a single death yet due to radiation exposure from Fukushima. But we do know that 15,000 people died in the tsunami.”
So why has the attention on the tsunami—and the risks posed by similar events—waned, while attention on the Fukushima leakage grows? “Radiation simply induces a lot of fear, and much of it isn’t supported by the facts,” said Muller. “This is like a man dying from an incurable disease, and he gets furious when he stubs his big toe. He can’t do anything about his disease, but he can at least get mad at whatever it is he stubbed his toe on. To deal with the real threat, the Japanese government would have to remove development for several miles inland all along its coast. They would have to close Tokyo harbor. Obviously, they can’t do that. It creates a sense of helplessness, a desire to do something, anything. So Fukushima is now seen as the problem. But it is general vulnerability to earthquakes and tsunamis that is Japan’s real problem.”
Posted on September 6, 2013 - 4:40pm