Following the nuclear disaster at
The meltdown last March of three nuclear reactors at the Fukushima Daiichi nuclear power plant in
Beginning this month, at least 1,000 sq km of land — much of it forest and farms — will be cleaned up as workers power-spray buildings, scrape soil off fields, and remove fallen leaves and undergrowth from woods near houses. The goal is to make all of
"Decontamination can be really effective, [but] what you have is a tradeoff between dose reduction and environmental impact," says Kathryn Higley, a radioecologist at
Given these drawbacks, an International Atomic Energy Agency fact-finding mission advised the Japanese authorities to "avoid over-conservatism" in their decontamination plans — in other words, not to clean up more than necessary to protect human health. Yet the health impacts of long-term exposure to low levels of radiation are not entirely clear. Many scientists believe exposure to even very low levels can slightly increase cancer risk, and many Fukushima residents feel they should not be forced to live with that risk — or the undercurrent of fear it brings.
But while the political debate over how much to clean up rages on, more practical preparations are already underway. On a frigid afternoon last month, about 160 workers wearing papery white jumpsuits and hot pink respirators filed up a winding road into a farming hamlet in Kawamata town, about an hour south-east of Fukushima and just inside the evacuation zone. Were it not for the bright blue plastic sheets, heavy-duty leaf vacuums, cranes, and trucks scattered everywhere, the village would have been picturesque. Now, the intricacy of the landscape — its tiny rice paddies, bamboo groves, woodlots, streams, and earth-walled barns — was adding to the challenges of decontamination.
The workers fanned out over the otherwise abandoned rolling hills and brown fields. One group climbed a hill to rake fallen leaves into large black bags, while another spread magnesium over fields to solidify the soil for later removal. Nearby, another of the indistinguishable white figures chopped down overgrown weeds.
The workers had been hired by Taisei Corporation, one of three large construction firms that won contracts from the Japan Atomic Energy Agency (JAEA) to test the effectiveness and efficiency of various decontamination technologies at 19 model sites throughout
Human exposure can be lowered without cleansing the entire landscape, of course. Japan's bans on hunting bears and wild pigs, selling wild mushrooms, and growing rice in certain areas fall into this category; so does the recommendation from Fukushima's agriculture department that farmers add potassium fertiliser to moderately contaminated fields in order to minimise cesium uptake by crops. As for forests, the focus for the time being is on decontaminating only patches close to homes because most people spend little time in remote woods.
But because the most heavily contaminated parts of
Radiological risk assessment expert John Till, president of the US-based Risk Assessment Corporation, says the fallout will probably be gone from the surface of plants within a few years, but attach strongly, through ion exchange, to soil — in particular to the clay soils common throughout Fukushima. From there the radiocaesium will move slowly into plants, at a rate — and level of risk — that is still unclear.
Remediation methods that work, Higley says, "seem kind of absurd but actually make sense": cutting, scraping, raking, and ploughing, to varying degrees of depth and severity. Government agencies, private companies, and academics are all experimenting to find the most efficient and effective methods for
Officials involved with the cleanup are well aware of the drawbacks to these approaches: huge amounts of radioactive waste that no one wants to store long-term; immense investments of money, labor, and time; damage to wildlife habitat and soil fertility; increased erosion on scraped-bare hillsides; and intrusion by people and machinery into every area scheduled for remediation.
"You remove leaf litter from the forest floor and radiation levels fall," said Shinichi Nakayama, a nuclear engineer at the JAEA who is overseeing the 19 decontamination pilot projects planned or underway. "You take away the deeper layers and they fall more. But you take it all away and the ecosystem is destroyed. Water retention goes down and flooding can occur."
Although no significant conservation areas lie within the most contaminated parts of Fukushima, some species on the prefecture's "red list" of endangered or threatened species — including the grassland butterfly and the Japanese peregrine falcon, both listed as "vulnerable" — are found there and could be impacted if projects like these are implemented on a large scale.
But Kiyomi Yokota, a naturalist and secretary of the Fukushima Nature Conservation Association, said that standing up for wildlife in the current situation would be difficult. "If people want to go home, I don't think I could tell them, 'No, stop the decontamination, save the fish,'" he said. Human health, in other words, trumps habitat.
But just how much fallout does the government need to remove in order to protect human health? On that key question the science is frustratingly inconclusive.
Past studies have shown that cancer rates rise in populations exposed to a dose of 100 millisieverts (mSv) of radiation. They reveal much less about the situation in
The release of contaminated water from the crippled
Some residents and activist groups like Greenpeace have called for a faster and more aggressive decontamination effort, while others believe most of
"Safe? What is safe?" Sumiko Toyoguchi, an elderly evacuee who used to live six kilometres from the nuclear plant and now lives in temporary housing in
· Ten months after the nuclear disaster, trust in the authorities is nearly non-existent. Without it,
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