JUDY WOODRUFF: Next, the unending aftermath of the Japanese tsunami and the meltdown at the Fukushima nuclear power plant.
Only recently have authorities acknowledged they misled area residents about the dangers.
John Sparks of Independent Television News got an inside look at the area around the nuclear plant.
JOHN SPARKS: This is the end of the road. Beyond a well-staffed checkpoint lies the 20-kilometer evacuation zone, a no-man's land that surrounds the Fukushima nuclear plant.
We were stopped, our papers checked. Then the police waved us through. We had won rare access to a world without people -- 80,000 residents were evacuated from this area when explosions rocked the nuclear facility in march. Vehicles were abandoned on the highway. Shops were shut, their shelves full of stock, and damage from the tsunami simply left to rust.
We are now 10 kilometers away from the Fukushima Daiichi nuclear plant. Our personal radiation monitor has begun to rise now, so we are going to head several kilometers back to a safer area. The threat posed by long-term exposure to radiation means former residents may never return home, this the cause of much pain.
But there is clarity at least. This area has been judged unsafe. On the other side of the 20-kilometer boundary, the situation is far more confused. The tsunami knocked out Fukushima's cooling systems, triggering explosions in four of its six reactors. Radioactive material spewed into the air and sea.
The 20-kilometer evacuation zone was thrown up around the plant. Later, the government created an outer evacuation preparation zone. Residents were largely left to choose whether to stay or go. Higher levels of radiation, here marked in red, have spread far beyond these evacuation areas, however, covering densely populated areas like Fukushima City and Minamisoma City, although some officials say the worst is over.
KATSUNOBU SAKURAI, mayor of Minamisoma City, Japan (through translator): Not that much time has passed since the accident. It is only five months now. And I don't think radioactive particles are spreading anymore.
JOHN SPARKS: That view smacks of complacency to this motley group of volunteers. They will spend their Sunday cleaning up radioactive contaminants in one part of Minamisoma City.
It is bright and early. It is baking hot. But there is a large group of volunteers all around this house. It's the home of a woman. She is seven months pregnant, and she still lives here.
The government has offered little assistance and no guidance on how to deal with radiation. So ordinary citizens with little training have stepped in. Armed with personal Geiger counters, they find and record high levels of radioactivity in the garden and on the roof.
The owners, Ms. Kitayama and her husband, face a terrible dilemma: Seek somewhere safer or stay put.
WOMAN (through translator): We stayed here for the dog, and I have a job to go to. There are other reasons, too, including the mortgage.
JOHN SPARKS: They did briefly relocate, but she said it made her unwell.
WOMAN (through translator): I got sick from the stress. And I was really worried it would affect the baby.
JOHN SPARKS: Minamisoma Junior High School, home to the highest level of radiation in town, it was discovered by another volunteer group in the swimming pool, readings here more than 2,000 times stronger than normal levels. The cleanup crew have got no time to lose. School starts in one week, although the man in charge thinks it's still too dangerous.
KITAYAMA BANSHO MIURA, environmental engineer (through translator): Even if we clean up all the houses and facilities in town, we just don't think people should live here.
JOHN SPARKS: Mr. Miura accuses public officials of hiding high radiation levels in their desire to get things back to normal. The mayor of Minamisoma says his badly damaged city is safe from radiation, and where high levels exist, well, the contamination will be cleaned up.
KATSUNOBU SAKURAI (through translator): The schools are working on cleanups. And that will help to reduce the radiation levels. We will be able to let the kids study in lower levels of radiation.
JOHN SPARKS: I just wonder, by asking people to come back, whether you're taking a risk, a significant risk, with people's health.
KATSUNOBU SAKURAI (through translator): I want people to come back, especially younger ones. But I'm not going to force them.
JOHN SPARKS: Japan has suffered greatly, but this crisis is far from over. Residents and activists are waging a new battle against an invisible enemy. But the threat posed by radiation to human health may last for years, or decades, or perhaps even centuries.