IWAKI, Japan — Kiyoko Okoshi had a simple goal when she spent about $625 for a dosimeter: She missed her daughter and grandsons and wanted them to come home.

Local officials kept telling her that their remote village was safe, even though it was less than 20 miles from the crippled Fukushima Daiichi nuclear-power plant. But her daughter remained dubious, especially because no one from the government had taken radiation readings near their home.

So starting in April, Okoshi began using her dosimeter to check nearby forest roads and rice paddies. What she found was startling. Near one sewage ditch, the meter beeped wildly, and the screen read 67 microsieverts per hour, a potentially harmful level. Okoshi and a cousin who lives nearby worked up the courage to confront elected officials, who did not respond, confirming their worry that the government was not doing its job.

With her simple yet bold act, Okoshi joined the small but growing number of Japanese who have decided to step in as the government fumbles its reaction to the widespread contamination, which leaders acknowledge is much worse than originally announced.

Some mothers as far away as Tokyo, 150 miles to the south of the plant, have begun testing for radioactive materials. And when radiation specialists recently offered a seminar in Tokyo on using dosimeters, more than 250 people showed up, forcing organizers to turn some people away.

Even some bureaucrats have taken the initiative: Officials in several towns in Fukushima prefecture are cleaning the soil in school yards without help from the central government, and a radiation expert with the Health Ministry who quit his job over his bosses' slow response to the nuclear accident is helping city leaders in Fukushima do their own monitoring.

Such activism would barely merit comment in the United States, but it is exceptional in a country where people generally trust their leaders to watch out for them. Driven by fear and even despair, that faith has been eroded by a sense that government officials have been, at best, overwhelmed by the enormousness of the disaster, and at worst, hiding how bad things are.

"They don't riot and they don't even demonstrate very much, but they are not just sitting on their hands, either," said Gerald Curtis, Burgess Professor of Political Science at Columbia University and a longtime Japan expert. "What the dosimeter issue reveals is that people are getting more nervous rather than less about radiation dangers."

It did not help that the government recently had to backtrack on the acceptable exposure levels for schoolchildren after a senior government adviser quit in a tearful news conference, saying he did not want children to be exposed to such levels, and parents protested. The recent discovery that radioactive beef made it into stores raised fresh alarms.

"We need to do strict research to make people feel assured," said Keiichi Miho, the mayor of Nihonmatsu, a city of 60,000 people west of the Daiichi plant. The mayor is one of a growing number of local officials who have tackled the issue directly, spending millions of dollars on steps like creating a radiation map of his city. "That's the only way to regain credibility."

After Okoshi's tests continued to show high levels of radiation, her cousin Chuhei Sakai, a farmer in the area, went with several other villagers to show her data to the mayor. He did not respond, Sakai said.

Since then, she has earned a reputation for her grass-roots monitoring. "Every time I have mentioned my name at meetings recently, city officials there say, 'Ah, you are the one who measured the radiation,' " she said.

Although dosimeter measurements taken by amateurs are considered crude because they only measure one kind of radiation emission and do not account for how long a person may have been exposed to it, Sato suspected Okoshi's fears were founded after he saw a map of airborne and soil readings made by the U.S. Department of Energy and the Japanese government. It, too, is relatively basic, but it showed a patch of bright yellow right over her village of Shidamyo, an indicator of high levels of cesium 134 and cesium 137.

The councilman, in turn, recruited Shinzo Kimura, the radiation expert who quit the Health Ministry. Kimura has since done extensive testing to see if Okoshi's readings were right. He says they are — and that is bad news.

Radioactive materials do not always fall in neat patterns; vagaries of wind direction and landscape can mean one area is hit badly, while others nearby are not. Although some areas of Iwaki showed relatively low levels of radioactive materials, soil samples from one farm in Shidamyo show levels of radioactive materials Kimura says are as high as those found in the evacuation zone around the site of the Chernobyl nuclear accident in Ukraine.

The city has finally decided to start monitoring for radioactive materials in the air, but has not yet determined how serious its problems are.