KORIYAMA, FUKUSHIMA PREF. – Some of the smallest children in Koriyama, a short drive from the ruined Fukushima No. 1 nuclear power plant, barely know what it’s like to play outside — fear of radiation has kept them indoors for much of their short lives.

Though the strict safety limits for outdoor activity set after the multiple meltdowns at the Fukushima plant in 2011 have now been eased, parental worries and ingrained habit mean many children still stay inside.

And the impact is now starting to show, with children experiencing falling strength, lack of coordination, some cannot even ride a bicycle, and emotional issues like shorter tempers, officials and educators say.

“There are children who are very fearful. They ask before they eat anything, ‘Does this have radiation in it?’ and we have to tell them it’s OK to eat,” said Mitsuhiro Hiraguri, director of the Emporium Kindergarten in Koriyama, some 55 km west of Fukushima No. 1.

“But some really, really want to play outside. They say they want to play in the sandbox and make mud pies. We have to tell them, ‘No, I’m sorry. Play in the sandbox inside instead.’ “

Following the 2011 quake and tsunami, a series of explosions and meltdowns caused the world’s worst nuclear disaster in 25 years, spewing radiation over a swathe of Fukushima, an agricultural area long known for its rice, beef and peaches.

An area with a 30-km radius around the plant was declared a no-go zone, forcing some 160,000 people from homes where some had lived for generations. Other areas, where the radiation was not so critically high, took steps such as replacing the earth in parks and school playgrounds, decontaminating public spaces like sidewalks, and limiting children’s outdoor play time.

The Koriyama Municipal Government recommended shortly after the disaster hit that children up to 2 years old not spend more than 15 minutes outside each day. Those aged 3 to 5 were urged to limit their outdoor time to 30 minutes or less.

These limits were lifted last October, but many kindergartens and nursery schools continue to adhere to them in line with the wishes of worried parents.

One mother at an indoor Koriyama playground was overheard telling her child: “Try to avoid touching the outside air.”

Even 3-year-olds know the word “radiation.”

Though a surge in thyroid cancer in European children was linked to the 1986 Chernobyl disaster, the United Nations said last May that cancer rates were not expected to rise after Fukushima.

Radiation levels around the Emporium Kindergarten in Koriyama are down to around 0.12-0.14 microsieverts per hour, from 3.1 to 3.7 right after the quake, said Hiraguri.

This works out to be lower than Japan’s safety level of 1,000 microsieverts a year, but levels can vary widely and at random, keeping many parents nervous about any outdoor play.

“I try to keep from going out and from opening the window,” said 34-year-old Ayumi Kaneta, who has three sons. “I buy food from areas away from Fukushima. This is our normal life now.”

But this lack of outdoor play is having a detrimental affect on Koriyama’s children, both physical and mentally.

“Compared to before the disaster, you can certainly see a fall in the results of physical strength and ability tests — things like grip strength, running and throwing balls,” said Toshiaki Yabe, a Koriyama official.

An annual survey by the Fukushima Prefectural Board of Education found that children in Fukushima weighed more than the national average in virtually every age group.

Five-year-olds were roughly 500 grams heavier, while the weight difference grew to 1 kg for 6-year-old boys. Boys of 11 were nearly 3 kg heavier.

Hiraguri said that the stress was showing with an increase in scuffles, arguments and even sudden nosebleeds among the children, as well as more subtle effects.

“There’s a lot more children who aren’t all that alert in their response to things. They aren’t motivated to do anything,” he said.

Koriyama has removed decontaminated earth in public places, sometimes more than once, and work to replace all playground equipment in public parks should finish soon.

Yabe said parental attitudes toward the risk of radiation may be slowly shifting. “These days, instead of hearing from parents that they’re worried about radiation, we’re hearing that they’re more worried because their kids don’t get outside.”

But Hiraguri said things are still hard. “I do sometimes wonder if it’s really all right to keep children in Fukushima. But there are those who can’t leave, and I feel strongly that I must do all I can for them.”