The time: mid-May. The characters: mothers and their children. The setting? A sandbox at the Fantasy Kids Resort Ebina indoor amusement park in Kanagawa Prefecture.

Scooping up the sand with his hands, whooping with joy, a child exclaims to his mother, "Mom, this sand is so white!" Joining him, she replied, "It's so powdery, isn't it?"

The sandbox was filled with white sand from Australia that had been polished four times and heated at 400 C. A manager from the amusement park said: "The sand is not only clean in appearance. It's been thoroughly washed and sterilized."

With parents increasingly concerned about the dirt factor of open sandboxes, sandbox play is changing. Parents want to see their children enjoying themselves. What they don't want, however, is sand that may be dirty.

Kurumi Sasa, 27, who with her 2-year-old son, Yusei, had traveled to Ebina from Atsugi, said, "He's at the age where he puts things into his mouth."

"The sandbox in our neighborhood park is full of cat feces and empty cans. I don't want my son to get near it," she said.

Fantasy Kids Resort Ebina may be one solution for anxious parents, but outdoor sandbox play is also being transformed.

Kametaka Koen, a park in Koto Ward, Tokyo, boasts a fairly traditional playground with swings and a slide. Its sandbox is somewhat a different affair, enclosed by a one meter-high fence, a door providing entry.

"Make sure your hands don't get caught in the sandbox door," a local 45-year-old homemaker warned her 2-year-old daughter.

The fence surrounding the sandbox is not made of net but translucent acrylic plates. Looking closer, a blue hard rubber roller sits on the top of the door, a device to prevent cats from entering the sandbox.

The homemaker said, "I don't want to overreact, but I'm relieved as the fence keeps the sandbox clean."

According to the Koto Ward office, she need not worry. The sand used in ward-operated parks is regularly replaced and sterilized through a heat process.

Despite these measures, an increasing number of residents requested fences to be built around all park sandboxes so that cats and dogs cannot defecate there.

The ward office finally acquiesced. Currently, fences have been built at 123 of 183 park sandboxes within the ward.

Other districts have decided to remove sandboxes from the parks altogether.

In Kokubunji, Tokyo, the city government has not included sandboxes in any parks newly built over the past five years.

A city government official in charge of the issue said: "Treating animal excrement and enforcing such park management measures is difficult. We can't leave the work to local residents."

According to the Land, Infrastructure, Transport and Tourism Ministry, the number of park sandboxes across the nation decreased from 63,415 in fiscal 2004 to 61,466 in fiscal 2007.

But why do people now view cats and dogs as being a problem, when in reality, they have coexisted with humans for eons?

A parks management official from Mitaka, Tokyo, which places netting and sheeting in about 80 percent of its city-managed parks, assumes it is because an increasing number of street and parks are hard-surfaced.

This has resulted in fewer places where cats can relieve themselves, burying their feces in dirt or sand, the official said.

Prof. Hiroyuki Kasama of Doshisha Women's College of Liberal Arts, who has written a book about children and sandbox play said, "It's natural for parents to demand that sandboxes be safe and secure."

But the young children's education researcher added: "Isn't it normal for children and infants, to a certain degree, to experience dirt and germs as is? I feel sympathy, not only toward those children unable to play in natural environments, but also toward cats and dogs, no longer able to live as nature intended."