Photo by Lan Lin / China Daily

"Sometimes, I have to take care of the lonely old people as if they were children," says Chen, in her mid 40s. "Thanks to the volunteer groups, I am not alone in caring for them now. Zhang is different from the others. She seldom asks for help. Instead, she helps the others."

Wei Guihua was one of Zhang's beneficiaries.

An illiterate woman from the countryside, Wei looked after her paralyzed husband Gan Hanzhong, a railway co-worker of Zhang's husband, from the early 1980s until his death in 2005, when she herself became paralyzed.

Since Gan's funeral, none of his five children by his first wife has visited stepmother Wei, who lives in a bungalow room roofed with asbestos shingles.

Zhang became a full-time nurse for Wei. Zhang cut a big hole in her bed so she would not have to be lifted to use the toilet.

"Her husband was a friend of my husband," Zhang says. "I had no excuse to be blind to their dangers as the only healthy person of the two families. I cannot leave her alone."

Since Zhang's husband died in 2000, her meager pension and her daughter's disability aid, about 200 yuan per month then, provided the only income for the family. Zhang's only son "seems to have disappeared" and has never visited since his father died.

To make ends meet, Zhang plants vegetables in the small patches of land along the dusty streets, collects scraps from the dustbin and works as a street cleaner in her neighborhood.