Rising popularity

"The Chinese customs require a list of all the titles, authors and prices of the books we import, which has to be made by the bookstore in London. The store also has to remove those that are not allowed to be imported to China before sending the consignment. That adds to their work and the time we have to wait," Zhang said.

The ocean journey from London to Shanghai takes about three weeks, then the books are sterilized and stored at the port for nine days before they can be transported to Zhang's warehouse.

"We sterilize them again to make sure they are safe, because most of my employees are parents and we are very careful with things for children," she said.

Although secondhand goods are becoming popular, many parents have raised concerns about whether they are clean and safe because young children tend to put everything in their mouths.

Zhao Ziqi, father of a 4-year-old, is relaxed about the issue. "Doctors say that exposing children to bacteria can help build their immunity, and all the secondhand children's stuff was only used by other children, who are just like my own daughter. When I think in this way, I don't feel worried," he said.

Last month, Zhang was busy packing imported picture books into boxes of about 1 cubic meter, because she and her husband plan to take their son to a Hope Primary School in the Inner Mongolia autonomous region to make a donation.

Her husband used to be a volunteer teacher at the Mingde School in Tumd Left Banner in Hohhot, Inner Mongolia's capital. The children there have a great thirst for books, and a donation of secondhand items is the gift they like most.

"My husband is from Inner Mongolia, but my son has enjoyed the resources of the capital since he was born. We want him to know that children in different parts of the world live in various conditions, so he will remain grateful," Zhang said.