Those childhood classics like "Cat in the Hat" and "Where the Wild Things Are" may contain trace amounts of lead.
This discovery has started a federal law banning more than minute levels of lead in most products intended for children 12 and under. So far, two libraries pulled children's books printed before 1986 from their shelves, according to the Associated Press.
But could they be hazardous to your children? Probably not, said the Centers for Disease Control and Prevention.
Out of several North County libraries, only one had taken any books off the shelves as a result of the warning, reported the North County Times.
"It comes at a really bad budget time, but it's really important to follow the law and uphold it," Cynthia Smith, Escondido deputy city librarian told the North County Times. She said 100 books had been removed there.
Lead poisoning has been linked to irreversible learning disabilities and behavioral problems. Lead was also used in printers ink until it was banned in 1986. This new federal law banning lead in books took effect February 10 of this year, after a string of toy recalls.
A Consumer Product Safety Commission (CPSC) spokesman told the Associated Press that, until more testing is done, the nation's more than 116,000 public and school libraries should take steps to make sure to keep children away from books that were printed before 1986.
The CPSC has come to the conclusion that these older books could include lead, but hasn't said that these books could be hazardous to children nor told libraries to take them off the shelves.
Health communications specialist Jay Dempsey said the lead-based ink in children's books poses little danger.
"If that child were to actually start mouthing the book, that's where the concern would be," said Dempsey.
Out of the two libraries that responded to this, one roped off the children's section and the other put a tarp over the children's books.