France's national library said Thursday it had removed four 19th-century books from its shelves whose emerald green covers were likely laced with highly poisonous arsenic.

The library said handling the books -- which were printed in Britain -- would probably cause only minor harm, but it was taking them away for further analysis.

"We have put these works in quarantine and an external laboratory will analyse them to evaluate how much arsenic is present in each volume," it said.

The Paris institution identified the offending copies after US researchers discovered publishers in the Victorian era had used the chemical to colour book bindings.

The arsenic-containing green pigments were called Paris Green, Emerald Green or even Scheele's Green after a German-born chemist.

Testing hundreds of book covers for heavy metals since 2019, researchers at the University of Delaware have drawn up a list of potentially dangerous volumes as part of the Poison Book Project.

The French library found its collection of more than 16 million titles included four copies of books on the list.

They include two volumes of "The Ballads of Ireland" by Edward Hayes published in 1855, a bilingual anthology of Romanian poetry by Henry Stanley from 1856, and the 1862-1863 book of the Royal Horticultural Society.

The National Library of France said it would also examine other green covered books "beyond the Poison Book Project list".

The World Health Organization warns long-term exposure to inorganic arsenic, mainly through drinking water and food, can lead to skin lesions and skin cancer.

But it makes no mention of contact with objects containing it.

The Poison Book Project says arsenic-laced green bindings present a health risk to librarians, booksellers, collectors and researchers, and should be handled and stored with caution.