Old editions of the 19th century should be handled with care and it is better not to touch them at all. Some paints on their covers contain heavy metals that are harmful to health – arsenic, lead, chromium. Participants of the crowdsourcing project “Toxic Books” discovered dangerous copies using the latest analytical methods.

Ian Kohu and Michaela Rutledge, librarians at Lipscomb University (USA), asked chemists to check the glossy cloth-bound books of the 19th and early 20th century in the Beeman School collection. Assistant Professor of Chemistry Joseph Weinstein Webb stepped in to help. He was familiar with the work of colleagues at the Winterthur Estate Museum, Garden and Library, who had examined 19th-century books for the presence of a green pigment known as Paris green. In fact, it is an arsenic compound, a mixture of copper acetate-arsenite. It turned out to be used in wallpaper, fabric and book covers in the Victorian era.

The Winterthur scientists’ discovery led to the creation of the crowdsourced “Toxic Books” project, in which participants search for toxic pigments in publications around the world using analytical research methods. In 2022, Weinstein-Webb joined the project with her research, along with her students Abigail Horman, Jafer Aljorani and Leila Ays.

“Antique books containing toxic paints can be found in universities, public libraries and private collections. We want to find a universal way to know if there is a risk of exposure and how to store such publications safely,” Horman explained in a presentation at the annual conference of the American Chemical Society, which is currently being held in a hybrid format.

Scientists used X-ray fluorescence analysis to detect arsenic or other heavy metals on book covers. Optical emission spectrometry with inductively coupled plasma (ICP-OES) helped determine the concentration of these substances. The X-ray diffractometric method (XRD) made it possible to determine the chemical compounds that make up the pigments. This method has already proven itself in the analysis of paintings and wallpapers, and was first applied to books.

The authors of the article were able to detect lead and chromium in books from the Lipscomb Library with the help of X-ray fluorescence analysis. To determine the amount, they cut small pieces from the covers and dissolved them in nitric acid. The ICP-OES method revealed that some samples contained high levels of these metals. These were then sent to an XRD analyzer, which showed the presence of lead(II) chromate in some of them. This compound is part of chrome yellow, a pigment that Van Gogh liked to use to paint sunflowers.

The analysis showed that there was much more lead than chromium, and that there should be an equal amount in yellow chromium. The authors may have suggested that the book inks contained other lead pigments such as lead(II) oxide or lead(II) sulphide. This point needs further clarification.

Some copies had levels of heavy metals on their lids that exceeded the limits set by the U.S. Centers for Disease Control and Prevention for long-term exposure. In many cases, lead was more than twice normal, and chromium was almost six times higher. Continued long-term inhalation of lead and chromium can cause cancer and damage to the lungs and reproductive functions.

According to the results of the research, colorful books of the 19th century were placed in zippered bags in the university library. Those that turned out to be poisonous were removed from public access, and those that had not yet been tested were sent to storage.