Airborne metals and microorganisms during work with historical books – Exposure and biomonitoring

Exposure to metals and microorganisms can pose health risks. Historical books often contain pigments with metals, and fungi. The aim of this study is to obtain knowledge about exposure to eight metals and microorganisms in a library in Denmark. Personal exposure of staff handling historical books (high-exposure group) and indoor and outdoor air samples were collected in three well-ventilated sites of a library. Urine samples were collected the next morning from the high-exposure group, a low-exposure group (colleagues not handling historical books), and a reference group. Eight metals were measured in air and urine samples using inductively coupled plasma mass spectrometry (ICP-MS). Bacteria and fungal species were identified using MALDI-TOF MS. Personal exposure to metals was higher than in stationary indoor and outdoor air samples, particularly for arsenic (As), lead (Pb), mercury (Hg), and cadmium (Cd), and some were spread to the indoor air. Personal exposure to As, Cd, and Hg showed a significant correlation with Pb levels. The overall indoor/outdoor ratio of personal exposure exceeded 1 for all metals except antimony (Sb) indicating potential indoor source. Additionally, Cd and As concentrations in some urine samples exceeded Biological Limit and Guidance Values. Most fungal species detected belonged to Aspergillus and Penicillium, and eight species are xerophilic. In conclusion, library staff were exposed to higher concentrations of metals as compared to outdoor air, warranting further research across different tasks and days for staff handling historical books to understand these risks better.