The hidden arsenic legacy in mid-19th century papered microscope slides

• Victorian microscope slides may contain arsenic pigments, posing health risks. • XRF analysis identified arsenic in both green and red pigments on Victorian slides. • Analysis of collection images suggests a significant potential for widespread arsenic presence. • Study highlights potential environmental hazard from historical slides. • The study proposes guidelines for safe handling and disposal of potentially hazardous slides. This study investigated the presence of arsenic in Victorian-era microscope slides, particularly those containing green pigments. X-ray fluorescence (XRF), Raman, Surface Enhanced Raman Spectroscopy (SERS) and Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES) were employed to analyse the elemental composition of pigments on the slides. The analysis identified arsenic primarily in green pigments containing emerald green but also in some red pigments. To assess the prevalence of slides potentially containing arsenic, a separate analysis was conducted examining the colour of slides in existing collections. Across two data sources, focusing on slides with accompanying images, around 10 % of slides were identified to contain green pigment. Extrapolating this prevalence to UK collections suggests a potential for hundreds of thousands of slides to contain arsenic, posing potential health risks during handling and raising concerns about proper disposal practices. This research highlights a previously unrecognised occupational and environmental hazard associated with historical slides. The study emphasises the importance of responsible handling and disposal practices for slides containing arsenic pigments, particularly those coloured green and red, to minimise health and environmental risks. We propose guidelines for safe handling and disposal practices, alongside outreach activities to raise awareness among stakeholders.