Early-effect biomarkers and hazard index approaches to assessing risks from multiple exposure to metals among battery recyclers in France

Battery-recycling may expose workers to several metals. To evaluate this multiple exposure, different tools are typically used, including early-effect biomarkers and mathematical models. This study investigates occupational exposure to metals in French battery-recycling plants, with a focus on kidney injury and oxidative stress biomarkers in urine samples. The aim was to explore the potential of these biomarkers to enhance risk assessment for workers exposed to multiple metals by examining correlations between urinary metals and effect biomarkers, and calculating a hazard index (HI) to assess cumulative exposure risk. 86 workers were recruited in 3 plants Metal exposure biomarkers (Cd, Co, Cr, Li, Mn, Ni), kidney injury biomarkers, and oxidative stress biomarkers were measured. Oxidative stress biomarkers were not sensitive enough to distinguish between exposed workers and administrative workers, with median levels reaching 43.4 and 2.85 g/g creatinine for malondialdehyde and 8-hydroxydeoxyguanosine, respectively. However, kidney injury biomarkers successfully differentiated recyclers from administrative workers, showing good correlations with urinary metals. The calculation of a HI proved effective in detecting multiple exposure to metals, offering a better risk assessment than considering metals individually. The quantification of urinary kidney injury biomarkers, such as retinol binding protein and 1-microglubulin, combined with a HI calculation, should be strongly considered in the risk assessment of workers exposed to multiple metals.