Use of Urinary β2-Microglobulin in the Assessment of the Health Risk from Environmental Cadmium Exposure

Cadmium (Cd) is a ubiquitous environmental pollutant with no nutritional value or physiological role in the body. It readily accumulates in various tissues as it is easily absorbed from the diet but only poorly excreted. Due to the widespread contamination of staple foods, exposure to this toxic metal is inevitable for most people. The health risk due to dietary Cd exposure has long been underappreciated. This is primarily due to the use of urinary excretion of β2-microglobulin (β2M) as an indicator of an adverse health effect. This study employed advanced benchmark dose (BMD) modeling in a Thai cohort (n = 799) to reassess health risks from dietary Cd exposure. The BMD limit for urinary Cd was identified as 0.17 μg/g creatinine when using a reduction in estimated glomerular filtration rate (eGFR) as the endpoint, whereas no reliable BMD could be established using β2-microglobulin excretion. Given that eGFR reduction is a more reliable indicator of chronic kidney disease, its use is recommended for deriving health-protective guidelines. The findings demonstrate that the current urinary Cd threshold of 5.24 μg/g creatinine is inadequate, supporting the adoption of a threshold below 0.20 μg/g creatinine in future exposure guidelines.