A meta-analysis of literature data relating to the relationships between cadmium intake and toxicity indicators in humans

The objective of the study was to determine the relationship between cadmium (Cd) intake and cadmium toxicity indicators by meta-analysis of literature data, in particular β2-microglobulin (β2MC), and to compare the results with the current Provisional Tolerable Weekly Intake (PTWI) set by FAO/WHO. The literature survey identified 79 feeding trials involving 27,537 people that were suitable for extraction of cadmium intake, levels in blood and urine and β2-microglobulin in urine. There was an exponential increase in β2-microglobulin with increases in cadmium intake above 302 μg/day, which corresponds to a PTWI of 3.02 μg/kg of body weight, when a safety margin of 10 is included. This compares with the current level set by FAO/WHO of 7 μg/kg of body weight. Cadmium in blood and urine were also positively related to cadmium intake and participants’ age. There were two principal components of variation in the data set, first: cadmium intake, concentrations of cadmium in blood, urine and β2-microglobulin in urine, and second: duration and age of exposure.