Derivation of biomonitoring equivalents (BE values) for zinc

Zinc is an essential nutrient in which deficiency or excess exposure can result in adverse health effects. Several organizations have established exposure guidance values to protect against deficiency and toxicity. Population-level biomonitoring data for zinc in whole blood, serum and urine are available from the Canadian Health Measures Survey (CHMS) and the US National Health and Nutrition Examination Survey (NHANES). This paper derived Biomonitoring Equivalent values (BEs) for zinc. BEs are tools based upon exposure guidance values to interpret biomonitoring data in the context of potential health risks. A regression between intake and serum/plasma concentration was derived to generate BEs for serum/plasma and whole blood. BEs for urine were derived using mass balance approach with a urine excretion fraction of 0.04. The BE values for deficiency ranged from 860 to 866, 6017-6059 and 159-206 μg/L for serum/plasma, whole blood and urine, respectively. BEs to protect against toxicity for serum/plasma, whole blood, and urine were in the range of 895-1281, 6265-8969 and 439-3489 μg/L, respectively. When interpreting biomonitoring data in a health-risk context, urinary zinc may be a more reliable biomarker of exposure than blood due to homeostasis in blood.