Derivation of whole blood biomonitoring equivalents for lithium for the interpretation of biomonitoring data

Abstract

Introduction Lithium salts have numerous industrial uses and are also used in the treatment of bipolar disorders. The main source of lithium exposure to the general population is drinking water and foods. Lithium is nephrotoxic at higher doses. Thus, oral exposure guidelines for lithium have been derived, including ICH's permitted daily exposure (PDE = 0.008 mg lithium/kg-bw/day) adopted by Health Canada and the United States Environmental Protection Agency's (U.S. EPA) provisional peer reviewed toxicity value (PPRTV = 0.002 mg lithium/kg-bw/day), both based on human data. Objective To derive whole blood biomonitoring equivalents (BEs) associated with PDE and PPRTV to interpret population-level biomonitoring data in health risk context. Method A simple kinetic relationship based on plasma clearance value (0.5 L/kg-bw/day) and the oral absorption fraction (100%) was used to derive blood BEs for PDE and PPRTV. Results This analysis resulted in BE values in plasma and whole blood of 16 and 10 μg/L, respectively, based on the PDE values developed by the Health Canada and of 4.2 and 2.7 μg/L, respectively, based on the PPRTV developed by U.S. EPA. Conclusion The derived BE values can be used to interpret population-level biomonitoring data.