Chemical Forms of Mercury in Blue Marlin Billfish: Implications for Human Exposure

Although fish is an important source of nutrients, including some the healthiest proteins, long-chain fatty acids, and essential selenium, species at top food chain frequently contain large amounts toxic mercury (Hg). The provisional tolerable weekly intake (PTWI) Hg from consumption calculated total concentration assuming that all speciated as organic methylmercury (MeHg). Using high energy-resolution X-ray absorption near-edge structure (HR-XANES) spectroscopy, we show blue marlin (Makaira sp.), a common predator consumed by humans, contains concentrations inorganic Hg(II) complexed 57 ± 10% Hg-tetraselenolate [Hg(Sec)4] 43 tiemannite (HgSe). stable Hg–Se chemical bond likely attenuates bioavailability counteracts its health hazards to consumers. Thus, monitoring MeHg, rather than Hg, in predators such would provide more robust measure potential exposure may be sufficient for safety controls. bonding atoms four selenocysteine (Sec) residues Hg(Sec)4 complex severely depletes stock bioavailable Se, quantification shows not chief dietary Se selenoenzyme synthesis activity.