title: Methods for Individualized Determination of Methylmercury Elimination Rate and De-Methylation Status in Humans Following Fish Consumption.
abstract: Methylmercury (MeHg) exposure via fish in the diet remains a priority public health concern. Individual variation in response to a given MeHg exposure and the biotransformation of MeHg that follows complicate our understanding of this issue. MeHg elimination from the human body occurs slowly (elimination rate (kel) approximately 0.01 day(-1) or approximately 70 days half-life [t1/2]) and is a major determinant of the Hg body burden resulting from fish consumption. The underlying mechanisms that control MeHg elimination from the human body remain poorly understood. We describe here improved methods to obtain a MeHg elimination rate via longitudinal Hg analysis in hair using laser ablation-inductively coupled plasma-mass spectrometry. We measured MeHg elimination rates in eight individuals following the consumption of 3 fish meals in two 75-day trials separated by a 4-month washout period. In addition, since MeHg biotransformation to inorganic Hg (I-Hg) is associated with Hg excretion, we speciated Hg in feces samples to estimate individual MeHg de-methylation status. We observed a wide range of MeHg elimination rates between individuals and within individuals over time (kel = 0.0163-0.0054 day(-1); estimated t1/2 = 42.5-128.3 days). The ratio of MeHg and I-Hg in feces also varied widely among individuals. While the %I-Hg in feces was likely influenced by dental amalgams, findings with subjects who lacked amalgams suggest that faster MeHg elimination is associated with a higher %I-Hg in feces indicating more complete de-methylation. We anticipate these methods will contribute to future investigations of genetic and dietary factors that influence MeHg disposition in people.
authors.affiliation: *Department of Environmental Medicine, matthew_rand@urmc.rochester.edu.
authors.forename: Mathew D
authors.initials: MD
authors.lastname: Rand
authors.affiliation: *Department of Environmental Medicine.
authors.forename: Daria
authors.initials: D
authors.lastname: Vorojeikina
authors.affiliation: *Department of Environmental Medicine, Department of Public Health Sciences, Eastman Institute for Oral Health, Department of Pediatrics.
authors.forename: Edwin
authors.initials: E
authors.lastname: van Wijngaarden
authors.affiliation: Trace Element Analysis Laboratory, Dartmouth College, Hanover, NH 03755.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Jackson
authors.affiliation: *Department of Environmental Medicine.
authors.forename: Thomas
authors.initials: T
authors.lastname: Scrimale
authors.affiliation: *Department of Environmental Medicine.
authors.forename: Grazyna
authors.initials: G
authors.lastname: Zareba
authors.affiliation: *Department of Environmental Medicine, Department of Biostatistics and Computational Biology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642.
authors.forename: Tanzy M
authors.initials: TM
authors.lastname: Love
authors.affiliation: *Department of Environmental Medicine, Department of Pediatrics, Department of Neurology.
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Myers
authors.affiliation: *Department of Environmental Medicine, Eastman Institute for Oral Health, Department of Pharmacology and Physiology.
authors.forename: Gene E
authors.initials: GE
authors.lastname: Watson
mesh_terms: D000328:Adult; D000818:Animals; D005243:Feces / Q000737:chemistry; D005260:Female; D005399:Fishes; D005506:Food Contamination; D006801:Humans; D066237:Intestinal Elimination; D008297:Male; D008745:Methylation; D008767:Methylmercury Compounds / Q000378:metabolism*; D008875:Middle Aged; D017747:Seafood
chemical_list: D008767:Methylmercury Compounds
keywords: de-methylation; element analysis in hair; elimination rate; inorganic mercury; laser ablation ICP-MS; methylmercury