Author: Rooney JP.
Source: Toxicol Appl Pharmacol.
Year: 2013
Comment:
The author of this review states, "In conclusion, the body of evidence points towards inorganic mercury in humans having a very long half-life in the brain – likely years or decades long. Evidence from cases of mercury poisoning indicates it is likely at least several years and possibly over 5 years. Probably the best estimate of half-life in humans remains the 1978 estimate by Sugita (Sugita, 1978) of 22 years although this is based on a strong assumption of a linear relationship between food consumption by age and organ mercury level."
Abstract / Excerpt:
“Reports from human case studies indicate a half-life for inorganic mercury in the brain in the order of years-contradicting older radioisotope studies that estimated half-lives in the order of weeks to months in duration. This study systematically reviews available evidence on the retention time of inorganic mercury in humans and primates to better understand this conflicting evidence. A broad search strategy was used to capture 16,539 abstracts on the Pubmed database. Abstracts were screened to include only study types containing relevant information. 131 studies of interest were identified. Only 1 primate study made a numeric estimate for the half-life of inorganic mercury (227-540days). Eighteen human mercury poisoning cases were followed up long term including autopsy. Brain inorganic mercury concentrations at death were consistent with a half-life of several years or longer. 5 radionucleotide studies were found, one of which estimated head half-life (21days). This estimate has sometimes been misinterpreted to be equivalent to brain half-life-which ignores several confounding factors including limited radioactive half-life and radioactive decay from surrounding tissues including circulating blood. No autopsy cohort study estimated a half-life for inorganic mercury, although some noted bioaccumulation of brain mercury with age. Modelling studies provided some extreme estimates (69days vs 22years). Estimates from modelling studies appear sensitive to model assumptions, however predications based on a long half-life (27.4 years) are consistent with autopsy findings. In summary, shorter estimates of half-life are not supported by evidence from animal studies, human case studies, or modelling studies based on appropriate assumptions. Evidence from such studies point to a half-life of inorganic mercury in human brains of several years to several decades. This finding carries important implications for pharmcokinetic modelling of mercury and potentially for the regulatory toxicology of mercury.”
Citation:
Rooney JP. The retention time of inorganic mercury in the brain - A systematic review of the evidence. Toxicol Appl Pharmacol. 2013; 274(3):425-435.