21.6.3.3 Organic Mercury Mercury excretion after methylmercury exposure is
predominantly via the feces. Methylmercury is slowly demethylated in the gut, and the
enterohepatic recirculation of methylmercury explains that most, if not all, of the mercury
excreted is in the demethylated inorganic form. Some elimination also occurs via urine. The
whole-body half-time of methylmercury is generally about 45 days, although higher
estimates have also been published. Laboratory animal studies have shown that
following acute dosage with methylmercury, blood mercury concentrations will initially
reflect organ concentrations reasonably well. Henceforth, an increasing fraction of the body
burden will be in the brain, muscles, and kidney.
The blood concentration might be a useful indicator of the body burden of mercury while
the erythrocyte mercury concentration is more specific for methylmercury exposure.
Accordingly, if exposure to mercury vapor or other inorganic mercury compounds is
suspected, mercury should be speciated or a serum sample analyzed. Mercury in hair,
when measured along the length of a hair strand, has also been used as an indicator of past
blood levels. When using hair as an indicator, it is important to note the history and condition
of the hair. Permanent waving may leach mercury from the hair while exogenous mercury
can increase its concentration. Cord blood (or cord tissue) measurement is the best method to
establish prenatal exposure levels.
21.6.3.3 Organic Mercury Mercury excretion after methylmercury exposure ispredominantly via the feces. Methylmercury is slowly demethylated in the gut, and theenterohepatic recirculation of methylmercury explains that most, if not all, of the mercuryexcreted is in the demethylated inorganic form. Some elimination also occurs via urine. Thewhole-body half-time of methylmercury is generally about 45 days, although higherestimates have also been published. Laboratory animal studies have shown thatfollowing acute dosage with methylmercury, blood mercury concentrations will initiallyreflect organ concentrations reasonably well. Henceforth, an increasing fraction of the bodyburden will be in the brain, muscles, and kidney.The blood concentration might be a useful indicator of the body burden of mercury whilethe erythrocyte mercury concentration is more specific for methylmercury exposure.Accordingly, if exposure to mercury vapor or other inorganic mercury compounds issuspected, mercury should be speciated or a serum sample analyzed. Mercury in hair,when measured along the length of a hair strand, has also been used as an indicator of pastblood levels. When using hair as an indicator, it is important to note the history and conditionof the hair. Permanent waving may leach mercury from the hair while exogenous mercurycan increase its concentration. Cord blood (or cord tissue) measurement is the best method toestablish prenatal exposure levels.
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