Methylmercury Excretion
The overall half-life of methylmercury in the body is 70-80
days. Reabsorption of methylmercury occurs within the bile
which results in this long half-life as indicated above.
Secretion occurs through a complexation between methylmercury
and glutathione, which then enters the bile via a glutathione
carrier protein. This complex may be reabsorbed by the gall
bladder or intestines and re-enter the bloodstream once
again. However, at some point, microorganisms in the intestinal
tract may break down the methylmercury into the inorganic
counterpart. This allows methylmercury to finally become
fecally excreted as mercuric mercury. Most excretion occurs
through the feces, however, as time increases urinary excretion
slightly increases as well (after approximately 100 days
urinary excretion is roughly 20%). Another form of unfortunate
excretion is through lactation. The clearance of methylmercury
from blood occurs faster for lactating mothers than those
who are not lactating, most likely due to increased food
intake, biliary action and changing levels of hormones.
This results in a higher concentration of mercury in breast
milk. “The ratio of mercury in breast milk to mercury
in whole blood was approximately 1:20 in women exposed to
methylmercury via contaminated grain in Iraq between 1971
and 1972. Evidence from the Iraqi poisoning incident also
showed that lactation decreased blood mercury clearance
half-times from 75 days in males and nonlactating females
to 42 days in lactating females; the faster clearance due
to lactation was confirmed in mice.” |
