revised final - Agency for Toxic Substances and Disease Registry ...

MERCURY 206
2. HEALTH EFFECTS
reabsorption rate of secreted or shed methylmercury in the gut implicitly accounts for the amount converted
(i.e., the amount of demethylated mercury that subsequently would not be reabsorbed).
Published data were used directly or to estimate values for the maternal and fetal extracellular space,
maternal plasma volume and flow expansion during pregnancy, and maternal and fetal organ volumes and
plasma flow.
The model was run with a single intravenous bolus dose of 1 mg/kg at various times during a 22-day rat
gestation period and compared with previously published (different author) maternal and fetal organ
concentrations. The model was also run with a daily dosing for 98 days, ending on Gd 20, to simulate a
typical human dietary exposure pattern for a frequent consumer of methylmercury-contaminated food.
Validation of the model. The Gray model simulations were validated against published values in the
literature for mercury concentrations in maternal and fetal rat tissue from a variety of dosing patterns over
the 22-day rat gestation period. Model-derived estimates of methylmercury half-life in red blood cells of
14.8 days for the rat were consistent with published values from 14 to 16 days. Consistent values were also
obtained for the timing of the peak mercury concentration in the brain. Model estimates were in agreement
with published values for most tissue mercury concentrations for dosing at various times, with percent
differences generally