The kinetics of blood deposition and clearance of methylmercury were measured in volunteers given a single meal of fish containing 18 to 22 microgram mercury/kg body weight. Peak blood concentrations were achieved within 4 to 14 hr. Disappearance from blood was biphasic, with average half-times of 7.6 hr and 52 days, respectively. The fraction of the dose deposited in the blood volume after completion of tissue distribution was 5.9%. Blood concentrations of total mercury reached as high as 60 ng mercury/ml, whereas inorganic mercury did not exceed 2 ng mercury/ml. The average red blood cell to plasma concentration ratio was 21 and the hair to blood ratio was 292. The kinetic parameters relating to blood deposition and clearance were used to calculate the expected relationship between average long-term daily intake of methylmercury and steady state blood concentration.

Samples of blood and head hair were analyzed for organic and inorganic mercury from a population which consumed large amounts of fish contaminated with methylmercury. Mercury levels in newly formed hair were found to reflect those in blood with the concentration in hair being approximately 300 times that in blood. Organic and inorganic mercury levels were linearly related in both hair and blood samples, with a mean inorganic/organic ration of 0.05 in blood and 0.21 in hair, but individual differences were found to exist. In addition, the total mercury concentration and inorganic/organic ratio in hair remained constant with time. Thus, longitudinal analysis of hair samples can provide a simple and accurate method of monitoring continuing exposure and an estimation of peak blood levels months to years after exposure.

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