Mercury in the body
Q
What is a common means used to measure methylmercury concentration in the body?
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A
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Hair is commonly used, for it concentrates the most in hair.
Some of the methylmercury contained in the body comes out into hair, nails, breast milk and urine.
Compared to levels in blood, methylmercury is over 200 times more concentrated in hair.
In other words, methylmercury in the body appears at concentrated levels in hair. It is for that reason, and also because it is easy to handle, that hair is used as an indicator for methylmercury intake.
Q
What form of mercury is easily absorbed from the digestive tract (small intestine)?
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A
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Among the forms of mercury present in nature, methylmercury is the most easily absorbed.
Among the forms of mercury present in nature, a majority of methylmercury gets absorbed from the digestive tract (small intestine). In contrast, only a few percent of inorganic mercury salts get absorbed that way.
Methylmercury, bound with a type of amino acid called cysteine, has a property of getting easily absorbed from the digestive tract and then penetrating into various parts of the body. Therefore, it can also make its way inside the brain and damage nerve cells, or cross the barrier of the placenta that connects a fetus with its mother, eventually entering the body of the fetus as well.
Metallic mercury, which hardly gets absorbed from the digestive tract, is easily vaporized and nearly 80% of inhaled metallic mercury vapor gets absorbed from the lungs. Depending on the volume absorbed, this may cause poisoning. There are examples of cases overseas that relate to exposure to vaporized mercury used in the process of gold mining.
Q
When methylmercury gets absorbed from the digestive tract (small intestine), where does it go first?
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A
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Methylmercury absorbed from the digestive tract (small intestine) gets carried to the liver first.
Various nutrients absorbed from the digestive tract (small intestine) get carried to the liver first via a blood vessel called the portal vein.
The liver is an organ that acts like a distribution center in the body, from which nutrients are delivered to all parts of the body, including the kidneys and brain.
Largely via the same routes as nutrients (amino acids) are delivered, methylmercury, after being absorbed, enters the liver once and then gets delivered all over the body.
Q
How much of the methylmercury contained in fish eaten today would still remain in the body after one year?
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A
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Approximately 3% would remain after one year.
It is said that the time required for half of a methylmercury body burden to be excreted (the biological half-life) is about 70 days in humans.
As this means that methylmercury remaining in the body would halve every 70 days, it could be calculated as dropping to 25% in 140 days, 12.5% in 210 days.... and, finally, 3.125% in 350 days (approximately one year).
Q
When one is exposed to methylmercury, is there a way to have it excreted?
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A
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Some food and drugs are known to have an effect of excreting methylmercury out of the body.
There are several foods and drugs known to have an effect of having methylmercury leave the body through excrements.
When exposure is noticed, it is critical to perform such excretion treatment as soon as possible.
Such intervention can also be expected to mitigate neurological and other symptoms potentially caused by methylmercury.