virtually none (less than 0.01%) of the mercury will enter your body through the
stomach or intestines, unless they are diseased. Even when a larger amount of metal mercury (a
half of a tablespoon, about 204 grams) was swallowed by one person, very little entered the body.
When you breathe in mercury vapors, however, most (about 80%) of the mercury enters your
bloodstream directly from your lungs, and then rapidly goes to other parts of your body, including
the brain and kidneys. Once in your body, metallic mercury can stay for weeks or months. When
metallic mercury enters the brain, it is readily converted to an inorganic form and is “trapped” in
the brain for a long time. Metallic mercury in the blood of a pregnant woman can enter her
developing child. Most of the metallic mercury will accumulate in your kidneys, but some
metallic mercury can also accumulate in the brain. Most of the metallic mercury absorbed into the
body eventually leaves in the urine and feces, while smaller amounts leave the body in the exhaled
breath.

If they are inhaled, they are not expected to enter your body as easily as inhaled metallic mercury vapor.
When inorganic mercury compounds are swallowed, generally less than 10% is absorbed through
the intestinal tract; however, up to 40% may enter the body through the stomach and intestines in
some instances. Some inorganic mercury can enter your body through the skin, but only a small
amount will pass through your skin compared to the amount that gets into your body from
swallowing inorganic mercury.
Once inorganic mercury enters the body and gets into the bloodstream, it moves to many different
tissues. Inorganic mercury leaves your body in the urine or feces over a period of several weeks or
months. A small amount of the inorganic mercury can be changed in your body to metallic
mercury and leave in the breath as a mercury vapor. Inorganic mercury accumulates mostly in the
kidneys and does not enter the brain as easily as metallic mercury. Inorganic mercury compounds
also do not move as easily from the blood of a pregnant woman to her developing child. In a
nursing woman, some of the inorganic mercury in her body will pass into her breast milk.

Methylmercury is the form of mercury most easily absorbed through the gastrointestinal tract
(about 95% absorbed). After you eat fish or other foods that are contaminated with methylmercury,
the methylmercury enters your bloodstream easily and goes rapidly to other parts of your body.
Only small amounts of methylmercury enter the bloodstream directly through the skin, but other
forms of organic mercury (in particular dimethylmercury) can rapidly enter the body through the
skin. Organic mercury compounds may evaporate slowly at room temperature and may enter your
body easily if you breathe in the vapors. Once organic mercury is in the bloodstream, it moves
easily to most tissues and readily enters the brain. Methylmercury that is in the blood of a
pregnant woman will easily move into the blood of the developing child and then into the child’s
brain and other tissues. Like metallic mercury, methylmercury can be changed by your body to
inorganic mercury. When this happens in the brain, the mercury can remain there for a long time.
When methylmercury does leave your body after you have been exposed, it leaves slowly over a
period of several months, mostly as inorganic mercury in the feces. As with inorganic mercury,
some of the methylmercury in a nursing woman’s body will pass into her breast milk.