Mercury testing is used to detect the presence of an excessive amount of mercury in a person's blood and/or urine sample. It may be ordered by a health practitioner to determine whether a person has had short-term exposure to a toxic level of mercury (acute exposure) or has been exposed over an extended period of time (chronic exposure). Testing may also be used to monitor those who may be exposed to mercury in the workplace.
To test for the various forms of mercury [see What is being tested?], more than one type of sample may be collected and tested.
Blood is primarily tested to detect the presence of methyl mercury. Other forms of mercury (metallic and inorganic) can also be detected in the blood, but the amount present will decrease by half about every 3 days as the mercury moves into organs such as the brain and kidneys. Therefore, blood testing must be done within days of suspected exposure.
Urine is used to test for metallic mercury and inorganic forms of mercury, but it cannot be used to determine exposure to methyl mercury.
Hair testing may be useful to detect methyl mercury exposures that occurred several months previously, but hair testing is relatively complex and is not used frequently.
Although not routinely ordered tests, mercury has been shown to be present in nails, breast milk, stool, and breath.
Mercury testing may be ordered when a person has signs and symptoms suggesting excessive exposure to mercury. Acute signs and symptoms may include:
Burning in the mouth and lungs
Cough, difficulty breathing, chest tightness
Difficulty urinating and decreased urine output
Nausea, vomiting, diarrhea, or abdominal cramping
Increased heart rate
Fever or chills
Those who are chronically exposed may have nonspecific symptoms that involve the lungs, kidneys, and nervous system. Some of the chronic symptoms may include:
Problems with hearing, taste and smell
Blurry vision or sometimes tunnel vision
Tingling or tremors in the arms or legs
Testing may also be ordered even in the absence of symptoms when it is known that a person has been exposed to mercury in order to help evaluate the extent of the exposure.
Mercury measurements may be ordered regularly as a monitoring tool for those people who work in industries that utilize mercury and may be ordered, along with tests to detect lead and/or other heavy metals, for individuals who work with a variety of potentially hazardous materials.
Levels of mercury in blood and urine are normally very low. A test result showing no mercury or a low level indicates that it is likely that the person tested has not been exposed to excessive levels of mercury, at least not in the window of time that the test is measuring.
An increased blood level suggests a relatively recent exposure to mercury. In general, a blood level greater than 10 mcg/L indicates an unusual level of exposure for someone who does not regularly work with mercury.
In contrast to levels of mercury in the blood, a 24-hour urine sample gives more of an average past history of exposure to metallic or inorganic mercury. Normal urine levels are typically less than 10 mcg/L for someone without risk of occupational exposure. (For information on occupational exposure levels, see the Related Pages tab.)
Levels of mercury in either the blood or urine will not indicate the form or quantity of mercury to which a person was exposed.
An increased level of mercury in hair testing may indicate exposure to increased levels of methyl mercury, but hair samples are rarely used because of issues involving testing standardization, sample contamination, and the fact that hair is subject to many pre-analytical variables (hair exposure to dyes, bleach, shampoo, etc.).
Measures have been taken in recent years to reduce and control the public's exposure to mercury. Stricter regulations and recommendations have lowered the amounts allowable in the air, water, soil, food, and in the workplace.
The high levels of mercury found in certain fish may harm the developing nervous systems in unborn babies and young children. The U.S. Food and Drug Administration (FDA) recommends that pregnant women, women who may become pregnant, young children, and nursing mothers avoid eating shark, swordfish, king mackerel and tilefish. It advises these groups to eat fish that are usually found to have lower levels of mercury such as canned light tuna, shrimp, or salmon.
This article was last reviewed on October 29, 2014. | This article was last modified on October 29, 2014.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
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