Mercury Test

About the Test

Purpose of the test

Testing detects the presence of an excessive amount of mercury in your blood and/or urine sample. A health care practitioner may order testing to determine whether you had short-term (acute) exposure to a toxic level of mercury or have 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, more than one type of sample may be collected and tested.

• Blood is primarily tested to detect methylmercury, the type found in fish and other seafood. Other forms of mercury (metallic and inorganic) can also be detected in the blood, but the amount present will decrease by half about every three days as the mercury moves into organs such as the brain and kidneys. 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 alone to determine exposure to dietary methylmercury.
• Hair testing may be useful to detect methylmercury exposures that occurred several months previously, but this type of testing is relatively complex and used infrequently.
• Although not routinely ordered tests, mercury has been shown to be present in nails, breast milk, stool, and breath.

Other general laboratory tests may be used to help evaluate the health of various organ systems in someone who has been exposed or thought to be exposed to toxic levels of mercury. Some examples include a comprehensive metabolic panel (CMP) and a complete blood count (CBC).

What does the test measure?

Mercury is an element that can be toxic in various forms, which are tested in different samples:

• Metallic or elemental mercury is a liquid often used in dental fillings, some thermometers, and batteries. Urine samples are typically tested to detect this form of mercury.
• Inorganic mercury salts, produced by the reaction of non-carbon based compounds with mercury, are normally in powder or crystal form. They are sometimes used in topical preparations such as skin-lightening or antiseptic creams. Urine samples are usually used to detect this form of mercury.
• Methylmercury and other organic mercury compounds are products of reactions between mercury and carbon-based organic compounds. Bacteria with elevated methylmercury levels are often in large, older predator fish such as sharks and king mackerel so eating those may expose you. Blood is primarily used to identify a high level of methylmercury.

The tiny amounts to which the vast majority of people are exposed do not generally cause health concerns. But you may develop mercury-related symptoms or complications if exposed to dangerous concentrations of mercury at a hazardous waste site or if you are exposed over long periods of time — especially when working with heavy metals.

Exposure to excessive amounts of mercury can be toxic. The amount of mercury you absorb and its effects on your health depend on the type of mercury, its concentration, and the nature of exposure.

According to the Agency for Toxic Substances and Disease Registry (ATSDR), very little metallic mercury (less than 0.01%) is absorbed by the body, even if it is swallowed. But if the same mercury is inhaled as a vapor, about 80% is absorbed into the bloodstream.

About 95% of methylmercury is absorbed by the digestive tract. The most common source of human exposure to methylmercury is eating contaminated seafood. Fish from contaminated waters and large predator fish that have eaten smaller fish may have significantly increased levels of methylmercury. It is important to know the source of the fish that you consume and to limit the quantity of large predator fish eaten.

Once mercury is absorbed, the body may deposit it in a variety of organs, including the kidneys and brain. The body will slowly rid itself of mercury through the urine and stool, but if an excessive amount accumulates, it can permanently damage the kidneys, nervous system, and brain.

Pregnant women with elevated levels of mercury can pass it on to their unborn baby, affecting development of the baby’s brain, kidneys, and nerves especially. Mercury can also be passed from mother to baby through breast milk during nursing.

When should I get this test?

Mercury testing may be ordered when you have signs and symptoms suggesting excessive exposure. 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
• Dizziness
• Headache

If you are chronically exposed you may have nonspecific symptoms that involve the lungs, kidneys, and nervous system. Some of these symptoms may include:

• Problems with hearing, taste and smell
• Blurry vision or sometimes tunnel vision
• Tingling or tremors in the arms or legs
• Difficulty walking
• Irritability
• Memory loss

To help evaluate the extent of the exposure, testing may also be ordered even in the absence of symptoms when it is known you have been exposed to mercury.

Mercury measurements may be ordered on a regular basis to monitor people who work in industries that use mercury. It 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.