At a Glance
Why Get Tested?
To detect excessive exposure to mercury
When to Get Tested?
When you have symptoms of mercury poisoning, to evaluate a known exposure to mercury, or to monitor occupational exposure to mercury
A blood sample taken from a vein in your arm and/or a urine collection
Test Preparation Needed?
The Test Sample
What is being tested?
Mercury is an element that exists in three forms:
- Metallic or elemental mercury. This form can be found in dental fillings, some thermometers and batteries.
- Inorganic mercury where it has combined with other elements such as oxygen or sulphur to form a salt.
- Organic mercury where it has combined with carbon to form a variety of organic compounds, the most common of which is methyl mercury. This form can be found in larger, older predator fish such as sharks and king mackerel due to bioaccumulation in the food chain.
This test measures the amount of mercury in blood, urine, or (rarely) hair to detect acute or chronic excessive exposure.
Mercury is found in small quantities throughout the environment. It is released by the breakdown of minerals in rocks and soils and as a by-product of fossil fuel combustion and waste incineration. It is inhaled with the air that we breathe, absorbed through the skin, and ingested with food. The tiny amounts to which the vast majority of people are exposed to do not generally cause health concerns but people who are exposed to dangerous concentrations of mercury (such as might be found at a hazardous waste site) or are exposed chronically to mercury (such as those who work with “heavy metals” in their occupation) may have mercury-related symptoms and complications.
Exposure to excessive amounts of mercury can be toxic. The amount of mercury absorbed by an individual and its effects on their health depends on the type of mercury, its concentration, and the exposure time. 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. However, if the same mercury is inhaled as a vapour, about 80% is absorbed into the bloodstream. About 95% of methyl mercury (the type found in fish and other seafood) is absorbed by the stomach and intestines. The most common source of human exposure to methyl mercury is as a result of eating contaminated seafood. Fish that come from contaminated waters and larger predator fish – fish that have eaten smaller fish – may have significantly increased concentrations of methyl mercury. This is why it is recommended that you know the source of the fish you consume and that you limit the quantity of large predator fish you eat.
Once mercury is absorbed, it finds its way into a variety of body organs, including the kidney and brain. The body will slowly get rid of mercury through the urine and stool, but if excessive amounts are present, it can permanently damage the kidneys, nervous system, and brain. Pregnant women with elevated blood concentrations of mercury can pass it on to their foetus, affecting development especially the foetus’s brain, kidneys, and nerves. Mercury can be passed from mother to baby through breast milk during nursing.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm, or a random or 24 hour urine sample may be collected. Rarely, another sample such as hair, breast milk, or nails may be tested.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
Ask a Laboratory Scientist
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.