Q: Should I be tested for mercury? I hear a lot about its danger—from fish, dental fillings, and pollution.
A: Not unless you know you’ve had high exposure to mercury (for instance, if you work with heavy metals at your job) or you have symptoms that your doctor thinks may be caused by mercury poisoning.
Mercury occurs naturally in the environment and also comes from industrial pollution. Since it’s widespread, almost all people have traces of it in their bodies. At high levels, mercury can cause gastrointestinal, kidney, and neurological damage and even death. Relatively low levels can harm fetuses, infants, and young children.
Routine screening for mercury is not recommended. There are different types of mercury and different ways to measure it. The choice of test depends largely on how a person was likely exposed. Urine tests, for example, can’t detect methylmercury (the type in fish), but blood tests can. Hair, saliva, and breath tests tend to be least reliable. In addition, no one knows what to do about mildly elevated levels.
The symptoms of mercury poisoning vary greatly, from subtle to severe, so it’s easy to blame nearly any problem on it. Thus, misleading results from mercury testing can be used to frighten people into having unnecessary, useless, or dangerous procedures, such as chelation therapy to remove heavy metals from the blood.
Because amalgam (“silver”) dental fillings contain mercury for strength and durability, some dentists (or other practitioners) do dubious mercury tests as a step toward replacing all the fillings. Amalgam may release minuscule amounts of mercury, but there is no clear evidence that these levels are toxic or that they cause disease or other harm.
This article first appeared in the UC Berkeley Wellness Letter. Originally published March 2012; updated November 2019.
Also see Cautions About Fish Consumption.