Sources of Mercury Exposure

Need another reason to avoid soda?  It may contain mercury!  I know, I know, for those of you who are seasoned SIBO warriors or health enthusiasts, avoiding soda is probably a “no brainer”.  It probably doesn’t even sound good to you!  But I couldn’t help but share a 2009 research article that analyzed a few brands of high fructose corn syrup for the presence of mercury.  Sure enough- it was in there.

My interest in researching sources of mercury exposure came from my suspicion that it could be an underlying cause for some people’s SIBO.  When I dug in deeper, I was surprised by how many different sources of mercury were out there.  We can’t completely avoid it, but we can certainly improve our detoxification pathways to help reduce the body burden that could accumulate.  Read on to learn more!

About Mercury:

Mercury is a highly toxic heavy metal that is naturally present in the environment.  It is released through volcanic activity as well as through the breakdown of minerals from rocks and soil.  However, human activity has resulted in an increased release of this toxic metal into the environment.  Mercury is listed as one of the top 3 substance priorities on a list produced by the U.S. Agency for Toxic Substances and Disease Registry.  The substance priority list is generated based on the frequency, toxicity, and potential for human exposure of the various chemicals on the list.

There are three different forms of mercury: organic, elemental, and inorganic.  Microorganisms (such as bacteria and fungi) can convert mercury between its different forms.  Organic mercury is recognized to be the most harmful form of mercury.  Additionally, both organic mercury and elemental mercury can cross the blood-brain barrier and reach the placenta of a developing fetus.  Inorganic mercury cannot cross either of these barriers and instead accumulates in the kidneys and can cause gastrointestinal issues. [1]

Below is a review of some of the various sources of mercury exposure.  It is not an exhaustive list, but contains many of the common sources as well as some of the more obscure ones.  For a more complete list of household items containing mercury, check out this comprehensive guide from the EPA.

Organic Mercury (such as methylmercury & ethylmercury):

  • Vaccines Containing Thimerosal [2]:
    • Thimerosal is a form of ethylmercury that has been used as a preservative in vaccines since the 1930s.  It is used to help prevent bacteria, fungi, and other germs from growing in the vaccine vial.  The CDC reports that since 2001 no new thimerosal-containing vaccines have been approved by the FDA for use in children. Additionally, the CDC reports that “all vaccines routinely recommended by [the] CDC for children younger than 6 years of age have been thimerosal-free, or contain only trace amounts of thimerosal.”  (The trace amounts come from processing).  If you are looking to reduce your exposure to mercury, but would still like to get vaccines, it may be wise to ask your doctor for an ingredient listing beforehand so that you can be an informed consumer.  This may be especially pertinent in regard to the flu vaccine.  According to the CDC, multi-dose vials of the 2014-2015 flu vaccine do contain thimerosal.
  • Fish [3]:
    • When it comes to mercury content, not all fish are created equally.  Typically, the larger fish have higher mercury contents due to their longer lifespan and accumulating the toxin from eating other fish.  The Natural Resources Defense Counsel (NRDC) has created a helpful brochure that can be used to determine the safest fish to eat.  The worst offenders (they recommend avoiding these completely) include king mackerel, marlin, orange roughy, shark, swordfish, tilefish, ahi tuna, and bigeye tuna.  The next most toxic (which they recommend eating no more than 3 servings per month) include bluefish, grouper, Spanish mackerel, gulf mackerel, Chilean sea bass, canned albacore tuna, and yellowfin tuna.
  • Animals Fed Fish Meal [4]:
    • If animals (such as poultry and farmed fish) are fed contaminated feed in the form of fish meal, the mercury tends to accumulate in their fat tissue and then when the fat from that animal is consumed by the human, it can create a source of exposure for the human.
  • Pesticides/Fungicides/Herbicides [5]:
    • Prior to 1995, some pesticides and related items used to kill weeds contained mercury.

Elemental Mercury (also called Metallic Mercury):

  • Dental Amalgams [6]:
    • A plethora of studies are available to show increased mercury levels in individuals with amalgam fillings.  A Spanish study published in 2015 found significantly higher levels of mercury in the hair of individuals with amalgam fillings than those without.  Interestingly, these individuals also had higher levels of aluminum, silver, and barium.
  • Thermometers [5]
    • Have you ever broken a glass thermometer?  Many body temperature thermometers contain mercury in a glass bulb at the end of the thermometer.  If the thermometer is intact it does not pose a problem.  However, if the thermometer breaks, it poses a risk of causing mercury toxicity.  For information on how to properly clean up a mercury spill, check out this website.  I use a mercury-free oral glass thermometer  from RG Medical Diagnostics which seems to provide accurate readings.
  • Thermostats [5]
    • I recently noticed that the thermostat used for adjusting the heat in my house has a warning label: “mercury contained inside.”  Some thermostats have mercury switches inside of them.  Similarly to thermometers, if the glass is not broken, the mercury does not cause a problem.  Non-mercury thermostats are available for extra caution.  Before you go demoing your next house, check out this resource to figure out how to properly dispose of thermostats and other mercury-containing items in your building.
  • Sphygmomanometers (Blood Pressure Cuffs) [5]
    • Same story as thermometers and thermostats- only an issue if glass tube containing mercury is broken.
  • Fluorescent Light Bulbs [5] 
    • Don’t break these either.  You can tell if a light bulb contains mercury by looking at the label on the box.  Incandescent, LED, and halogen bulbs do not contain mercury, but they are less energy efficient.  Make sure to properly dispose of mercury-containing light bulbs at the end of their lives.  Here are instructions for cleaning up mercury from a broken light bulb.
  • Mercury-Containing Latex Paints [7]
    • A chemical known as phenylmercuric acetate was used as a preservative to deter the growth of bacteria and fungi in latex paint.  In 1990 the EPA banned the addition of this ingredient in paint manufacturing.  Before this time, one-third of all latex (water-based) paints contained mercury.  A study found that individuals living in homes painted with these paints had higher urinary excretion levels of mercury.  Have any pre-1990 paint sitting around the house?  You may want to check the ingredients and contact your local agencies to figure out how to properly dispose of it.
  • Mercuric Oxide & Button Cell Batteries [8]
    • As of 1996, the US has been phasing out the use of mercury in batteries.  Most batteries produced in the US today do not contain mercury.  The two types of batteries that do still contain mercury are mercuric oxide batteries and button cell batteries.

Inorganic Mercury (mercury salts):

  • Tap Water [9]
    • The amount of inorganic mercury permitted in drinking water is currently restricted by the FDA & EPA to 2 parts per billion.  A water filter can be purchased to purify your drinking water.  Here is a guide to help you determine what may be in your local water supply and how to select a water filter that meets your needs.
  • Cosmetics Purchased Internationally [10]
    • Cosmetics sold in the United States are forbidden by the FDA from containing mercury.  However, if you purchase a cosmetic from another country (such as via the internet), make sure to search the label for any of the following ingredients: mercurous chloride, calomel, mercuric, mercurio, or mercury.  The products containing mercury are typically advertised as skin lighteners and anti-aging skin creams.
  • Teething Powders [11]
    • Similarly to cosmetics, this is not a major problem in the United States today as these products have been banned.  However, teething powders used to contain mercury in the form of mercurous chloride (or “calomel”) and would cause a condition called pink disease (acrodynia).


[1] Patrick L. Mercury toxicity and antioxidants: Part 1: role of glutathione and alpha-lipoic acid in the treatment of mercury toxicity. Altern Med Rev. 2002;7(6):456-71.
[4] Dórea JG. Fish meal in animal feed and human exposure to persistent bioaccumulative and toxic substances. J Food Prot. 2006;69(11):2777-85.
[6] Cabaña-muñoz ME, Parmigiani-izquierdo JM, Bravo-gonzález LA, Kyung HM, Merino JJ. Increased Zn/Glutathione Levels and Higher Superoxide Dismutase-1 Activity as Biomarkers of Oxidative Stress in Women with Long-Term Dental Amalgam Fillings: Correlation between Mercury/Aluminium Levels (in Hair) and Antioxidant Systems in Plasma. PLoS ONE. 2015;10(6):e0126339.
[7] Agocs MM, Etzel RA, Parrish RG, et al. Mercury exposure from interior latex paint. N Engl J Med. 1990;323(16):1096-101.
[11] Weinstein M, Bernstein S. Pink ladies: mercury poisoning in twin girls. CMAJ. 2003;168(2):201.

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