Broken thermometer containing mercury/© Adobe Stock
Mercury is a heavy metal that occurs in three main forms: organic, inorganic, and elemental. All three forms can be found in water, but organic mercury is particularly dangerous because it’s easily absorbed by the human body, making it more toxic than inorganic mercury compounds. When mercury enters well water, it can pose health risks to humans and wildlife if consumed.
Mercury can accumulate in the body over time and cause various health problems, particularly affecting the nervous system. The U.S. Environmental Protection Agency lists mercury as a primary contaminant and includes erosion of natural deposits, discharge from refineries and factories, runoff from landfills and croplands as sources of contamination.
What are the effects of mercury in well water?
Potential health risks include:
Nervous system problems such as mood swings, insomnia, and headaches
Muscle weakness or twitching
Respiratory failure, kidney damage, and death at high levels
When should I test for mercury in my well water?
The safe level of mercury in well water is less than 0.002 milligrams per liter, or 2 parts per billion, according to the USEPA. If you have specific concerns about the cadmium levels in your well water, it is recommended to consult with your local health department or a licensed health professional for further guidance.
To ensure you are protecting your family’s health, we have developed a set of recommendations for testing that are provided in our article, "What do I need to know about sampling my well water?". When testing your well water you will very rarely be testing for only one thing, like mercury, and instead testing for a suite of constituents that are important to identify if in your drinking water.
What treatment should I use if there is cadmium in my well water?
Once you test and have decided to treat your water to remove mercury, contact a water treatment professional for guidance on choosing the right treatment for your situation.
The Minnesota Department of Health has developed a Home Water Treatment Guide that covers treatment for common constituents in well water. Even though it does not cover mercury, it is still a helpful guide to water treatment systems.
The most important advice we can provide you is if you are going to add treatment to your home water system, be sure the treatment device has been certified to remove cadmium by an independent third-party certification organization.
Where can I get local help and information about cadmium in my well water?
Contact your local health department – They can help you interpret your sample results and may have information on the best treatment options for your situation. If they personally aren’t able to answer your questions, they will know who to contact who will be able to help you, likely at your state health department.
Contact a water treatment professional - we would recommend contacting a water treatment professional who has been certified through the Water Quality Association’s Professional Certification Program.
State or Federal Geologic or Water Resource Agency – they may have completed field studies of your area or collected samples from water wells to map and understand the water quality in your state. In addition, they may house water well logs, including yours, or be able to provide additional information about the aquifer your well is getting water from.
Consult your well driller or drilling contractor – the contractor that drilled your well, and other local contractors, may be aware of the water quality issues nearby including high mercury, and might have worked with other well owners in your area to solve this issue .
Research online – you should be inquisitive; it will help you significantly because there may be great information available online. Use search terms like “my state (CA, ME, IL, etc.) water well logs”, “my state groundwater quality”, or “my state well water quality”.
Contact us directly – if these other local sources don’t work out for you, we may be able to help. We may be able to provide direct assistance, and/or direct you to a technical assistance provider in your area who can help answer your questions (free service funded by USEPA).
Additional Resources
Home Water Treatment. Minnesota Department of Health.
Your Household Water Quality: Mercury in your water. University of Georgia Extension.
Want to learn more about your private well and how to care for it?
Sign up for the free 10-week email course from PrivateWellClass.org. The class is a project of RCAP and the University of Illinois, with funding from USEPA.
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