Mercury in Water

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Mercury is a silver-white metal that is known to cause long-term health complications if consumed in drinking water.

This glossary will discuss mercury in water, including how water becomes contaminated with mercury, the potential health effects of mercury, and how to protect your family from this naturally occurring metal.

❔ What is Mercury?

💡 Mercury is a metal and a chemical element that is used in electronic and electrical applications, and in the manufacture of industrial chemicals. Mercury is also used as a topical disinfectant and antiseptic, fungicide, and wood preservative.

Also known as “quicksilver”, mercury is present in three forms on earth: organic, inorganic, and elemental. Mercury is often present alongside zinc, cadmium, silver, carbon, and gold, as mercuric chloride, sulfides, and oxides. All three forms of mercury are considered dangerous in water; however, organic mercury is easily absorbed by the human body, making it more toxic than inorganic mercury compounds.

In Water AsHg, Hg2+, Hg1+, Methyl Mercury
SourcesNatural degassing
Combustion of fossil fuels
Rainfall, runoff, and soil seepage
Contaminant Levels (MCLs)
US EPA: 0.002 mg/L; 0.002 mg/L (MCLG)
WHO Guideline: 0.006 mg/L
EWG: 0.0012 mg/L
Potential Health RisksMood swings, irritability, and other emotional changes
Muscle weakness, twitching, atrophy
Risk of respiratory failure, damage to the kidneys, and death at high levels
TreatmentsGranular Activated Carbon
Sub-Micron Filters
Reverse Osmosis

🩺 What are the Potential Health Effects of Mercury?

Mercury has known potential health effects when consumed in water or inhaled in air. According to the EPA, some of the potential symptoms and health effects of consuming mercury are:

  • Mood swings, irritability, and other emotional changes
  • Tremors
  • Insomnia
  • Headaches
  • Muscle weakness, twitching, atrophy
  • Poor mental function
  • Memory loss
  • Nervous system damage
  • Skin rashes
  • A “pins and needles” feeling in the hands and feet
  • Loss of peripheral vision

High exposure to mercury may lead to mercury poisoning, with the following health effects:

  • Respiratory failure
  • Damage to the kidneys
  • Death

Some sources claim that high levels of mercury can cause cancer, but currently, there isn’t sufficient evidence to determine whether or not mercury is cancer-causing.

Woman having headache

🚰 How Does Mercury Get Into Drinking Water?

Mercury is found naturally in the earth’s crust, and enters the environment through natural degassing. It may also be dumped into the environment as a result of incorrect disposal from human activities, or from runoff from farmland and landfills. Combustion of fossil fuels also increases the mercury levels in the atmosphere.

Mercury in the earth’s crust, rocks, soils, and the atmosphere gets into water through rainfall, runoff, and soil seepage. When water flows over or seeps through rocks or soil with high mercury levels, some of this metal leaches into water. Water then travels to aquifers and reservoirs, many of which are used as public drinking water supplies.

📉 Do Water Treatment Facilities Monitor Levels of Mercury in Drinking Water?

Yes, drinking water treatment facilities must test for, monitor, and remove mercury from water to prevent kidney damage and the other known health effects of prolonged exposure to high levels of mercury in water.

There are several national guidelines and regulations that water facilities must adhere to for mercury:

  • Environmental Protection Agency (EPA) Maximum Contaminant Level: 0.002 mg/L (or 2.0 PPB)
  • EPA Maximum Contaminant Level Goal: 0.002 mg/L (or 2.0 PPB)
  • World Health Organization (WHO) Guideline: 0.006 mg/L (or 6.0 PPB)

What do these guidelines mean? The EPA’s Maximum Contaminant Level is the highest level of mercury that’s allowed in drinking water, while the Maximum Contaminant Level Goal is the highest amount of mercury that is known to occur with no health effects.

All regions within the United States government must follow EPA regulations, and some states may have their own more stringent requirements for mercury exposure in water.

According to the Environmental Working Group’s Tap Water Database, many states have mercury contamination, but no states report inorganic mercury above the regulations. However, the EWG believes that the current MCL for mercury is too high, and sets its own health guidelines of 1.2 PPB.

Mercury in a tube

🔎 How Can I Tell if Mercury is in My Drinking Water?

Mercury doesn’t have a distinct taste in water, although very high levels of organic and inorganic mercury may have a metallic taste. You can’t see or smell mercury in water. Usually, you won’t be able to tell that your water contains mercury by taste, smell, or sight.

The only effective way to find out how much mercury your water contains is to conduct a water test. Laboratory testing is the most thorough, accurate means of testing for mercury. A lab test report should tell you exactly what concentrations of the various forms of mercury your water contains.

Aside from lab testing, you can also find out the concentrations of mercury in your water by viewing your annual Water Quality Report, or Consumer Confidence Report (CCR). All water suppliers must provide annual CCRs to their customers, once a year and on request. Note that a CCR only tells you how much mercury your water contains on a given testing day, and may not be representative of the fluctuating levels of this contaminant throughout the year.

Tap Score Water Report

👩🏽‍⚕️ How Can I Protect My Family from Mercury in Drinking Water?

The best way to protect your family from mercury in drinking water is to install a water treatment system in your home. Most systems cost $150-$1,200 and have an annual maintenance spend of $50-$250.

Water filters that remove mercury are:

  • Granular activated carbon filters, which are installed in point of entry or point of use filtration systems, and are found in pre-coat or solid block designs. GAC filters remove more than 90% of mercury, as well as pesticides, chlorine, and semi-volatile and organic compounds.
  • Sub-micron filters with adsorption media, which are often found in under-sink systems or pitcher filters. These filters have pore sizes ranging from 1 to 100 microns and their adsorption media makes them capable of removing more than 90% mercury, organic chemicals, chlorine and chloramine, bacteria, unpleasant tastes and odors, and more.
  • Reverse osmosis filtration systems, which are typically installed as under-sink or countertop units. Reverse osmosis units force water through a semipermeable membrane, which removes virtually all total dissolved solids, including 95% to 97% of mercury. RO filtration also involves carbon and sediment filtration, providing thorough water treatment.
  • Distillers, which boil water until it evaporates and condenses, leaving contaminants behind in the boiling chamber. Distillation removes up to 100% mercury and produces purified water. Most systems take up to five hours to produce a batch of distilled water.

If you discover high levels of mercury, especially organic mercury, after testing your water, switch to bottled water while you decide on a suitable water treatment system to remove this contaminant.

Activated carbon filter cartridges of a countertop water filter

⚠️ How Else Can I Be Exposed to Mercury?

Drinking water is a major source of mercury exposure. Other sources of mercury exposure are:

  • Consuming fish and shellfish (such as shark, swordfish, tilefish, and king mackerel) containing methylmercury, which is formed when microorganisms in soil and water convert inorganic and elemental mercury into an organic compound
  • Being in close contact with a product containing metallic mercury, such as dry cell batteries and fluorescent light bulbs, which break, releasing toxic mercury vapor into the air
  • Swallowing metallic mercury from broken fever thermometers or swallowing jewelry made from metallic mercury (most likely to happen in children)
  • Treating tooth decay with a direct filling material known as dental amalgam, which contains mercury
  • Gold mining
  • Atmospheric deposition and industrial release, such as combustion of fossil fuels
  • Use of skin lighteners and anti-ageing products containing trace levels of mercury that are illegally shipped to the US

The second most likely source of mercury is eating fish that have consumed mercury from the environment, due to the ease at which mercury can enter the food chain. Mercury in light bulbs and batteries is being phased out, but it’s wise to be wary with these items in your home if you’re unsure what they contain.

📝 Where Can I Get More Information?

To learn more about mercury in water, including the potential health risks of this contaminant, follow the links below.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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