Does Your Water Contain an Unsafe Level of Mercury?

Like me, you probably want to know more about what’s in your family’s drinking water. In this article, we’ll look at Mercury and how it can affect water quality and your health.

Mercury is a naturally occurring heavy metal found in air, water, and soil. Three ways it can get into our drinking water supply are: 1) through the erosion of natural deposits, 2) from refineries and factories, or 3) from runoff from landfills or farms. Consuming water containing Mercury at levels greater than or equal to 0.002 mg/L can cause adverse health effects.

Fortunately, Mercury is one of the drinking water contaminants regulated by the EPA. This means public water companies are required to monitor their water supply for Mercury and work to ensure the water they provide their customers does not exceed the legal limit for the contaminant. However, even with this standard in place, it’s still possible for your tap water to contain excessive amounts of Mercury.

How Mercury Can Affect Water Quality and Your Health

Both natural processes (e.g., erosion of naturally occurring deposits in the Earth’s crust) and human activities (e.g., waste disposal) can contaminate our water supply with Mercury.

What is Mercury, exactly? Mercury, a heavy metal and known neurotoxin, exists in the following forms:

  1. Elemental Mercury: A liquid at room temperature, Elemental Mercury has been used in thermometers, electrical switches, and fluorescent lightbulbs.
  2. Inorganic Mercury Compounds: When Mercury combines with other elements, like Sulfur or Oxygen, Inorganic Mercury Compounds called Salts are formed. Mercury Salts, which can occur naturally, are used for the manufacturing of chemicals and other industrial applications.
  3. Organic Mercury Compounds: Certain microscopic organisms can combine Mercury with Carbon to form the Organic Mercury Compound known as Methylmercury. Methylmercury accumulates in the food chain and can be found in some fish or shellfish.

Exposure to all three forms of Mercury could cause adverse health effects, but the EPA’s drinking water standards for Mercury pertain to Inorganic Mercury Compounds, specifically.

How can drinking water that contains Mercury affect your health? If you consume water that contains elevated levels of Mercury over many years, you may develop kidney damage.

At what level can Mercury cause health problems? Mercury is known to cause adverse health effects when its concentration in drinking water is at or above 0.002 mg/L.

In an effort to protect our health, the EPA established legally enforceable standards to limit the amount of Mercury in our drinking water. Public water companies are required to ensure the concentration of Mercury in the water they provide their customers is kept at or below 0.002 mg/L.

Given available treatment technology, water utility companies should be able to provide drinking water that meets this quality standard. However, at least one public water system violated the regulatory limit for Mercury in 2019.

Does Your Drinking Water Contain a Harmful Amount of Mercury?

Public water companies are required to provide customers with an annual water quality report, also known as a Consumer Confidence Report (CCR). Inside this report, you’ll find important information about your drinking water, including where it comes from, and whether it tested positive for any regulated contaminants like Mercury.

If you’re curious to know how much Mercury was found in your city’s drinking water, grab a copy of the latest CCR and look for the section of the report that covers “Inorganic Contaminants.” Here, you’ll find test results for Mercury as well as other contaminants like Arsenic, Barium, and Cyanide.

How to Interpret Your Water Quality Report

When looking at your water quality report, you’ll see test results for Mercury reported in Parts per Billion (ppb). 1 mg/L equals 1,000 ppb, so 0.002 mg/L is equivalent to 2 ppb.

Below is an example of what you might see on your annual water quality report if Mercury is detected in your town’s drinking water:

Example Water Quality Report

MCLG (1)MCL (2)Average
Your Water

Definitions from the EPA:
1. Maximum Contaminant Level Goal (MCLG) – The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.
2. Maximum Contaminant Level (MCL) – The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.

In this example, water samples contained an average of 3 ppb of Mercury, exceeding both the public health goal level (MCLG) and the legal limit (MCL) for the contaminant.

Will You Be Notified If Your Water Contains an Unsafe Level of Mercury?

In addition to providing you with an annual quality report, your water company is required by the EPA to notify you if they identify a problem with your drinking water.

If your water company delivers water that could negatively impact your health, they have to notify you of the situation within the timeframe set by the EPA. Depending on the severity of the issue, the company is given 24 hours to 30 days to provide this notice.

If your city’s water exceeds the Maximum Contaminant Level (MCL) for Mercury, your water company must notify you within 30 days of the violation. Typically, you will receive this notice via the media or through the mail.

What Can You Do to Remove Mercury from Your Tap Water?

Fortunately, if you want to limit your family’s exposure to Mercury, there are several affordable yet effective options for removing the contaminant from your tap water.

But how can you tell which products work and which ones don’t? Well, if you want peace of mind, I recommend choosing a water treatment product that is certified by NSF International (NSF) to be effective at removing Mercury from water.

What does the NSF certification represent? When a product is NSF certified to remove Mercury, you can rest assured that:

  • the manufacturer’s contaminant reduction claims have been verified;
  • the system was tested to confirm it adds nothing harmful to the water;
  • the system has been found to be structurally sound;
  • the product’s advertising, literature, and labeling have all been verified as accurate;
  • and there is testing in place to determine whether the quality of the product is consistent over time.

Do all NSF certified water filters work against Mercury? Water treatment devices can earn certification for meeting one or more NSF standards or protocols. But only those products that meet NSF standard NSF/ANSI 53 for Mercury are certified to reduce the amount of the contaminant that’s in your water.

One such product, the Clean Water Machine by Aquasana, is NSF certified to remove over 96% of the Mercury found in your tap water. The device sits on your countertop and does not require a lengthy installation process so you can set it up in a matter of minutes.

3 steps for selecting the right water treatment system for your family:

  1. Review your area’s annual water quality report to find out what’s in your drinking water.
  2. Determine which contaminants you’d like to reduce from your water.
  3. Select a water treatment product that is NSF certified to work effectively against those contaminants you’d like to reduce from your tap water.

Just remember, no matter which water treatment product you choose, you need to make sure to perform the routine maintenance suggested by the manufacturer. This will help keep the device in proper working order and limit your family’s exposure to Mercury.



I’ve moved several times over the years, so I know just how stressful it can be to relocate. I want to help put your mind at ease. That’s why I research and write about all the things I think you should consider when moving to a new town.

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