Mercury in water is similar to lead in that it is a bio accumulative toxin. This means that even small amounts of organic mercury can lead to negative health effects like mercury poisoning over time.
This guide will walk through how exactly mercury gets into our water supply, and what you can do to protect yourself from dangerous mercury exposure.
- Mercury gets into our water supply as it naturally evaporates from the earth’s crust, or from industrial waste like fluorescent light bulbs, battery cells, and thermometers.
- Organic mercury is much more toxic to human health than inorganic mercury because organic forms are easily absorbed into the body. Long-term exposure can lead to nervous system and kidney damage.
- The EPA maximum contaminant level for inorganic mercury in water is .002 milligrams per liter (mg/L).
- The best water filters for removing mercury are activated carbon filters, reverse osmosis systems, and water distillers.
What Exactly Is Mercury
Mercury (Hg) is a heavy metal that naturally occurs in the Earth’s crust. There are three forms of mercury: elemental (metallic), inorganic, and organic. Inorganic mercury is the type that is most likely to enter the drinking water supply. Elemental mercury is the element in its liquid form, also called quicksilver or metallic mercury. Upon contact with air, elemental mercury is absorbed into the atmosphere as a harmful vapor.
Though exposure to any form of mercury is concerning, organic mercury is more harmful to humans and wildlife than inorganic. When inorganic mercury compounds react with organic matter, methylmercury forms; methylmercury is also referred to as organic mercury.
How Does Mercury Get Into Our Water Supply?
Mercury can accumulate in surface water due to natural erosion and industrial waste. Although human activity can instigate mercury to be further released into the environment.
Mercury commonly gets into our drinking water from industrial waste like:
- Mercury switches
- Thermometers & barometers
- Battery cells
- Fungicides & antiseptics compounds
- Mining and construction activity
Atmospheric deposition is when mercury from the air settles into soil and water, potentially contaminating our drinking water supply.
Mercury enters our water supply as snow and rain carry it from the air into surface water supplies like rivers, lakes, and streams. Mercury occurs in surface waters primarily in the ionic form since the solubility of metallic mercury is very poor. From there, our drinking water can be contaminated with the heavy metal.
Public water systems are required to monitor mercury levels and keep them below the EPA standard, however well water may be more likely to contain higher levels of mercury.
You can find your county’s estimated levels of mercury using this USGS map. The states with the highest estimated levels of mercury in the water supply are Texas, Pennsylvania, and Ohio due to the presence of coal-fired power plants. The US Geological Survey (USGS) provides resources, research updates, and press releases on all things related to potential environmental hazards to humans.
It isn’t a straightforward process of how mercury is emitted into the environment. This all depends on:
- The form of mercury emitted
- The location of the emission source
- The surrounding terrain
- Weather patterns
Mercury never really goes away, it circulates in the environment by changing its chemical form; this has deemed mercury a persistent bioaccumulative toxin.
Is Mercury Soluble In Water?
The solubility of mercury depends on its type.
- Inorganic mercury: soluble in water
- Methylmercury: insoluble in water
- Elemental mercury: insoluble in water
How People Are Exposed to Mercury?
The most common instance of mercury exposure is through eating seafood contaminated with mercury. To avoid mercury poisoning, the EPA has separate guidelines on eating fish potentially contaminated with mercury.
Mercury pollution in the environment leads to mercury infiltrating our water supply. This can occur through industrial waste and coal-fired power plants. When inorganic mercury enters water sources, it can react with other compounds to form methylmercury. It can end up in drinking water or can accumulate in fish. When humans consume fish, especially those that are higher on the food chain, humans can also bioaccumulate methylmercury.
Elemental mercury contamination usually occurs when mercury is released from a container or something that contains mercury breaks. Examples of this are thermometers, dental fillings, gold mining, novelty jewelry, fluorescent light bulbs, and other consumer products. However, most products have been discontinued or regulated, but some dated objects or products still exist among us.
Elemental mercury contamination is the most serious when the liquid mercury quickly evaporates into mercury vapor. When it is accidentally ingested in small amounts, it tends to not be that harmful to humans.
What Are The Health Effects Of Mercury In Drinking Water?
The three different types of mercury cause different types of mercury poisoning. Inorganic mercury is the least harmful to humans, which is the type likely to end up in drinking water.
Inorganic mercury poisoning (consumed at high levels):
- Digestion or gastrointestinal issues
- Neurological issues (mood swings, memory loss, mental disturbances)
- Skin rashes and dermatitis
- Muscle weakness
Symptoms of methylmercury (organic mercury) poisoning:
- Peripheral vision impairment
- “Pins and needles” feelings, usually in the hands, feet, and around the mouth
- Impaired coordination
- Impairment of speech, hearing, or walking
- Muscle weakness
As it does in fish, mercury accumulates in the body, so long-term exposure to small amounts of methylmercury can have long-term health consequences.
Methylmercury’s long-term effects may include:
- Kidney damage
- Nervous system damage
- Developmental issues in children
Mercury is a neurotoxin, meaning it can pass the blood-brain barrier. It can lead to nervous system damage, notably from mercury vapors since vapors can get to the brain faster.
Symptoms of elemental mercury poisoning are:
- Emotional changes
- Neuromuscular changes
- Disturbances in sensations
- Changes in nerve responses
- Poor performance on tests of mental function
Populations Particularly Sensitive to Methylmercury Exposures
Though methylmercury is less likely to be found in drinking water, it can occur. The long-term effects of inorganic mercury are unknown.
Pregnant or breastfeeding women should take care to limit their total mercury exposure through drinking water and fish consumption, as this toxin can impact fetal development. The developing brain of young children is also more susceptible to brain and nervous system damage from methylmercury and inorganic mercury.
As with many contaminants, other vulnerable populations may be more negatively affected by exposure to mercury such as the elderly and immunocompromised individuals.
What Are The Regulatory Limits For Mercury In Water?
Mercury levels in drinking water are required to be monitored under the Safe Drinking Water Act (SDWA) established by the EPA.
Here are the regulatory levels for Inorganic mercury in water:
- For bottled water, the Food And Drug Association (FDA) has a limit of 0.002 mg/L (2 ppb).
- For public water systems, the EPA’s Maximum Contaminant Level (MCL) and MCLG are 0.002 mg/L (2 ppb).
- The EWG Health Guideline for mercury (inorganic) in tap water is 0.0012 mg/L (1.2 ppb).
- In Australia, the set maximum for health purposes is 0.001 mg/L (1 ppb).
- In Canada, the maximum is also 0.001 mg/L (1 ppb).
How To Test For Mercury In Water
There are two ways to have your water tested for mercury at a laboratory. You can test it yourself with a DIY test kit or use a laboratory test kit involves collecting a water sample and sending it to a certified lab.
Using a laboratory test kit is the most accurate method to detect mercury in your drinking water. These kits include everything you need to properly collect a water sample and send it to a certified lab to be analyzed for mercury concentrations.
I recommend the Freshnss Labs water test kit that scans not only for mercury but dozens of other heavy metals and harmful contaminants. Within 3 business days of the lab receiving your sample, you will get back a detailed report showing the exact contamination levels, any health or plumbing alerts, and the best treatment methods based on your test data.
DIY Home Test
An at-home water test may be used as a do-it-yourself test for mercury in water. Simply dip a color test strip into a glass of water filled with tap water. Swirl the test strip around for one minute. Then remove the strip from your water sample and wait 30 seconds. Match the color from the strip to the closest match on the provided color code.
Observations For Mercury
Unfortunately like many contaminants, mercury in water can’t be detected via smell, taste, or appearance. As a first line of defense, check the USGS map, and consider the industries/manufacturing in your area. These are a good first step in determining if there may be harmful levels of mercury in your well water.
Recommended Treatment Methods For Mercury In Water
Pre-treatment may be needed to remove mercury from water, and all treatments may not be adaptable to whole-house or point-of-entry systems.
Reverse osmosis (RO) can remove 95-97% of mercury from your water supply, drastically improving the water quality. RO is a common filtration system that will filter out a broad spectrum of contaminants from drinking water. RO filters are available as a whole-house system, countertop, or more commonly, as point-of-use filters.
Granular Activated Carbon
Granular activated carbon (GAC) uses raw materials like wood, coal, and coconut shells to serve as a medium for the adsorption of contaminants. It sounds complicated, but this is the best filtration system to use to remove mercury from drinking water.
Water distillation systems will result in the purest form of water as it will remove mercury and all other contaminants. The downsides are that water distillation is a slow process, and the end result will have a flat or unappealing taste.
Frequently Asked Questions
Does tap water contain mercury?
Yes, according to the Environmental Working Group (EWG), there are trace amounts of mercury in tap water in 40 states. However, these levels are under the EPA’s set MCL of .002 PPM.
Does mercury float in water?
No, mercury has a very high density, so it sinks in water.
Does boiling water remove mercury?
No, boiling water leads to an increase in the total mercury concentration. As the water evaporates, there will be more mercury present.
Is there mercury in fresh water fish?
Yes, mercury is present in both freshwater and saltwater fish. Since mercury contaminates our lakes and surface waters, fish tissue is frequently contaminated with mercury.