What is mercury poisoning

Mercury is a metal that occurs naturally in the environment, mercury is found in air, water and soil. Mercury is also released to the environment through many types of human activity. Exposure to mercury occurs from breathing contaminated air, ingesting contaminated water and food, and having dental and medical treatments. Mercury, at high levels, may damage the brain, kidneys, and developing fetus ¹. Mercury has several forms (e.g., organic mercury and inorganic mercury) which lead to different mercury poisoning or mercury intoxication syndromes. Metallic mercury is a shiny, silver-white, odorless liquid. If heated, metallic mercury is a colorless, odorless gas. Metallic mercury is used to produce chlorine gas and caustic soda, and is also used in glass thermometers, dental fillings, and button batteries.

Mercury is a neurotoxin. How someone’s health may be affected by an exposure to mercury depends on a number of factors:

• the form of mercury (for example, methylmercury or elemental (metallic) mercury)
• the amount of mercury in the exposure;
• the age of the person exposed (the fetus is the most vulnerable)
• how long the exposure lasts
• how the person is exposed — breathing, eating, skin contact, etc.
• the health of the person exposed.

The effects of mercury exposure can be very severe, subtle, or may not occur at all, depending on the factors above.

The inorganic mercury could be further subdivided into elemental mercury (also known as “quicksilver” or metallic mercury) and mercury salts. Elemental exposures are typically from mercury-containing devices such as thermometers. Mercury salt exposures can be seen with disc battery ingestion or laxative abuse. Organic mercury can also be subdivided into short-chain and long-chain compounds. Organic mercury exposure usually occurs from ingestion of contaminated seafood, paints containing mercury, or ingestion/injections of thimerasol.

Mercury combines with other elements, such as chlorine, sulfur, or oxygen, to form inorganic mercury compounds or “mercury salts”, which are usually white powders or crystals. Mercury salts are sometimes used in skin lightening creams and as antiseptic creams and ointments. Mercury also combines with carbon to make organic mercury compounds. The most common one, methylmercury, is produced mainly by microscopic organisms in the water and soil. More mercury in the environment can increase the amounts of methylmercury that these small organisms make.

Mercury gets into the air from a number of sources. Once in the air, mercury eventually settles into bodies of water like lakes and streams, or onto land, where it can be washed into water. Microorganisms in waterbodies can change it into methylmercury, where it builds up in fish, shellfish and animals that eat fish. It is this type of mercury (methylmercury) that is present in fish. Methylmercury can be harmful to the brain and nervous system if a person is exposed to too much of it over time. The levels of methylmercury in fish and shellfish depend on:

• what they eat,
• how long they live, and
• how high they are in the food chain.

In a given water body, the highest concentrations of methylmercury are generally found in large fish that eat other fish. Fish is a beneficial part of people’s diet, and we encourage people to eat fish low in methylmercury.

The nervous system is very sensitive to all forms of mercury. Exposure to high levels can damage the brain and kidneys. Pregnant women can pass the mercury in their bodies to their babies. Methylmercury and metallic mercury vapors are more harmful than other forms, because more mercury in these forms reaches the brain. Exposure to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, kidneys, and developing fetus. Effects on brain functioning may result in irritability, shyness, tremors, changes in vision or hearing, and memory problems.

Short-term exposure to high levels of metallic mercury vapors may cause effects including lung damage, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation.

It is important to protect your family from mercury exposure:

• Carefully handle and dispose of products that contain mercury
• Limit your consumption of fish with higher levels of mercury (see the chart in Figure 1 below)

What happens to mercury when it enters the environment?

• Inorganic mercury (metallic mercury and inorganic mercury compounds) enters the air from mining ore deposits, burning coal and waste, and from manufacturing plants.
• It enters the water or soil from natural deposits, disposal of wastes, and volcanic activity.
• Methylmercury may be formed in water and soil by small organisms called bacteria.
• Methylmercury builds up in the tissues of fish. Larger and older fish tend to have the highest levels of mercury.

Is there methylmercury in all fish?

Nearly all fish contain at least traces of methylmercury. Fish absorb methylmercury from the food they eat. It tends to build up more in some types of fish than others, especially in larger fish that eat other fish and those fish that live longer.

Should I not eat fish during pregnancy in order to avoid mercury?

No, fish can contribute to a healthy diet before and during pregnancy and while breastfeeding. Studies with pregnant women have found that the nutritional benefits of fish, like other protein-rich foods, are important for their child’s growth and development during pregnancy and childhood. This is especially true when the fish is lower in mercury. Most people eat less than the recommended amount of fish, both in general and during pregnancy. A 2005 U.S. Food and Drug Administration (FDA) survey found pregnant women typically ate only 2 ounces of fish a week ². The chart in Figure 1 below shows which fish are the best choices for women who are pregnant, might become pregnant, or are breastfeeding, or for young children.

Are there other contaminants in fish?

Yes, however, FDA has found that the levels of other contaminants in commercial fish generally do not raise human health concerns. For many years, FDA has sampled and tested commercial seafood for pesticides and industrial chemicals as well as other heavy metals besides mercury and the results are available on FDA’s website:

• Pesticide Program Residue Monitoring (https://www.fda.gov/Food/FoodborneIllnessContaminants/Pesticides/ucm2006797.htm)
• Total Diet Study Analytical Results (https://www.fda.gov/Food/FoodScienceResearch/TotalDietStudy/ucm184293.htm)

Levels of other contaminants vary by location and fish species. State and local health departments or fish and game agencies provide advice on other contaminants, such as polychlorinated biphenyls (PCBs) in fish from particular bodies of water. People who catch their own fish for recreation or as a source of protein in their diets should check for fish advisories for both fresh and marine waters.

It is a good idea to remove skin, fat, and internal organs where other types of harmful pollutants may accumulate for fish you and your friends catch before you cook these fish. This is particularly true because fish from some local waters may be more likely to contain other contaminants.

And remember – eat a variety of fish, not just the same type every time you eat fish. There are plenty of fish shown on the chart to choose from, so there are fish for every taste.

How likely is mercury to cause cancer?

There are inadequate human cancer data available for all forms of mercury. Mercuric chloride has caused increases in several types of tumors in rats and mice, and methylmercury has caused kidney tumors in male mice. The United States Environmental Protection Agency (EPA) concluded that “no human data currently ties mercury exposure to cancer, but the data available are limited. In very high doses, some forms of mercury have caused increases in several types of tumors in rats and mice”. When EPA published its Cancer Guidelines in 2005, the Agency concluded that environmental exposures to inorganic mercury and methylmercury are not likely to cause cancer in humans ³.

How does mercury affect children?

Very young children are more sensitive to mercury than adults. Mercury in the mother’s body passes to the fetus and may accumulate there. It can also can pass to a nursing infant through breast milk. However, the benefits of breast feeding may be greater than the possible adverse effects of mercury in breast milk.

Mercury’s harmful effects that may be passed from the mother to the fetus include brain damage, mental retardation, incoordination, blindness, seizures, and inability to speak. Children poisoned by mercury may develop problems of their nervous and digestive systems, and kidney damage.

What is thimerosal?

Thimerosal is an organic mercury compound that has been used in small amounts as a preservative in some vaccines. Although it is generally regarded as safe, the use of thimerosal is now being phased out. Thimerosal is no longer used as a preservative in any childhood vaccine, except for the influenza vaccine ⁴.

Is it safe for children to receive an influenza vaccine that contains thimerosal?

Yes. There is no convincing evidence of harm caused by the small doses of thimerosal preservative in influenza vaccines, except for minor effects like swelling and redness at the injection site.

Recent research suggests that healthy children under the age of 2 are more likely than older children and as likely as people over the age of 65 to be hospitalized with flu complications. Therefore, vaccination with thimerosal-preservative containing influenza vaccine and thimerosal-reduced influenza vaccine is encouraged when feasible in children, including those that are 6-23 months of age.

Is it safe for pregnant women to receive an influenza vaccine that contains thimerosal?

Yes. A study of influenza vaccination examining over 2,000 pregnant women demonstrated no adverse fetal effects associated with influenza vaccine. Case reports and limited studies indicate that pregnancy can increase the risk for serious medical complications of influenza. One study found that out of every 10,000 women in their third trimester of pregnancy during an average flu season, 25 will be hospitalized for flu related complications.

Additionally, influenza-associated excess deaths among pregnant women have been documented during influenza pandemics. Because pregnant women are at increased risk for influenza-related complications and because a substantial safety margin has been incorporated into the health guidance values for organic mercury exposure, the benefits of thimerosal–reduced influenza vaccine or thimerosal-preservative containing influenza vaccine outweighs the theoretical risk, if any, of thimerosal.

Has the federal government made recommendations to protect human health?

• The EPA has set a limit of 2 parts of mercury per billion parts of drinking water (2 ppb).
• The Food and Drug Administration (FDA) has set a maximum permissible level of 1 part of methylmercury in a million parts of seafood (1 ppm).
• The Occupational Safety and Health Administration (OSHA) has set limits of 0.1 milligram of organic mercury per cubic meter of workplace air (0.1 mg/m3) and 0.05 mg/m3 of metallic mercury vapor for 8-hour shifts and 40-hour work weeks.

How do you get mercury poisoning

Mercury exists in various forms, and people are exposed to each in different ways. The most common way people in the U.S. are exposed to mercury is by eating fish containing methylmercury ⁵. Other exposures may result from using or breaking products containing mercury ⁵.

Mercury is found in small quantities throughout the environment. It is released by the breakdown of minerals in rocks and soils and as a byproduct of fossil fuel combustion and waste incineration. It is inhaled with the air that we breathe, absorbed through the skin, and ingested with food. Mercury is also used in some mirror coatings, pharmaceuticals, and agricultural chemicals. Energy efficient compact fluorescent light (CFL) bulbs contain small amounts of mercury, which is also used to make electrical equipment, wire, and switching devices.

The tiny amounts to which the vast majority of people are exposed do not generally cause health concerns. However, people may develop mercury-related symptoms or complications if they are exposed to dangerous concentrations of mercury, such as might be found at a hazardous waste site, or are exposed chronically to mercury over long periods of time, especially if they work with heavy metals on the job.

Exposure to excessive amounts of mercury can be toxic. The amount of mercury absorbed by an individual and its effects on his or her health depends on the type of mercury, its concentration, and the nature of exposure. According to the Agency for Toxic Substances and Disease Registry (ATSDR), very little metallic mercury (less than 0.01%) is absorbed by the body, even if it is swallowed. However, if the same mercury is inhaled as a vapor, about 80% is absorbed into the bloodstream.

Methylmercury, a highly toxic organic compound, is the form of mercury people in the U.S. encounter most frequently ⁵. Almost all people in the world have at least trace amounts of methylmercury in their bodies, reflecting its prevalence in the environment. However, most people have mercury levels in their bodies below the level associated with possible health effects.

About 95% of methylmercury, which is the type found in fish and other seafood, is absorbed by the digestive tract. The most common source of human exposure to methyl mercury is as consumption of contaminated seafood. Fish that come from contaminated waters and large predator fish that have eaten smaller fish may have significantly increased levels of methyl mercury. It is important to know the source of the fish that you consume and to limit the quantity of large predator fish eaten.

Once mercury is absorbed, the body may deposit it in a variety of body organs, including the kidneys and brain. The body will slowly rid itself of mercury through the urine and stool, but if an excessive amount accumulates, it can permanently damage the kidneys, nervous system, and brain.

Pregnant women with elevated levels of mercury can pass it on to their unborn baby, affecting development of the baby’s brain, kidneys, and nerves especially. Mercury can also be passed from mother to baby through breast milk during nursing.

There are 3 different forms of mercury that cause health problems. They are:

1. Elemental mercury, also known as liquid mercury or quicksilver
2. Inorganic mercury salts
3. Organic mercury

Where mercury is found

Elemental mercury can be found in:

• Glass thermometers
• Electrical switches
• Fluorescent light bulbs
• Dental fillings
• Some medical equipment

Inorganic mercury can be found in:

• Batteries
• Chemistry labs
• Some disinfectants
• Folk remedies
• Red cinnabar mineral

Organic mercury can be found in:

• Older germ-killers (antiseptics) such as red mercurochrome (merbromin) (this substance is now banned by the FDA)
• Fumes from burning coal
• Fish that have eaten a form of organic mercury called methylmercury

There may be other sources of these forms of mercury.

How might you be exposed to mercury?

• Eating fish or shellfish contaminated with methylmercury.
• Breathing vapors in air from spills, incinerators, and industries that burn mercury-containing fuels.
• Release of mercury from dental work and medical treatments.
• Breathing contaminated workplace air or skin contact during use in the workplace.
• Practicing rituals that include mercury.

Metallic Mercury Poisoning

Metallic mercury is the pure form of mercury. Metallic mercury is a shiny, silver-white, odorless liquid much heavier than water that is used in thermometers, dental fillings and batteries and is also used in the production of chlorine gas and caustic soda. Exposure to high levels of metallic mercury can permanently damage the brain, kidneys, and developing fetus. Effects on brain functioning may result in tremors, changes in vision or hearing, irritability, shyness and memory problems. Short-term exposure to high levels of metallic mercury vapors may cause effects including lung damage, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation. Skin contact alone does not result in significant mercury absorption into the body, but inhalation exposure to mercury vapor may be likely in environments in which significant skin contact occurs.

Metallic mercury is also used in religious practices in some Hispanic communities. It is sold under the name azogue (pronounced ah-SEW-gay) in stores, sometimes called botánicas, which specialize in religious items used in Espíritismo (a spiritual belief system native to Puerto Rico), Santería (a Cuban-based religion that venerates both African deities and Catholic saints), and voodoo.

The use of azogue is recommended in some Hispanic communities by family members, spiritualists, card readers, and santeros. Typically, azogue is carried on one’s person in a sealed pouch prepared by a spiritual leader or is sprinkled in the home or automobile. Some botanica owners suggest mixing it in bath water or perfume and placing it in devotional candles.

Metallic mercury key facts

Metallic mercury is a hazardous chemical that can cause serious health problems, either short- or long-term. It is best to avoid contact with mercury altogether and all products that may contain mercury should be handled and disposed of carefully.

Anyone who handles mercury is at risk. Over the past two decades, there is a continuing pattern of metallic mercury exposure to children and teenagers who have obtained metallic mercury from school laboratories and abandoned industrial facilities. Exposure of persons using metallic mercury in certain folk medicines or participating in certain ethnic or religious practices is presumed to occur, but the extent of such exposures is unknown. All such exposures should be avoided in the interest of safety.

Sources of exposure to metallic mercury

Sources of common potential exposure to metallic mercury are described below.

Fever thermometers

It is not uncommon for children to break fever thermometers in their mouths. When a thermometer containing mercury breaks in a child’s mouth and the child might have swallowed some mercury, be aware that the mercury swallowed poses a low risk in comparison to breathing mercury vapor.

What NEVER to Do After a Mercury Spill

• NEVER use a vacuum cleaner to clean up mercury. The vacuum will put mercury into the air and increase exposure.
• NEVER use a broom to clean up mercury. It will break the mercury into smaller droplets and spread them.
• NEVER pour mercury down a drain. It may lodge in the plumbing and cause future problems during plumbing repairs. If discharged, it can cause pollution of the septic tank or sewage treatment plant.
• NEVER walk around if your shoes might be contaminated with mercury. Contaminated clothing can also spread mercury around.

Any amount of mercury spilled indoors can be hazardous. The more mercury is spilled, the more its vapor will build up in air and the more hazardous it will be. Even a small spill, such as from a broken thermometer, can produce hazardous amounts of vapor if a room is small enough, warm enough and people spend a good deal of time there, as in a small bedroom.

The health effects that can be caused by breathing mercury depend on how much mercury vapor you breathe and how long you breathe the vapors. Health problems can result from short-term or long-term mercury exposure.

The following groups of people are particularly sensitive to the harmful effects of metallic mercury:

• Pregnant women – Mercury can pass from a mother’s body to her developing fetus.
• Infants – Mercury can also be passed to nursing infants through breast milk.
• Young children – They tend to play on floors where mercury may have been spilled, and are more likely to breathe more vapors than an adult because they breathe faster and have smaller lungs.

Health effects caused by short-term exposure to high levels of mercury vapors:

• Cough, sore throat
• Shortness of breath
• Chest pain
• Nausea, vomiting, diarrhea
• Increase in blood pressure or heart rate
• A metallic taste in the mouth
• Eye irritation
• Headache
• Vision Problems

Health effects caused by long-term exposure to mercury vapors:

• Anxiety
• Excessive shyness
• Anorexia
• Sleeping problems
• Loss of appetite
• Irritability
• Fatigue
• Forgetfulness
• Tremors
• Changes in vision
• Changes in hearing

Mercury spill cleanup instructions

• Put on rubber, nitrile or latex gloves.
• If there are any broken pieces of glass or sharp objects, pick them up with care. Place all broken objects on a paper towel. Fold the paper towel and place in a zip locking bag. Secure the bag and label it as directed by your local health or fire department.
• Locate visible mercury beads. Use a squeegee or cardboard to gather mercury beads into small mercury balls. Use slow sweeping motions to keep mercury from becoming uncontrollable. Take a flashlight, hold it at a low angle close to the floor in a darkened room and look for additional glistening beads of mercury that may be sticking to the surface or in small cracked areas of the surface. Note: Mercury can move surprising distances on hard-flat surfaces, so be sure to inspect the entire room, including any cracks in the floor, when searching.
• Use the eyedropper to collect or draw up the mercury beads. Slowly and carefully squeeze mercury onto a damp paper towel. Alternatively, use two pieces of cardboard paper to roll the mercury beads onto the paper towel or into the bag. Place the paper towel in a zip locking bag and secure. Make sure to label the bag as directed by your local health or fire department.
• After you remove larger beads, put shaving cream on top of small paint brush and gently “dot” the affected area to pick up smaller hard-to-see beads. Alternatively, use sticky tape, such as duct tape, to pick up any remaining small glass fragments. (Peel the tape very slowly from the floor to keep the mercury beads stuck to the tape.)
• Place all materials used with the cleanup, including gloves, in a trash bag. Place all mercury beads and objects into the trash bag. Place the trash bag outside in a secured area and label it as directed by your local health or fire department.
• Contact your local health department, municipal waste authority or your local fire department for proper disposal in accordance with local, state and federal laws.
• Remember to keep the area well ventilated to the outside (i.e., windows open and fans in exterior windows running) for at least 24 hours after your successful cleanup. Continue to keep pets and children out of cleanup area. If sickness occurs, seek medical attention immediately.

Novelty jewelry

Some necklaces imported from Mexico contain a glass pendant that contains mercury. The mercury-containing pendants can come in various shapes such as hearts, bottles, balls, saber teeth, and chili peppers. If broken, they can release metallic mercury to the environment.

Other consumer products

Metallic mercury is often found in school laboratories. It is also in some thermometers, barometers, switches, thermostats, and electrical switches. View a list of products that contain mercury.

Dental fillings

Mercury is used in dentistry in dental amalgam, also known as “silver filling”. Dental amalgam is a direct filling material used in restoring teeth. It is made up of approximately 40-50% mercury, 25% silver, and 25-35% blend of copper, zinc and tin. Amalgam use is declining because the incidence of dental decay is decreasing, and because well-performing substitute materials are available for restoring teeth.

Gold mining

Metallic mercury is sometimes used in artisanal and small-scale gold mining at locations outside of the United States. Mercury is mixed with gold-containing materials, forming a mercury-gold amalgam. The amalgam is then heated, vaporizing the mercury and leaving the gold. This process is very dangerous and can lead to significant mercury exposure. Miners working tailings in areas where mercury was previously used can also be inadvertently exposed to the residual mercury in these deposits.

Less common exposures

On rare occasions, people can suffer serious health consequences after exposures to very high levels of mercury vapor, especially if the exposure has occurred over a prolonged period. Two examples of very high exposures, with serious health effects:

• In 1989, an adult was melting dental amalgam in a casting furnace in the basement of his home in an attempt to recover silver from the amalgam. Mercury fumes released during the operation apparently had entered air ducts in the basement and had circulated throughout the house. He and the other residents of the home suffered serious health consequences.
• Also in 1989, several pounds of liquid mercury spilled in a child’s bedroom. The mercury was not cleaned up sufficiently. He and his two sisters continued to be exposed to high levels of evaporating mercury for a prolonged period, and they suffered serious health consequences.

Who’s at risk of metallic mercury poisoning?

Exposure to metallic mercury and the vapors that it releases may result from some dental work and medical treatments or even from a broken thermometer. In addition, workers in chemical and other industries that use mercury may be exposed by breathing contaminated air.

Adults using certain folk medicines or participating in certain religious or ethnic practices may expose themselves and their families to metallic mercury’s effects. Because metallic mercury vaporizes into the air at room temperatures, it presents an immediate health risk to anyone spending a significant amount of time in a room where metallic mercury is sprinkled or spilled onto the floor, or where opened containers of metallic mercury are present. The use of metallic mercury in a home or apartment not only poses a threat to persons currently residing in that structure, but also to those who subsequently occupy that dwelling and are unaware of the past mercury use.

Can metallic mercury poisoning be prevented?

Yes. First, if possible, avoid using metallic mercury altogether. In addition, take the following precautions:

• Carefully handle and dispose of products that contain mercury, such as thermometers or fluorescent light bulbs.
• Do not vacuum up spilled mercury because it will vaporize and increase exposure.
• If a large amount of mercury has been spilled, contact your health department.
• Teach children not to play with shiny, silver liquids.

Appropriate substitutes are available for nearly all uses of metallic mercury. Make arrangements to safely dispose of whatever metallic mercury you might have. If you do need to use metallic mercury, make sure it is safely stored in a leak-proof container. Keep it in a secure space (e.g., a locked closet) so that others cannot easily get it. Use of metallic mercury in a controlled environment helps to reduce the risk that contamination will occur.

Mercury poisoning from fish

For most people, the risk from eating contaminated fish and shellfish is not a health concern. However, some groups of people such as pregnant women, children and the elderly are at a greater health risk than others. Additionally, some individuals are at a higher risk simply because they eat substantially more fish than others.

The United States Environmental Protection Agency (EPA) and the U.S. Food and Drug Administration (FDA) provide advice on eating fish and shellfish for women about 16-49 years old, especially pregnant and breastfeeding women, and young children ⁶. Fish and shellfish provide protein, are low in saturated fat, are rich in many micronutrients, and provide certain omega-3 fatty acids that the body can not make and are important for normal growth and development. However, as a result of natural processes and human activity, fish also contain mercury in the form of methylmercury. Methylmercury can negatively affect the central nervous system, particularly the developing brain of a fetus.

The agencies have concluded that the following people should eat more fish that is lower in mercury for important developmental and health benefits:

• Women of childbearing age (about 16-49 years old)
• Pregnant and breastfeeding women
• Young children

The advice recommends that women and children eat two to three servings (8-12 ounces for adults and children over age 10, smaller amounts for younger children) of a variety of fish and shellfish each week. The advice includes a chart showing how often to eat more than 60 types of fish and shellfish and supplemental questions and answers.

Figure 1. EPA and FDA advice on eating fish and shellfish (you can use this chart to help you choose which fish to eat, and how often to eat them, based on their mercury levels. The “Best Choice” have the lowest levels of mercury)

Footnote: This advice is geared toward helping women who are pregnant or may become pregnant – as well as breastfeeding mothers and parents of young children – make informed choices when it comes to fish that is healthy and safe to eat.

[Sources ⁶, ⁷ ]

How do to use the chart

Fish are a high quality protein source, and lower mercury fish are a good choice for everyone. This advice is specifically for women who are pregnant, might become pregnant or are breastfeeding, and for young children, but everyone can follow this advice.

• Use the chart to help you choose which fish to eat each week. Eating a variety of fish is better for you and your child than eating the same type every time.
• You can eat 2 to 3 servings a week of fish in the “Best Choices” category, based on a serving size of four ounces, in the context of a total healthy diet.
• You can eat 1 serving a week of fish in the “Good Choices” category.
• You should NOT eat fish in the “Choices to Avoid” category or feed them to young children. However, if you do, eat fish with lower mercury levels in the following weeks.
• Eat a variety of fish.
• Serve 1 to 2 servings of fish a week to children, starting at age 2.
• If you eat fish caught by family or friends, check for fish advisories. If there is no advisory, eat only one serving and no other fish that week. Some fish caught by family and friends, such as larger carp, catfish, trout and perch, are more likely to have fish advisories due to mercury or other contaminants. State advisories will tell you how often you can safely eat those fish.

How can some fish be in more than one category?

There are different types (or species) of tuna, such as albacore, bigeye, and yellowfin. Some types of tuna that are bigger or live longer tend to have higher mercury levels, and that is why they are in different categories. So, canned light tuna is in the “Best Choices” category. Albacore (or white) tuna and yellowfin tuna are in the “Good Choices” category, and bigeye tuna is in the “Choices to Avoid.” In addition, fish of the same species that are caught in different geographic locations can vary in mercury content. For example, tilefish are in two categories because tilefish in the Gulf of Mexico have higher mercury levels than those in the Atlantic Ocean

Why are some fish not on the chart?

If you are looking for a species of fish that is not on the chart, such as mussels, that means the EPA and the FDA did not have enough reliable mercury data to include it. The agencies are planning to update the chart as they get more data.

What is a serving?

For adults, a typical serving is 4 ounces of fish, measured before cooking. Our advice is to eat 2 to 3 servings of a variety of cooked fish, or about 8 to 12 ounces, in a week.

How can I tell how much 4 ounces is?

Four ounces is about the size and thickness of an adult’s palm.

What happens if I eat less fish than the 2 to 3 servings a week you recommend?

You could miss out on the high quality protein, minerals and vitamins present in fish that are beneficial to overall health. Simply try to eat the recommended amount from a variety of fish in the following weeks. Our advice is provided as a general guideline for how much fish to eat weekly.

What happens if I eat more than 3 servings of fish in a week?

Try to vary the fish you eat. If you eat more than 3 servings in a week and some include fish with higher mercury levels, try to eat fish with lower mercury levels in the following weeks.

Should I make any changes to the advice based on my weight?

The advice provided here is intended as a general guideline. Women who weigh less than the average (165 pounds) may wish to eat smaller portions or to eat two servings of fish a week instead of three.

Should children eat fish and if so, how much?

Yes, fish, like other protein-rich foods, is good for a child’s growth and development. We recommend serving fish to children 1-2 times per week from a variety of fish, but the portion sizes should be smaller than adult portions and right for your child’s age and total calorie needs. On average, a serving size is about 1 ounce for children ages 2-3 years, 2 ounces for children ages 4-7 years, 3 ounces for children ages 8-10 years and 4 ounces for children 11 years and older.

At what age can I start giving my child fish?

Parents can feed fish to young children, but should not feed fish to children younger than 6 months of age. Because fish, and particularly shellfish, are regarded as major potential allergens, parents feeding fish to their children for the first time should monitor for signs of an allergic reaction before feeding a second time.

Can cleaning or preparing (e.g., cooking) my fish reduce the amount of mercury that might be present?

No. Mercury is found throughout the tissue in fish, so cleaning or cooking will not reduce the amount of mercury. The way to reduce the amount of mercury is to eat the fish shown on the chart identified as the “Best Choices.”

Should I be concerned if I eat one serving of the fish listed in the “Choices to Avoid” category?

No, but going forward, choose from fish from the “Best Choices” or “Good Choices” categories. Just try to avoid eating the “Choices to Avoid” fish or feeding them to children. We recommend you eat a variety of fish from the “Best Choices” and “Good Choices” categories on the chart.

Does this advice consider fishery sustainability issues?

No. This advice focuses on the benefits of fish consumption and the number of fish meals per week that could be eaten based on mercury levels in fish. This advice does not reflect concerns about fishery sustainability issues. For more information, see the National Oceanic and Atmospheric Administration’s website at (http://www.fishwatch.gov)

What nutrients are in fish and why are they good for you?

Most fish are an excellent source of high quality protein. Fish are also important sources of selenium, zinc, iodine, iron, and other minerals needed by the body. Fish are natural sources of many B vitamins, and oily fish provide vitamins A and D. Studies with pregnant women have found that the nutritional benefits of fish, like other protein-rich foods, are important for their children’s growth and development during pregnancy and childhood. Most fish are low in fat, and most of the fat that is present in fish is healthy polyunsaturated fat. The polyunsaturated omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are also present in many types of fish. Research is still underway to determine the health benefits of omega-3 fatty acids.

Is it true that pregnant women and young children should avoid raw fish?

Yes. The 2015-2020 Dietary Guidelines for Americans (https://health.gov/dietaryguidelines/2015/) and FDA recommend that pregnant women and young children should only eat foods with fish, meat, poultry, or eggs that have been cooked to safe internal temperatures to protect against microbes that might be in those foods. This includes raw fish served as part of sushi or sashimi (Japanese-style foods) that are available in many restaurants and food stores. Pregnant women and young children often have weaker immune systems and are more at risk for foodborne illnesses.

What if I cannot or do not eat fish? Will my baby be okay?

Fish is one source of high quality protein, minerals and vitamins that are beneficial to overall health. You can have a healthy baby even if you don’t eat fish.

I’m a woman who could have children but I’m not pregnant. Why should I follow this advice?

If you could become pregnant in the next year, we encourage you to begin following this advice now. Eating 2 to 3 servings of a variety of fish a week along with other protein-rich foods can help your child’s growth and development, and following the recommendations for how often to eat the various fish types is also important. That’s because mercury in fish can accumulate in your body over time. While mercury is removed from the body naturally, the process can take several months. So, following this advice before pregnancy can benefit the developing child, especially during the important first trimester.

What advice do you have about eating fish for people who are not pregnant, will not become pregnant, or are not breastfeeding?

Fish are a high quality protein source, and lower mercury fish are a good choice for everyone. This advice is specifically for women who are pregnant, might become pregnant or are breastfeeding, and for young children, but everyone can follow this advice.

Tuna

What is the difference between albacore (white) tuna and canned light tuna?

Albacore, or white tuna, is larger and lives longer than the fish generally used in canned light tuna. Meanwhile, canned light tuna can be a mix of a variety of generally smaller tuna species, most often skipjack.

I eat a lot of tuna, especially canned light tuna because it is particularly affordable. Is this okay?

Yes. Canned light tuna is in the “Best Choices” category and it is fine to eat 2 to 3 servings per week. We recommend that you eat a variety of fish. You may wish to try other affordable fish in the “Best Choices” category such as canned salmon or sardines, frozen fish, or fresh fish that are at a reduced price.

I eat a lot of tuna, but prefer to eat albacore tuna. Is this okay?

Albacore tuna, also known as white tuna, typically contains three times more mercury than canned light tuna. You can eat albacore or any of the other fish from the “Good Choices” category once a week.

Fish Caught By Family and Friends

What if I eat fish caught by family and friends?

When eating fish you or others have caught, pay attention to fish advisories on those water bodies. There are waters where there may have been little or no monitoring and, therefore, the extent of potential mercury contamination is unknown. If advice isn’t available, you should limit your consumption of that fish to one serving per week and not eat any other fish that week. Adults should eat no more than 6 ounces that week, children under the age of six should limit their consumption of these fish to 1 to 2 ounces per week, and older children (ages six to twelve) should limit their consumption to 2 to 3 ounces per week. Again, neither adults nor children should eat other fish that week.

Where do I get information about the safety of fish caught by family or friends?

Check the applicable fishing regulations booklet or website for information about recreationally caught fish. Local, state, and tribal health departments and fish and game agencies also have information about advisories for consuming fish in their jurisdiction.

Mercury poisoning from fillings

Members of the public will occasionally become concerned about exposure to mercury from dental amalgams. Sometimes referred to as “silver filling,” dental amalgam is a silver-colored material used to fill (restore) teeth that have cavities. Dental amalgams (teeth fillings) are made up of about 50% metallic mercury. Dental amalgam is made of two nearly equal parts:

• liquid mercury, and
• a powder containing silver, tin, copper, zinc and other metals.

Amalgam is one of the most commonly used tooth fillings, and is considered a safe, sound, and effective treatment for tooth decay. Restorative dentistry has used a mercury-silver amalgam for approximately 150 years as a filling material in hundreds of millions of patients around the world ⁸.

A small amount of mercury (2-20 mcg/day) is released from a dental amalgam when it was mechanically manipulated, such as by chewing. The habit of gum chewing can cause release of mercury from dental amalgams greatly above normal. The normal bacterial flora present in the mouth converts a fraction of this to Hg(+2) and CH(3)Hg(+), which was shown to be incorporated into body tissues. The World Health Organization safety standard for daily exposure to mercury is 45 mcg/day. Thus, if one had no other source of exposure, the amount of mercury released from dental amalgams is not significant ⁹. Many foods contain mercury. For example, commercial fish considered safe for consumption contain <0.3 mcg/g of mercury, but some game fish contain >2.0 mcg/g and, if consumed on a regular basis, contribute to significant body burdens.

When amalgam fillings are placed in or removed from teeth, they can release a small amount of mercury vapor. Amalgam can also release small amounts of mercury vapor during chewing. People can absorb these vapors by inhaling or ingesting them. However, the U.S. Food and Drug Administration (FDA) considers dental amalgam fillings safe for adults and children over the age of six ¹⁰.

FDA regulates dental amalgam as a medical device. FDA is responsible for ensuring that dental amalgam is reasonably safe and effective. Among other things, FDA also makes sure the product labeling for dentists has adequate directions for use and includes applicable warnings.

Since the 1990s, FDA, the Centers for Disease Control and Prevention (CDC) and other government agencies have reviewed the scientific literature looking for links between dental amalgams and health problems. CDC reported in 2001 that there is little evidence:

• that the health of the vast majority of people with dental amalgam is compromised, or
• that removing amalgam fillings has a beneficial effect on health.

In 2002, FDA published a proposed rule to classify dental amalgam as a class II medical device with special controls. In 2008, FDA reopened the comment period for that proposed rule. After reviewing all comments, FDA issued a rule in 2009 ⁸ – the U.S. Food and Drug Administration (FDA) has determined that dental amalgams are safe for adults and children over age 6.

Why is mercury used in dental amalgam?

Approximately half of a dental amalgam filling is liquid mercury and the other half is a powdered alloy of silver, tin, and copper. Mercury is used to bind the alloy particles together into a strong, durable, and solid filling. Mercury’s unique properties (it is a liquid at room temperature and that bonds well with the alloy powder) make it an important component of dental amalgam that contributes to its durability.

Is the mercury in dental amalgam the same as the mercury in some types of fish?

No. There are several different chemical forms of mercury: elemental mercury, inorganic mercury, and methylmercury. The form of mercury associated with dental amalgam is elemental mercury, which releases mercury vapor. The form of mercury found in fish is methylmercury, a type of organic mercury. Mercury vapor is mainly absorbed by the lungs. Methylmercury is mainly absorbed through the digestive tract. The body processes these forms of mercury differently and has different levels of tolerance for mercury vapor and methylmercury.

If I am concerned about the mercury in dental amalgam, should I have my fillings removed?

If your fillings are in good condition and there is no decay beneath the filling, FDA does not recommend that you have your amalgam fillings removed or replaced. Removing sound amalgam fillings results in unnecessary loss of healthy tooth structure, and exposes you to additional mercury vapor released during the removal process.

However, if you believe you have an allergy or sensitivity to mercury or any of the other metals in dental amalgam (such as silver, tin, or copper), you should discuss treatment options with your dentist.

Are there alternatives to using dental amalgam fillings?

Presently, there are five other types of restorative materials for tooth decay:

• resin composite
• glass ionomer
• resin ionomer
• porcelain
• gold alloys

The choice of dental treatment rests with dental professionals and their patients, so talk with your dentist about available dental treatment options.

What is bioaccumulation?

Bioaccumulation refers to the build-up or steadily increasing concentration of a chemical in organs or tissues in the body. Mercury from dental amalgam and other sources (e.g., fish) is bioaccumulative. Studies of healthy subjects with amalgam fillings have shown that mercury from exposure to mercury vapor bioaccumulates in certain tissues of the body including kidneys and brain. Studies have not shown that bioaccumulation of mercury from dental amalgam results in damage to target organs.

Mercury poisoning linked to skin products

The U.S. Food and Drug Administration (FDA) cautions that you should avoid skin creams, beauty and antiseptic soaps, and lotions that contain mercury.

How will you know if mercury’s in the cosmetic, especially one that’s marketed as “anti-aging” or “skin lightening”? Check the label. If the words “mercurous chloride,” “calomel,” “mercuric,” “mercurio,” or “mercury” are listed on the label, mercury’s in it—and you should stop using the product immediately.

The products are usually marketed as skin lighteners and anti-aging treatments that remove age spots, freckles, blemishes, and wrinkles. Adolescents may use these products as acne treatments.

In the past few years, FDA and state health officials have discovered numerous products that contain mercury, and there have been cases in which people exposed to such products have had mercury poisoning or elevated levels of mercury in their bodies.

Signs and symptoms of mercury poisoning:

• irritability
• shyness
• tremors
• changes in vision or hearing
• memory problems
• depression
• numbness and tingling in hands, feet or around mouth

Symptoms of high exposures to inorganic mercury include:

• skin rashes and dermatitis,
• mood swings,
• memory loss,
• mental disturbances, and
• muscle weakness.

Mercury poisoning signs and symptoms

Signs and symptoms suggesting excessive exposure to mercury.

Acute signs and symptoms of mercury poisoning may include:

• Burning in the mouth and lungs
• Cough, difficulty breathing, chest tightness
• Difficulty urinating and decreased urine output
• Nausea, vomiting, diarrhea, or abdominal cramping
• Increased heart rate
• Fever or chills
• Dizziness
• Headache

Those who are chronically exposed to mercury may have nonspecific symptoms that involve the lungs, kidneys, and nervous system. Some of the chronic symptoms may include:

• Problems with hearing, taste and smell
• Blurry vision or sometimes tunnel vision
• Tingling or tremors in the arms or legs
• Difficulty walking
• Irritability
• Memory loss

Methylmercury effects

Effects on People of All Ages

Exposure to methylmercury most commonly occurs when people eat kinds of fish and shellfish that have high levels of methylmercury in their tissues. Almost all people have at least small amounts of methylmercury in their bodies, reflecting the widespread presence of methylmercury in the environment. U.S. Centers for Disease Control and Prevention (CDC) data ¹¹ show that most people have blood mercury levels below levels associated with possible health effects. Methylmercury, however, is a powerful neurotoxin, and people exposed to high levels may experience adverse health effects. If you are concerned about your exposure to methylmercury, you should consult your physician.

Possible symptoms of methylmercury poisoning may include:

• loss of peripheral vision
• “pins and needles” feelings, usually in the hands, feet, and around the mouth
• lack of coordination of movements
• impairment of speech, hearing, walking
• muscle weakness

Effects on Infants and Children

Infants in the womb can be exposed to methylmercury when their mothers eat fish and shellfish that contain methylmercury. This exposure can adversely affect unborn infants’ growing brains and nervous systems. These systems may be more vulnerable to methylmercury than the brains and nervous systems of adults are.

Children exposed to methylmercury while they are in the womb can have impacts to their:

• cognitive thinking,
• memory,
• attention,
• language,
• fine motor skills, and
• visual spatial skills.

Elemental (metallic) mercury

Elemental metallic mercury is usually harmless if it is touched or swallowed. It is so thick and slippery that it usually falls off the skin or leaves the stomach and intestines without being absorbed.

A lot of damage can occur, though, if elemental mercury gets into the air in the form of small droplets that are breathed into the lungs. This often occurs by mistake when people try to vacuum up mercury that has spilled onto the ground.

Breathing in enough elemental mercury will cause symptoms right away. These are called acute symptoms. Long-term symptoms will occur if small amounts are inhaled over time. These are called chronic symptoms.

Chronic symptoms may include:

• Metallic taste in the mouth
• Vomiting
• Difficulty breathing
• Bad cough
• Swollen, bleeding gums

Depending on how much mercury is inhaled, permanent lung damage and death may occur. Long-term brain damage from inhaled elemental mercury can also occur.

Inorganic mercury

Unlike elemental mercury, inorganic mercury is usually poisonous when swallowed. Depending on how much is swallowed, symptoms may include:

• Burning in the stomach and throat
• Bloody diarrhea and vomiting

If inorganic mercury enters your bloodstream, it can attack the kidneys and brain. Permanent kidney damage and kidney failure may occur. A large amount in the bloodstream may cause massive blood and fluid loss from diarrhea and kidney failure, leading to death.

Organic mercury

Organic mercury can cause sickness if it is breathed in, eaten, or placed on the skin over long periods of time. Usually, organic mercury causes problems over years or decades, not right away. This means that being exposed to small amounts of organic mercury every day for years will likely cause symptoms to appear later. But, a single large exposure can also cause problems.

Long-term exposure will likely cause symptoms in the nervous system, including:

• Numbness or pain in certain parts of your skin
• Uncontrollable shaking or tremor
• Inability to walk well
• Blindness and double vision
• Memory problems
• Seizures and death (with large exposures)

Being exposed to large amounts of the organic mercury called methylmercury while pregnant may cause permanent brain damage in the baby. Most health care providers recommend eating less fish, especially swordfish, while pregnant. Women should talk to their provider about what they should and should not eat while pregnant.

How to test for mercury poisoning

Mercury testing is used to detect the presence of an excessive amount of mercury in a person’s blood and/or urine sample. It may be ordered by a health practitioner to determine whether a person has had short-term exposure to a toxic level of mercury (acute exposure) or has been exposed over an extended period of time (chronic exposure). Testing may also be used to monitor those who may be exposed to mercury in the workplace.

Mercury testing may be ordered when a person has signs and symptoms suggesting excessive exposure to mercury.

Testing may also be ordered even in the absence of symptoms when it is known that a person has been exposed to mercury in order to help evaluate the extent of the exposure.

Mercury measurements may be ordered regularly as a monitoring tool for those people who work in industries that utilize mercury and may be ordered, along with tests to detect lead and/or other heavy metals, for individuals who work with a variety of potentially hazardous materials.

Mercury is an element that can be toxic in various forms, which are tested in different samples:

• Metallic or elemental mercury is a liquid often used in dental fillings, some thermometers, and batteries. Urine samples are typically tested to detect this form of mercury.
• Inorganic mercury salts, which are produced by the reaction of non-carbon based compounds with mercury, are normally in a form of powder or crystal and sometimes used in topical preparations such as skin-lightening or antiseptic creams. Urine samples are usually used to detect this form of mercury.
• Methyl mercury and other organic mercury compounds are products of reactions between mercury and carbon-based organic compounds. Bacteria with elevated levels of methyl mercury are often found in large, older, predator fish such as sharks and king mackerel. People who eat these fish may be exposed to this form of mercury. Blood is primarily used to identify a high level of methyl mercury.

To test for the various forms of mercury, more than one type of sample may be collected and tested.

• Blood is primarily tested to detect the presence of methyl mercury. Other forms of mercury (metallic and inorganic) can also be detected in the blood, but the amount present will decrease by half about every 3 days as the mercury moves into organs such as the brain and kidneys. Therefore, blood testing must be done within days of suspected exposure.
• Urine is used to test for metallic mercury and inorganic forms of mercury, but it cannot be used to determine exposure to methyl mercury.
• Hair testing may be useful to detect methyl mercury exposures that occurred several months previously, but hair testing is relatively complex and is not used frequently.
• Although not routinely ordered tests, mercury has been shown to be present in nails, breast milk, stool, and breath.

Other general laboratory tests may be used to help evaluate the health of various organ systems in someone who has been exposed or thought to be exposed to toxic levels of mercury. Some examples include a comprehensive metabolic panel (CMP) and a complete blood count (CBC).

What does the test result mean?

Levels of mercury in blood and urine are normally very low. A test result showing no mercury or a low level indicates that it is likely that the person tested has not been exposed to excessive levels of mercury, at least not in the window of time that the test is measuring.

An increased blood level suggests a relatively recent exposure to mercury. In general, a blood level greater than 10 mcg/L indicates an unusual level of exposure for someone who does not regularly work with mercury.

In contrast to levels of mercury in the blood, a 24-hour urine sample gives more of an average past history of exposure to metallic or inorganic mercury. Normal urine levels are typically less than 10 mcg/L for someone without risk of occupational exposure.

Levels of mercury in either the blood or urine will not indicate the form or quantity of mercury to which a person was exposed.

An increased level of mercury in hair testing may indicate exposure to increased levels of methyl mercury, but hair samples are rarely used because of issues involving testing standardization, sample contamination, and the fact that hair is subject to many pre-analytical variables (hair exposure to dyes, bleach, shampoo, etc.).

Mercury poisoning treatment

General treatment for mercury exposure includes the steps just below. Treatment for exposure to different forms of mercury are given after this general information.

The person should be moved away from the source of exposure.

The health care provider will measure and monitor the person’s vital signs, including temperature, pulse, breathing rate, and blood pressure.

Tests that may be done include:

• Blood and urine tests
• Chest x-ray
• ECG (electrocardiogram) or heart tracing

Treatment may include:

• Activated charcoal by mouth or tube through the nose into the stomach, if mercury is swallowed
• Dialysis (kidney machine)
• Fluids through a vein (by IV)
• Medicine to treat symptoms

Although there are a number of treatments currently available, none are completely satisfactory and additional development of treatment drugs and protocols is needed. In general, even the inorganic mercury, that are considered to be more easily chelated, are difficult to remove from the body and are not treated without some side effects. Infants and young children are particularly difficult to treat, sometimes requiring exchange transfusion or other more elaborate measures. Reducing the body burden or toxic effects of mercury in pregnant women presents an even greater challenge (i.e., treatment must be effective for both the mother and the developing child), and specific treatment protocols are needed.

The type of exposure will determine what other tests and treatments are needed.

Elemental mercury

Inhaled elemental mercury poisoning may be difficult to treat. The person may receive:

• Humidified oxygen or air
• Breathing tube into the lungs
• Suctioning of mercury out of the lungs
• Medicine to remove mercury and heavy metals from the body

Inorganic mercury

For inorganic mercury poisoning, treatment often begins with supportive care. The person may receive:

• Fluids by IV (into a vein)
• Medicines to treat symptoms
• Activated charcoal, a medicine that soaks up many substances from the stomach
• Medicines called chelators to remove mercury from the blood

Organic mercury

Treatment for exposure to organic mercury usually consists of medicines called chelators. These remove mercury from the blood and move it away from the brain and kidneys. Often, these medicines will have to be used for weeks to months.

One popularly used chelator, dimercaprol or BAL, has two sulfhydryl groups that can bind mercury and compete with its binding to sulfhydryl groups in body tissues ¹². BAL is one of the more effective chelators for inorganic mercury salts. BAL is administered intramuscularly and is the preferred chelator when oral dosing is impractical ¹². Approximately 50% of the dimercaprol-mercury complex is excreted through the kidneys, while the remainder is eliminated in the bile and feces. Thus, this chelator is preferred when renal impairment has occurred. BAL therapy, however, has several limitations. Significant reabsorption of mercury from the bile occurs ¹³. Also, multiple toxic side effects including urticaria, elevated blood pressure and heart rate, nausea and vomiting, headache, conjunctivitis, lacrimation, and paresthesias have been reported ¹⁴. Children may develop fevers, and individuals with a glucose-6-phosphatase deficiency (G6PD) may develop hemolysis. BAL treatment is contraindicated for elemental and organic mercury compounds because it has been shown to increase brain levels of mercury in animal studies when used to treat exposures to phenylmercury or methoxyethylmercury compounds ¹⁵ or elemental mercury vapor ¹⁴, indicating the possibility of increased neurotoxicity.

Another currently used mercury chelator is D-penicillamine. This drug has been used somewhat effectively to reduce the toxicity of elemental and inorganic mercury exposures. It can be taken orally, and its metabolism is slight in humans. Penicillamine is removed though the kidneys ¹². However, acute allergic reactions to penicillamine may occur ¹⁴. An experimental drug, N-acetyl-D,L-penicillamine (NAP), is very similar to its analog, penicillamine, in its properties of absorption, metabolism, and excretion; however, it may be more mercury-specific in its chelating abilities and less toxic ¹⁴. A high success rate (88%) has been reported by investigators using n-acetyl-D,L-penicillamine (NAP) to treat victims of mercury inhalation ¹².

2,3-Dimercaptosuccoinic acid (DMSA), an analogue of BAL, is another experimental chelating agent. DMSA can be given orally and is primarily excreted through the kidneys ¹⁶. It has been shown to be an effective chelator for both inorganic and methylmercury ¹⁷. Comparative studies have demonstrated that DMSA is as effective, if not more so, as dimercaprol, penicillamine, and n-acetyl-D,L-penicillamine (NAP). Data also suggest that this chelating drug produces fewer adverse effects than NAP ¹². 2,3-Dimercaptopropane-1-sulfonate (DMPS) is another BAL analogue that is an orally effective chelator for mercury. Reports differ with respect to which of these analogues is less toxic ¹⁸. Better results were obtained in rats with DMPS than with DMSA when the chelating agent was administered at least 24 hours following exposure to mercuric chloride . However, early oral administration of DMPS (within 24 hours) resulted in increased mercury retention ¹⁸. In contrast, DMSA resulted in decreased mercury retention irrespective of when it was administered.

Hemodialysis with infusion of a chelator (cysteine, N-acetylcysteine, NAP) has been reported to be effective in some severe cases of poisoning where renal failure is a complication ¹⁹. It has been reported to be advantageous to begin the hemodialysis before substantial renal damage has occurred ¹⁹. Because methylmercury undergoes enterohepatic recirculation, nonabsorbable agents have been used to “trap” methylmercury excreted into the bile ²⁰. A polystyrene resin containing sulfhydryl groups added to food at a concentration of 1% doubled the elimination rate of methylmercuric chloride when administered to mice. The elimination half-life decreased from 65 to 20 days ²¹. Excretion of methylmercury may also be enhanced by bile drainage either through catheterization and drainage of the choledochal duct or by surgical establishment of gallbladder drainage ¹⁵. However, this method has not been used therapeutically.

Mercury poisoning prognosis

Breathing in a small amount of elemental mercury will cause very few, if any, long-term side effects. However, breathing in larger amounts can lead to a long hospital stay. Permanent lung damage is likely. There may be brain damage. Very large exposures will likely cause death.

A large overdose of inorganic mercury may cause massive blood and fluid loss, kidney failure, and likely death.

Chronic brain damage from organic mercury poisoning is difficult to treat. Some people never recover, but there has been some success in people who receive chelation treatment.

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